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									    GEMINI NEAR INFRARED SPECTROGRAPH
             INTEGRAL FIELD UNIT

               INTERFACE CONTROL DOCUMENT

                        Version 3.0

                       17 May, 2000


Revised by:
                                 C. M. Dubbeldam,
                                 Senior Mechanical Engineer


Reviewed by:
                                 J.R. Allington-Smith,
                                 Work Package Scientist


Approved by:
                                 D.J. Robertson,
                                 Work Package Manager




                                 N. Gaughan
                                 GNIRS Project Manager




University of Durham       Page 1 of 7                        21 October, 2011
                                             GNIRS IFU INTERFACE CONTROL DOCUMENT




                                                           TABLE OF CONTENTS




1. DESCRIPTION................................................................................................................................... 3
   1.1 PURPOSE OF THE DOCUMENT ....................................................................................................... 3
   1.2 SCOPE OF THE DOCUMENT ........................................................................................................... 3
2. APPLICABLE DOCUMENTS AND DRAWINGS .............................................................................. 3
   2.1 GNIRS OPTICAL DESIGN AND ALIGNMENT .................................................................................... 3
   2.2 GNIRS MECHANICAL INTERFACES ................................................................................................ 3
3. INTERFACES .................................................................................................................................... 3
   3.1 MECHANICAL INTERFACES ............................................................................................................ 4
       3.1.1 General Mechanical Considerations ............................................................................ 4
       3.1.2 Slit Mechanism (Slide) .................................................................................................. 4
       3.1.3 Decker Mechanism (Slide) ............................................................................................ 4
       3.1.4 Mechanical Installation Tolerances for the Slit/Decker Slides ................................. 5
       3.1.5 Mechanical Repeatability of the Slit Mechanism ........................................................ 5
       3.1.6 Mechanical Installation Tolerances for the IFU .......................................................... 5
       3.1.7 IFU Stability with respect to the GNIRS Optical Axis ................................................. 6
   3.2 ELECTRICAL INTERFACES ............................................................................................................. 6
   3.3 THERMAL INTERFACES ................................................................................................................. 6
   3.4 OPTICAL INTERFACES ................................................................................................................... 6
       3.4.1 Input ................................................................................................................................ 6
       3.4.2 Output ............................................................................................................................. 7
       3.4.3 Baffling, Vignetting and Stray Light Control .............................................................. 7
4. SOFTWARE....................................................................................................................................... 7
5. OPTICAL ALIGNMENT OF THE IFU MODULES WITHIN GNIRS .................................................. 7




University of Durham                                               Page 2 of 7                                                  21 October, 2011
                                GNIRS IFU INTERFACE CONTROL DOCUMENT




                                     INTERFACE CONTROL DOCUMENT




1. DESCRIPTION


1.1 PURPOSE OF THE DOCUMENT
This is a listing of the interface control documents (ICDs) necessary for the design, installation, and
adjustment of the Integral Field Unit (IFU) to the Gemini Near InfraRed Spectrograph (GNIRS). Where
such documents do not exist, this document provides the information required. Information on the
date of document release, and responsibility for the documents is also supplied. Note that electronic
versions of this document or information may be available; in cases of discrepancies the printed
version shall be considered authoritative.


1.2 SCOPE OF THE DOCUMENT
This document provides the information on the interfaces between the GNIRS and the IFU. These are
the mechanical, electrical, thermal, software and optical interfaces. Additional information is provided
on installation and alignment.


2. APPLICABLE DOCUMENTS AND DRAWINGS


2.1 GNIRS OPTICAL DESIGN AND ALIGNMENT
AD 2.1.1     Long blue and red cameras with 111 line grating at 65 K, and short blue and red cameras
             with 111 line grating at 65 K, Ming Liang, May 1999.
             Includes glass tables and clear apertures.
AD 2.1.2     The Tolerance Analysis for GNIRS (Error Budget), Ming Liang, 11/09/1997.
AD 2.1.3     GNIRS Adjustment Strategy (SDN003.20), B. Gregory, 06/02/1999.


2.2 GNIRS MECHANICAL INTERFACES
AD 2.2.1     IFU to Slit Slide Interface, Drawing 89-NOAO-4204-1001 Rev. C, 04/12/2000.


3. INTERFACES
The location of the optical axis, focal plane (slit plane) and acquisition field are shown on the interface
drawing (AD 2.2.1).
Drawings are defined at room temperature (293 K).




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                                GNIRS IFU INTERFACE CONTROL DOCUMENT




3.1 MECHANICAL INTERFACES


3.1.1    General Mechanical Considerations


IFU Materials:
                                                                                              -6
Vacuum compatibility: All IFU materials are to be compatible with vacuum operation at 10 torr. This
is to include all material used for stray light control within the IFU.
Cryogenic compatibility: All IFU materials are to be compatible with operation at a temperature of 60
K.


Fasteners:
All IFU fasteners are to be provided with vents, weep holes, or other means of minimising trapped
gases during evacuation.
All IFU fasteners are to be made of a corrosion resistant material to minimise outgassing in vacuum.
Metric standard fasteners are to be used throughout the IFU.
All interface dimensions are given in both US customary and SI (metric) units; all parts made at
NOAO will be made using the US customary dimensions and associated tolerances.


3.1.2    Slit Mechanism (Slide)
Reference Drawing 89-NOAO-4204-1001 Rev. C (AD 2.2.1).
The IFU optical assemblies must fit within the envelopes allocated on the slit slide mechanism. The
envelope for each assembly is defined by the drawing.
The weight of each optical assembly module shall be < 1 kg.
The IFU optical assembly is attached to the slit slide using a 3-point mount plus a reference edge
(datum) on the edge of the slide.
The mounting surfaces will be bare aluminium; other surfaces will be NOAO standard black anodise.
The interfaces to the two IFU assemblies are assumed to be identical; this is not an absolute
requirement.


3.1.3    Decker Mechanism (Slide)
Two decker positions will be provided in the GNIRS decker slide for the two IFU modules. The decker
can be thought of as a thin plate which is in sliding contact with the slit slide mechanism. Its rear
surface is therefore located 0.079 in (2.00 mm) in front of the slit mechanism focal plane.
The decker holes will be sized to accommodate the fields of view of 1.04  1.50 arcsec and 3.15 
4.46 arcsec for the High Resolution and Low Resolution IFU Modules, respectively. The dimensions
will be 0.039  0.047 in (1.0  1.2 mm) and 0.091  0.126 in (2.3  3.2 mm).


Adjustments:
No adjustments to decker positions are provided.
Positioning of the decker in the translation direction is repeatable to an accuracy of 50 m or better.
There is no provision for adjustment of the slit or decker along the slit.




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                                  GNIRS IFU INTERFACE CONTROL DOCUMENT



3.1.4    Mechanical Installation Tolerances for the Slit/Decker Slides
Slit/decker slide assembly tolerances relative to optical axis (at 60 K) are:
Perpendicular to slit:                        125 m (Note that the IFU position can be adjusted to
                                             make up for errors in this direction by simply moving the
                                             mechanism a specified number of steps.)
Along slit:                                   125 m
Along optical axis:                           125 m
Rotation about optical axis:                 < 0.5 mrad (Note that the slits are treated as effectively
                                             defining the coordinate system about this axis, i.e., the
                                             detector will be aligned to the slits.)
Rotation about axis along slit:              < 0.5 mrad
Rotation about axis perpendicular to slit:   < 0.5 mrad


3.1.5    Mechanical Repeatability of the Slit Mechanism
Translation direction:                       < 1.55 m
Perpendicular direction:                     < 14 m
Along optical axis:                          < 22 m
Tilt perpendicular to slit:                  < 0.4 mrad
Rotation about optical axis:                 < 0.07 mrad
Tilt about slit axis:                        < 0.6 mrad
Slit to Detector mapping: the slit can be positioned on the detector to ~1 pixel perpendicular to the slit.


3.1.6    Mechanical Installation Tolerances for the IFU
The IFU’s installation tolerances relative to optical axis (at 60 K) are:
Perpendicular to slit:                        125 m
Along slit:                                   20 m
Along optical axis:                           50 m
Rotation about optical axis:                  2.0 mrad
Rotation about axis along slit:               1.0 mrad
Rotation about axis perpendicular to slit:    0.4 mrad


Adjustments:
Adjustment of IFU Module relative to the slit slide: In order to meet the specified installation
tolerances, the IFU will be aligned during installation inside the instrument. This will be achieved by
introducing shims at the three mounting points. Installation and alignment of the IFU inside the GNIRS
Instrument will be the responsibility of NOAO with Durham providing assistance.
Durham may provide additional adjustments internal to the IFU optical assembly.
No adhesive bonds are to be used in attaching or adjusting the IFU optical assembly to the slide.
The repeatability of positioning of the IFU optical assembly that will be provided by the slide
mechanism is specified in Section 3.1.5.
No additional adjustment of the IFU optical assembly will be required once the IFU has been installed
and aligned in the instrument.



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                                GNIRS IFU INTERFACE CONTROL DOCUMENT



The IFU optical assembly will be installed and removed on the slit slide, which can be installed and
removed from its mechanism while installed in the instrument.


Installation and Removal:
Two methods for installing and removing the IFU modules are provided.
1. Initial installation can be done into the slide before the slide mechanism is assembled into the
   instrument.
2. Following integration of the slide mechanism into the instrument, the IFU modules (as well as the
   standard slits) can be accessed by driving the slide to its limits and removing an access cover on
   the bench. This provides access to the front face of the slide, including the mounting screws for
   the IFU modules.


3.1.7    IFU Stability with respect to the GNIRS Optical Axis
Total flexure excursion for the slit/decker slide assembly is  3.1 m in any axis for  90 degree
rotation of the gravity vector ( 1 g) (in angle).
Observation flexure excursion is 0.8 m for 15 degree rotation of the gravity vector (largest possible
excursion during a 1-hour observation).
Flexure for IFU module has been assessed by means of a finite element analysis. The results of this
analysis are presented in the CDR Documentation.
Observation flexure excursion (IFU to slit slide) of 0.5 m for a 15 degree rotation of the gravity vector
(largest possible excursion during a 1-hour observation).


3.2 ELECTRICAL INTERFACES
There are no electrical interfaces to the IFU.


3.3 THERMAL INTERFACES
The IFU modules will be cooled through the 3-point interface to approximately 60 K by conduction.
The IFU modules will not be provided with heater resistors for warm-up.


3.4 OPTICAL INTERFACES


3.4.1    Input
Axial position: The input focal plane of the IFU will be coincident with the output focal plane of the
Offner relay, which is the plane of the slit. The assembly errors of the IFU to the slide are summarised
in Section 3.1.6. It should be understood that the detector focus mechanism can be used to correct for
small focus errors, but will not correct for any additional effects, such as astigmatism. The GNIRS
collimator will be adjusted for optimum focus on the GNIRS slit mask.
Angular position: The input of the IFU will be parallel with the optical axis of the GNIRS as defined at
the slit centre. The tolerances are equal to the installation tolerances of the IFU relative to the optical
axis (see Section 3.1.6).
Input operational offsets: Operational offsets in X and Y for the input beam will be provided by
Durham.




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                                GNIRS IFU INTERFACE CONTROL DOCUMENT




3.4.2    Output
Axial position: Operation of the IFU will not require a change in GNIRS detector focus greater than 1
mm.
Angular position: The output of the IFU will be parallel with the GNIRS optical axis. The IFU will be
installed in such a way that the output beam is not vignetted by the spectrograph pupil stop.
Output operational offsets: Durham will provide operational offsets in X and Y for the output beam.


3.4.3    Baffling, Vignetting and Stray Light Control
There will be no direct path through the IFU for stray light.
All IFU surfaces exposed to the optical beam will be made “black” between 1 to 2.5 m wavelengths
via anodising or other surface coating (surface coating TBD, to be provided by Durham). Any coating
used should not pose a risk of contamination to drive mechanisms, optics, or the detectors.
Durham is responsible for baffle design and evaluation of the stray light performance of the IFU
modules. This evaluation should assume that no significant amount of light can enter the module
except through the decker aperture, as defined in 3.2.3, and that the only exit from the module is
through the slot in the slit slide cover plate (AD 2.2.1).
The input and output of the IFU, including offsets will be compatible with the GNIRS baffles. This
means that the input and output beams must fall within the footprint defined by the GNIRS acquisition
field (AD 2.2.1).


4. SOFTWARE
Durham will provide information on the approximate positions of the GNIRS mechanisms that are
required for operation of the IFU. Specifically, this would comprise mechanical offsets of the slit and
decker mechanisms, as well as grating tilt or focus adjustments (if any).


5. OPTICAL ALIGNMENT OF THE IFU MODULES WITHIN GNIRS
Alignment tolerances: the IFU modules will require alignment beyond installation to the datums, which
will be implemented though shimming at the three interface points (see Section 3.1.6). Durham will
assist NOAO during this process.
Alignment procedure: no alignment procedure is required.
Any procedure(s) for required verification of alignment during assembly, integration, and test shall be
developed jointly by Durham and NOAO.




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