AUSTRALIAN NATIONAL UNIVERSITY

System Design Note 3.02

Created: 19 February 2001

Last modified: 26 March 2001

FUNCTIONAL AND PERFORMANCE REQUIREMENTS DOCUMENT

Jan van Harmelen

Research School of Astronomy and Astrophysics

Institute of Advanced Studies

Australian National University

Revision History

Revision No.	Author & Date	Approval & Date	Description
Revision 1	Jan van Harmelen 01 October 1999	Peter J. McGregor 14 October 1999	Original document.
Revision 2	Jan van Harmelen 13 February 2000	Peter J. McGregor 13 February 2000	Initial FPRD
Revision 3	Peter McGregor 04 April 2000		Reformatted for Word 2000.
Revision 4	Jan van Harmelen 09 January 2001	Peter J. McGregor 19 February 2001	Updated for CDR
Revision 5	Jan van Harmelen 27 March 2001	Peter J. McGregor 27 March 2001	Update of Requirements Tabulation

Contents

1 Purpose. 7

2 Applicable Documents. 7

3 Introduction. 8

4 Optical Requirements. 9

4.1 Science Requirements. 9

4.1.1 ALTAIR. 9

4.1.2 Wavelength Coverage. 9

4.1.3 Spatial Resolution. 9

4.1.4 Field-of-View.. 9

4.1.5 Spectral Resolution. 9

4.1.6 System Sensitivity. 9

4.1.7 Scattered Light Level 9

4.1.8 Ghost Images. 9

4.1.9 Contrast Ratio. 9

4.1.10 Polarimetry. 9

4.1.11 OIWFS. 9

4.1.12 Calibration. 10

4.2 Image Quality and Optical Tolerances. 10

4.2.1 Strehl Ratio. 10

4.3.2 OIWFS Wavelength Sensitivity. 11

4.3.3 OIWFS Focus. 11

4.4 Baffling. 11

4.4.1 Optical Baffling. 11

4.5 Internal Instrument Background. 11

4.5.1 System Emissivity. 11

4.5.2 Background due to Dust on Entrance Window.. 11

4.6 Throughput 11

4.6.1 System Efficiency. 11

4.6.2 Vignetting. 12

4.6.3 Order Sorting Filters. 12

4.7 General Optical Requirements. 12

4.7.1 Cold Stop. 12

4.7.2 Coatings. 12

4.7.3 Vacuum Environment 12

4.7.4 Thermal Cycling. 12

5 Detector Requirements. 13

5.1 Science Detector Performance Requirements. 13

5.1.1 Detector Read Noise. 13

5.1.2 Dark Current 13

5.1.3 Stability. 13

5.2 Science Detector Requirements. 13

5.2.1 Detector Format 13

5.2.2 Characteristics. 13

5.2.3 Mechanical Interface. 13

5.2.4 Thermal Interface. 14

5.2.5 Optical Interface. 14

5.2.6 Electrical Interface. 14

5.3 Science Detector Controller. 14

5.3.1 Mechanical Interface. 14

5.3.2 Thermal Interface. 14

5.4 OIWFS Detector. 14

5.4.1 Optical Interface. 14

5.4.2 Electrical Interface. 14

5.5 OIWFS Detector Controller. 14

5.5.1 Mechanical Interface. 14

5.5.2 Thermal Interface. 14

6 Mechanical Requirements. 16

6.1 Rigidity. 16

6.1.1 Alignment of the Instrument to the Telescope Optics. 16

6.1.2 Movement of Spectra on the Detector. 16

6.1.3 Tracking with the OIWFS. 16

6.2 Mechanical and Thermal Tolerances. 16

6.3 Thermal Performance. 16

6.3.1 Temperature Gradients. 16

6.3.2 Thermal Transients. 16

6.4 Space Requirements. 16

6.4.1 Electronic Enclosures. 16

6.4.2 Access to Electronic Enclosures. 16

6.4.3 Access to Vacuum Ports. 16

6.4.4 Access to Cooling Water Ports. 17

6.4.5 Access to Dry Air Ports. 17

6.4.6 Mechanical Connections. 17

6.5 Mass and Center of Gravity Requirements. 17

6.5.1 Total Mass. 17

6.5.2 Center of Gravity. 17

6.5.3 Balance Tolerance. 17

6.5.4 Ballast Weight 17

6.6 Cryogenic Cooling System.. 17

6.6.1 Cool Down Time. 17

6.6.2 Warm Up Time. 17

6.6.3 Thermal Stability. 18

6.6.4 Vibration. 18

6.7 Vacuum System.. 18

6.7.1 Staging and Holding Areas. 18

6.7.2 Vacuum Pump Capacity and Selection. 18

6.7.3 Operating Procedure and Set-Up. 18

6.7.4 Test Set-Up. 18

6.8 Operational Requirements for Mechanisms. 18

6.8.1 Safety. 18

6.8.2 Time to Function. 18

6.8.3 Repeatability of Configuration. 18

6.9 Instrument Handling. 18

6.10 Metric Dimensioning. 19

6.10.1 Metric Dimensions on Drawings. 19

6.10.2 Metric Fasteners. 19

7 Control System Requirements. 20

7.1 Operability. 20

7.2 Configuration Time. 20

7.3 General Control System Requirements. 20

7.3.1 Impact on Mechanism Accuracy. 20

7.3.2 Impact on Scientific Performance. 20

7.4 Temperature Control 20

7.4.1 Detector Temperature. 20

7.4.2 Optical Elements Temperature. 20

7.4.3 Limiting Rate of Temperature Change. 20

7.4.4 Speeding the Warming Up. 20

8 Electrical and Electronic Requirements. 21

8.1 Electronic Design Requirements. 21

8.1.1 Grounding and Shielding. 21

8.1.2 Electrostatic Discharge. 21

8.1.3 Power Dissipation. 21

8.2 Cassegrain Cable Wrap Interfaces. 21

8.3 Temperature Monitoring. 21

8.3.1 Temperature Sensor Locations. 21

8.3.2 Temperature Sensor Interfaces. 22

9 Software Requirements. 23

9.1 Software Design Requirements. 23

9.1.1 Use of EPICS. 23

9.1.2 EPICS System.. 23

9.1.3 Use of the Core Instrument Controller Software Package. 23

9.1.4 Interfaces to the Gemini System.. 23

9.2 Gemini Furnished Software. 23

9.3 Engineering Interface. 24

9.3.1 Physical Interface. 24

9.3.2 User Interface. 24

9.3.3 Command and Control 24

9.3.4 Data Capture. 24

9.4 Data Processing. 24

10 NIFS Specific Requirements on Gemini Systems. 26

10.1 Observatory Control System.. 26

11 External Interfaces. 27

11.1 Cassegrain Rotator Interfaces. 27

11.1.1 Instrument Support Structure Interface. 27

11.1.2 Helium Interface. 27

11.1.3 Electric Power Interface. 28

11.1.4 Cooling Water Interface. 28

11.1.5 Signal, Control, and Data Interfaces. 29

11.1.6 Vacuum Interfaces. 30

11.1.7 Dry Air Interface. 30

11.2 Control Systems Interfaces. 31

11.2.1 Observatory Control System to NIFS Instrument Sequencer. 31

11.2.2 Observatory Control System to NIFS Components Controller. 31

11.2.3 Observatory Control System to NIFS Detector Controller. 31

11.2.4 Acquisition and Guidance Unit to NIFS OIWFS Components Controller. 31

11.2.5 Acquisition and Guidance Unit to NIFS OIWFS Detector. 32

11.2.6 Data Handling System Interface. 32

11.2.7 Interlock System Interface. 32

11.2.8 Events Bus Interface. 32

11.2.9 Synchro Bus Interface. 32

11.2.10 Time LAN Interface. 33

12 Environmental Requirements. 34

12.1 Altitude Environment 34

12.1.1 Transportation Altitudes. 34

12.1.2 Storage Altitudes. 34

12.1.3 Operation Altitudes. 34

12.2 Temperature Environment 34

12.2.1 Operational Environment 34

12.2.2 Survival Environment 34

12.2.3 Transport Environment 34

12.3 Humidity Environment 34

12.4 Vacuum Environment 34

12.4.1 Creating the Vacuum.. 34

12.4.2 Vacuum Quality and Duration. 35

12.5 Mechanical Environment 35

12.5.1 Telescope Slew Rates. 35

13 Other Requirements. 36

13.1 Documentation. 36

13.1.1 User’s Manual 36

13.1.2 Service and Calibration Manual 36

13.1.3 Software Maintenance Manual 36

13.1.4 As-Built Drawings. 36

13.1.5 Drawing Standards. 36

13.1.6 Drawing Numbering System.. 36

13.1.7 Drawing Filing System.. 36

13.3.3 Continuous Duty. 37

13.4 Maintainability and Serviceability. 37

13.4.1 Standard Components. 37

13.4.2 Modularity. 37

13.4.3 Access. 37

13.4.4 Alignment 37

13.4.5 Relative Equipment Arrangements. 37

13.4.6 Subassemblies. 37

13.4.7 Handling. 37

13.4.8 Revisability. 37

13.5 Lifetime. 38

13.6 Materials. 38

13.6.1 Toxic Products and Formulations. 38

13.7 Electromagnetic Radiation. 38

13.7.1 Electromagnetic Radiation Generation. 38

13.7.2 Susceptibility to Electromagnetic Radiation. 38

13.8 Workmanship. 38

13.9 Safety. 38

13.10 Human Engineering. 38

14 Appendices. 39

14.1 List of Acronyms. 39

14.2 Requirements Tabulation. 40

1 Purpose

The Gemini Near-infrared Integral Field Spectrograph (NIFS) Operational Concept Definition Document (OCDD; SDN0003.01) defines the scientific requirements of the NIFS instrument and describes operational scenarios. These are translated into technical requirements in the NIFS Functional and Performance Requirements Document (FPRD). Other technical requirements for Gemini facility instruments derive from the NIFS Conceptual Design Study Statement of Work. The scientific and technical requirements are summarized in this FPRD, and their relationships are identified so that all functional and performance requirements can be traced from top-level science requirements.

The two purposes of the NIFS FPRD are to provide the Gemini scientific community with an understanding of what NIFS will do and how quickly or how well it will do it, and to provide engineers with the requirements on which to base the NIFS design. The design is derived from this document. This document takes precedence over other design and fabrication documents. The design must serve the requirements in this document completely. Every feature of NIFS should be traceable to a requirement in this document, and there should be no features of NIFS that are not required by this document.

NIFS will be designed in stages, with a review after each stage is complete. Comments from the review committee will be folded into the design, so the requirements will change as the design changes. Therefore, this document will be updated as needed after each major design review to maintain the correspondence between requirements and design. This current version reflects the status at the Critical Design Review.

2 Applicable Documents

Document ID	Source	Title
GEM00196A	IGPO	NIFS CoDR Statement of Work
GEM00234A	IGPO	NIFS Statement of Work
SDN0003.01	RSAA	NIFS Operational Concept Definition Document
SPE-C-G0037	IGPO	Gemini Software Design Description
RPT-O-G0047	IGPO	Gemini Telescopes f/16 Optical Design Summary
ICD 1.1.1/1.9	IGPO	Telescope Structure, Drives, and Brakes to Science Instruments ICD
ICD 1.1.11/1.9	IGPO	Telescope Control to Science Instruments ICD
ICD 1.1.13/1.9	IGPO	Interlock System to Science Instruments ICD
ICD 1.5.3	IGPO	Instrument Support Structure IDC
ICD 1.5.3/1.9	IGPO	Instrument Support Structure to Science Instruments ICD
ICD 1.9/3.2	IGPO	Science Instruments to Data Handling ICD
ICD 1.9/3.6	IGPO	Science Instruments to System Services ICD
ICD 1.9.4	IGPO	Instrument Components Controller ICD
ICD 1.9.5	IGPO	Instrument Sequencer ICD
ICD 1.10	IGPO	On-Instrument Wavefront Sensor ICD
ICD 1.10.1	IGPO	OIWFS Feed Optics System ICD
ICD 1.10.2	IGPO	OIWFS Camera/Controller ICD
SPE-S-G0041	IGPO	Gemini System Error Budget Plan
SPE-ASA-G0008	IGPO	Gemini Electronic Design Specification
	AT&T Bell Laboratories, 1988	Ott, H. W., Noise Reduction Techniques in Electronic Systems, Second Edition

3 Introduction

This document represents the current understanding of the capabilities and performance of the Near-infrared Integral Field Spectrograph to be designed, fabricated, tested, delivered, and commissioned by the Australian National University for use on the Gemini 8-m telescopes.

The Gemini 8-m telescopes are designed to achieve unprecedented image quality using adaptive optics techniques. Diffraction-limited images have been demonstrated at 2.2 mm and should be achievable over most of the 1.0‑2.5 mm wavelength range in good observing conditions. A near diffraction-limited, moderate spectral resolution, near-infrared, integral-field spectrograph has been identified as a desirable complement to GNIRS in order to realize the scientific potential of both Gemini telescopes at high spatial resolution. NIFS is a fast-tracked instrument which is intended to provide this capability on the shortest possible timescale and at low cost.

NIFS is intended for use with ALTAIR, the facility adaptive optics system on Gemini North. NIFS uses a reflective integral-field unit (IFU) to divide its 3.0²´3.0² field of view on the sky into 29 slitlets each 0.103² wide and 3.0² long and simultaneously obtain spectra for each 0.04² pixel along each slitlet. Four fixed-angle reflection gratings will be used with a fixed focal length camera to obtain spectra with two-pixel resolving powers of R ~ 5300 in any one of the Z, J, H, or K bands. This spectral resolution is sufficient to work between the OH airglow emission-lines shortward of 2.2 mm, greatly reducing the detected sky background at these wavelengths. The velocity resolution of ~ 60 km s^‑1 is well-matched to minimum rotational velocities expected in galaxies at high redshift. The 0.1² slitlet width slightly under-samples the <0.06² spatial resolution in the wavelength range between 1.0 and 2.5 mm expected with ALTAIR in good observing conditions.

Several requirements listed in the following sections state that NIFS performance should be equal to, or better than, the performance achieved by NIRI. It was expected that by the time of the NIFS CDR the NIRI performance would have been characterized and hence the final NIFS requirements would have been formulated. Unfortunately, this is not the case and further amendment of the NIFS requirements will be needed when the NIRI performance is known.

4 Optical Requirements

4.1 Science Requirements

The optical requirements in this section flow directly from the science cases considered in the OCDD. They are defined in the OCDD and are repeated here. NIFS shall meet all science requirements listed below.

4.1.1 ALTAIR

REQ-OCD-0001: NIFS will be capable of operation with ALTAIR, the facility adaptive optics system.

4.1.2 Wavelength Coverage

REQ-OCD-0002: NIFS will meet the throughput requirement of REQ-OCD-0007 over the full 0.95‑2.5 mm region with > 50% atmospheric transmission from Mauna Kea.

4.1.3 Spatial Resolution

REQ-OCD-0003: NIFS will have slit widths of ~ 0.1² and a scale of ~ 0.04²/pixel in the spatial direction.

4.1.4 Field-of-View

REQ-OCD-0004: NIFS will have a field-of-view of ~ 3.0²´3.0² with distortion less than 1 pixel.

4.1.5 Spectral Resolution

REQ-OCD-0006: NIFS will deliver spectral resolving powers of ³ 5000 in each of the J, H, and K bands and ³ 4500 in the Z band

4.1.6 System Sensitivity

REQ-OCD-0021: NIFS should be capable of detecting extended sources with a K band surface brightness of 13.5 mag arcsec^‑2 and emission-line sources in the K band with a surface brightness of 1.5´10^‑22 W cm^‑2 arcsec^‑2 in 1800 s with a signal-to-noise ratio of 10 at 0.1²´0.1² spatial resolution.

4.1.7 Scattered Light Level

REQ-OCD-0009: The total amount of scattered light illuminating the science detector must be < 10% of the total amount of light entering the NIFS instrument within the science beam in the spectral bandpass of interest.

4.1.8 Ghost Images

REQ-OCD-0010: Ghost images generated in the NIFS optics must be at a level below 10^‑4 at radii > 2² from the parent image.

4.1.9 Contrast Ratio

REQ-OCD-0011: NIFS should be capable of accurately recording data at radii > 0.25² from point sources with K ³ 3 mag.

REQ-OCD-0022: NIFS should be capable of accurately recording data from point sources with K ³ 3 mag over its full field-of-view.

4.1.10 Polarimetry

REQ-OCD-0020: NIFS will have a K filter and wire grid analyzer in the Filter Wheel.

4.1.11 OIWFS

REQ-OCD-0014a: NIFS will have an OIWFS sensitive in the range 1‑2.5 mm for tip-tilt and focus correction.

REQ-OCD-0014b: The OIWFS field-of-view will have a diameter of ≥180² and should extend to within 15² of the science field center with no vignetting by the pick-off mirror.

REQ-OCD-0014c: The OIWFS should be capable of performing offsets of 0.05² with an accuracy of 0.005².

REQ-OCD-0014d: The OIWFS should have a positioning repeatability of 0.005².

REQ-OCD-0014e: The OIWFS should be able to determine the centroid of a star with K < 19 mag to an RMS accuracy of one tenth of the image full width at half maximum in a 10 s exposure and sense tip-tilt and focus corrections in 0.1 s exposures on stars with K < 15 mag.

4.1.12 Calibration

REQ-OCD-0019a: The Focal Plane Mask wheel will have one blocked position.

REQ-OCD-0019b: The Filter wheel will have one blocked position.

REQ-OCD-0019c: An array of slits will be supplied for calibration purposes in the Focal Plane Mask wheel.

REQ-OCD-0019d: NIFS will derive artificial calibration sources from the facility Gemini Calibration Unit.

4.2 Image Quality and Optical Tolerances

4.2.1 Strehl Ratio

REQ-OCD-0005: The total wavefront error introduced by the NIFS spectrograph optical system will be no greater than 120 nm rms over the wavelength range 0.95 - 2.5 microns. This corresponds to a Strehl ratio of >0.8 at a wavelength of 1.6 microns.

4.2.2 Alignment

REQ-FPR-0002: The ability to accurately align the instrument with the telescope is critical to minimizing background flux. A means of establishing alignment of the cold stop to within 1% of the projected size of the secondary mirror shall be provided.

Notes and Comments

1. This requirement does not necessarily lead to the inclusion of interactive alignment aids in the design. Off-telescope alignment, together with a verification test could suffice.

4.2.3 Focus

REQ-FPR-0003: To justify the omission of a focusing mechanism, analysis of the design must show that defocus resulting from wavelength change and the use of different filters will be less than the resolution of the instrument.

4.3 OIWFS

4.3.1 OIWFS Feed

REQ-FPR-0005: NIFS shall provide an optical feed inside the cryostat compatible with the operation of the On-Instrument Wavefront Sensor module for which the design is to be copied from NIRI.

4.3.2 OIWFS Wavelength Sensitivity

REQ-FPR-0008: The OIWFS beam shall contain as much of the energy from the telescope beam in the wavelength range of 1.0 to 2.5 mm as it is practical to provide.

REQ-FPR-0007: The OIWFS shall have interchangeable filters to be able to match its wavelength sensitivity to the bandpass selected for the NIFS spectrograph.

4.3.3 OIWFS Focus

REQ-FPR-0009: To justify the omission of the OIWFS focusing mechanism, analysis of the design must show that defocus resulting from wavelength change and the use of different filters will be less than the resolution of the OIWFS.

4.4 Baffling

NIFS shall provide baffling of ambient thermal radiation, radiation from field sources other than the scientific target and from stray radiation from the target, with the goal of minimizing the impact of such radiation on the detection of the scientific target.

4.4.1 Optical Baffling

REQ-FPR-0010: NIFS shall be baffled such that scattered light illuminating the science detector is less than 10% of the total amount of light entering the spectrograph within the spectral bandpass of interest.

4.5 Internal Instrument Background

4.5.1 System Emissivity

REQ-OCD-0008: NIFS shall have an internal instrument background less than either the natural background from the observed science field or the dark current of the detector, whichever is greater. At wavelengths of 2.2 mm and longer, the instrument effective emissivity should be below 1%. Instrument effective emissivity is the ratio of the internal instrument background, including emission and reflection of the entrance window, compared to that of an ambient temperature black body. At l < 1.9 mm the photon background should be less than one half the detector dark current at its nominal operating temperature.

4.5.2 Background due to Dust on Entrance Window

Although not strictly ‘internal’, the contribution to instrument background from ambient temperature dust on the NIFS entrance window can be significant.

4.5.2.1 Dust Cover

REQ-FPR-0012: NIFS shall be fitted with a dust cover, which is operated by the control system and can be operated manually in case of power failure.

REQ-FPR-0013: NIFS design shall include a dry air blowing dust removal system, which will also avoid condensation on the window.

4.6 Throughput

4.6.1 System Efficiency

REQ-OCD-0007: NIFS will have a total system throughput over its required wavelength range of ³ 15% including the telescope, blocking filter, grating, IFU, spectrograph, and detector, but not including the throughput of the ALTAIR science path.

4.6.2 Vignetting

REQ-FPR-0014: The vignetting effects unique to the diffraction limited nature of the NIFS optics shall be addressed in the design.

4.6.3 Order Sorting Filters

REQ-FPR-0015: NIFS shall have one order sorting filter for each grating. Order sorting filters will have an on-band transmission greater than 80%, and an off-band transmission less than 10^‑4.

4.7 General Optical Requirements

NIFS shall meet the general optical requirements listed below.

4.7.1 Cold Stop

REQ-FPR-0017: NIFS shall provide a cold stop at an image of the telescope pupil (the secondary mirror).

4.7.2 Coatings

REQ-FPR-0018: The characteristics of all optical coatings shall be specified in design documentation.

REQ-FPR-0019: All coatings shall be unaffected by repeated thermal cycling over the operating, storage, and transportation temperature ranges.

4.7.3 Vacuum Environment

REQ-FPR-0021: All optical components and coatings shall meet all performance requirements when operated in a vacuum of less than 10^‑5 Torr at operational temperatures down to 70 K.

4.7.4 Thermal Cycling

REQ-FPR-0022: The performance of all optical components and coatings shall not be degraded by repeated thermal cycling at a maximum rate of temperature change of 0.25 K/minute.

Notes and Comments:

1. The optical coating characteristics are expected to be the same as for NIRI. At the time of the CDR, the NIRI “as-built” information was not yet available.

5 Detector Requirements

The NIFS detector systems shall conform to the following requirements.

5.1 Science Detector Performance Requirements

5.1.1 Detector Read Noise

REQ-OCD-0012: NIFS should employ read noise reduction techniques, such as linear fitting up the ramp, to achieve an effective read noise of < 10 e.

5.1.2 Dark Current

REQ-OCD-0013: The NIFS detector should have a dark current < 0.1 e s^‑1 pix^‑1 with a goal of < 0.01 e s^‑1 pix^‑1.

5.1.3 Stability

5.1.3.1 Bias Variations

REQ-FPR-0100: Over a period equal to the longest integration time of 3600 s, bias variations shall be less than the read noise.

5.1.3.2 Gain Variations

REQ-FPR-0101: Over a period equal to the longest integration time of 3600 s, gain variations shall be less than the photometric stability of the atmosphere, which is taken to be 1%.

5.2 Science Detector Requirements

5.2.1 Detector Format

REQ-FPR-0102: NIFS shall be designed to use a HgCdTe/Sapphire or HgCdTe/CdZnTe science detector array with a format of 2048´2048, with 18 mm square pixels.

5.2.2 Characteristics

REQ-FPR-0104: The NIFS shall be designed to take the fullest possible advantage of an HAWAII-2 HgCdTe detector with the following characteristics:

a) Number of pixels: 2048 (H) ´ 2048 (V).

b) Architecture: 4 independent 1024´1024 quadrants.

c) Pixel size: 18 mm, square.

d) Effective fill factor: 90%.

e) Maximum frame rate: 1 frames/second.

f) IR material: HgCdTe.

g) Full well: 60,000 electrons at 0.5 V bias.

h) Wavelength range: 0.9-2.5 mm.

i) Nominal operating temperature: 77 K.

j) Dark current: <1 electron/second, goal 0.01 electron/second.

k) Read noise: <15 electrons (rms), goal 5 electrons (rms).

l) Quantum efficiency: >50% (0.9-2.5 mm).

5.2.3 Mechanical Interface

REQ-FPR-0115: The detector shall be mounted such that, once adjusted, it can be removed and reinstalled without necessitating optical realignment.

5.2.4 Thermal Interface

REQ-FPR-0116: The science array will be thermally coupled to the cold head by high thermal conductivity material. The detector shall be actively maintained at operating temperature by an electric heating element.

5.2.5 Optical Interface

REQ-FPR-0117: Convenient means will be provided to measure the science detector defocus error under operational conditions, and then adjust the position of the science detector with a precision which is finer than that corresponding to the resolution of the instrument.

5.2.6 Electrical Interface

REQ-FPR-0118: The electrical interface to the detector is through a suitable socket.

5.3 Science Detector Controller

REQ-FPR-0119: NIFS will use an SDSU-2 controller as the science detector controller.

5.3.1 Mechanical Interface

REQ-FPR-0120: The controller shall be mounted on an external wall of the cryostat. The controller power supply shall preferably be mounted in one of the electronics enclosures.

5.3.2 Thermal Interface

REQ-FPR-0121: The controller and its power supply (if not mounted in a thermal cabinet) shall be actively cooled with the coolant supplied via the Cassegrain Rotator Utilities Box.

Notes and Comments

1. Cooling by heat sinking into the NIFS vacuum jacket is permitted, but the requirement of REQ-FPR-0121 is to be preferred.

5.4 OIWFS Detector

REQ-FPR-0122: The NIFS OIWFS detector will be of the same type as that of NIRI, a HAWAII-1 1024´1024 array, or of a type of similar performance.

5.4.1 Optical Interface

REQ-FPR-0126: Convenient means will be provided to measure the defocus error of the OIWFS detector under operational conditions, and then adjust the position of the OIWFS detector (and its attached reimaging optics) with a precision which is finer than that corresponding to the resolution of the OIWFS.

5.4.2 Electrical Interface

REQ-FPR-0127: The electrical interface to the detector is through a suitable socket.

5.5 OIWFS Detector Controller

REQ-FPR-0123: NIFS will use an SDSU-2 controller as the OIWFS detector controller.

5.5.1 Mechanical Interface

REQ-FPR-0124: The controller shall be mounted on an external wall of the dewar. The controller power supply shall preferably be mounted in one of the electronics enclosures.

5.5.2 Thermal Interface

REQ-FPR-0125: The controller and its power supply (if not mounted in a thermal cabinet) shall be actively cooled with the coolant supplied via the Cassegrain Rotator Utilities Box.

Notes and Comments

1. Cooling by heat sinking into the NIFS vacuum jacket is permitted, but the requirement of REQ-FPR-0121 is to be preferred.

2. The OIWFS ICDs are:

· OIWFS (ICD 1.10)

· OIWFS Feed Optics System (ICD 1.10.1)

· OIWFS Camera/Controller (ICD 1.10.2)

6 Mechanical Requirements

6.1 Rigidity

NIFS shall be designed to be rigid, and to meet all the requirements listed below.

6.1.1 Alignment of the Instrument to the Telescope Optics

REQ-FPR-0200: The alignment of the NIFS cold stop with the secondary mirror shall be maintained to the accuracy specified in REQ-FPR-0002 in any attitude of the telescope and rotator.

6.1.2 Movement of Spectra on the Detector

REQ-FPR-0201: NIFS shall be designed so that flexure in the instrument shall result in the image of the spectra on the detector moving less than 0.1 pixel per any 15° attitude change of the instrument.

6.1.3 Tracking with the OIWFS

REQ-FPR-0202: Tracking performance when using the NIFS OIWFS shall result in less than 0.1 pixel tracking error per any 15° attitude change of the instrument.

6.2 Mechanical and Thermal Tolerances

REQ-FPR-0204: Where adequate mounting precision cannot be provided by dead reckoning, convenient means will be provided to measure the misalignment of optical components of the spectrograph under ambient conditions, and then adjust their alignment with a precision which allows the optical performance specification to be met. Where thermally induced misalignment is significant, theoretically derived compensation will be applied.

6.3 Thermal Performance

6.3.1 Temperature Gradients

REQ-FPR-0205: Thermal effects due to temperature gradients outside the dewar, inside the dewar, and near the detector shall be considered in the design of NIFS. Realistic limits will be set according to the NIRI performance. [TBD]

6.3.2 Thermal Transients

REQ-FPR-0206: Thermal transient effects during cool-down or warm-up shall be considered in the design of NIFS. Realistic limits will be set according to the NIRI performance. [TBD]

6.4 Space Requirements

REQ-FPR-0207: NIFS shall be designed to fulfill the space requirements for an instrument attached to the ISS.

6.4.1 Electronic Enclosures

REQ-FPR-0208: All NIFS electronic enclosures mounted on the ISS shall be counted in the space requirements given above.

6.4.2 Access to Electronic Enclosures

REQ-FPR-0209: The electronic enclosures shall be accessible without removing NIFS from the ISS.

6.4.3 Access to Vacuum Ports

REQ-FPR-0210: Vacuum ports on NIFS shall be accessible without removing the instrument from the ISS.

6.4.4 Access to Cooling Water Ports

REQ-FPR-0211: Cooling water ports on NIFS shall be accessible without removing the instrument from the ISS.

6.4.5 Access to Dry Air Ports

REQ-FPR-0212: Dry air ports on NIFS shall be accessible without removing the instrument from the ISS.

6.4.6 Mechanical Connections

REQ-FPR-0213: All mechanical connections on NIFS shall be accessible without removing the instrument from the ISS and while mounted with other instruments.

Notes and Comments

1. Space requirements are specified in ICD 1.1.1/1.9.

6.5 Mass and Center of Gravity Requirements

NIFS shall meet all mass and center of gravity requirements listed below.

6.5.1 Total Mass

REQ-FPR-0214: NIFS, including its support frame, thermal enclosures, electronics, and all cabling and services connections, shall have a mass of 2000 kg.

6.5.2 Center of Gravity

REQ-FPR-0215: NIFS, including its support frame, thermal enclosures, electronics, and all cabling and services connections, shall have a center of gravity on the port axis 1000 mm from the mechanical interface on the ISS.

6.5.3 Balance Tolerance

REQ-FPR-0216: In any orientation of the telescope and rotator, the out of balance caused by NIFS must not exceed 400 Nm with respect to the telescope elevation axis. This will include static imbalance and any change in mass moment due to moving elements.

6.5.4 Ballast Weight

REQ-FPR-0217: A ballast weight and its supporting structure shall be supplied as required to meet the above requirements.

Notes and Comments

1. Mass and center of gravity requirements are specified in ICD 1.5.3/1.9.

6.6 Cryogenic Cooling System

NIFS shall meet all cooling system requirements listed below.

6.6.1 Cool Down Time

REQ-FPR-0219: The NIFS cryogenic cooling system shall have the capability to cool the instrument from room temperature to operating conditions in TBD hours or less. Realistic limits will be set according to the NIRI performance.

6.6.2 Warm Up Time

REQ-FPR-0220: NIFS shall not require more than TBD hours to warm up the entire instrument from operating conditions to room temperature. Realistic limits will be set according to the NIRI performance.

6.6.3 Thermal Stability

REQ-FPR-0218: The surface on which the spectrograph optical system is mounted shall have an active temperature control system providing a variable temperature to be referenced to the center of the cold work surface between 65 K and 75 K with a stability of ±0.5 K.

REQ-FPR-0221: The NIFS detector assembly shall have an active temperature control system providing a variable temperature to be set at the optimum temperature for the detector between 60 K and 70 K, with a stability allowing it to meet the bias stability requirements of REQ-FPR-0100.

6.6.4 Vibration

REQ-FPR-0222: Adequate measures shall be taken to ensure that the use of cryogenic closed cycle coolers shall not introduce sufficient vibrations into the mechanical structure to prevent meeting all rigidity, alignment, tracking, and other performance requirements.

6.7 Vacuum System

6.7.1 Staging and Holding Areas

REQ-FPR-0223: NIFS will use the same vacuum system facilities in the staging and holding areas as NIRI.

6.7.2 Vacuum Pump Capacity and Selection

REQ-FPR-0224: NIFS will use the same vacuum pump as NIRI.

6.7.3 Operating Procedure and Set-Up

REQ-FPR-0225: NIFS will use the same vacuum system operating procedures and set-up as NIRI.

6.7.4 Test Set-Up

REQ-FPR-0226: The vacuum system test set-up for NIRI will also be used for NIFS.

6.8 Operational Requirements for Mechanisms

The NIFS mechanisms shall meet the requirements listed below.

6.8.1 Safety

REQ-FPR-0227: No mechanism shall move in the event of loss of electrical power.

6.8.2 Time to Function

REQ-OCD-0015: Individual NIFS mechanisms should be set within 30 s, and a complete reconfiguration of the instrument should be achieved in < 1 min.

6.8.3 Repeatability of Configuration

REQ-FPR-0231: The total error at the detector resulting from reconfiguration of all mechanisms shall be less than 0.5 pixel.

6.9 Instrument Handling

REQ-FPR-0232: The NIFS support frame shall have feet allowing the instrument to be stored free-standing, and attachment points for the Gemini instrument handling facilities.

6.10 Metric Dimensioning

REQ-FPR-0228: Metric dimensions shall be used in NIFS.

6.10.1 Metric Dimensions on Drawings

REQ-FPR-0229: Metric dimensions in millimeters shall be used in all as-built drawings, with dimensions called out to 0.01 mm.

6.10.2 Metric Fasteners

REQ-FPR-0230: All screws, bolts, nuts, tapped holes, and fasteners shall be of standard metric sizes, and called out as such on the as-built drawings.

7 Control System Requirements

NIFS shall meet all general control system requirements given below.

7.1 Operability

REQ-FPR-0300: Filter and grating change mechanisms, and other controllable features of NIFS shall be controllable by computer through the standard EPICS control paths from the Instrument Control System.

7.2 Configuration Time

REQ-FPR-0301: The control system overhead on the mechanism configuration times shall be such that the total NIFS configuration time is within the limit set by REQ-OCD-0015.

7.3 General Control System Requirements

7.3.1 Impact on Mechanism Accuracy

REQ-FPR-0302: The control system for NIFS shall be designed so that the accuracy of the controllable mechanisms is not limited by the performance of the control system.

7.3.2 Impact on Scientific Performance

REQ-FPR-0303: The control system shall not impact on the scientific performance of NIFS. In particular, attention shall be given to the impact of the control actuators and sensors on the thermal regime of the instrument, including their thermal radiation.

Notes and Comments

1. Besides being controllable from the ICS, the dust cover can be moved by hand, to permit closing it manually in the event of a loss of power to the instrument.