SSUSI Overview by wuxiangyu


									SSUSI:Special Sensor Ultraviolet
   Spectrographic Imager

            Dr. Larry J. Paxton
        SSUSI Principal Investigator
       The Johns Hopkins University
        Applied Physics Laboratory
             Laurel, MD 20723
           SSUSI Supports Operational
              and Basic Research
SSUSI is designed to remotely sense
ionospheric, atmospheric, and auroral
environmental parameters on a global basis.
SSUSI obtains FUV spectrographic
observations of the atmosphere and aurora
and visible light photometric measurements
of the aurora and nightglow.
The radiance observations will be used to
    •   Electron Density Profiles (day and night)
    •   Neutral Density Profiles(day)
    •   Auroral Energy Deposition Rate (day and night)
    •   Auroral Oval Location (day and night)
and provide a unique database for the
production of environmental parameters,
validation of operational models, and extend
the validity of the "nowcast".
SSUSI was launched on October 18, 2003.
           -   There will be four more DMSP flights with a
    From 1989 to First Launch
The SSUSI program started in 1989 when DMSP
  solicited proposals from AFRL and APL to
  build a follow-on to the Polar BEAR AIRS and
  HiLat AIM sensors.
In 1992 we were asked to design automated
  data processing software for the SSUSI data
  stream. Software was delivered in 1996.
By 1994 the first SSUSI (SN01) had been built
  and delivered. The last (SN05) was delivered
  in 1996.
SSUSI and the SSUSI Ground Data Analysis
  System (GDAS) were designed to meet DMSP
  needs for near-realtime ionospheric
  specification and auroral imagery.
What We Are Doing and Where
       We Are Going

SSUSI was launched on DMSP
 F16 on October 18, 2003
 • What is SSUSI?
 • How does it work?
 • How do we get information out of the
   data stream?
 • How is the user supported?
  SSUSI on S20 Spacecraft
The first SSUSI to be launched was installed on
  the S20 spacecraft.
   • DMSP spacecraft are numbered as they are constructed.
   • Currently numbers 16 through 20 have been built.
   • Only S20 has been flown.
Once the spacecraft is launched the flight is
  given a number, the most recent launch was
  the F16 spacecraft.
The current schedule and past experience
  indicate that launches should occur every 1
  ½ to 2 years.
   • The last SSUSI should be launched in 2009 to 2011.
   • With a 3 year design lifetime there will be 3 operating
     SSUSIs during most of this decade.
       SSUSI is the Next Generation
      of Remote Sensing Instrument
 Nadir imagery of the Earth’s upper atmosphere is best
  done in the Far Ultraviolet or FUV (115 to 180 nm)
     • sunlight doesn’t penetrate the atmosphere below about 80 km
     • proven concept
     • simple and relatively low-cost sensors can be flown

Mission/Instrument    Operational Dates     Instrument Type
HILAT/AIM             1983                  Single color imaging
Polar BEAR/AIRS       1986-1987             2 color imaging
Delta 180             1985                  Imagers and spectrometers
Delta 181             1987                  Spectrographs and imagers
Delta 183             1989-1991             Imagers
MSX/UVISI             1996-2000             Spectrographic imagers and
DMSP/SSUSI            2003-2012             Scanning imaging spectrograph
TIMED/GUVI            2002-2007             Scanning imaging spectrograph
         Hyperspectral Imagers

Panchromatic imagers                    Sunshade

 combine all the light they                                     Telescope

 receive into a single image.
                                 white light from scene

                                                                                       2D detector

Multispectral sensors sample
 light in several non-adjacent                                                to detector electronics

 color bands.                                     to detector

                                                                2D detector

            imagers sort the         Collimating Mirror
 incoming light into a                                                                       Grating

 hundred or more mutually          white light from scene
 exclusive and complete
 bins.                                     Telescope             Filter/slit mechanism    Telescope
                                           sunshade                                       Mirror
          SSUSI Provides Required
         Environmental Data Records
               and Parameters
      MJCS 154-86 Ranking      Environmental Parameter
         5                     Electron Density Profile
         12                    Neutral Number Density Profile
         16                    Solar Radiation (UV integrated flux)
         18                    Auroral Emissions and Airglow
         24                    Precipitating Electrons and Ions
         26                    Electric Fields (low latitude)
         31                    Ionospheric Scintillation

SSUSI meets or exceeds SESS Sensor Requirements Specifications for the
NPOESS sensors (see SESS Sensor Requirements Document; 1999).
SSUSI is not, however, slated for flight on NPOESS.
         SSUSI Consists of a
       Hyperspectral Imager and
        a Photometer System
The Spectrographic Imaging Spectrograph (SIS)can
  obtain an horizon-to-horizon images
   • in five "colors" in the wavelength range 110nm to 180nm
       - by using a scan mirror (IMAGING MODE) or it can operate with the
          mirror in a fixed position (SPECTROGRAPH MODE).
   • Three slits are available to optimize the combination of spatial,
     spectral, and altitude resolution.
The Nadir Photometer System is optimized for
  observations of the nightside ionosphere and
  detection of the auroral boundary.
   • 630nm photometer to observe the O(1D) radiation field
   • 629nm photometer to deduce the background at 6300Å
   • 428nm photometer to observe the N2+ 1Neg band at 4278Å
630 and 629 nm Photometers

           428 nm Photometer    Hyperspectral Imager – the Scanning
                                Imaging Spectrograph (SIS)
               SSUSI on S20
The SSUSI SIS and NPS are visible as
  mounted on the Earth-facing panel of
  the DMSP spacecraft.

                                           SIS (with cover
                                           closed for launch)

                                          NPS (covered by a

                                         GLOB (a sun
                                         shield for the OLS)
                           SSUSI NPS
The SSUSI NPS is the first
  flight of a system that
  allows one to accurately
  remove the effects of the
  planetary albedo
  (reflections from clouds)
  from the measurement of
  the 630 nm signal.
   • This enables the more
     accurate measurement of
     the height of the nightside
The SSUSI NPS also allows
  us to use the 630 and 428
  nm photometers to locate
  the auroral boundary,
  independent of the SIS.
A Novel Hyperspectral Imager
        Details of the SSUSI
          Scan Geometry
                                    Scan Mirror


         n                                                            160 spectral ele ments
      ca                          an
   bS                           Sc
Lim        m                  ck
       5k s                Tra ls
    44 ixel              s
                       os ixe                                         16 spatial elements
     8p            ° Cr 24 p
                                                  11 .8 ° FOV

                                                                Along Track Motion
                                                                  148 km/22 sec

                                                                  10 Km x 10 Km resolution
                                                  153 Km                 16 pixels

                                                                 124.8° Cross Track Scan
                                                                        156 pixels
                                                                   (h orizon to horizon)       +Z
          SSUSI Spectrograph Design
           is Optimized for the DMSP
                 nadir                             slit mechanism   telescope mirror
                                                                                            SSUSI design is simple
     cross track scan range
                                                                                              and robust.
                                                                                               • An off-axis parabaloid
                                                                                                 telescope feeds a simple,
                                                                                                 Rowland circle,
                                                                                  140nm          spectrograph.
      scan mirror
                                                                                               • Minimizes the number of
      toroidal grating        secondary detector                         primary detector           - FUV reflectivity is low

Two detectors are implemented to
meet lifetime requirements.
    We’re not worried about failure
    so much as our ability to
    characterize changes in
              SSUSI “Color” Definitions
SSUSI produces
 images by
 extracting “colors”
 from the observed
   • Indicated by
     highlighted areas
   • preserves the
     science content for
   • data rate reduced by
     factor of 30.
      Scanning Imaging
 Spectrograph Data Has a High
     Information Content
Use of data in an
operational environment
requires that higher level
data products be produced
and that the user have an
interface to all levels of the
The interface has to
convey the information
about required parameters
while reducing the user

                                 Sample image from GUVI
                 SSUSI Images the Earth
SSUSI will routinely provide intensity maps and environmental
  parameters to AFWA.

    Day                 Night                            Aurora
    O/N2 on disk        Total Electron Content (TEC)     Q,E0 images
    O, N2, O2 on limb   Height of Peak in F region       Height of Peak in E
                        (HmF2)                           region (HmE)
    Qeuv                Number Density of Electrons at   Number Density of
                        F-region Peak (NmF2)             Electrons at E-region
                                                         Peak (NmE)

                        Cross-hatched area indicates SSUSI
                        coverage on one orbit - over 10,000
                        ionospheric observations per orbit.
  SSUSI Data are Monitored and Evaluated
        at APL and Used at AFWA

            SSUSI data recorded on S/C and downlinked

                      Data reformatted for processing
        Calibration applied to convert from counts to radiance
                 Each pixel is located on the Earth

Radiance data are regridded into superpixels - Sensor Data Records (SDR)

       Pixels are separated by region: Day, Night, and Aurora
          Each regions data are processed to produce the
                Environmental Data Records (EDR)

 SSUSI data are ingested by models to produce higher level forecast
                       and nowcast products
                 SSUSI scans are recorded in key wavelength
                    bands and downlinked and calibrated,
                 geolocated and gridded to form Sensor Data

SSUSI observes spectra.      SSUSI downlinks scan images.   SDRs are formed at AFWA.

 SSUSI SDRs are processed to form
 Environmental Data Records (EDRs) that
 support the warfighter.
           AFWA provides value-added processing to
 support specific customer requirements.
      User Interface Supported
         Through PVWave
The SSUSI User Interface
was designed over 10
years ago.
At that time the AF chose
PVWave as the language
for coding.
The current user interface
allows the user to interact
with the data by cjhoosing
color table, product, map
projection, contouring, etc.
   We are Looking at Enhancing SSUSI’s
           Utility to AFWA Users
                                           AFWA will use SSUSI to predict
                                             ionospheric perturbations that
                                             impact s/c operations &
                                               • Provides location of auroral
                                                 boundary and energy deposition
                                                   - s/c anomaly resolution
                                                   - changes in neutral
                                                     atmosphere composition and
                                               • Indicates probable areas of
                                                 disruptions or degradation
                                                   - High frequency
                                                     communications, precision
                                                     geopositioning, over-the-
                                                     horizon radar, predictions
                                                     from PRISM
                                                   - Images nightside ionosphere
                                                     for bubbles and scintillation
                                                     signatures in the equatorial
Scans perpendicular to S/C orbital plane             ionosphere
and onto the limb
            SSUSI Software History
The SSUSI Ground Data Analysis Software (GDAS)
  translate data numbers into key parameters:
  •   32,000 lines of MilSpec 2167A documented Ada code
  •   28,000 line of 4GL code to drive interactive displays
  •   Software Users Manual and Science Interpretation Manual provided
  •   near real-time processing of data
  •   near real-time display
The GDAS was delivered to 55th Weather Squadron.
  • Displays delivered March 1995.
  • Algorithms delivered June 1996.
The GDAS re-delivery October 2001 at AFWA.
  • Changes to the software were required in order to meet changes in the
    platforms and operating environment.
             Current SSUSI GDAS
           Accommodates Differences
            Between AFWA and 55th
Raw DMSP                         AFSFC
Data                             System

  Data Reformatter    System Access
       Algorithms                                 Interface
       Data Product Algorithms

   Data Tables                    Data Products         Preferences
         SSUSI GDAS Components
         Have Varied Requirements
The SSUSI GDAS consists of three elements
  • “Data Reformatter” ingests
      - the raw SSUSI sensor data and DMSP satellite ephemeris
        data currently formulated as an RSDR
      - indices from the Air Force solar & geomagnetic databases
  • “Data Product Algorithms” generates SSUSI data products
      - Sensor Data Records (SDRs)
      - Environmental Data Records (EDRs)
  • “User Interface” ingests the SDRs and EDRs and displays
    them through a tailorable graphical user interface.
      - The operator interface is menu driven and has built in help
     SSUSI GDAS is Supported by
      APL on the Same Type of
The APL plan has always been that the SSUSI
  algorithms will be run here at APL on the same
  platform and same environment as that at the host
  site (AFWA).
The approach ensures
   • better support for the user
       - we will have most of the same operating environment
   • faster and cheaper upgrades
       - work can be done and tested here then installed at AFWA
   • proven bug fixes are produced, tested, and delivered
       - nothing is worse than a bug fix that doesn’t work - except a new
   • that we can test and evaluate enhancements to the SSUSI code
     without impacting AFWA operations and still be assured that it will
          SSUSI Software Ready to
         Produce Standard Products
SSUSI data are produced as Sensor Data Records (SDRs)
 and Environmental Data Records (EDRs).
   • SDRs are strip images in Rayleighs binned to 25 x 25 km2 grid
   • EDRs are product files binned to 25 x 25 km2 grid for aurora and 100 x
     100 km2 for day and night
SSUSI swaths are about 6000 km across.
   • And produce over 10,000 values/orbit or 150,000/day.
                    Standard SSUSI EDRs
Day                  Night                           Aurora
O/N2 on disk         Total Electron Content (TEC)    Q,E0 images
O, N2, O2 on limb    Height of Peak in F region      Height of Peak in E
                     (HmF2)                          region (HmE)
Qeuv                Number Density of Electrons at   Number Density of
                    F-region Peak (NmF2)             Electrons at E-region
                                                     Peak (NmE)
          Block 5D3 Sensors Support SSUSI
          Observations and Enhanced Data
Other mission sensors, often referred to as special sensors, provide other
  meteorological data, depending on the spacecraft configuration.
SSIES-3           Thermal Plasma Monitor/ Scintillation Detector
SSJ/5             Precipitating Electron/Ion Spectrometer
SSM               Triaxial Fluxgate Magnetometer
SSUSI             Special Sensor Ultraviolet Spectrographic Imager
SSULI             Special Sensor Ultraviolet Limb Imager
The other Block 5D3 sensors will contribute data that can be used for on-orbit
  validation of parts of the SSUSI EDRs.
SSJ/5 will provide in situ energetic particle measurements, SSM auroral boundary
  information, and SSIES ionospheric parameters. SSULI looks in track while SSUSI
  images the disk and the cross-track limb thus providing a three-dimensional picture
  of the ionosphere.
 SSUSI Data and Data Products are
  Being Calibrated and Validated
The SSUSI algorithm approach has been tested
  using data from the GUVI instrument on
The SSUSI cal/val period covers the first 13
  months of operations.
The data will be embargoed until the time that
  the sponsor agrees that the data and data
  products are of sufficient quality as to
  guarantee their utility.
The SSUSI data stream and data products are
            GUVI Data Will Contribute to the
             Validation of SSUSI Products
TIMED is the first of NASA’s Solar
  Terrestrial Probe line.
TIMED goals
    • Determine temperature, density, and
      wind structure of the MLTI including
      seasonal and latitudinal variations
    • Determine the relative importance of
      the various radiative, chemical,
      electrodynamical, and dynamical
      sources and sinks of energy for the
      thermal structure of the MLTI
GUVI emphasis
    • neutral composition
    • high latitude energy inputs
        - conductivities and Joule heating
Ground truth and ground-based
  measurements are an important              The STP line provides products that will support SSUSI
  component of the effort.                   algorithm validation and enhancement.
            Concurrent Flight of SSUSI and GUVI
            Offer Opportunities to Improve Space
                     Weather Products
DMSPF16 will also manifest the the
   SSJ/5 electron and ion energy and
   flux measurement
SSJ/5 will provide an inflight validation
   of the boundaries, fluxes and energies
   deduced by SSUSI.
TIDI will measure the thermospheric
   vector wind field
     •   SABER will measure the energy loss terms
     •   SEE will measure the solar inputs
During the TIMED mission one may expect
  more than one SSUSI operating
     •   improved coverage of high latitude inputs
     •   greater local solar time coverage
Data from TIMED and from NASA/NSF
   supported ground sites will help validate
   SSUSI SDRs and EDRs.
APL End-to-End Capability in
 Space Weather Enhances
Basic Research   Knowledge Transfer
                                       System Support

                                         System Requirements
       Instrument      Tech Transfer
                                        Operational Software
Flight on                     Flight on Operational
Research Satellite            Satellite
   SSUSI is Poised to Take
 Advantage of Concurrent APL
SSUSI hardware is built and awaiting flight.
SSUSI SN05 was launched on DMSP S20 on
 October 18, 2003.
   • F16 is now in orbit and operating nominally
SSUSI GDAS software has been delivered to
SSUSI cal/val plan is in place.
The next step is analyze SSUSI data
   • evaluate the instrument performance
   • validate the data products
   • improve the product
The SSUSI team includes: Bernie Ogorzalek, Daniel Morrison,
  Michele Weiss, Bill Wood, Yongliang Zhang, Hyosub Kil,
  Brian Wolven, Jim Eighert, Rob Barnes, Ron Denissen, Ching
  Meng, Peter Silverglate, John Goldsten, John Boldt, Lloyd
  Linstrom, Dave Persons, and Dave Humm at APL. Many
  others at APL have contributed over the years.
The SIS was fabricated by SSG, Inc.
The SSUSI GDAS was supported by Computational Physics,
  Inc. : Doug Strickland, Scott Evans, and Kip Wright.
The user interface was developed by Tom Spisz and updated by
  Dan Engfer.
Ken Williams and Dave Artis did original GDAS design work
  along with Margie Hopkins and Geoff Crowley.
The cooperation of our colleagues at the Aerospace Corp.,
  especially Paul Straus, is gratefully acknowledged.
Jack Heiss and Glen Fountain were earlier program managers
  for SSUSI.

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