INTEGRAL FIELD UNIT REVIEW
March 9, 1999
INTEGRAL FIELD UNIT REVIEW
March 9, 1999
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Introductory remarks |
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Current GNIRS Status
Overview of repackaging New Layout Overview of slit/decker mechanism design |
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Current IFU status
Slicer work Optical design work |
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Interface Issues
Envelope growth Which direction benefits design? How much is feasible? Goal: agree on new envelope limits |
(Durham)
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Lunch | |
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Interface Issues
Positioning tolerances Can IFU live with slit mechanism tolerances? If not, are there viable alternatives? Goal: agree on mechanism performance Alignment & Test Outline alignment and test procedure What are tolerances for alignment to instrument? What information (if any) is missing? What test fixtures/equipment needed? Goal: specify opto-mechanical tolerance on interface Schedule
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(Durham) (Durham)
(NOAO)
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Action Items
What do we need to work on tomorrow (10th)? What information does Durham need to take away? |
GNIRS INTEGRAL FIELD UNIT INTERFACE
CONTROL DOCUMENT
10 March, 1999
Draft Version 2.0
Issued by: GNIRS Project Group
1.0 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.
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.
2.0 Applicable Documents and Drawings (as of 3/10/99)
2.1 GNIRS Optical Design: 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; Min.g Liang, 26 Aug. 98 (NOAO) . Includes glass tables and clear
apertures
2.2 Drawing of collimator mirror.
Documents not currently included:
2.3 Packaging of the Optics, Woon-Yin Wong, 3/27/97
(NOAO)
2.4 The Tolerance Analysis for GNIRS (Error budget),
Ming Liang, 11/9/97 (NOAO)
2.5 Revised Notes on the Alignment of the Gemini
Near-Infrared Spectrograph (Draft), Daniel Vukobratovich, 21 April
1998 (NOAO)
2.6 GNIRS Drawings:
2.7 IFU Drawings
2.8 Notes on GNIRS IFU Discussions (16th – 18th February
1998), Version 2, D.J. Robertson (Durham)
2.9 GNIRS IFU PDR Report (provisional)
3.0 Interfaces
3.1 GNIRS coordinate system (Ref: Packaging of the
Optics, Woon-Yin Wong, 3/27/97)
The location of the optical
axis and acquisition field are shown on the slit slide interface drawing.
Drawings are defined at
room temperature.
3.1.1 Center: At vertex
of optical entrance window
3.1.2 Z axis: Centered
on optical entrance window, positive in direction away from ISS and into
instrument
3.1.3 X axis: Perpendicular
to Z axis, parallel to Offner assembly optical axis, positive in direction
towards Offner
3.1.4 Y axis: Perpendicular
to Z axis, positive in direction towards double fold mirror
3.2 Mechanical Interfaces
3.2.1 General mechanical
interfaces
3.2.1.1 IFU materials
3.2.1.1.1 Vacuum compatibility: All IFU materials are to be compatible
with vacuum operation at 10-6 torr.
This is to include all material used for stray light control within the
IFU.
3.2.1.1.2 Cryogenic compatibility: All IFU materials are to be compatible
with operation at a temperature of 65 K.
3.2.1.2 Fasteners
3.2.1.2.1 All IFU fasteners are to be provided with vents, weep holes,
or other means of minimizing trapped gases
during evacuation
3.2.1.2.2 All IFU fasteners are to be made of a corrosion resistant material
to minimize outgassing in vacuum
3.2.1.2.3 Metric standard fasteners are to be used throughout the IFU
3.2.1.3 All interface dimensions given in SI (metric) units; soft conversion
used for GNIRS documentation. (Drawing
conversion by NOAO)
3.2.2 Slit Mechanism (Slide)
3.2.2.1 The IFU optical assemblies must fit within the envelopes allocated
on the slit mechanism slide
(Ref. DWG. No. XXXXXXXX).
3.2.2.2 The weight of each optical assembly module shall be <1 kg [TBD]
3.2.2.3 The IFU optical assembly is attached to the slide using a 3-point
mount plus a reference edge (datum) on the
edge of the slide. (Ref DWG. No XXXXX). The mounting surfaces will be bare
aluminum; other surfaces will be
NOAO standard black anodize.
3.2.2.4 The interfaces to the two IFU assemblies are assumed to be identical;
this is not an absolute requirement.
3.2.2.5 Adjustments:
3.2.2.5.1 Adjustment of IFU optical assembly relative to slide: in principle,
no alignment should be required.
However, if it is necessary to introduce shims at the three mounting points,
Durham shall provide the necessary
flexures and/or shims at the module attachment points.
3.2.2.5.2 Durham may provide additional adjustments internal to the IFU
optical assembly.
3.2.2.5.3 No adhesive bonds are to used in attaching or adjusting the IFU
optical assembly to the slide.
3.2.2.5.4 The repeatability of positioning of the IFU optical assembly
is specified by the requirements of SDN0002.
3.2.2.6 No adjustment of the IFU optical assembly will be required while
the IFU is installed in the instrument.
3.2.2.7 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.
3.2.3 Decker Mechanism (Slide)
3.2.3.1 Two decker positions will be provided in the GNIRS decker slide
for the two IFU modules. The locations of
the decker positions are indicated on DWG YYYYYY. The decker holes will
be sized to accommodate a field of
view of 0.9 x 1.1 arcsec and 3.5 x 5.5 arcsec for the “fine” and “coarse”
IFU modules, respectively. (UDurham,
will update these values by 5/28/99).
3.2.3.2 Adjustment
3.2.3.2.1 No adjustments to decker positions are provided.
3.2.3.2.2 Positioning of the decker in the translation direction is repeatable
to an accuracy of 1 ?m or better.
3.2.4 Mechanical repeatability
of the slit mechanism
3.2.4.1 Translation direction: 1.55 ?m
3.2.4.2 Perpendicular direction: 14 ?m
3.2.4.3 Along optical axis: 22 ?m
3.2.4.4 Tilt perpendicular to slit: 0.6 mrad
3.2.4.5 Rotation about optical axis: 0.07 mrad
3.2.4.6 Tilt about slit axis: 0.6 mrad [consult with Larry G.]
3.2.5 IFU stability with
respect to the GNIRS optical axis
3.2.5.1 Total flexure excursion for the slit/decker wheel assembly is +/-
3.1 microns in any axis for +/- 90 degree
rotation of the gravity vector (+/- 1 g) [TBD] [in angle]
3.2.5.2 Observation flexure excursion is 0.8 microns for 15 degree rotation
of the gravity vector (largest possible
excursion during a 1-hour observation)
3.2.5.3 Flexure for IFU module is TBD
3.2.6 Mechanical installation
tolerances for the IFU
3.2.6.1 Slit/decker wheel assembly tolerances relative to optical axis
(at 65 K):
3.2.6.1.1 Perpendicular to slit: +/- 125 microns {TBD]
3.2.6.1.2 Along slit: +/- 25 microns [TBD]
3.2.6.1.3 Along optical axis: +/- 25 microns [TBD]
3.2.6.1.4 Tilt errors? [TBD]
Slit to Detector mapping: the slit can be positioned on the detector
to +/- 10 pixels [unless it can be jogged – TBD].
3.3 Electrical Interfaces – there are no electrical interfaces to the IFU
3.4 Thermal Interfaces
3.4.1 The IFU modules will
be cooled through the 3-point interface to 65 K by conduction.
3.4.2 The IFU modules will
not be provided with heater resistors for warm-up
3.5 Optical interfaces
3.5.1 Input:
3.5.1.1 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. (Field curvature effects: use plane
defined by center of field)(Tolerance TBD,
supplied by Durham)
3.5.1.2 Angular position: The input of the IFU will be parallel with the
optical axis of the GNIRS as defined at the slit
center (Tolerance TBD, supplied by Durham).
3.5.1.3 Input operational offsets: Operational offsets in X and Y for the
input beam will be provided by Durham.
3.5.2 Output
3.5.2.1 Axial position: Operation of the IFU will not require a change
in GNIRS focus greater than TBD.
3.5.2.2 Angular position: The output of the IFU will be parallel with the
GNIRS optical axis (Tolerance TBD, supplied
by Durham)
3.5.2.3 Output operational offsets: Durham will provide operational offsets
in X and Y for the output beam.
3.5.3 Baffling and stray
light control
3.5.3.1 There will be no direct path through the IFU for stray light
3.5.3.2 All IFU surfaces exposed to the optical beam will be made “black”
between 1 to 2.5 micron wavelengths via
anodizing or other surface coating (surface coating TBD, to be provided
by Durham)
3.5.3.3 The input and output of the IFU will be compatible with the GNIRS
baffles (Baffle configuration TBD, to be
supplied by NOAO)
4.0 Software
4.1 Durham will provide information on the positions
of the GNIRS mechanisms that are required for operation of the IFU.
4.2 No additional software will be provided by NOAO
or Durham for IFU operation.
5.0 Optical Alignment of the IFU Modules within GNIRS
5.1 Alignment tolerances: the IFU modules should not require alignment beyond installation to the datums.
5.2 Alignment procedure: no alignment procedure is required
5.3 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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