MDIS Calibration and Testing Plan

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					MDIS Calibration
and Testing Plan

    Louise Prockter
     Scott Murchie
     Keith Peacock
    Hugo Darlington
     Bruce Gotwols
      Ed Hawkins
    Howard Taylor
      Ben Bussey
      Chris Hash
    Mark Robinson
    Noam Izenberg




     VERSION 7.0




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                                                                   TABLE OF CONTENTS

1. INTRODUCTION......................................................................................................................................... 3
   1. MDIS DESIGN AND CALIBRATION REQUIREMENTS ............................................................................................................................ 3
   2. TEST PROCEDURES ............................................................................................................................................................................. 6
         Table 1: MDIS ground calibration schedule............................................................................................................................. 6
2. ON-GROUND CALIBRATION REQUIREMENTS/TESTS ................................................................. 7
   2.1 DETECTOR CHARACTERIZATION ...................................................................................................................................................... 7
   2.2 PIVOT CALIBRATION ......................................................................................................................................................................... 9
   2.3 OPTICAL IMAGING FACILITY CALIBRATION................................................................................................................................... 11
      2.3.1 Test Priorities ....................................................................................................................................................................... 11
      2.3.2. Dark current ........................................................................................................................................................................ 12
      2.3.3. Leaked light test................................................................................................................................................................... 13
      2.3.4 Frame Transfer (Readout) Smear – no compression.......................................................................................................... 14
      2.3.5. Hardware compression ....................................................................................................................................................... 15
      2.3.6. Flat Field (Response Uniformity)....................................................................................................................................... 16
      2.3.7. Radiometric Responsivity.................................................................................................................................................... 17
      2.3.8. Filter Bandpasses/Out of band rejection (spectral leakage)/Cross-talk .......................................................................... 18
      2.3.9. Picked Up Noise/Power cycling ......................................................................................................................................... 19
      2.3.10. Linearity, Read Noise, Gain, SNR as a function of DN................................................................................................... 20
      2.3.11. Point Spread Function (PSF), Field of View (FOV) measurement ................................................................................ 21
      2.3.12. Search for optical ghosting............................................................................................................................................... 23
      2.3.13 Relative Alignments of WA and NA Imagers..................................................................................................................... 24
      2.3.14. Calibration validation (hand samples)............................................................................................................................. 25
      2.3.15. “Real World” test.............................................................................................................................................................. 26
   2.4 SOFTWARE PERFORMANCE ............................................................................................................................................................ 27
          Table 2: On-ground calibration summary............................................................................................................................... 28
3. IN-FLIGHT CALIBRATION ................................................................................................................... 29
        3.1 Dark current ............................................................................................................................................................................ 29
        3.2 Flat field................................................................................................................................................................................... 30
        3.3 Linearity................................................................................................................................................................................... 31
        3.4 Responsivity ............................................................................................................................................................................. 32
        3.5 Point spread/in-field scattered light ....................................................................................................................................... 33
        3.6 Out of field scattered light ...................................................................................................................................................... 34
        3.7 Field of View (FOV)................................................................................................................................................................ 35
        3.8 Pointing, coalignment of WAC and NAC, orientation of pivot plane in spacecraft reference frame.................................. 36
        3.9 Solar spectrum calibration...................................................................................................................................................... 37
           Table 3: Post-Launch calibration plan (L+60 days) ............................................................................................................... 38
           Table 4: Cruise calibration plan .............................................................................................................................................. 38
4. CROSS-CALIBRATION REQUIREMENTS/TESTS........................................................................... 39
        4.1 Calibration validation correlation between MDIS and VIRS (ON-GROUND) ................................................................... 39
        4.2 Relative Alignments of WA Imager and VIRS (IN_FLIGHT)................................................................................................ 40
5. DELIVERABLES TO SOC ....................................................................................................................... 41
   5.1 DRIVERS FOR SOC PRE-FLIGHT CONFIGURATION .......................................................................................................................... 41
   5.2 PRODUCTS TO BE RECEIVED FROM APL’S CALIBRATION FACILITIES ............................................................................................. 41
   5.3 TRANSFER OF DATA FROM CALIBRATION FACILITIES TO SOC ....................................................................................................... 41
   5.4 DELIVERY TO PDS ......................................................................................................................................................................... 41
      5.4.1 Pre-flight calibration data ................................................................................................................................................... 42
      5.4.2 Post-launch/cruise calibration data .................................................................................................................................... 42
         Table 5: Planned MDIS data deliveries to PDS...................................................................................................................... 42
   5.5 DATE FOR COMPLETION OF CALIBRATION PAPERS ......................................................................................................................... 42
APPENDIX 1: VARIATION OF CCD AND FILTER WHEEL TEMPERATURES........................... 43
APPENDIX 2: OCF CALIBRATION PROCEDURE ............................................................................... 44
APPENDIX 3: WIDE ANGLE FILTERS.................................................................................................... 54
APPENDIX 4: PROPOSED HAND SAMPLES ......................................................................................... 54

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                                    1. INTRODUCTION

1. MDIS design and calibration requirements
     MDIS is comprised of wide- and narrow-angle cameras sensitive to visible wavelengths.
Mission goals are to produce a global monochrome map at 250-m average resolution or better
and a color map at 2-km average resolution or better. Mercury's eccentric orbit poses a challenge
to the design of the spacecraft, with the intensity of the solar radiation varying from about 4.6 -
10.6 times the total irradiance falling on the Earth. Because of this severe thermal environment, a
sunshade protects the spacecraft from direct solar illumination, but strongly constrains its range
of pointing. To compensate for this limited pointing capability, the dual cameras of MDIS are
mounted on either side of a rotating platform, pivoted about a common axis. The two cameras
will be co-aligned to within the pointing accuracy of the spacecraft of 0.1˚. The pivot platform
design enables the instrument to acquire optical navigation (OpNav) images and star field
calibrations, and greatly increases opportunities to image key features with minimal impact on
spacecraft pointing. The nominal scan range of the platform is 40˚ in the sunward direction to
50˚ planetward.
     The wide-angle camera (WAC) has a 10.5˚ field-of-view (FOV) and consists of a refractive
telescope using a dogmar- like design having a collecting area of 48 mm. A 12-position
multispectral filter wheel provides color imaging over the spectral response of the CCD detector
(395 - 1040 nm). Ten spectral filters are defined to cover wavelengths diagnostic of different
surface compositions and have bandwidths from 10 - 40 nm. A medium-band filter provides fast
exposures for high-resolution imaging, and the last filter is panchromatic for OpNavs. In order to
achieve diffraction limited image quality, residual chromatic aberration is removed by varying
the optical thickness of each filter, optimized for the center wavelength of the filter's passband,
as was done for the Multi-Spectral Imager on the NEAR Shoemaker spacecraft. The narrow-
angle camera (NAC) has a 1.5˚ FOV and uses a reflective design with a single medium-band
filter with a passband identical to the one used in the WAC (650 - 850 nm). Each image will
include four columns of dark reference elements in order to correct for variations in operating
temperature. Both cameras have identical detector electronics contained in a modular focal plane
unit (FPU). Due to thermal constraints, only one camera will operate at a time.
     Protective covers for optical components are very desirable during ground-based testing,
launch, and trajectory maneuvers requiring large thruster burns. However, due to the severe mass
limitations on MESSENGER, a conventional protective cover for MDIS was not practical.
Instead, the critical first optic of each telescope can be protected by rotating the platform 180˚
from nadir, such that both cameras look downward into the deck. This innovative approach
ensures a circuitous path for any particulate or molecular contamination.
     In order to minimize mass, defocusing, and misalignment effects resulting from operating
over a wide range of temperatures, the pivot platform and most of the components are made of
magnesium. The instrument deck and the bracket will remain near room temperature. The entire
instrument and bracket assembly are covered with multilayer insulating blankets.
     The design of the detector electronics is based on the CONTOUR/CRISP instrument, and is
identical for both the wide and narrow-angle cameras. The detector is an Atmel TH7888A CCD
array with 1024 x 1024 pixels with built-in antiblooming control. The fill factor for the 14 x 14
µm pixels is 71%. The maximum frame rate is 1 Hz with a frame transfer time of 3 ms. Optical
navigation using MDIS is critical to the success of the MESSENGER mission. To increase the
low-light sensitivity, the maximum exposure is approximately 9.9 s with a readout time of 1 s.
Typical exposures will be 100 ms. An autoexposure algorithm similar to that used on NEAR will

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also be used regularly. Although the peak of the quantum efficiency of the CCD is only about
18%, the expected signals at Mercury are large. We have assumed a reflectance spectrum for
Mercury to be the same as a laboratory spectrum of the Apollo 16 lunar sample 62231. The FPU
electronics perform a correlated double sample of each pixel then digitize it to 12-bits resulting
in a 12 Mb full image. At the expected acquisition rates of 100 images/day, the two 8 Gb solid-
state recorders (SSR) on board would be filled in less than two weeks. MESSENGER is not
equipped with a high gain antenna, and so downlink opportunities are less frequent. To reduce
the image downlink, yet minimize the effect on the science return, a number of imaging and
compression modes are utilized. On-chip pixel binning of 2 x 2 and 4x 4 are available within the
FPU.
    Once the data are transferred to the DPU, they can be streamed directly to the solid state
recorder (SSR), or compressed in hardware using a variety of 12-to-8 bit lookup tables,
differencing of adjacent pixels, and/or the FAST algorithm. These data are then sent to the SSR
over a high-speed link. The spacecraft's main processor (MP) can read both the hardware-
compressed images as well as the raw images from the SSR. The MP can then perform
additional binning, extract image subframes, and use much more sophisticated compression
algorithms to substantially reduce the total downlink.




   Figure 1: Artistic rendering of MDIS.



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   The calibration goals for the Mercury Dual Imaging System (MDIS) are driven by science
requirements:
   • Radiometrically accurate multispectral mapping to determine compositional variations
       (absolute, and relative in 2D).
   • Ensure image quality to characterize small-scale surface morphology.
   • Alignment knowledge of Wide Angle (WA) and Narrow Angle (NA) cameras to create
       seamless photomosaics.
   • Alignment knowledge of VIRS and MDIS to understand geologic context of surface
       spectral variations.
   • Pointing knowledge for accuracy of digital terrain models from stereo imaging.

    The role of calibration involves determining MDIS’s attributes and deriving the algorithms
needed to convert images into useful data products. There are three major aspects to this
calibration, which are:

   a. Radiometric calibration, which allows derivation of parameters to characterize the MDIS
sensor. These parameters are fed into the “calibration equation”:


                   Radiance0 x . y. f .T .t =
                                                {[ DN   x . y . f .T .t                 ]             }
                                                                          − Darkx . y.t .T − Smearx . y.t • 100
                                             Flat x . y. f • Coef f • Re sp f .T • Expt
   where DNx.y.f.T.t is raw DN measured by the pixel in column x, row y, through filter f at
exposure time t and temperature T. Darkx.y.t.T is the dark level modeled for this pixel at exposure
time t and temperature T, derived from short and long dark field exposures at the same
temperature. Smearx.y.t is the scene dependent smear for the pixel at exposure time t. Flatx.y.f is the
flat field for filter f. Coeff is the calibration coefficient for filter f, and Respf.T is the relative
responsivity for this filter at temperature T. Expt is the exposure time in milliseconds, and the
constant 100 is the exposure time in milliseconds for which the calibration coefficient Coeff is
applicable.
    The parameters are either/or
            • Derived from data (dark, scatter, flat, coef, resp)
            • “Knowns” whose accuracy is tested and confirmed (smear, exp)

    b. Geometric calibration, which allows the field of view of each imager to be characterized,
so that the resolution of each pixel can be accurately determined. In addition, the pointing
relationship between the Narrow Angle (NA) and Wide Angle (WA) imagers will be determined.

   c. System performance. The entire assembled instrument is characterized in addition to its
components, to identify sources of noise, linearity of the CCD, filter bandpasses, and software
functionality.




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2. Test Procedures
   The tests required to fully characterize MDIS are described in sections 2 and 3 and are
categorized as on-ground and/or in-flight tests. For the purposes of this document, the tests are
split up in order to describe what is needed to characterize a specific property of the instrument.
However, some of the data sets required are the same for more than one test and will be used
accordingly. When this is the case, they will usually be analyzed differently according to the goal
of each test.
   We propose to use an alternative test procedure than that used for CONTOUR, in which a
different dataset was acquired for each individual test. Instead, we plan to obtain a continuous
series of measurements that will then be sorted and utilized wherever appropriate. The purpose
of this approach is to minimize the time and resources needed to set up and carry out the tests.
    The Wide Angle camera (WAC) and Narrow Angle camera (NAC) CCD’s will be
characterized to a first order as outlined section 2.1. The purpose of this is to understand the
response of the CCD before assembly with the MDIS optics, and to flag any potential problems
early on. Once this part of the calibration has been satisfactorily accomplished, the pivot
assembly will be tested as described in section 2.2. Finally, the assembled instrument will be
calibrated in the Optical Calibration Facility (OCF) according to the test procedure described in
section 2.3 and appendix 2. Measurement goals are given at the beginning of each test, and are
based on requirements from the concept study.
    In addition to carrying out a full and complete calibration of the imagers, the MDIS
instrument team is tasked with supplying the Science Operations Center (SOC) with calibration
algorithms in forms suitable for application to flight images and delivery to the PDS. The MDIS
team is also responsible for the publication of calibration results.
    At the time of writing, MDIS is running behind schedule and it is looking unlikely that we
will be able to carry out full pre-environmental testing. If such testing is possible, we aim to
carry out all of the tests outlined in section 2 (except the real world test) at room temperature,
and if time allows, at -40˚C. We expect that the entire calibration sequence (at room temperature
and three additional temperatures) can be carried out within 2 weeks, if no major problems arise.
This is well within the bounds of the time presently allotted to calibration. The current schedule
for assembly and calibration is as follows:


Table 1: MDIS ground calibration schedule

Calibration procedure                               Date
Characterization of flight CCDs                     September 2002
Focus tests of integrated telescopes and FPUs       Late September 2002
Pivot assembly calibration (without cameras)        October 2002
Instrument assembly (minus heat pipes)              October 2002
Preliminary calibration with EM DPU                 November 2002
Add thermal assembly to MDIS                        November/December 2002
MDIS Environmental tests                            December 2002
MDIS Final calibration                              December 2002/January 2003
Delivery to payload integration                     February 2003




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            2. ON-GROUND CALIBRATION REQUIREMENTS/TESTS

2.1 Detector Characterization
    Tests of the detector on the focal plane unit (FPU) without any optics, in the Detector
Characterization Chamber (DCC), are made as part of the normal test flow before instrument
integration. These tests are similar to calibration but usually have a lower accuracy than the
instrument calibration requires. The DCC is a vacuum chamber with a cold plate and light source
suited for spot measurements. We plan to add some monochromatic flood sources to give rough
flat field measurements.
    Tests conducted in the chamber are measured over a range of temperatures and exposure
times, and consist of:

     •   Dark current
     •   Spot spectral response
     •   Spot linearity (not a good measurement)
     •   Spot saturation (antiblooming efficacy)
     •   Spot intrapixel response
     •   Flat field spectral response
     •   Flat field linearity

Flight unit calibration procedure
        For this series of calibration tests, an input current of 2 Amps will be used as standard
lamp setting, with 1.5 Amps as an alternative. The use of ND filters beyond 2.5 gives too much
light leakage to be very useful.
   After initial setup and test at room temperature a sequence of tests at about -40 °C, -30 °C and
-20°C will be made.

Calibration of light source and light filters
    Before starting the Flight Unit calibration tests it is necessary to calibrate the light source and
ND filters that will be used. Insert the calibrated photo diode detector (Graseby Optronics Model
221 Silicon Sensor Head) into the vacuum chamber. Make sure the lamp is set to 2.0 A. Center
the detector under the light source for maximum signal. Initially, measure the output using the
700 nm filter (ND 0) every five minutes for one hour. This is to determine the stability of the
light source and only needs to be done once. Measure the output for each spectral filter. This
should also be done for a number of ND filters (ND 0, 0.5, 1.0, 1.5), and for all ND filters at the
wavelengths 500 nm, 700 nm, and 1000 nm.

Description of tests
   Shutter values are listed in decimal. Temperature monitors. Base and filter are permanent.
Attach flying ones to CCD bracket, and electronics board with Kapton tape (check with Lead
Engineers). Evacuate chamber. Bring CCD board to temperature, and allow to settle. Perform
tests 1 to 6. Record all temperatures (4) before and after each set of measurements.

1.      Measure CCD dark current and noise.
     Record 8 frames of data. Several shutter values should be used, suggest 1, 10, 100, 950 ms.


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2.        Measure shutter linearity.
    Record an image for a range of shutter values between 1, 10, 100, 950 ms. This should be
done with three different filters (400nm, 700nm, and 950nm). The light source should be held at
a constant supply current of 2.00 A. At the high shutter values, it may be necessary to use an ND
filter. If it is necessary to use the ND filters, ensure there are sufficient overlap readings.

3.    Measure CCD linearity.
  CCD linearity tests should be performed using three different filters (400nm, 700nm, and
950nm). Set output to near full scale (POW ∆ 3000), for ND = 0 by varying the shutter value.
Record a frame for ND = 0, 0.1, 0.3, 0.5, 1, 1.5, 2, 2.5.

4.      Measure spectral response.
   Keeping the lamp voltage and shutter constant, record three images for each filter. Repeat this
for shutter values of 10, 100 and 950.

5.       Sub pixel scans at extreme wavelengths
   (400 nm short and 1000 nm long). Record at steps of 1 across greater than 1 pixel (15 to 20
steps), in both x and y directions. Use a pixel near the image center and max DN values ∆ 3000.

6.      Blooming test.
   Set to near full output (DN∆3000) with ND 2.5 by adjusting exposure time at 400nm, 700nm,
and 1000nm. Record images with ND 0, 0.1, 0.3, 0.5, 1, 1.5, 2, 2.5.

Code information for Detector characterization
File Nomenclature     FUabcde.Day (where Day is the day of the year 2002)
   a is the temperature code, R ∆ 20°C, H ∆ -20°C, M ∆ -30°C, L ∆ -40°C
   b is the test abbreviation (see below)
   c is the spectral filter code (see below)
   d is the neutral density filter code (see below)
   e is the exposure code (1 = 1 ms, 2 = 10 ms, 3 = 100 ms, and 4 = 950 ms).

Test Abbreviations (b)
  D Dark Image
  S Shutter variability test
  L CCD Linearity test
  W Spectral Calibration test

Spectral Filter Code (c)
                     Width
  0 No Filter        Broad Band
  1 300 nm           10 nm
  2 450 nm           40 nm
  3 550 nm           57 nm
  4 650 nm           40 nm
  5 700 nm           40 nm
  6 850 nm           40 nm
  7 950 nm           40 nm


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ND Filter Code         (d)
  0 No Filter
  1 0.1
  2 0.3
  3 0.5
  4 1.0
  5 1.5
  6 2.0
  7 2.5

Header Code
  The following information must be recorded for each saved image file:

               Sh      Shutter value
               ND      Neutral Density Filter
               SF      Spectral Filter (nm center)

    Any other pertinent information will be added as needed. For each file note will be written
containing the data in the header code and any comments in the calibration log sheet which will
be kept with the calibration chamber.



2.2 Pivot calibration
   The MDIS instrument consists of a pivot actuator which can rotate the dual cameras on a
pivoting platform in the range of 237.5 deg. The motion of the actuator is limited by physical
hard stops located at each end of travel. The motor uses redundant windings which are controlled
by the redundant DPUs. The two phase 5 degree stepper motor drives a planetary gear system
with a gear ratio of 4.8:1, providing the input torque needed for a 120:1 harmonic drive. An eight
speed electrical resolver provides the absolute position of output shaft relative to an end stop.
The purpose of this test is to generate a look-up table for each resolver output to absolute
position, and to verify the repeatability of these measurements. The resolver output is digitized to
14-bits for each octant of motion. With knowledge of the octant, the pivot position is known to
17-bits (214+3).

Pivot Calibration Plan
    The unit under test is mounted on the high precision rate table located in the basement of
Building 1. The unit must be adjusted on the fixture to ensure that the axis of rotation is normal
to the table, and the shaft of the actuator is co-aligned with the rotating axis of the table. A mirror
is mounted to the rotating shaft or platform. Using a theodolite and manually commanding the
motion of the rate table, the motor/fixture are adjusted until motion of table and a compensating
motion of the actuator show a negligible change in elevation over all azimuthal motions.
    A HeNe laser is mounted on the optical bench next to the table and reflected from the mirror
located on the output shaft of the pivot actuator into a position sensitive device (PSD). The PSD
provides two output channels: 1) A position error signal (A-B)/(A+B); 2) The sum (A+B). Here
A and B correspond to the two detectors of the PSD. Channel 2, the sum, is fed back into the rate
table as a safety measure to shut down the table in the event of losing the beam or the beam is


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blocked. Channel 1, the position error signal is fed back into the software of the rate table so as
to move the rate table so as to center the laser beam in the PSD.

Test Procedure
                   ** NEVER MOVE THE TABLE UNLESS IT IS FLOATING **
    The pivot actuator (PA) is driven by the MDIS/DPU Motor controller board. This board talks
to the I2C bus, which is emulated in the MDIS GSE computer. LabView interacts with the bus to
actually move the PA, and through TCP/IP can query the state of the rate table and its position.
The two main LabView programs (written by Doug Oursler) are called ``manual.vi'' and
``test.vi''. It is important never to run both programs simultaneously. The steps given below
should be followed EXACTLY so as to ensure the safety of the rate table.

1. Turn-on the MDIS pivot actuator GSE computer

2. Ensure the toggle switch on the pivot actuator control electronics is set to ``R'', then turn on
the two power supplies and press the ``output'' button.

3. Flip the toggle switch on the control electronics away from ``R''.

4. Open the manual.vi program, click the large white arrow to begin running the program, then
move the pivot actuator beyond the CCW stop (step=-1000). Stop the manual.vi program.

5. Enable the compressor (across the hall from the rate table room).

6. Turn-on the fluke meter, oscilloscope, and HeNe laser, and the two PSD controllers.

7. Turn-on the air pressure to the rate-table and wait until pressure exceeds 300 psi.

8. Carefully adjust weights on rate table to eliminate vibrations.

9. Turn-on computer that controls the rate table. CTRL-ALT-DEL to get a login prompt. The
username is Jim and there is no password (just RETURN). This system MUST be booted prior to
turning on the SYSTEM POWER switch on the Rate Table Power Amplifier rack.

10. Turn-on the SYSTEM POWER switch on the Rate Table Power Amplifier rack and wait.

       N.B., A window on the computer should indicate software is being downloaded to the
       distribution box. The alpha-numeric display on the electronics rack will display a
       ``welcome'' message when initialized. The system automatically zeros the rate table
       encoder, and since the PA was previously moved to its CCW hard stop, all motions
       should start from 0 deg.

11. From the rate table control computer, double click on the icon ``Rate Table Controller''.

12. Enable the rack by pressing and turning the large DISABLE knob at the base of the controller
rack.




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13. From the menu bar of the program Rate Table Controller: Edit→Configure →Aux Position
Sensor MODE→''ON''→OK. At this point the table should be tracking the laser.

14. From the MDIS motor control computer, open the LabView test.vi program.

15. Set the DELAY=10 ms, and STEP=10 (clockwise motion).

16. After pressing the white arrow button, enter a filename for the test.

17. To reverse the motion the STEP size should be negative (CCW motion).

   To shut down the system, basically reverse the order given above. Most critical item is to
press the red DISABLE knob on the rate table controller rack. Do not forget to disable the
compressor across the hall before leaving.


2.3 Optical Imaging Facility Calibration

2.3.1 Test Priorities
    Tests will be prioritized according to the following rules. If there are sufficient time and
resources (facilities, manpower, etc.), all tests will be completed. If resources are limited for any
reason, specific test groups will take priority. Whether or not a test is dropped completely may
depend on whether it is pre- or post- environmental testing, and whether it may be carried out in-
flight. Within each group, the tests will be carried out according to the procedure in
appendix 2, which is designed to take facility configurations into account. This includes, for
example, carrying out radiometric tests with the sphere early on while it remains calibrated (the
bulb intensity degrades somewhat after 40 or so hours) Note that almost all the tests will be
carried out at one temperature, then the chamber temperature will be changed and the tests will
be repeated, and so on.

       1.      Both pre and post-environmental on-ground testing required

       2.      Pre-environmental on-ground testing required; post-environment testing
               desirable but not essential.

       3.      Post-environmental on-ground testing required, pre-environmental testing
               desirable but not essential.

       4.      In-flight testing preferred but calibration goals may be achieved on-ground

       5.      In-flight testing required in addition to on-ground testing.

       A.      Test is essential to characterize instrument sufficiently to meet science goals

       B.      Test would be useful in characterizing instrument but is not absolutely essential

    The temperatures given throughout the on-ground test section are for the CCD only. We aim
to hold the filter wheel at a corresponding temperature according to the graph in Appendix 1.

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2.3.2. Dark current
    • Varies with row, exposure time, temperature, MET.
    • Expected to be linear function of exposure time.
    • Accurate removal needed to track subtle color changes near shadowed areas or changes
        in PSF, i.e., cases where signal is non-uniform and low
        Dark strips provide potential sampling for each image, but relationship of dark current in
        dark strip to dark current scene must be confirmed. Check no leaked light into dark
        current strip from active areas of CCD.
    • Independent dark model saves need for downlinking strips, but strips can be used to
        confirm it periodically.

Goal of the calibration: Measure dark current to within 0.2 DN.

WAC and NAC

A. Testing:
Description of test
       Obtain sequence of 10 images through one WAC filter (750 nm), and NAC while
       pointing at darkened collimator, which is turned off. Images taken at a range of 10
       exposures from short to long, and over a range of CCD temperatures bracketing operating
       range (-40˚, -30˚, -20˚, -10˚, 0˚). Measure dark current across each column of dark strip
       and compare with dark current measurements made across whole CCD. Use different
       pixel-binning modes for each set of conditions (unbinned, 2x2). Important that stage
       motor is OFF.
What properties are being characterized?
       Noise due to (a) dark current from thermal electrons, (b) added bias, and (c) low level
       periodic noise from spacecraft electronics. Check no leaked light into dark current strip.
       Determine if dark current appears to change in pixel binning mode.
What is the priority for this test?
       1A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available.

B. Analysis:
Description of the analysis
       Plot dark field DN levels per pixel against exposure times, and row, and temperature.
       Repeat for dark strip. Determine equation to predict in-field dark current from dark strip.
       Software can be adapted from MSI approach.
What is the product of the analysis?
       Coefficients for calibration equation in terms of pixel location, exposure time and
       temperature at MET = 0.
Schedule for completion of the analyses
       Priority: within 1 week of data acquisition.




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2.3.3. Leaked light test
   On the NEAR MSI instrument, light coming through the cover of the CCD was a problem.
This test is intended to confirm that leaked light is not an issue for MDIS, either from the active
areas of the CCD into the dark strip, or through the CCD cover.

Goal of the calibration: Confirm no leaked light through cover of readout zone, or into dark
strip from active areas of CCD.

WAC and NAC

A. Testing:
Description of test
       To check for light leaking into dark strip, obtain 1 image of integrating sphere at each of
       10 different exposure times (0, 2, 4, 6, 10, 50, 100, 200, 500, 1000 ms exposures). The 0
       ms exposures are used to test that no light has leaked through the cover; other exposures
       are to test for light leaking into the dark strip. All WAC filters plus NAC, one
       temperature (-40˚). Obtain 1 true dark image for each exposure.
What properties are being characterized?
       Leaked light.
What is the priority for this test?
       2A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available.

B. Analysis:
Description of the analysis
       For dark strip: Remove dark and frame transfer smear. Plot ∆DN against ∆exposure time.
       If no light has leaked into the dark strip, signal should be 0. Check for average of each
       dark pixel column.
       For leaked light through cover: For 0 ms exposures remove frame transfer smear. Find
       average DN and plot as a function of exposure time. Line should come out perfectly flat
       if no leaked light.
What is the product of the analysis?
       Plots showing presence or absence of leaked light.
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.




                                                13
2.3.4 Frame Transfer (Readout) Smear – no compression
    • Accumulated during 3.7-ms frame transfer from image to memory zone.
    • Depends on scene illumination, responsivity, frame transfer time.
    • Remove by modeling analytically based on known exposure, frame transfer times, scene
       DN.
    • Proper removal characterizes focal plane function.

Goal of the calibration: Determine that frame transfer smear can be removed to the level of
noise at ~3x minimum frame transfer time without pixel binning, and at ~2x minimum transfer
time with binning.

WAC and NAC

A. Testing:
Description of test
       Use hand sample (e.g., halon plate) or small integrating sphere mounted on aperture,
       viewed through collimator (require unsaturated circular illuminated area, tens/hundreds
       of pixels in diameter). Find setting for illumination/intensity of source where saturation
       occurs at ~10 x frame transfer time.
       Obtain 10 images through 1 WAC filter (750 nm) and NAC filter, at 1 temperature (-40˚,
       can be any temperature), at 7 exposure times (2, 4, 6, 10, 20, 30, 40 ms exposures). Take
       10 true dark frames at each exposure time (rear chamber window covered). Could be part
       of linearity test.
What properties are being characterized?
       Removal of frame transfer smear.
What is the priority for this test?
       2A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF. Halon disk, mirror.

B. Analysis:
Description of the analysis
       Subtract darks from images. If combined with linearity test: Determine linearity
       (∆signal/∆T) vs. DN level. Verify signal vs. time at short exposures corresponds with
       predictions. Determine residuals in frame transfer smear “tail” vs. exposure time. Frame
       transfer smear correction exists; otherwise need average over box in raw or dark-
       subtracted images (IDL).
What is the product of the analysis?
       Confirmation of frame transfer time, testing of removal algorithm, lower limit to
       exposure time, linearity correction if applicable.
Schedule for completion of the analyses
       Priority: within 1 week of data acquisition.




                                               14
2.3.5. Hardware compression
    MDIS has several compression modes available on camera, including 2x2 pixel binning, 12
to 8-bit compression, and FAST compression. Pixel binning is tested elsewhere. This test
analyses the effect of 12 to 8-bit compression, with and without FAST compression, and verifies
that it does not adversely affect frame transfer smear.

Goal of the calibration: Determine effect of hardware compression on frame transfer smear.

WAC and NAC

A. Testing:
Description of test
       Use same source and setup as in 2.3.2, however, source is now placed at edge of field of
       view, producing a gradient in illumination across CCD. Aim to create scene with large
       dynamic range. Test hardware compression (12 to 8 bit ± Fast), using DN ~3000 (this is
       about the point where the CCD response starts to become non-linear. This value may
       change depending on CCD characterization prior to instrument calibration). Carry out
       entire sequence three times: (1) without compression (2) with 12 to 8 bit compression but
       without FAST compressions, and (3) with 12 to 8 bit compression with FAST
       compression.
What properties are being characterized?
       Behaviour of frame transfer with respect to exposure time.
What is the priority for this test?
       2A.
What is the schedule for performing this test?
       See appendix 2..
What facilities are needed to perform this test, and are they available?
       OCF. Halon disk, mirror.

B. Analysis:
Description of the analysis
       Remove darks. Compare compressed and uncompressed images to determine how
       compression affects frame transfer removal. Take 12-bit image and apply same function
       used by MDIS processor to convert into 8-bit image. Subtract new image from original
       12-bit image. Result should be 0 if hardware compression works correctly. Perform same
       analysis for 8 bit images with and without fast compression.
What is the product of the analysis?
       Verification of hardware compression function.
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.




                                              15
2.3.6. Flat Field (Response Uniformity)
     Radiometric calibration requires removal of nonuniformities in imager response
(reproducible, pixel-to-pixel variations in responsivity, determined from uniform, field-filling
source (integrating sphere)). May arise from a variety of sources: optical vignetting; cos4ϑ fall-
off of image illumination, CCD window, optical elements of telescope, nonuniformity in
responsivity of CCD. Generally, responsivity is linear as a function of temperature, but at longer
wavelengths, it can be more sensitive, so the flat field may be weakly filter dependent. Therefore
it is essential that the responsivity is well characterized with the long wavelength filters, and that
the filter wheel temperature is monitored. It is essential that the white integrating sphere is well-
calibrated for this test.

Goal of the calibration: Correct flat field variations should within 0.1%.

WAC and NAC

A. Testing:
Description of test
       Obtain stack of 10 images of white integrating sphere through each filter, filling FOV
       (either 1 view (NA) or n x m matrix (WA) to overlap spot sufficiently to cover entire
       FOV). Take at 2 exposure times yielding DN 1000 and 2500 (1000 is a good general DN
       level to aim for; 2500 is a reasonably safe place to measure DN before the CCD response
       starts to become non-linear). Obtain stack of 10 background images of un-illuminated
       sphere at same exposures. Important that motion stage turned OFF. Repeat one exposure
       time in 2x2 binning mode, at 1/4 exposure time (to avoid saturation). Repeat at 3
       temperatures bracketing operating range (-40˚, -25˚, -10˚).
What properties are being characterized?
       Pixel-to-pixel variations in responsivity across the CCD at different temperatures.
       Variations in flat field in pixel binning mode.
What is the priority for this test?
       1A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available. Large aperture white sphere.

B. Analysis:
Description of the analysis
       NA: Subtract average of 10 backgrounds from average of 10 sphere images, remove
       frame transfer smear from difference file. Divide by scene mean (gives you an image of
       the flat field with an average value of 1).. WA: As above, but merge each position in
       matrix to provide complete flat field file.
What is the product of the analysis?
       Flat field files.
Schedule for completion of the analyses
       Priority: within 1 week of data acquisition.

DESCOPE OPTION: If there is insufficient time to carry out all the calibration procedures as
proposed, this test can be carried out at one exposure only (sufficient to reach 2500 DN).

                                                 16
2.3.7. Radiometric Responsivity
     Key measurement is NIST-traceable integrating sphere. Requires correction for fused silica
window to vacuum chamber. Integrating sphere must be well calibrated.
     Absolute radiometric calibration: Obtains calibration factor which converts instrument signal
(DN level) to units of radiance at the center wavelength of each filter. Absolute calibration
expected to vary with CCD temperature because of decreasing sensitivity of CCD at longer
wavelengths at lower temperatures. In addition, filters may exhibit temperature dependent
variations in responsivity (about 0.1 nm/degree), which may be an issue in the longer wavelength
filters.
     Relative radiometric calibration: Relative filter to filter radiometric calibration.

Goal of the calibration: Measure absolute responsivity to within 5%; measure relative
responsivity to within 1% for 2 adjacent filters, and to within 2% for any two non-adjacent
filters.

WAC and NAC

A. Testing:
Description of test
       Obtain stack of 10 images of white integrating sphere through each filter, filling FOV
       (either 1 view (NA) or n x m matrix (WA) to cover entire field). Take at 2 exposure times
       yielding DN 1000 and 2500. Obtain stack of 10 background images of un-illuminated
       sphere at same exposures. Important that motion stage turned OFF. Conduct test at 4
       temperature configurations (-40˚, -25˚, -10˚). Repeat one exposure time with pixel
       binning turned on.
What properties are being characterized?
       Calibration coefficients to convert dark-, smear-, flat-, exposure-corrected DN/ms to W
       cm-2 sr-1 ∆λ-1. Determine effects of temperature and pixel binning on responsivity.
What is the priority for this test?
       1A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available.

B. Analysis:
Description of the analysis
       Subtract average of 10 background images from average of 10 sphere images; remove
       frame transfer smear from results. Divide by exposure time. Divide by sphere radiance
       convolved with bandpass (2.3.8).
What is the product of the analysis?
       Radiometric calibration coefficients as function of filter, temperature.
Schedule for completion of the analyses
       Priority: within 1 week of data acquisition.


DESCOPE OPTION: If there is insufficient time to carry out all the calibration procedures as
proposed, this test can be carried out at one exposure only (sufficient to reach 2500 DN).

                                               17
2.3.8. Filter Bandpasses/Out of band rejection (spectral leakage)/Cross-talk
    Characterize band pass of each filter (see appendix 3). Determine that response corresponds
to manufacturer’s predictions. Response is product of lens transmission, filter transmission, and
detector response.

Goal of the calibration: Determine relative bandpass transmission amplitude and half width of
each filter. Fully characterize “wings” of bandpass.

WAC and NAC

A. Testing:
Description of test
       Monochromator scan over wavelengths encompassing manufacturer-supplied bandpass,
       using small extended source. Crucial to have motion stage OFF.
       For WA, 1 nm step to 10 nm on either side of band; for NA, 5 nm steps to 25 nm either
       side of band. In addition, for both: 20 nm increments to 20 steps out of band on each side
       of center wavelength. All WAC filters, NAC filter, 2 temperatures (-40˚, -10˚).
       Determine optimum exposure from test measurement at center of bandpass. Scan at
       longer exposures to fully characterize wings of bandpass. Scan at relevant 2nd order for
       each filter of > 830 nm to determine any cross-talk (e.g., 830 nm filter may have first
       order transmission at 415 nm, etc.), at 1 nm increments to 10 nm on either side of
       expected 2nd order passband. Obtain 10 background images at each exposure time.
       Cross-talk may be a problem because we are at 11 sols. Third order effects likely
       insignificant.
What properties are being characterized?
       Bandpass transmittance, half width, spectral leakage.
What is the priority for this test?
       3A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available. Need holographic grating blazed for visible (exists). Need > 800 nm
       (long pass) filter for leakage test (Dave Humm thinks we may have, doesn’t know for
       sure). Need to manufacture correct pinhole and verify that enough light will be present
       (need spot to be at least 5 pixels across).
B. Analysis:
Description of the analysis
       Average 10 background images, subtract from corresponding monochromator image.
       Remove frame transfer smear. Integrate across smallest possible box around spot to
       obtain maximum signal DN in that area. Plot background subtracted, smear corrected DN
       against wavelength. Compare with manufacturer’s specifications.
What is the product of the analysis?
       Response vs. wavelength for each filter.
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.

DESCOPE OPTION: If there is insufficient time to carry out all the calibration procedures as
proposed, this test can be carried out at one temperature only (-25˚).

                                               18
2.3.9. Picked Up Noise/Power cycling
    Derived from groups of dark images taken with possible noise sources operative and not.
Most likely culprits are pivot motor, filter wheel motor, but could possibly have other sources
such as the heaters.

Goal of the calibration: Search for systematic noise within images, and determine cause (i.e.,
whether from instrument operation or OCF).

WAC and NAC

A. Testing:
Description of test
       Point at darkened monochromator. Determine potential noise sources, e.g. pivot motor,
       filter wheel etc., also environmental variables e.g., stage, etc. Obtain 10 dark images
       during each state (i.e., with one potential noise source turned on), through 1 WAC filter
       (750 nm) and NAC filter, at 1 temperature (-40˚). Two different exposure times in each
       state, at 10 ms and 1010 ms (since instrument operates at 1 Hz, we may see something
       across the 1 second boundary). Desirable to make readout noise and filter wheel
       movement occur simultaneously, so carry out in binned and unbinned mode (is it possible
       to take image unbinned but force filter wheel to move immediately?).
What properties are being characterized?
       Noise, under different conditions.
What is the priority for this test?
       2A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available

B. Analysis:
Description of the analysis
       Desmear images. Search for systematic noise patterns in images by visual inspection,
       using techniques such as movies and blinking between pairs of images. To assess fixed-
       pattern noise, check standard deviation of values in individual frames. To assess noise
       that varies pixel-to-pixel with time, use standard deviation of pixel values from stack of
       images. Adapt CONTOUR Concal algorithms for MDIS data.
       Investigate odd/even pixel differences by computing average absolute value of
       differences. Perform on both raw images (in case phase changes) and on stacked
       averaged images.
What is the product of the analysis?
       Characterize noise levels at different temperatures and exposure times. If necessary,
       determine how best to remove/avoid it.
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.

ADDITIONAL TEST IF TIME/FACILITIES ALLOW: Get CCD as cold as possible (-45˚),
forcing heaters to kick in. Take 10 images at every degree of temperature rise until –40˚ is
reached.

                                               19
2.3.10. Linearity, Read Noise, Gain, SNR as a function of DN
    • Linearity: CCD is expected to respond in a linear fashion until full well is approached.
        This test will characterize the upper DN limit of linear behaviour with exposure time.
    • Gain: set by the output electronics and determines how the amount of charge collected in
        each pixel will be assigned to a DN in the final image. T
    • Read noise: Consists of two inseparable components:
           1. Conversion from analog signal to DN, which is not perfectly repeatable
           2. Spurious electrons from electronics, yielding random fluctuations in the output.

Goal of the calibration: Determine that CCD response is linear, find point at which response
begins to fall off. Find gain, determine signal to noise ratio and read noise.

WAC and NAC

A. Testing:
Description of test
       Groups of ten white sphere images obtained through one filter (750 nm), one temperature
       (-40˚), repeat groups at 20 exposure times, evenly spaced from 2 ms until saturation is
       reached. Obtain ten background images at shortest exposure. Crucial that motion stage is
       OFF.
What properties are being characterized?
       Linearity, read noise, gain, S:N as function of DN.
What is the priority for this test?
       2A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available.

B. Analysis:
Description of the analysis
       For gain, read noise, slope: For each brightness, make “cube” of images, find standard
       deviation of pixel values “looking down into cube” (eliminates flat-field effects). Plot
       square of noise in RAW images against background-subtracted DN. Desmear???
       For linearity: plot ∆DN/∆ exposure time.
What is the product of the analysis?
       For gain, read noise, slope: Slope yields 1/gain, i.e., 1/ (e-/DN). x / sqrt (y) is SNR for a
       given signal level; sqrt y(0) is read noise in DN; sqrt y(0) * gain is read noise in e-. For
       linearity: Fall-off defines onset of non-linear response near full-well.
Schedule for completion of the analyses
       Priority: within 1 week of data acquisition.




                                                20
2.3.11. Point Spread Function (PSF), Field of View (FOV) measurement
    Scattered light can lead to a wide Point Spread Function (PSF). The PSF comes from optics,
not the CCD, but spreading is more apparent with smaller pixels. This measurement can be
challenging on-ground because of scattered light.
    The Field of View (FOV) measurement yields the number of microradians per pixel for each
imager.

Goal of the calibration: Characterize the point spread function and the field of view/plate scale
test.

WAC and NAC

A. Testing:
Description of test
       (1) For central part of PSF: Obtain 5x5 dithers of bright sub-pixel point source in sub-
       pixel steps (the one with the highest fraction of light in 1 pixel is the one best centered on
       a pixel) using ND3 filter. Repeat dither in 3x3 matrix across CCD. Repeat for all filters,
       at three temperatures (-40˚), with exposure times set for DN ~2500. Repeat entire
       sequence with supersaturated (ND0) images to characterize wings of PSF. Obtain 10
       background images before dither at each exposure time throughout. Unsaturated images
       will be used to determine FOV.
       (2) For distal part of PSF: Obtain ten images of fat point (multi-pixel spot) for 3x3 matrix
       across CCD, using ND3 filter. Obtain ten background images in each position. Repeat for
       all filters, at 2 temperatures (-40˚). Repeat using ND0 filter.
What properties are being characterized?
       Point spread function and field of view/plate scale.
What is the priority for this test?
       See appendix 2.
What is the schedule for performing this test?
       1A.
What facilities are needed to perform this test, and are they available?
       OCF, available. Point source (actual size TBD).

B. Analysis:
Description of the analysis
       PSF is built up as the composite of 4 zones.
       (1) Zones 1-3 of PSF: Find mean of 10 background frames at each exposure time, and
       subtract mean background from corresponding image. For each ND0 image, define
       saturated zone and replace with corresponding area from ND3 image, multiplied by 1000.
       Analytically subtract frame transfer smear. For each 5x5 dither, find ND3 image with
       largest fraction of light in central pixel, multiply by 1000. This defines central, or inner
       zone, 1-2 pixels wide. ND0 image at corresponding position defines 2nd zone, several
       pixels wide.
       For remaining ND0 images, co-register brightness centroid within central pixel of PSD,
       and take the mean of the 24. This becomes the 3rd zone, 10’s pixels wide (depends on
       scattered light characteristics of instrument). Normalize to unity by dividing by value in
       peak pixel.


                                                 21
       (2) Zone 4 of PSF is obtained in test 1.2.5. Extrapolation will probably be needed
       between the 3rd and 4th zones.
       This analysis yields 9 PSFS for each filter (each position in 3x3 matrix). The 9 can be
       averaged to get a typical PSF for each scene. Variation between the 9 can be used to
       determine uncertainties in the PSF correction.
       FOV: Distance between brightest pixel in each 5x5 dither is determined. All distances
       between different points are measured (in pixels) and the average and standard deviation
       of this set is found. Since the focal length is known, this result can be used to determine
       the size of a pixel in µrads.
What is the product of the analysis?
       FOV measurement, PSF. Correction requires Fourier filtering using well-determined
       PSF, INVFFT (FFTscene/PSF).
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.




                                               22
2.3.12. Search for optical ghosting
    Reflected light can result in ghost images from optics, in the form of a coherent reflection of
generalized image gradient. Either (a) determine that this effect is not present, or is negligible or
(b) characterize for correction. Ghost images are determined from bright, extended source in and
out of field

Goal of the calibration: Find any “ghost” signal in the images and if present, characterize
changes in location, geometric shape and intensity with different source positions and filters.

WAC and NAC

A. Testing:
Description of test
       Break image into 21 position grid, put bright, extended source (~1 mm pinhole) at each
       grid point, and at some points outside field. Obtain one frame in each position, at one
       temperature (-40˚). All filters, unsaturated and supersaturated exposures (e.g., one with
       ND3 filter, one with ND0 filter). Exposure times set for DN ~2500 in ND3. Obtain 1
       background image before each exposure.
What properties are being characterized?
       Unanticipated optical reflections.
What is the priority for this test?
       1A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available. Need correct “fat” (1 mm?) pinhole (available? TBD).
B. Analysis:
Description of the analysis
       Subtract background images from each exposure. Replace saturated part of ND0 image
       with 1000 x ND3 image, then remove smear. Visually inspect results and deduce pixel
       location and intensity of ghost signal, or magnitude of gradient, in each image.
What is the product of the analysis?
       Characterize position and intensity of any ghost images.
Schedule for completion of the analyses
       Priority: within 1 week of data acquisition.




                                                 23
2.3.13 Relative Alignments of WA and NA Imagers

Goal of the calibration: Characterize alignment of WA and NA imagers to within 1 pixel.

WAC and NAC

A. Testing:
Description of test
       Obtain 5x5 dithers of bright sub-pixel point source in sub-pixel steps (the one with the
       highest fraction of light in 1 pixel is the one best centered on a pixel) using ND3 filter, at
       known angular separation. Repeat in 3x3 pattern across CCD. All WA filters, NA filter.
       Set optimum exposure time for each filter to give DN = 3000. 3 temperatures (-40˚, -25˚,
       -10˚). Obtain ten background images before each dither sequence, for each filter.
What properties are being characterized?
       Coalignment of WA and NA cameras. Determine how position of brightest pixel in each
       camera varies with temperature. Use as reference after launch.
What is the priority for this test?
       1A.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF.

B. Analysis:
Description of the analysis
       Background subtract, smear correct images. 3x3 patterns will have different angular
       separations for NA and WA. Need to measure offset and “twist” between corresponding
       points on each imager. Do this by fitting a line through 3 corresponding points for each
       camera. This can be plotted on a graph of stage angle vs. pixel position. Each line will
       have a slope (angle/per pixel). Determine difference between slope of each line; this
       gives variation in alignment.
What is the product of the analysis?
       Location of brightest pixel in each camera; change in location with temperature.
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.




                                                 24
2.3.14. Calibration validation (hand samples)
    Test to determine whether multicolor images are obtained from which accurate brightness
and spectral data may be extracted, and in which spectrally different materials can be spatially
resolved. To verify calibration accuracy, measure standard samples in OCF, using very well-
characterized source lamp. Use same samples as all planetary imagers/spectrometers, from R.
Morris at JSC, provided at no cost to all missions (See appendix 4). Image rough sides of sample.
Keep light sources in OCF constant throughout test.
    In addition, both MDIS and (especially) VIRS calibration will benefit from the acquisition of
a good solar spectrum once in cruise. A piece of reference material mounted on the inside of the
adaptor ring will be imaged by MDIS after launch, and should be characterized during
calibration.

Goal of the calibration: Accurately represent shape and depth of different absorption bands for
known rock samples.

WAC and NAC

A. Testing:
Description of test
       Set up with mirror looking down at zero emission angle; illuminate at 30˚ incidence if
       possible. Set exposure for each filter so that Halon yields ~3000 DN (or whatever DN
       occurs before linearity begins to fall off). For background images, use darkest standard
       and block source. Obtain images of 10 reference hand samples plus solar spectrum
       material, through each filter, at one temperature (-40˚), obtain 10 background exposures.
       Test autoexposure functionality; do 1 run using manual exposure, then test reflectance
       standards with autoexposure.
What properties are being characterized?
       Response of cameras to “real” samples. Can we identify them correctly from color
       imaging? If not, why not?
What is the priority for this test?
       3B.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       OCF, available. Lamp, mirror (need to be selected).

B. Analysis:
Description of the analysis
       Background subtract, smear correct images. Plot maximum reflectance ratio to Halon
       against wavelength for each central bandpass, for each sample. Compare resulting spectra
       with known spectrum of sample. Determine spectrum of reference material.
What is the product of the analysis?
       Reflectance spectrum relative to Halon, for each sample.
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.




                                               25
2.3.15. “Real World” test
    Put MDIS in environment box, take it to a window, and obtain images (e.g., of Moon, tower
near Bldg. 23, etc.). Image Venus and Mercury if visible from Building 4 (will depend on when
calibration takes place).

Goal of the calibration: Determine that images of “real” objects outside the lab can be obtained.
Perhaps obtain first image of Mercury with MDIS(!).

WAC and NAC

A. Testing:
Description of test
       Obtain 10 images of target through each filter, at room temperature, using optimum
       exposure time per filter. Obtain one background image before each exposure.
What properties are being characterized?
       Camera functionality.
What is the priority for this test?
       3B.
What is the schedule for performing this test?
       See appendix 2.
What facilities are needed to perform this test, and are they available?
       Environment box – availability unknown.

B. Analysis:
Description of the analysis
       Background subtract, smear correct images. Visually inspect images. Determine
       autoexposure levels are consistent with manual exposure levels.
What is the product of the analysis?
       Image for each target.
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.




                                               26
2.4 Software Performance

Software performance will be tested where appropriate to a given test, as follows:


   •   Autoexposure functionality
             Test on hand samples, 2.3.14.

   •   Hardware compression (12 to 8 bit ±DPCM ±Fast)
             Test 2.3.5.

   •   MP compression (subframing ±wavelet compression)
            On spacecraft in thermal vac. Pixel binning tested on radiometric calibrations.

   •   Image and header integrity after switching settings
              Any of the tests with pixel binning.

   •   Filter wheel function etc.
               Tersts 2.3.8, 2.3.9, etc.




                                               27
   Table 2: On-ground calibration summary.


ON-GROUND




                                                                                                                                                                                              Total number of
                                                                                                                                                                          frames per test
                                                                           (ND0/ND3 etc)



                                                                                           (e.g., unbinned,
                                            Temp. settings




                                                                                                                                    Stage postn(s)
                                                                                            2x2, 4x4 etc)
                                                                                            binning states




                                                                                                                                                                                               unique frames
                                                                                                              8/Fast comp.




                                                                                                                                                          Test priority
                                                                                             No. of pixel
                                                             No. of exp.




                                                                                                                No. of 1 2 -




                                                                                                                                                                             Total # of
CALIBRATION




                                                                             attenuator




                                                                                                                states or
                                                                                                                 autoexps
                                                                              settings
                                   Target




                                                                               No. of
                                                                times
 number




                  name
  Test




                  Test




                               Darkened
2.3.2     Dark current/strip   collimator   5                10                1                2                              1                     1A                   3000              3000

                                 White
2.3.3     Leaked light          sphere      1                10                1                1                               1                    2A                   140               140
                                 Hand
                               sample or
          Frame transfer         small
2.3.4     smear                 sphere      1                7                 1                1                               1                    2A                   210               210
                                 Hand
                               sample or
          Hardware               small
2.3.5     compression           sphere      1                7                 1                1                 3            1                     2A                   630               630

                                White
2.3.6     Flat field            sphere      3                2                 1                2                              5                     1A                   8400              8400

          Radiometric           White
2.3.7     responsivity          sphere      3                2                 1                2                               5                    1A                   8400               0

          Bandpass/spectral  MC/Fat
2.3.8     leakage/x-talk      point         2                1                 1                1                               1                    3A                   1080              1080
          Picked-up
          noise/power       Monochro
2.3.9     cycling             mator         1                2                 1                2                               1                    2A                   120               ~600

       Linearity/read           White
2.3.10 noise/gain/SNR           sphere      1                20                1                1                              1                     2A                   600               200
                               Sub-pixel
       PSF/Focal length          point
2.3.11 (FOV) central            source      1                1                 2                1                               9                    1A                   6030              6030

          PSF/Focal length
  "       (FOV) distal         Fat point    1                1                 2                1                              9                     1A                   2520              2520
                               Extended
       Optical ghost            pinhole
2.3.12 search                   source      1                1                 2                1                              121                   1A                   3388              3388

       WA and NA             Point
2.3.13 alignment            source          3                1                 1                1                               9                    1A                   9045              120
                             Hand
       Hand samples        samples
       (calibration          (JSC
2.3.14 validation)        standards)        1                1                 1                1                 2            1                     3B                   280               280
                              Far
                           targets,
2.3.15 Real world imaging   Venus           1                1                 1                1                               1                    3B                   131               131




                                                                                   28
z
                             3. IN-FLIGHT CALIBRATION

      Most of the in-flight calibration will be carried out to verify on-ground testing. Some
measurements will be carried out at period intervals during cruise. See section 4 for additional
instrument in-flight cross-calibration tests.


3.1 Dark current
        We will have already developed an independent dark model on-ground, which will save
downlinking strips. However, strips can be used periodically to determine any changes in dark
current. In addition, periodically determine dark current from full images to verify
intercalibration of dark strip and field; dark strips with images. We need to establish a good dark
current model by the time we reach Mercury.

WAC and NAC

A. Testing:
Description of test
       MDIS obtains sequence of 15 images through one filter (the least sensitive filter) while
       pointing at bland space. Images obtained at short and long exposures (e.g. 6 ms, 1 sec).
       Measure dark current through strip along edge of CCD, and compare with dark current
       measurements made across whole CCD.
What properties are being characterized?
       Noise due to (a) dark current from thermal electrons, (b) added bias, and (c) low level
       periodic noise from spacecraft electronics. These produce a fixed pattern.
What is the priority for this test?
       4A.
What is the schedule for performing this test?
       4 months after launch (to characterize any unexpected spacecraft noise), then every 120
       days thereafter (15 iterations).

B. Analysis:
Description of the analysis
       Plot dark field DN levels against exposure times. Compare strip levels with analysis of
       dark current across entire CCD.
What is the product of the analysis?
       Improved coefficients for calibration equation.
Schedule for completion of the analyses
       Priority: within 1 week of data acquisition.




                                                29
3.2 Flat field
        Flat field is expected to degrade over time, as absolute sensitivity of pixels may vary.
This change is due to radiation and is not fast. Flat field does not change linearly, so need new
flat field periodically. Pixel to pixel sensitivity is ~2%, so 10 images will be sufficient for
characterization.

WAC and NAC

A. Testing:
Description of test
       Stack of 10 images of brightest, most uniform object available (Venus), through one
       filter. Obtain darks.
What properties are being characterized?
       Pixel-to-pixel variations across the CCD that can result in a grainy image.
What is the priority for this test?
       4A.
What is the schedule for performing this test?
       1 year after launch, then every 360 days (5 iterations).

B. Analysis:
Description of the analysis
       Subtract dark signal from each file, remove frame transfer smear from each file, average
       each stack of files. Determine rms variations in flat fields and confirm reproducibility
       between filters.
What is the product of the analysis?
       rms variations in flatfield
Schedule for completion of the analyses
       Intermediate: within 1 month of data acquisition.




                                               30
3.3 Linearity
       Not expected to change, therefore has very low priority. Need large, unflickering source
(the Sun is ideal but not practical). Can use subframe.

WAC and NAC

A. Testing:
Description of test
       Subframe image obtained of Venus through one filter at 5 exposure times. Obtain darks.
What properties are being characterized?
       Verifying on-ground radiometric response of CCD linearity.
What is the priority for this test?
       5B.
What is the schedule for performing this test?
       Venus flyby (1 iteration).

B. Analysis:
Description of the analysis
       Subtract dark signal and frame transfer smear from file. Plot average DN in 5x5 box
       against exposure time. Plot dark-corrected DN/ms against raw DN. Onset of non-
       horizontal trend indicates upper DN limit of linear behavior. Upper DN limit * gain in e-
       /DN = “full well” in e-.
What is the product of the analysis?
       Confirm rate of accumulation per ms at each exposure time. Confirm DN level at which
       CCD begins to level off (i.e. begins to reach saturation).
Schedule for completion of the analyses
       Two weeks following Venus flyby.




                                              31
3.4 Responsivity
       Verify with Moon (relative) and Canopus (absolute), in all filters. Moon is relatively
bland (Highlands, especially Apollo 16 landing site, Orientale ejecta, NW Orientale province).
Canopus is a black body to first order, with known magnitude. Also is near South Celestial pole
so can point at it while solar panels are pointed at the Sun (76˚S). Either slew across target or
take images in multiple positions. Convolve calibration factors derived on-ground with spectral
response of filters.

WAC and NAC

A. Testing:
Description of test
       Relative: Subframe image(s) of Moon in all filters.
       Absolute: Subframe of Canopus in all filters soon after launch and every 60 days
       thereafter.
What properties are being characterized?
       Confirm/determine calibration coefficients to convert dark-, smear-, flat-, exposure-
       corrected DN/ms to W cm-2 sr-1 ∆λ-1
What is the priority for this test?
       4A.
What is the schedule for performing this test?
       Relative (Moon): soon after launch (if possible).
       Absolute (Canopus): L+60 days. (2 iterations)

B. Analysis:
Description of the analysis
       Subtract average of 10 background images from average of 10 moon/Canopus images;
       remove frame transfer smear from results. Divide by exposure time. Divide by known
       moon/Canopus radiance convolved with bandpass (2.3.8).
What is the product of the analysis?
       Radiometric calibration coefficients
Schedule for completion of the analyses
       Two weeks after data obtained.




                                               32
3.5 Point spread/in-field scattered light
        Multiple images of Canopus in all filters, 60 days after launch and after each Mercury
flyby. Numerous images allow improved determination, reduction in noise, smoothing of far
parts of PSF. Confirm no crud on lens after launch.


A. Testing:
Description of test
       Obtain numerous subframes of Canopus. Keep Canopus in center of pixel (if possible)
       and do diagonal scan that avoids linking corners of pixels. Repeat in all filters. Test all
       binning modes: 2x2, 4x4, 8x8.
What properties are being characterized?
       Point spread function.
What is the priority for this test?
       4A.
What is the schedule for performing this test?
       2 months after launch, 2 months after each Mercury flyby (when we are closer to Earth
       and have a higher downlink rate)(3 iterations).

B. Analysis:
Description of the analysis
       Determine pixel with highest DN in each position. Characterize extent of PSF on either
       side of brightest pixel using method described in section 2.3.11.
What is the product of the analysis?
       Focus measurement, PSF.
Schedule for completion of the analyses
        Two weeks after obtaining data.




                                               33
3.6 Out of field scattered light
        Measure point spread function from source outside field of view. Location of target body
can be deduced from spacecraft pointing knowledge. Ideal situation is when the target body is
much smaller than the field of view, i.e., 50 pixels across. At the distal parts of the frame it will
essentially appear as a point source, allowing the far portions of the point spread function to be
characterized.

WAC and NAC

A. Testing:
Description of test

       Image Earth and Venus in and out of field, all filters. Obtain 3x3 or 5 x 5 set of images,
       with the target body in the center image. Each image to be obtained twice, at two
       exposure times (one saturated). Earth to be imaged during post-launch checkout when it
       is ~ 5 WA pixels in diameter; Venus to be imaged during the second flyby, at a time
       TBD. Pixel binning OK.
What properties are being characterized?
       Response of MDIS to out of field scattered light.
What is the priority for this test?
       4A.
What is the schedule for performing this test?
       Earth, post launch, second Venus flyby.

B. Analysis:
Description of the analysis
       Characterize extent of scattered light from outside source using method described in
       section 2.3.11, but use source outside FOV. Compare to scattered light function obtained
       during ground-based calibration, also compare Earth and Venus measurements.
What is the product of the analysis?
       Scattered light characterization.
Schedule for completion of the analyses
       Two weeks after both Earth flyby and second Venus flyby (1 iteration).




                                                 34
3.7 Field of View (FOV)
        Not expected to change over time; assume athermal. Measure after launch along with
pointing calibration. Image star clusters as angles between them are known to great accuracy
(e.g. CFI was to within 0.33% uncertainty), e.g. Plaeides.

WAC and NAC

A. Testing:
Description of test
       Full frame image of known star cluster in all filters in center of CCD, and in one filter in
       four corners of CCD.
What properties are being characterized?
       Field of view.
What is the priority for this test?
       4A (check once after launch).
What is the schedule for performing this test?
       2 months after launch (1 iteration)


B. Analysis:
Description of the analysis
       Determine pixel with highest DN in each position. Measure distance between brightest
       pixel in each position and compare to known distances from telescopic observations.
       Determine extent of correlation, as described in section 1.2.4.
What is the product of the analysis?
       Focal length
Schedule for completion of the analyses
       2 weeks after data is obtained.




                                                35
3.8 Pointing, coalignment of WAC and NAC, orientation of pivot plane in spacecraft
reference frame
     • Pointing is expected to change over time, and with different deck temperatures.
     • At least 3 star fields imaged at different in-plane angles.
     • From s/c attitude knowledge at each image, known star positions, and known in-plane
         angles at each image, multiple vectors in s/c reference frame define best-fit pivot plane
         (in-flight measurement only). MDIS “boresight” is the pole of the plane described as it
         points. Ideally measure 5 points (minimum 3) across the plane.
     • Repetition during orbit will track changes in orientation due to thermal distortion in
         spacecraft. Measure every 2 months during cruise and 4 times per day during orbit
         (before and after imaging swaths).

WAC and NAC

A. Testing:
Description of test
       WAC: Subframe image of known star cluster in all filters at one position, and in one filter
       at 4 additional positions.
       NAC: Subframe image of same star cluster in same 5 positions.
What properties are being characterized?
       Boresight position of each camera w.r.t. spacecraft deck and each other. Orientation of
       pivot plane in spacecraft reference frame/
What is the priority for this test?
       4A.
What is the schedule for performing this test?
       2 months after launch and every 2 months thereafter while in cruise (33 iterations).

B. Analysis:
Description of the analysis
       Determine star location in FOV. Use to determine boresight position of each camera with
       respect to instrument deck and to each other.
What is the product of the analysis?
       Boresight position, orientation of pivot plane to spacecraft.
Schedule for completion of the analyses
       2 weeks after data is obtained. Must have excellent pointing knowledge in place before
       orbit insertion.




                                               36
3.9 Solar spectrum calibration
        Both MDIS and (especially) VIRS calibration will benefit from the acquisition of a good
solar spectrum once in cruise. The optimum time to do this is at about 0.8 AU, just prior to the
spacecraft flip, when the sun will be illuminating the back of the adaptor ring in a geometry that
can be “seen” by pivoting MDIS.

WAC and NAC

A. Testing:
Description of test
       MDIS images reference target attached to inner adaptor ring. Imaging occurs during
       spacecraft tilt of <15˚. 10 images in all filters.
What properties are being characterized?
       Response of cameras to solar spectrum reference sample. Comparison to ground
       spectrum.
What is the priority for this test?
       4A.
What is the schedule for performing this test?
       The optimum time to do this test is at about 0.8 AU, just prior to the spacecraft flip, when
       the sun will be illuminating the back of the adaptor ring in a geometry that can be “seen”
       by pivoting MDIS.

B. Analysis:
Description of the analysis
       Background subtract, smear correct images. Plot maximum reflectance for each central
       bandpass. Correct for variations from solar spectrum deduced from on-ground
       calibration.
What is the product of the analysis?
       Solar spectrum.
Schedule for completion of the analyses
       2 weeks after data is obtained. Data needed for VIRS calibration.




                                                37
Table 3: Post-Launch calibration plan (L+60 days)




                                                                                                                                                                                                    volume (Mb)
                                            Window size




                                                                                 No. of filters




                                                                                                                                                                                                                       Downlinked
                                                                                                                                                      Final comp.


                                                                                                                                                                    Final comp.
                                                                                                                                        comp. ratio




                                                                                                                                                                                                                       volume/Mb
                                                                                                                          Bits/ pixel




                                                                                                                                                                                     Iterations

                                                                                                                                                                                                    Recorder
                                                                                                               exposure
                                                                                                   positions
                                                          Raw vol.

                                                          /window
                                 Camera




                                                                      frames/




                                                                                                                                        Hdwre
                  Target




                                                                      No. of




                                                                                                   No. of


                                                                                                               No. of

                                                                                                               times
                                                          (Mb)
Test




                                                                                                                                                      type
Radiometry       Moon           both        256           0.79        1          13                1           1          12            2.5           none          1                2              130.86            20.45
PSF              Earth          both        256           0.79        1          13                9           2          12            2.3           none          1                1              1280.17           184.03
Opnav test,      stars          WA          64            0.05        5          1                 1           1          12            1             none          1                3              188.74            0.74
no on-chip
binning for
stars (3x)
                 earth          WA          128           0.20        1          1                 1           1          12            1             none          1                3              37.75             0.59
                 stars          WA          64            0.05        5          1                 1           1          12            1             none          1                3              188.74            0.74
                 earth          NA          1024          12.58       1          1                 1           1          12            1             jail          8                3              37.75             4.72
                 stars          WA          64            0.05        5          1                 1           1          12            1             none          1                3              188.74            0.74
Opnav test,      stars          WA          32            0.01        5          1                 1           1          12            1             none          1                3              47.19             0.18
on-chip
binning for
stars (3x)
                 earth          WA          128           0.20        1          1                 1           1          12            1             none          1                3              37.75             0.59
                 stars          WA          32            0.01        5          1                 1           1          12            1             none          1                3              47.19             0.18
                 earth          NA          1024          12.58       1          1                 1           1          12            1             jail          8                3              37.75             4.72
                 stars          WA          32            0.01        5          1                 1           1          12            1             none          1                3              47.19             0.18
PSF_Jitter       Canopus        NA          512           3.15        1          1                 1           16         12            2.5           none          1                1              80.53             50.33
PSF              Canopus        WA          128           0.20        1          12                1           2          12            2.5           lsls          2.5              1              1932.74           30.20
                                                                                                                                                                                     6
FOV-WA           Pleiades       WA          1024          12.58       1          1                 9           2          12            2.5           lsls          2.5              1              90.60             90.60
FOV-NA           Pleiades       NA          1024          12.58       1          1                 1           2          12            2.5           lsls          2.5              1              10.07             10.07
VIRS             Earth          WA          256           0.79        1          1                 81          1          8             4             wvle          8                1              254.80            7.96
coalign
Solar            Adaptor        WA/         256           0.79        1          13                1           2          12            2.3           none          1                1              142.24            20.45
spectrum         ring           NA
                                                                                                                                                               TOTAL (MB)                           4780.80           427.46

Note: WA =12 filters; NA=1 filter


Table 4: Cruise calibration plan
CRUISE CALIBRATION OPERATIONS (L + 120 days through MOI)
                                                                                                                                                                                                   Total
                                                            Raw vol.        No. of                          No. of                  Comp. vol.                                                      raw
                                                Window         (Mb)       f r a m e s / No. of   No. of   exposure Comp.            /iteration                                                    volume          Downlinked
    Time       Target      Measurement            size      / w i n d o w windows f i l t e r s positions   times  ratio Iterations    (Mb)                                                        (Mb)           volume/Mb
L + 120,                                       Full
420, 360….    Bland space Dark current         frame              12.63          1                  2               1             2     2.5                  15                   20.21            757.80             303.12
Second                                         Full
Venus flyby   Venus       Scattered light      frame              12.63          1                 13               1             1         2                   1                 82.10            164.19              82.10
L + 360,      Lamp in                          Full
620,….        base, Venus Flat field           frame              12.63         10                  2               1             1         2                   5         126.30 1263.00                               631.5
Mercury
flybys + 2                 Point spread
months        Canopus      function            256x256             0.79          1                 13              16             1     2.5                     2                 65.42            327.10             130.84
Every 2
months        Starfield    Pointing            100x100             0.12          3                  2               2             1     2.5                  33                    0.58             47.51              19.00

                                                                                                                                                                                                  2559.60           1166.56

Note: WA =12 filters; NA 1 filter




                                                                                                  38
              4. CROSS-CALIBRATION REQUIREMENTS/TESTS

4.1 Calibration validation correlation between MDIS and VIRS (ON-GROUND)
        The MDIS part of this test is covered in 1.2.6 and 1.2.7, the measurement of standard
samples and the reflectance standard material that will be mounted on the inner adaptor ring for a
solar spectrum. For cross-correlation, each instrument needs to make measurements on the same
samples (not different samples of the same reference material). To achieve this, we need to
coordinate with each other and JSC so that the samples can be measured by one instrument, then
sent to the other.

WAC and NAC

A. Testing (MDIS):
Description of test
       Set up with mirror looking down at zero emission angle; illuminate at 30˚ incidence if
       possible. Set exposure so that Halon yields ~3000 DN. For background image, use
       darkest standard and block source.
       Obtain images of 10 reference hand samples through each filter, one temperature,
       optimum exposure time per filter. Then flip each sample over and repeat sequence.
What properties are being characterized?
       Relative response of each instrument to “real” samples, and to solar reference sample.
What are the important parameters to characterize?
       Accurately represent shape and depth of different absorptions and correlate between
       instruments.
What is the priority for this test?
       3B.
What is the schedule for performing this test?
       Perform with 1.2.6 and 1.2.7, coordinate sample calibration with VIRS calibration
       schedule.
What facilities are needed to perform this test, and are they available?
       OCF, available. Lamp, mirror (need to be selected).

B. Analysis:
Description of the analysis
       Take spectra obtained in tests 1.2.6 and 1.2.7. Compare spectra with those obtained by
       VIRS.
What is the product of the analysis?
       Comparison MDIS and VIRS reflectance spectra for each sample (relative to Halon).
Schedule for completion of the analyses
       Before launch; a good understanding is required before early post-launch operations.




                                               39
4.2 Relative Alignments of WA Imager and VIRS (IN_FLIGHT)
    • Very important because this will be the best calibration of VIRS pointing: pixel location
       of VIRS in WA FOV links pointing of the two VISIR spectral investigations. Requires
       planetary source for VIRS detection.
    • Only Earth or Moon after launch and Mercury just before MOI allow VIRS pointing
       without violation of off-sun constraints.
    • Current plan for payload checkout and early operations has MDIS and MASCS scheduled
       for turn on and initial calibration on days 41 and 42 post launch. At this time, the Moon
       will be too small for useful calibration (less than 2 WA pixels across), but the Earth will
       be 5 WA pixels and slightly over 2 VIRS pixels across. This should be sufficient for
       pointing calibration. Pointing calibration between MDIS and VIRS will be verified before
       Mercury orbit insertion.

A. Testing:
Description of test
       Take corresponding images of Earth post launch, and of Mercury prior to MOI. MDIS
       obtains overlapping subframed images of target, VIRS obtains crosshair scan of target.
What properties are being characterized?
       Coalignment between VIRS and MDIS.
What are the important parameters to characterize?
       Exact location of source in VIRS and MDIS fields of view.
What is the priority for this test?
       4A. High priority for VIRS as this is the only chance they will get to determine their
       alignment.
What is the schedule for performing this test?
       As early as possible; currently around L+41.

B. Analysis:
Description of the analysis
       Determine pixel location of Mercury in MDIS image and in VIRS scan. Determine
       relative position of each instrument with respect to spacecraft instrument deck and with
       each other.
What is the product of the analysis?
       Position of VIRS boresight with respect to MDIS boresight.
Schedule for completion of the analyses
       MDIS: 2 weeks after data are obtained.




                                               40
                             5. DELIVERABLES TO SOC

   MDIS is the only instrument that will use the SOC during calibration. The SOC needs to be
up and running before calibration begins. The SOC will be tested using PDS data from existing
missions, CONTOUR data, and if possible, test MDIS data obtained during CCD calibration (see
Appendix 1).

   The SOC will fulfill two major functions with respect to calibration data:

   1. Dissemination of calibration data, possibly with some pipeline or other processing
   included (TBD).
   2. Delivery of calibration data to PDS. This needs to be delivered no later than 6 months after
   launch, but it is desirable to deliver this as soon as is feasible after calibration is over.
   Updates to prior calibrations can be made throughout the mission.

5.1 Drivers for SOC pre-flight configuration
        It is our intention to utilize existing or new “quick look” software in the OCF for rapid
identification of potential problems during calibration. Once the data has been verified during
this process, it will be transferred into the SOC. Some of the data may undergo processing within
the SOC, while other data will be delivered in raw format for processing by the analysts. The
exact nature of processing requirements from the SOC is TBD and will depend on what analysis
tools are required and whether these already exist, or can be easily adapted from current
software. It is possible that ACT will be asked to develop or provide analysis tools where
appropriate (TBD).
        The necessary configuration for the SOC will be determined using the Science Team
calibration plan (this document), and the expected data volume (TBD).

5.2 Products to be received from APL’s calibration facilities

   •   Frame grabber images with embedded meta-data
   •   Various file formats: CCSDS, raw, FITS (the current plan involves transfer to the SOC of
       files in FITS format).
   •   History logs, calibration plans, other documentation.
   •   On-ground calibration manuscript.
   •   In-flight calibration manuscript.

5.3 Transfer of data from calibration facilities to SOC
       Data will be transferred to the SOC immediately after it has been verified by the analyst
/engineer in the OCF using “quick-look” software. The Instrument Scientist will supply the SOC
with the desired paths for file dissemination in order to facilitate fast calibration analysis.
Transfer of data will be via FTP (Login and password protected).

5.4 Delivery to PDS
       Imaging data will be handled by the PDS imaging node. Updates to prior calibrations can
be made throughout the mission.


                                               41
5.4.1 Pre-flight calibration data
        All pre-flight calibration data needs to be delivered to PDS no later than 6 months after
launch. Calibration data (not calibrated data), needs to be delivered PDS in a timely fashion, and
it is desirable to do this soon after calibration is complete, and certainly before launch. We
should aim to deliver all the calibration data no later than 6 months after completion of
calibration (currently Jan 2003). If there is no slip in the current schedule, this should be by the
end of July 2003 (table 4).

5.4.2 Post-launch/cruise calibration data
        The first post-launch data will be acquired about 6 weeks after launch, given current
power constraints. Data delivery of this event is planned to occur simultaneously with the first
Venus flyby data (table 4). Similarly, we will be collecting data at periodic intervals throughout
cruise (see table 3). It is planned to submit these data to the PDS along with the next significant
data delivery (e.g., routine star calibrations obtained between the second Venus flyby and the
first Mercury flyby will be delivered with the Mercury flyby 1 data).

Table 5: Planned MDIS data deliveries to PDS

Event                               Date                           Planned data submission date
On-ground calibration               October 2002 –January 2003     July 2003
Launch                              March 10 2004                  --
Post launch checkout                April 20/21 2003               December 2003
Venus flyby 1                       June 24 2003                   December 2003
Venus flyby 2                       March 16 2006                  September 2006
Mercury flyby 1                     July 21 2007                   January 2007
Mercury flyby 2                     April 11 2008                  October 2008
Mercury orbit insertion             April 6 2009                   --


5.5 Date for completion of calibration papers
        Initial on-ground calibration paper to be submitted 6 months after end of calibration tests
(this deadline assumes that data analysis will continue for up to 3 months after end of calibration
measurements), at the same time that the initial calibration data is delivered to the PDS (July
2003). The in-flight calibration paper will be submitted 6 months after Mercury orbit insertion
(October 6, 2009).




                                                 42
              APPENDIX 1: VARIATION OF CCD AND FILTER WHEEL
                              TEMPERATURES

                                         Thermal Model Results


               20




               10
Temperature




                0
Wheel)




                                                                                       Average
              -10                                                                      Maximum
                                                                                       Minimum
(Filter
Platform




              -20




              -30




              -40
                 -50   -45   -40   -35   -30     -25      -20    -15   -10   - 5   0
                                          WA CCD Temperature




                                                   43
                APPENDIX 2: OCF CALIBRATION PROCEDURE

General

1. The test director will have the authority to modify the test procedure during the test as
   necessary to (a) perform additional tests if indicated by the results, (b) reduce excessive data
   if necessary because of redundancy or schedule limitations, (c) perform additional
   characterization tests if time allows.

2. The test director can limit the personnel in the OCF to only those necessary for the conduct
   of the tests during test activities.

3. Any ancilliary data that cannot be automatically collected will be written down in a log book.
   Other collected data may be added to the file headers at a later date. All data required for
   preliminary calibration analysis will be inserted into the file headers once the data is
   transferred from the OCF to the SOC, and before the data is made available to the science
   team.

Preliminary Tests

Monochromator Spectral Calibration

A spectral calibration of the monochromator is performed as follows:
   a. A mercury arc source is imaged onto the entrance slit of the monochromator.
   b. The location of the zero order is recorded.
   c. The spectrum is scanned and the relationship between the monochromator readout and
       the wavelengths of the mercury lines is established.
   d. This test is repeated using an argon arc lamp to cover the longer wavelength range.

       Analysis:
          A linear relationship will be established between the monochromator readout and the
          wavelength of the identified spectral lines. Mercury has prominent lines at 404.7,
          435.8, 546.1, and 579.1 nm. Argon has prominent lines at 696.5, 706.5, 727.3, 738.4,
          751, 772.4, 794.8, 800.6/801.5, 826.5, and 840.8/842.5 nm. As the relationship is
          linear the spectral calibration will be accurate to better than 1 Angstrom.

OCF Beam Calibration
             To measure the spectral response of the instrument the irradiance of the incoming
        beam must be measured with a calibrated detector. This detector must be located at
        the instrument and be on the motion stage so it can be scanned through the beam to
        measure the integrated irradiance at the instrument aperture.
             The source for the test is an incandescent source with the filament imaged onto
        the entrance slit of the monochromator. The slit widths shall be set to a width than
        transmits a spectral range of 2 Angstroms. The beam will be calibrated by recording
        its output as the monochromator is scanned through the spectral range 390-1100 nm.
        (To eliminate higher spectral orders the monochromator long-pass filters have to be
        inserted at the appropriate wavelengths. The detector will have been calibrated prior
        to installation in the OCF.)

                                                44
               The spectral scan will be performed twice, once with the detector located at the
           center of the NAC aperture and once with it at the aperture of the WAC.
               The beam uniformity will be measured over an area larger than the combined
           apertures of the two imagers. This will be performed at four wavelengths over the
           MDIS range. (If there is no significant uniformity variation with wavelength, the
           single irradiance measurement at the center of each aperture shall be considered to be
           sufficiently accurate.)
               As this measurement is to determine a second order effect, (the spectral response
           of the WAC will be primarily determined by the filter transmission profiles) high
           accuracy is not required and only a relative spectral response calibration is needed.

           Analysis:
              The results provide a direct relationship between beam irradiance and
           monochromator wavelength.


Initial Conditions for MDIS Calibration

The following procedure assumes the following instrument configuration:

       1. The MDIS is mounted via a bracket to the motion stage in the OCF vacuum chamber.
       2. The instrument is connected to the flight data handling system.
       3. The data handling system is connected to the ground data test set.
       4. The computer can operate the motion stage and the monochromator.
       5. Thermocouples are attached to monitor the instrument temperature.
       6. Two silicon photodiodes on the instrument and one on the sphere are being monitored.
       7. The Oriel spectrograph is monitoring the output of the sphere.
       8. Sufficient initial tests have been performed to verify the file recording procedure and
       the signal levels expected.


Several sets of test will be performed in the OCF. These are:
         1. Radiometric calibration
         2. Optical performance measurements
         3. Absolute response versus wavelength.
         4. Stray light measurement.
         5. Sample verification.




                                               45
                                     Test Configurations

The tests use several configurations. They are as follows:

Configuration M        (Monochromator for spectral scans)

                   1. Monochromator and collimator mounted.
                   2. Monochromator slit heights set at 4 mm. (Lamp filament is 4.2 x 2.3 mm.
                      After demagnification the image height is 4/1430 = 0.16°, approx 110
                      pixels for the NAC and 16 pixels for the WAC.)
                   3. Initial slit widths set at 0.05 mm. (Corresponding to 14 x 0.05 = 0.7 nm.)
                   4. Quartz-halogen lamp running at rated current from a stabilized supply.
                   5. Lamp filament imaged onto entrance slit as the source.
                   6. Set wavelength to zero order.
                   7. Set monochromator filter to position ???.
                   8. Set MDIS to view collimator.


Configuration C1 (Collimator for resolution and distortion)
.
1. Collimator with fused silica window as the vacuum seal.
2. Source with pinhole array set up as a source outside the collimator window. (For the WAC
   the demagnification is 78/1430 = 0.055; a 0.015-mm pinhole is a small fraction of a single
   detector pixel. For the NAC the demagnification is 550/1430 = 0.38; a 0.015-mm pinhole is
   approximately 0.4 pixel.)
3. Ensure pinhole array is within 1-mm of collimator focus. (Depth of field is given by
   (1430/550)^2 x .014 x 22 mm = 2 mm for one-half pixel blur.)
4. Quartz-halogen lamp running at rated current from a stabilized supply
5. Lamp set to illuminate diffuser behind the pinhole array.
6. Set MDIS to view collimator.


Configuration C2       (Collimator for focus test)

         1.   Replace the point source in C1 with the focus test slit.
         2.   Locate center of slit at collimator focus.
         3.   Quartz-halogen lamp running at rated current from a stabilized supply.
         4.   Lamp set to illuminate diffuser behind the pinhole array.
         5.   Set MDIS to view collimator.




                                                46
Configuration CS      (Collimator for sample measurements)

         1.  Collimator with fused silica window as the vacuum seal.
         2.  Mount a front-surface mirror at a 45° angle close to the window.
         3.  Locate geological test specimens below the mirror at the focus of the collimator.
             (Because of the depth of focus accurate setting is not required.)
         4.  Illuminate the specimen with a stabilized incandescent lamp.
         5.  Set MDIS to view collimator.
         6. View the NAC image and adjust the specimen location if necessary for focus.

Configuration R       (Radiometric test with integrating sphere)

         1.    Mount integrating sphere six inches from the rear window of the OCF vacuum
         chamber.
         2.    Ensure that the chamber window can be removed and installed without disturbing
         the sphere.
          3. Point MDIS at the integrating sphere
          4. Monitor sphere, Oriel spectrograph, instrument silicon photodiodes, and chamber
          conditions.

Measurement Sequences

The following sequences will be used repeatedly so they are listed here.

Sequence D     (Dark signal measurement)

         1.    Filter selection is arbitrary for steps (2) and (3) for the WAC.
         2.    Cover the chamber port with the opaque mask.
         3.    Record 10 frames of dark signal for exposure times of 5, 10, 20, 50, 100, 200,
               500, 700, 1000 msec.
         4.    Repeat (2) and (3) for the NAC.

Sequence B     (Background light measurement)
        1.     Remove chamber port cover and view non-illuminated sphere.
        2.     Record 10 frames of signal through each filter of the WAC at an integration time
               of 100 msec.
         3.    Record one frame of signal for exposure times of 1, 2, 5, 10, 20, 50, 100, 200,
               500, 700, 1000 msec. for each filter of the WAC.
         4.    Repeat (2) and (3) for the NAC.

Sequence T     (Establishing the integration times)
        1.     Turn on all sphere lamps (setting 1) and allow TBD minutes to stabilize.
        2.     Select filter 1 of WAC.
        3.     Record frame for integration times of 1, 2, 5, 10, 20, 50, 100, 200, 500, 700, 1000
               msec. Monitor WAC response and terminate sequence when detector enters
               saturation.
         4.    Repeat (2) and (3) for each WAC filter.
         5.    Repeat (3) for the NAC.

                                               47
         6. Select setting 2 (see table) for the sphere.
         7. Repeat steps (2) through (5).
         8. Repeat (2) through (5) for each sphere setting.

Sequence R1 (Radiometric calibration sequence)
      1. Turn on all sphere lamps (setting 1) and allow TBD minutes to stabilize.
      2. Select filter 1 of WAC.
      3. Record signal for integration times as determined in initial tests using sequence 3.
      4. Record 10 images when DN count is approximately 500, and again when it is
         approximately 2500.
      5. Repeat (2) through (4) for each WAC filter.
      6. Repeat (3) and (4) for the NAC.
      7. Select setting 2 (see table) for the sphere.
      8. Repeat steps (2) through (6).
      9. Repeat (2) through (6) for each sphere setting.


Sphere Sequence (S1)

(The following sequence is selected to minimize the time used in waiting for bulb stabilization.
As it is quicker to turn bulbs off, rather than on, the sequence starts with the bulbs all on.)

  Setting       150 Watt #1    150 Watt #2     45 Watt #1      45 Watt #2     Total Power
     1              On             On             On              On            390 W
     2              On             On             On               -            345 W
     3              On             On              -               -            300 W
    4*               -             On             On              On            240 W
     5               -             On                             On            195 W
     6               -             On                 -            -            150 W
    7*               -              -                On           On             90 W
     8               -              -                On            -             45 W
     9               -              -                 -            -              0W

At steps 4 and 7 there is a delay for the lamps to stabilize after turn-on.
Selection of lamps 1 and 2 for each power can be varied from test to test to equalize the times
that they are on.

Sequence SR1          (Spectral response measurement)

         1. Select filter 1 of the WAC.
         2. Set monochromator to a wavelength within spectral band of the filter. (1:420 nm,
            2:482 nm, 3:560 nm, 4:630 nm, 5:700 nm, 6:750 nm, 7:700 nm, 8:830 nm, 9:900
            nm, 10:950 nm, 11:1000 nm, 12:1010 nm.)
         3. Select monochromator neutral-density filter to give an MDIS signal of >2500 DN.
         4. Record the WAC detector signals while scanning the monochromator in steps of 20
            nm from 300 to 600 nm.
         5. Set monochromator filter longpass filter to ???.

                                                48
6. Record the WAC detector signals while scanning the monochromator in steps of 20
    nm from 600 to 1200 nm.
7. Repeat steps 2 through 6 for each WAC filter.
8. Repeat steps 2 through 6 for the NAC
9. Select filter 1 of the WAC.
10. Set monochromator filter longpass filter to ???.
11. Record the signal while scanning the monochromator in 2 nm steps from 390 to
    450 nm.
12. Select filter 2 of the WAC.
13. Set monochromator filter longpass filter to ???.
14. Record the signal while scanning the monochromator in 2 nm steps from 470 to
    490 nm.
15. Select filter 3 of the WAC.
16. Set monochromator filter longpass filter to ???.
17. Record the signal while scanning the monochromator in 1 nm steps from 550 to
    570 nm.
18. Select filter 4 of the WAC.
19. Set monochromator filter longpass filter to ???.
20. Record the signal while scanning the monochromator in 1 nm steps from 620 to
    640 nm.
21. Select filter 5 of the WAC.
22. Set monochromator filter longpass filter to ???.
23. Record the signal while scanning the monochromator in 1 nm steps from 690 to
    710 nm.
24. Select filter 6 of the WAC.
25. Set monochromator filter longpass filter to ???.
26. Record the signal while scanning the monochromator in 1 nm steps from 740 to
    760 nm.
27. Select filter 8 of the WAC.
28. Set monochromator filter longpass filter to ???.
29. Record the signal while scanning the monochromator in 1 nm steps from 820to 840
    nm.
30. Select filter 9 of the WAC.
31. Set monochromator filter longpass filter to ???.
32. Record the signal while scanning the monochromator in 1 nm steps from 890 to
    910 nm.
33. Select filter 10 of the WAC.
34. Set monochromator filter longpass filter to ???.
35. Record the signal while scanning the monochromator in 1 nm steps from 940 to
    960 nm.
36. Select filter 11 of the WAC.
37. Set monochromator filter longpass filter to ???.
38. Record the signal while scanning the monochromator in 2 nm steps from 980 to
    1020 nm.
39. Select filter 12 of the WAC.
40. Set monochromator filter longpass filter to ???.
41. Record the signal while scanning the monochromator in 0.5 nm steps from 980 to
    1050 nm.

                                   49
         42. Set monochromator filter longpass filter to ???.
         43. Record the NAC signal while scanning the monochromator in 10 nm steps from
             ??? to ???.
         44. Close the gate valve on the entrance to the collimator.
         45. Record 10 frames of dark signal for both the NAC and the WAC (any filter).

Sequence RNAC       (Resolution and distortion of NAC)
        1. Adjust the stage so the source at the collimator focus is centered in the NAC.
        2. Zero the stage location.
        3. Adjust source and/or integration time to give a signal of approx. 60% full-scale
             (2500 DN’s.) for the NAC.
        4. Record five frames at the central location.
        5. Move motion stage in a two-dimensional raster scan from –0.8° to 0.8°, in
           0.32°steps in azimuth for elevations of –0.8° to 0.8°, in 0.32° steps. (Result is a 36-
           position matrix of points.)
        6. Record a dark frame for dark signal removal.

Sequence RWAC         (Resolution and distortion of WAC)
                   1. Adjust the stage so the source at the collimator focus is centered in the
                      NAC.
                   2. Zero the stage location.
                   3. Adjust source and/or integration time to give a signal of approx. 60% full-
                      scale (2500 DN’s.) for filter 1
                   4. Record five frames at the central location.
                   5. Move motion stage in a two-dimensional raster scan from –5.25° to 5.25°,
                      in 2.1°steps in azimuth for elevations of –5.25° to 5.25°, in 2.1° steps.
                      (Result is a 36-position matrix of points.)
                   6. Record a dark frame for dark signal removal.
                   7. Repeat steps 5 through 8 for each WAC filter.

Sequence FNAC           (Focus of the NAC)
                   1.   Zero the stage location.
                   2.   Adjust source and/or integration time to give a signal of approx 60% full
                        scale.
                   3.   Record NAC signal at each of the following five motion stage positions:
                        (0°, 0°), (-0.5°, -0.5°), (-0.5°, 0.5°), (0.5°, -0.5°), (0.5°, 0.5°).
                   4.   Record a dark frame through each filter for dark signal removal.
                   5.   Set WAC filter to 1.
                   6.   Record WAC signal at the following five motion stage positions: (0°, 0°),
                        (-4°, -4°), (-4°, 4°), (4°, -4°), (4°, -4°).
                   7.   Repeat 5 and 6 for each WAC filter.
                   8.   Repeat steps 5 through 7 for source positions of –50 and +50 mm. (A 10-
                        mm shift of the source changes the focus of the NAC by 1.4 mm resulting
                        in a blur circle increase of 1.4/22, or 0.064 microns, 4 pixels. For the
                        WAC the focus change is 0.036 mm, resulting in a blur circle increase of
                        an undetectable 4 microns.)



                                                50
Sequence SL            (Stray light measurement)

                   1. Record frame with image centered.
                   2. Record WAC and NAC images at each of the following motion stage
                      positions: (0°, 10°), (0°, 7.5°), (0°, 5°), (0°, 2.5°), (0°, 1°), (0° -1°), (0°, -
                      2.5°), (0°,-5°), (0°, -7.5°), (0°, -10°), (-10°,0°), (-7.5°, 0°), (-5°, 0°), (-2.5°,
                      0°), (-1°, 0°), (1° 0°), (2.5°, 0°), (5°, 0°), (7.5°, 0°), (10°, 0°).
                   3. Change monochromator filter to ??.
                   4. Repeat (2).
                   5. Change monochromator filter to ??.
                   6. Repeat (2).\

Sequence SAMP          (Sample and smear measurement)

          1. Set up configuration CS.
          2. View the 2%, 10%, and halon reflectance samples to establish suitable exposure
             times for each WAC filter and for the NAC.
          3. Select WAC filter 7 (wideband at 750 nm).
          4. Take 10 images at seven exposure times as determined in step 2.
          5. Take 10 images through each WAC filter and with the NAC using a suitable
             exposure as determined in step 2.
          6. Close valve on collimator.
          7. Take 10 dark frames at each exposure used in steps 4 and 5.

Test Activities

Initial room-temperature calibration

This initial calibration will establish a matrix of sphere and exposure times for use in the
remaining radiometric calibration.

Chamber door open, or window removed:

1.   Set up configuration R.
2.   Perform sequence D.
3.   Perform sequence T.
4.   Install chamber window

Room-temperature radiometric calibration

5. Perform sequence R1.

Room-temperature focus and image quality test

6.      Set up configuration C2.
7.     Perform sequence FNAC.
8.      Set up configuration C1.
9.      Perform sequence RNAC.

                                                  51
10.      Perform sequence RWAC.

Initial vacuum tests

      11. Evacuate the chamber.
      12. Repeat steps 6 through 10.
      13. Set up configuration R.
      14. Perform sequence R1.
      15. Perform sequence T.
      16. Perform sequence D.

      Analysis:
             a. Compare signal levels with and without the chamber mask to determine the level
                of background light.
             b. Average files, subtract dark signal, and divide to find window correction factor.
             c. Determine maximum exposure time for each filter and sphere power level. Create
                a measurement matrix of sphere illumination level and integration for each filter.
             d. Measure the image quality and distortion for each filter.
             e. Process data to give the following information:
                      i. Linearity with exposure time
                     ii. Linearity with source radiance
                   iii. Flat field uniformity
                    iv. Signal to radiance conversion factors
                     v. Readout smear
                    vi. SNR
                   vii. Performance at room temperature
                  viii. Dark signal at room temperature
                    ix. Room temperature focus accuracy
                     x. Room temperature image quality

Temperature Variation.

      1. Repeat steps (6) through (10) and (13) through (16) at detector temperatures of -40°C, -
         25°, and -10°C.
      2. Repeat for chamber temperatures of ??C, ??C, and ??C. (TBD)

Measure the off-axis response to the extent possible.

Spectral Response with each filter

                            1. Instrument temperature set at ??°C. Detector temperature at ??°C .
                               (TBD)
                            2. Set up configuration M.
                            3. Perform test sequence SR1.

Analysis
       Comparison of the results with the detector calibration gives the spectral response of each
camera. It also provides a check for spectral leakage through any of the filters.

                                                 52
Stray light measurement

            1.   Instrument temperature set at ??°C. Detector temperature at ??°C .(TBD)
            2.   Set up configuration M.
            3.   Set monochromator ND filter to ??
            4.   Select filter 5 of WAC.
            5.   Set monochromator slits to give a signal >2000 DN.
            6.   Record dark signal by closing gate valve on collimator.
            7.   Perform sequence SL.

Analysis:
      Saturated images allow the stray light to be measured around the image of the
monochromator slit. The extended angular range checks for stray light from beyond the FOV.

Sample and Smear Measurements

                      1. Instrument temperature set at ??°C and detector temperature at ??°C.
                         (TBD)
                      2. Set up configuration CS.
                      3. Perform sequence SAMP.

Analysis:
        Use images to determine the magnitude of the frame transfer smear and establish a
correction algorithm. Verify the ability of the MDIS to identify “real” rock samples.


Questions:
What instrument and detector temperatures will we test at?
Where should we perform the binning and compression measurements?




                                                  53
                      APPENDIX 3: WIDE ANGLE FILTERS

           Filter                    Wavelength (nm)                      Width
             1                             415                              40
             2                             480                              10
             3                             560                              5
             4                             630                              5
             5                             700                              5
             6                             750                              5
             7                             700                             600
             8                             830                              5
             9                             900                              5
            10                             950                              7
            11                            1000                              15
            12                            1020                              40



                    APPENDIX 4: PROPOSED HAND SAMPLES

The following samples have been requested from Dick Morris at JSC. We need to coordinate our
efforts so that both MASCS and MDIS can calibrate with exactly the same samples.

   •   5 Brightness standards (99%, 50%, 20%, 5%, 2%)
   •   3 Wavelength Standards (Dysprosium Oxide, Erbium Oxide, Holmium Oxide)
   •   Mineral samples optimized for mercury analogs:
   •   Olivine (1-2)
   •   Pyroxenes (2-3)
   •   Minerals with hydroxides (~2 mostly to confirm sensitivities at 1400 nm)
   •   Glasses (~2?)
   •   Anorthosites (`2-3)
   •   A subset with varying Fe-Ti Oxide contents (~3)




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