Purpose of This Document

Applicable Documents

Acronym List

100     Cassegrain Rotator Interfaces

    110     Instrument Support Structure Interface

    120     Helium Interface

    130     Electric Power Interface

    140     Cooling Water Interface

    150     Signal, Control, and Data Interfaces

    160     Liquid Nitrogen Interface

    170     Vacuum Interface
 
 

200     Control Systems Interfaces

    210     Observatory Control System Interface

    220     Telescope Control System Interface

    230     Engineering Interface

    240     Interlock Bus Interface

    250     Events Bus Interface

    260     Synchro Bus Interface

    270     Time LAN Interface

    280     reserved

    290     General Control System Requirements
 
 

300     Array and Array Controller Interfaces

    310     Science Detector Array Interface

    320     Science Array Controller Interface

    330     Data Handling System Interface

    340     OIWFS Detector Array Interface

    350     OIWFS Array Controller Interface

    360     Telescope Control System Interface
 
 

400     Environmental Requirements

    410     Altitude Environment

    420     Temperature Environment

    430     Humidity Environment

    440     Vacuum Environment

    450     Mechanical Environment
 
 

500     Optical Requirements

    510     Science Requirements

    520     Science Options

    530     Image Quality and Optical Tolerances

    540     OIWFS Feed

    550     Target Acquisition

    560     Baffling

    570     Internal Instrument Background

    580     Throughput

    590     General Optical Requirements
 
 

600     Mechanical Requirements

    610     Rigidity

    620     Tolerances

    630     Thermal Performance

    640     Space Requirements

    650     Mass and Center of Gravity Requirements

    660     Cooling System

    670     Vacuum System

    680     Mechanisms

    690     Instrument Handling

    6A0     Metric Dimensioning
 
 

700     Electrical and Electronic Requirements

    710     Electronic Design Requirements

    720     Cassegrain Cable Wrap Interfaces

    730     Temperature Monitoring

    740     Heat Dissipation
 

800     Software Requirements

    810     Software Design Requirements

    820     EPICS Compatibility

    830     Gemini Furnished Software
 

900     Other Requirements

    910     Documentation

    920     Training

    930     Reliability

    940     Maintainability and Serviceability

    950     Lifetime

    960     Safety
 
 

The purpose of the Functional and Performance Requirements (document) for the Gemini Near Infrared Spectrograph ("GNIRS FPRD") is to provide the Gemini scientific community with an understanding of what the GNIRS will do and how quickly or how well it will do it, and engineers with the requirements to use to design the GNIRS. This document answers the question "What?", but not the question "How?". The "How" is the design that is derived from, and traceable to, this document. That is, this document takes precedence over the design and fabrication documents.

The design must serve the requirements in this document completely. This means every feature of the GNIRS should be traceable to a requirement in this document, and there should be no features of the GNIRS that are not required by this document. The GNIRS 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 document was written using the Design Requirements (document) for the Gemini Near Infrared Spectrograph ("GNIRS DRD") as a guide. The GNIRS DRD contains more than engineering requirements, including a brief description of the science goals driving the requirements, suggestions of good design practice, and other information useful to the engineering team designing the GNIRS. The authors of the FPRD attempted to capture this information in the DRD and to cast it into engineering requirements that could be used to design the GNIRS. Upon approval by all parties named on the signature page, this document supersedes the DRD and defines the GNIRS capabilities and performance.
 
 

Controlling Documents. The following documents control the GNIRS design:

1. GNIRS Statement of Work

2. GNIRS Quality Assurance Plan, to be written

3. Critical Design for the Cassegrain Assembly, RPT-I-G0044, 6 June 94
 
 

Reference Documents. The following documents will be useful in the GNIRS design:

1. Gemini Software Design Description, SPE-C-G0037, 7 March 95

2. Gemini Instrumentation Control Document, ICD-G-0009, [Very Rough Draft], 20 July 94

3. Gemini System Error Budget Plan, SPE-S-G0041, Version 2.1, 1 February 94

4. Mountain, M., A Scientific Perspective on the Requirements for the 1- 5 m m Spectrograph, TN-PS-G0020, 1 July 94

5. Gemini Electronic Design Specification, SPE-ASA-G0008, 23 February 94

6. Gemini IR Array Controller Performance Requirements, 7 August 95

7. Fowler, et al., "Next Generation In InSb Arrays: ALADDIN 1024 x 1024 InSb Focal Plane Array Development Project Status Report", SPIE Volume 2198, pp. 623- 629, 13-14 March, 1994

8. Ott, Henry W., Noise Reduction Techniques in Electronic Systems, Second Edition, AT&T Bell Laboratories, 1988

9. Gemini ICD 07a, ICS Subsystem Interfaces, 22 February 95

AO                 Adaptive Optics

CICS              Core Instrument Control System

DHS              Data Handling System

EPICS          Experimental Physics and Industrial Control System

GNIRS         Gemini Near Infrared Spectrograph

ICD              Interface Control Document

ICS              Instrument Control System

IGPO          International Gemini Project Office ("Gemini" or "the Project")

IOC             Input/Output Controller

ISS             Instrument Support Structure (the "cube")

OIWFS     On Instrument Wavefront Sensor

OCS          Observatory Control System

TCS         Telescope Control System

USGP      United States Gemini Program
 
 
 

100     Cassegrain Rotator Interfaces
 

        110     Instrument Support Structure Interface

        The GNIRS shall interface mechanically to the Gemini Instrument Support Structure (ISS).

       111     Ports

        The GNIRS shall be capable of being mounted on and used at any side-looking science instrument ISS port or the upward-looking port at the bottom of the ISS.

        112     Instrument Mounting Plate Flatness

        The GNIRS mounting interface shall be repeatable within the optical tolerances of the alignment between GNIRS and ISS when removed and replaced.

        113     Instrument Mounting Plate Material

        The GNIRS mounting interface shall take into account the material of which the ISS is made and shall hold differential temperature effects to a level that permits the GNIRS to meet all optical alignment requirements over the entire operating temperature range.

       114     Fasteners

        The fasteners that are engaged for load transfer from the Cassegrain handling rig shall be sized for a safe working load that includes a static and dynamic factor of safety to accommodate predicted loads on the Gemini telescope.

        115     Optical Feed

        The GNIRS shall accept and use the Gemini telescope optical feed, which is approximately f/16 with a focal length of 128 meters. The beam comes to a focus 300 mm from the ISS mounting surface inside the GNIRS.

1. The ISS to Science Instrument ICD is 1.5.3/1.9. The 1.5.3 ISS Introductory ICD is also relevant.

2. Fastener design must accommodate the changing direction of the gravity vector due to rotation of the ISS and positioning of the telescope.

3. The largest field of view of the GNIRS is 3 arc-min. in diameter. Due to the weak power of the entrance window, the effective f-number of the telescope inside the dewar is stronger than specified above.

4. Telescope focal length is given in Gemini Telescopes f/16 Design Summary, RPT-0-G0047, 6 July 1994.
 
 
 
 
 
 

120 Helium Interface

The GNIRS shall obtain helium for its cryocoolers and return low-pressure helium through the connectors provided in the Cassegrain Rotator Utility Box appropriate to each instrument port. The helium interface is described in ICD 1.9/3.7.

       121     Number of Helium Connections

        The GNIRS shall have one high pressure connection for the entire instrument, and one low pressure return for the entire instrument. Each of these lines shall have appropriate tees on the instrument to service the cryocooler heads.

       122     Length of Helium Line Runs

        The high and low pressure lines to the Cassegrain Rotator Utility Box shall be of a length that permits the GNIRS to meet Requirement 111. If good design practice dictates, coupling hoses of different lengths shall be supplied for mounting the GNIRS on different ISS ports.

       123     Helium Line Flexibility

        The high and low pressure lines to the Cassegrain Rotator Utility Box shall be flexible enough to permit easy routing, connection, disconnection, and dressing for operation.

       124     Type of Helium Connectors

The high pressure line shall connect to the Cassegrain Rotator Utility Box using a connector described in ICD 1.9/3.7.
 
 

1. It is expected that Gemini will provide a helium supply of (TBD) liters/minute at a pressure of (TBD) units. The low pressure return line is expected to carry (TBD) liters/minute at a pressure of (TBD) units. All helium delivered to the GNIRS is expected to be 99.999% pure. It is expected that details of the helium supply will be added to ICD 1.9/3.7.

2. Details of the helium interface are expected to be obtained from the Quantum Study, due 29 February 1996.

130     Electric Power Interface

The GNIRS shall derive its electric power through the connectors provided on the Cassegrain Rotator Utility Box appropriate to each instrument port. The power interface is part of ICD 1.9/3.8, Science Instruments to System Cables.
 
 

        131     Number of Electrical Connections

        The GNIRS shall have two electric power connections for the entire instrument. One connection will provide "clean" power for the computer and electronics, while the other will provide "dirty" power for the cryo coolers and fans. The "dirty" connection should provide optional 220 V./3 phase power for the cryo coolers. The GNIRS shall have appropriate runs from a junction box to serve all instrument power needs. The ICD 1.5.2/1.9 describes cable wrap connector plates.

       132     Length of Electrical Line Runs

        The power line to the Cassegrain Rotator Utility Box shall be of a length that permits the GNIRS to meet Requirement 111. If good design practice dictates, a means of dressing the power cable to a length appropriate for different ports shall be provided.

       133     Electric Power Line Flexibility

        The electric power line to the Cassegrain Rotator Utility Box shall be flexible enough to permit easy routing, connection, disconnection, and dressing for operation.

       134     Type of Electrical Connectors

        AC power is provided to the science instrument via two, dual 3-prong, 120 VAC outlets (NEMA 5-15) mounted on the cable wrap interface plate. One outlet pair is UPS conditioned power and the other is building mains power. The cable connector at the interface to the instrument is a circular MIL-style connector, MS3106R16-10S. The corresponding instrument connector must be an MS3100R16-10P. AC voltage at both observatories will be 120 VAC. Line frequency for Cerro Pachon is 50 Hz, while the Mauna Kea frequency is the US standard 60 Hz.

1. Gemini will provide an electric power supply as given in ICD 1.9/3.8.

2. The GNIRS may require 220 to 260 volts AC, 60 Hz, 3 phase power for cryocooler operation. This type of power is not currently provided by the ISS.
 
 
 
 

140     Cooling Water Interface

The GNIRS shall derive cooling water supply (and return) for electronic enclosures and any other use through the connectors provided on the Cassegrain Rotator Utility Box appropriate to each instrument port.

       141     Number of Plumbing Connections

        The GNIRS shall have one cooling water supply connection and one return line connection for the entire instrument. The GNIRS shall have appropriate tees from these lines to serve all instrument cooling water needs.

       142     Length of Cooling Water Runs

        The cooling water lines to the Cassegrain Rotator Utility Box shall be of a length that permits the GNIRS to meet Requirement 111. If good design practice dictates, a means of dressing the cooling water lines to a length appropriate for different ports, or lines of different lengths for different ports, shall be provided.

       143     Cooling Water Line Flexibility

        The supply and return lines to the Cassegrain Rotator Utility Box shall be flexible enough to permit easy routing, connection, disconnection, and dressing for operation.

       144     Type of Plumbing Connectors

        The cooling water lines shall connect to the Cassegrain Rotator Utility Box using a connector of type (TBD) and of gender (TBD), compatible with (TBD) vendor model number (TBD). The connector shall not permit more than a drop or two of coolant to escape the system when connecting or disconnecting the supply and return lines, and shall not leak during normal operation.

       145     Resistance to Glycol

        The cooling water lines and connectors shall not be damaged in any way when used with a cooling solution containing glycol.

1. It is expected that Gemini will provide a cooling water supply of (TBD) liters/minute at a pressure of (TBD) units and a temperature of (TBD)C. The low pressure return line is expected to carry (TBD) liters/minute at a pressure of (TBD) units and a temperature of (TBD)C.

2. Plumbing connection standards may already exist within the Gemini project.

3. Coolant mixture is expected to be 50/50 water/glycol.

4. The cooling water interface is covered in ICD 1.9/3.6.

150 Signal, Control, and Data Interfaces

The GNIRS shall receive and provide all signal, control, and data paths through the connectors provided on the Cassegrain Rotator Utility Box appropriate to each instrument port.
 
 

        151     Number of Signal, Control, and Data Connections

        The GNIRS shall have one connection for the entire instrument to the appropriate Cassegrain Rotator Utility Box for each of the following, if needed:
 

        152     Length of Signal, Control, and Data Runs

        The signal, control, and data lines to the Cassegrain Rotator Utility Box shall be of a length that permits the GNIRS to meet Requirement 111. If good design practice dictates, a means of dressing these lines to a length appropriate for different ports, or lines of different lengths for different ports, shall be provided.

       153     Signal, Control, and Data Line Flexibility

        The signal, control, and data lines to the Cassegrain Rotator Utility Box shall be flexible enough to permit easy routing, connection, disconnection, and dressing for operation.

1. The ICD 1.9/3.8 contains references to all but the video LAN and Interlock System.

2. There is also an auxiliary boot RS-2332 to each instrument IOC control. Control, Time, Synchro and Event LANs are in/out connector pairs.

160 Liquid Nitrogen Interface

1. It is not anticipated that LN₂ will be added through the ISS. This requirement is intended to provide for cool down of the instrument via a separate set of connections when the GNIRS is on the telescope.

2. Addition of LN₂ is likely to be by hand carried dewars.

3. No LN₂ interface currently exists.
 
 
 

170 Vacuum Interfaces

The GNIRS shall be provided with interfaces for the connection of vacuum lines when the instrument is attached to the ISS at the telescope.
 
 

1. It is not intended to provide vacuum lines in the ISS. This requirement is to provide for the ability to evacuate the GNIRS when the instrument is attached to the ISS at the telescope.

2. Under normal conditions the instrument will be evacuated in the pump room. If necessary, portable equipment will be used to evacuate the GNIRS at the telescope.

3. No vacuum interface currently exists.

200 Control Systems Interfaces
 
 

210 Observatory Control System Interface

1. The Observatory Control System Interface is covered by ICD 1.1.11/1.9.
 
 
 
 

220 Telescope Control System Interface

The only required connection between GNIRS and the TCS shall be provided by the OIWFS components controller software package.
 
 

1. Although Gemini provides both the OIWFS components controller and the Telescope Control System, and must demonstrate that these items work together, the GNIRS team must integrate the OIWFS array controller into the GNIRS and make it work in the instrument environment at the ISS.

2. The Telescope Control System must provide a coordinate position for the OIWFS pick-off with respect to the GNIRS coordinates.

3. Currently there are three ICDs shown for the OIWFS: Intro, 1.10; Cooling, 1.10/3.6 and Cables 1.10/3.8.

230 Engineering Interface

The GNIRS shall provide a means for command and control of GNIRS mechanisms and science array controller, and data capture from the science array without the need for having Gemini control systems (i.e., the Observatory Control System and the Telescope Control System) present or connected.
 
 

231 Physical Interface

The Engineering Interface shall run on a Sun/Solaris workstation that is compatible with Gemini workstations.
 
 

232 User Interface

To the extent practicable, the user interface in the Engineering Interface should appear to a user to be very similar to the user interface in the CICS.
 
 

233 Command and Control

The Engineering Interface shall:

1. 1    Interface to the Gemini-provided science detector controller;
2. 2    Control all instrument mechanisms;
3. 3    Read all instrument sensors;
4. 4    Log sensor data;
5. 5    Display status and health information for the instrument and its mechanisms;
6. 6 Allow execution of diagnostic tests.

The Gemini-furnished detector controller software is responsible for capturing science data from the GNIRS and transferring it to the DHS. The Engineering Interface shall be provide the necessary connections to the detector control software.
 
 

1. The intent of this requirement is to permit the GNIRS to be operated in the laboratory for Pre-Ship Acceptance testing.

2. There is no need to provide an Engineering Interface to command or control, or capture data from, the OIWFS. Some means of testing set-up routines for the OIWFS/slit viewer combination is required.

3. It is expected (but not required) that the Engineering Interface would use at least a part of EPICS in its implementation.

4. Not all data readout modes need be supported. The data that is captured may require extensive processing normally done by the GNIRS Instrument Control System or the Gemini Data Handling System to be intelligible. There is no requirement for the Engineering Interface to perform this data processing, which may be done off-line on another system to analyze results.
 
 

240 Interlock System Interface

1. No GNIRS interlocks require a complete stop of the telescope.

2. Some local interlocks should immediately notify the operator that the GNIRS has shut down. For example: a helium failure or overheating of the electronics.

3. The physical interface is described in ICD 1.9/3.8.

250 Events Bus Interface

1. The physical interface is included in ICD 1.9/3.8.

260 Synchro Bus Interface

At this time there is no requirement for the GNIRS to connect to the Synchro Bus.
 
 

1. The physical interface is included in ICD 1.9/3.8.

2. The Synchro Bus In/Out Connector is dual SC fiber.

270 Time LAN Interface

At this time there is no requirement for the GNIRS to connect to the Time LAN.
 
 

1. The physical interface is included in ICD 1.9/3.8.

2. The Time LAN to IOC thermal enclosure is BNC in and BNC out.
 
 

280 reserved

290 General Control System Requirements

The GNIRS shall meet all general control system requirements given below.
 
 

291 Operability

All mechanisms and other controllable features of the GNIRS shall be managed by computer through the standard EPICS control paths from the GNIRS Engineering Interface, or from the Instrument Console developed as part of the OCS by Gemini.
 
 

292 Configuration Time

The goal for configuration of the GNIRS for an observation from any previous observation configuration is 3 minutes or less.
 
 

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

300 Array and Array Controller Interfaces
 
 
 

310 Science Detector Array Interface

The GNIRS design shall make provision for the Gemini-furnished InSb science detector array.
 
 

311 Characteristics

The GNIRS shall be designed to take the fullest possible advantage of an InSb detector with the following characteristics:

Number of pixels                                                 1024 (H) x 1024 (V)

Architecture                                                         4 independent 512 x 512 quadrants

Pixel size                                                             27 m m, square

Effective fill factor                                             100%

Number of outputs                                         32 (8 per quadrant)

Maximum frame rate                                         20 frames/second

IR material                                                         Thinned InSb

Full well                                                             300,000 electrons at 0.8 V bias

Wavelength range                                         0.9-5.5 m m

Nominal operating temperature                     35 K

Dark current                                                     <0.1 electron/second

Read noise                                                     <25 electrons (rms)

Quantum efficiency                                     80% (0.9-5 m m)
 
 

312 Mechanical Interface

(TBD)

313 Thermal Interface

(TBD)

314 Optical Interface

(TBD)

1. Both the array and array controller are furnished by Gemini. Therefore, the interface between the array and its controller is not described in this document, as that interface is not the responsibility of the GNIRS team. Size, weight, and mechanical connection information concerning the array are required.

2. The GNIRS requires information on the number of electronics boards and racks required for the array and array controller. Information is required on the length of cable runs and the maximum distance between the array and the preamp.

3. An estimate of heat dissipation and power requirements for the array electronics is required.

4. The detector ICD is 1.9.2

5. The detector controller ICD is 1.9.3.

6. The Instrument Components Controller ICD is 1.9.4.

7. The Instrument Sequencer ICD is 1.9.5.

320 Science Array Controller Interface

The GNIRS design shall make provision for the Gemini-furnished science array controller.
 
 

321 Mechanical Interface

(TBD)
 
 

322 Thermal Interface

(TBD)
 
 

323 Optical Interface

(TBD)

324 Software Interface

(TBD)

1. Both the array and array controller are furnished by Gemini. Therefore, the interface between the array and its controller is not described in this document, as that interface is not the responsibility of the GNIRS team.

330 Data Handling System Interface

The GNIRS will provide the software necessary to log data. Data logging shall be used when the instrument is operating in the Gemini-prescribed debug modes. Data logging may also occur during normal operation for the purpose of reflecting instrument health over time.
 
 

1. The software for transfer of science data is part of the Gemini-furnished array controller software.

2. The physical interface is included in ICD 1.9/3.8.

340 OIWFS Detector Array Interface

(TBD)
 
 

2. The OIWFS ICDs are:

(TBD)
 
 

1. The interface between the OIWFS and GNIRS is very critical in defining the overall configuration of the instrument. Early release of this interface requirement is essential for maintaining the GNIRS schedule.

2. The OIWFS ICDs are:

400 Environmental Requirements

410 Altitude Environment

The GNIRS shall be capable of being transported, stored, and operated in a wide range of altitude environments.

  411 Transportation Altitudes

The GNIRS shall be capable of being transported at any altitude between -200 feet and 14,000 feet by any transportation mode. The GNIRS shall be capable of being transported by commercial jet with pressurized cargo compartments at altitudes up to 50,000 feet.

  412 Storage Altitudes

The GNIRS shall be capable of being stored in or out of its shipping container at any altitude between -200 feet and 14,000 feet.

  413 Operation Altitudes

The GNIRS shall be capable of being operated at any altitude between -200 feet and 14,000 feet.
 
 

1. The GNIRS must work at the Hilo Base Facility, at an altitude of approximately sea level, and at the telescope on Mauna Kea, at an altitude of approximately 13,900 feet.

2. The pre-ship acceptance test may be run in Tucson at an altitude of approximately 2,200 feet and on Kitt Peak at an altitude of approximately 7,000 feet.

3. After the GNIRS is commissioned on Mauna Kea, it might be shipped to Cerro Pachon. The base facility at La Serena has an altitude of a few hundred feet, and the telescope site on Cerro Pachon has an altitude of almost 9,000 feet.

420 Temperature Environment

421 Operational Environment

The GNIRS operational environment shall be limited to -15 to +25 ^oC.

422 Survival Environment

The GNIRS shall be capable of surviving a temperature range of -20 to +50 ^oC without damage.

423 Transport Environment

The GNIRS shall be capable of withstanding without damage a temperature range of -20 to +50 ^oC during transport without damage.
 
 

1. Storage and shipping temperature environments should be limited to those given in MIL-STD-810E, (222 to 344 K, or -51 to 71 ^oC).

2. During operation any temperature below -7 ^oC may affect the operation of external motors and ferro-fluidic feed throughs.

430 Humidity Environment

1. Operation of the GNIRS at high relative humidity levels will cause condensation on the dewar window. Using heaters on the window or a hot air system are incompatible with the thermal management of the telescope.
 
 

440 Vacuum Environment

If required by good design practice, the GNIRS shall maintain a vacuum inside the dewar.
 
 

441 Creating the Vacuum

The GNIRS shall provide a means to evacuate its dewar while the instrument is on its handling rig in the instrument support area, and while it is attached to the ISS.
 
 

442 Vacuum Quality and Duration

The GNIRS shall be capable of being kept cold and operated without measurable degradation of performance for 3 months. If needed the instrument shall be capable of being kept at room temperature without measurable contamination of the detector or internal optics for at least 3 months without pumping.
 
 

1. Early Gemini documentation mentions a vacuum line in the ISS utility services box. This is no longer being provided. Instead, instruments will be pumped down in the instrument support facility, then transported to the telescope.

2. Operating vacuum may only be obtained with a cold instrument. The facility requires that the cryogenic cooldown system be disconnected during operation on the telescope.

450 Mechanical Environment

The GNIRS shall be capable of operating in the mechanical environment of the Gemini telescopes and their base facilities, and shall be capable of withstanding shipment among Tucson, Mauna Kea, and Cerro Pachon.

451 Telescope Slew Rates

The GNIRS shall be capable of withstanding slew rates of 2&deg; per second in azimuth and 0.75&deg; per second in elevation, or any combination of these, along with rotation of the Cassegrain rotator to maintain alignment with the parallactic angle as it changes at these slew rates. All optics and mechanisms shall meet their flexure and alignment specifications at these rates.
 
 

500 Optical Requirements

510 Science Requirements

The GNIRS shall meet all science requirements listed below.
 
 

511 Wavelength Range

The GNIRS shall operate as a spectrograph in the wavelength range 0.9 m m through 5.0 m m.
 
 

512 Detector Format

The GNIRS shall use an InSb science detector array with a format of 1024 x 1024, with 27 m m square pixels.
 
 

513 Spectral Resolution

The GNIRS shall provide a low dispersion mode with R ~ 1800 that permits most atmospheric windows to be covered by the detector array. The GNIRS shall also provide an intermediate dispersion mode with R 5000.
 
 

514 Pixel Scale

The GNIRS shall be capable of using 0.1-0.2 arcsecond slits with sampling of approximately 0.05 arcsecond/pixel.
 
 

515 Slit Length

The GNIRS shall provide an entrance slit with a length = 50 arcseconds. For the cross dispersion module the entrance slit length will be less than 50 arc-seconds.
 
 

516 Polarizing Prism

The GNIRS design shall incorporate a polarization analyzer prism. The prism will not be included in the instrument as delivered.

1. There is no need for an on-instrument calibration source. Gemini will provide a calibration source on the ISS that can be fed to the GNIRS.

2. There is no need to provide a focus adjustment controllable from the ICS within the instrument. The OIWFS will be used to provide final focus provided focus meets 300 mm standoff specification at any orientation.

3. The post-slit viewer may use refractive optics.

4. Image parity is not a concern, so a fold mirror may be introduced anywhere in the optical path.

5. IGPO will provide the detector arrays and array controllers.

6. The 3-micron window cannot be covered at R=1800 due to its width, R=1300 is required.
 
 
 
 

520 Science Options

The GNIRS shall include the science options or upgrade paths listed below.
 
 

521 Cross Dispersion

The GNIRS should have a cross dispersion mechanism with positions for 3 dispersive elements plus a mirror. The cross dispersion mechanism shall provide the use of full slit length or work cross dispersed with minimum JHK coverage for any camera. The dispersive elements will be two cross dispersion prisms (one for each camera) and one Wollaston prism. The Wollaston prism will not be included in the instrument as delivered.
 
 

522 Multi-slit Capability

The GNIRS will not have a multi-slit capability.
 
 

523 Long Slit
 
 

The GNIRS will have a slit length of 100 arcseconds for the short camera.
 
 

524 Short Camera

The GNIRS should provide a second plate scale of 0.15 arcsecond/pixel. The camera required to provide this capability for wavelengths greater than 2.5 m m will be designed but will not be included in the instrument as delivered.
 
 

525 Higher Spectral Resolution

The GNIRS should have higher spectral resolution of approximately 18,000 accessible with the long-focus (0.05 arcsec pixel) camera.
 
 

526 Integral Field Mode

The GNIRS should have the capability to add an integral field mode image slicer or its functional equivalent.
 
 

1. The integral field mode has the highest scientific priority with the IRISWG, but has the lowest implementation priority due to perceived technical problems of implementation.
 
 

530 Image Quality and Optical Tolerances

This section lists both "Goals" and "Requirements"; if a "Goal" is met then the corresponding "Requirement" does not need to be met.

531 Pre-Slit Image Quality at Telescope Focus

The image quality at the edge of a 30 arc-second field of view at the telescope focus shall be such that 50 % of the energy of a spot is within less than 0.1 arc-second and 85% of the energy of a spot is within less than 0.4 arc-second.

The image quality goals at the slit, following the fore-optics within the GNIRS, is evaluated for three case: on-axis, off-axis, and with adaptive optics. The specific science cases should be used to determine which goals should drive (or not drive) the design .

531a On-Axis

Goal: The increase in 50% encircled energy diameter (including diffraction) of the 10^th percentile best seeing, perfectly tip/tilt-corrected image as delivered to the slit within GNIRS shall be less than or equal to the following:
 
 

Wavelength	1.2 m m	1.6 m m	2.2 m m	3.7 m m	4.8 m m
50% eed increase, arcsec	0.096	0.097	0.104	0.124	0.162

531b Off-Axis by 25 arcsec

Goal: The increase in 50% encircled energy diameter (including diffraction) of the 10^th percentile best seeing, perfectly tip/tilt-corrected image as delivered to the slit within GNIRS shall be less than or equal to the following:
 
 

Wavelength	1.2 m m	1.6 m m	2.2 m m	3.7 m m	4.8 m m
50% eed increase, arcsec	0.101	0.102	0.108	0.132	0.167

532b Adaptive Optics

Goal: The increase in 50% encircled energy diameter (including diffraction) of the 10^th percentile best seeing, perfectly tip/tilt-corrected image as delivered to the slit within GNIRS shall be less than or equal to the following:
 
 

Wavelength	1.2 m m	1.6 m m	2.2 m m	3.7 m m	4.8 m m
Strehl degradation	0.66	0.79	0.88	0.96	0.97

532 Image Quality at Spectrograph Focus

532a Post-Slit Image Quality - without AO

Requirement: At the spectrograph focus 85% of the light should be within a 27 micron diameter, at 25 arc-seconds from the center of the field, neglecting diffraction effects.

The "Goal" image quality at spectrograph focus is specified in both the spatial and spectral directions. The specific science cases should be used to determine which goals should drive (or not drive) the design.

The goal specification is expressed in terms of the diameter that encloses 50% of the encircled energy (50% eed). The image quality is assessed at the detector surface, which is assumed to be a 1024 x 1024 array with 27 m m square pixels. The overall wavelength range for the baseline system is 0.9-5.5 microns.

532a-1 Spectral Direction, without AO

Goal: The degradation in image quality in the spectral direction shall produce less than a 10% change in the resolution. In the dispersion direction, the image quality should be assessed with telescope aberrations excluded but including diffraction. The specifications must be maintained for the image of a long slit which extends over the full width of the field (as specified in 515 or 523) for all wavelengths which fall on the array detector up to a maximum of 0.4 x central wavelength or 0.8 x central wavelength, depending on science case.

532a-2 Spatial Direction, without AO

Goal-1 is more important than Goal-2

Goal-1: On the optical axis the degradation in image quality in the spatial direction shall produce an increase in the 50% eed of less than 10% of the 50% eed of the 10^th percentile seeing image. In the spatial direction, along the slit, the image quality should be assessed with telescope aberrations and diffraction included. The specification must be maintained for the image of a long slit which extends over the full width of the field (as specified in 515 or 523) for all wavelengths which fall on the detector up to a maximum of 0.4 x central wavelength or 0.8 x central wavelength, depending on science case.

Goal-2: Within 10 arcseconds of the optical axis, the degradation in image quality in the spatial direction shall produce an increase in the 50% eed of less than 10% of the 50% eed of the 10^th percentile seeing image.

532b Post-Slit Image Quality - with AO

Requirement: The use of GNIRS with Adaptive Optics is not part of the baseline requirements.

The goal image quality should be assessed with telescope aberrations included. The image quality at spectrograph focus is evaluated for two cases: with the long camera, with the slit narrowed to take advantage of the smaller AO image, and with an IFU. In each case image quality at the spectrograph focus is specified in both the spatial and spectral direction.

532b-1 Spectral Direction with Narrow Slit

Goal: The degradation in image quality in the spectral direction shall produce less than a 10% change in the resolution given by the narrow slit. In the dispersion direction, the image quality should be assessed with telescope aberrations excluded but including diffraction. The specification must be maintained for the image of a long slit which extends over the full width of the isoplanatic field or the field specified in 515, whichever is less.

532b-2 Spatial Direction with Narrow Slit

Goal-1 is more important than Goal-2

Goal-1: On the optical axis the degradation in image quality in the spatial direction shall produce an increase in the 50% eed of less than 10% of the 50% eed of the AO-corrected image. In the spatial direction, along the slit, the image quality should be assessed with telescope aberrations and diffraction included.

Goal-2: The specification must be maintained for the image of a long slit which extends over the full width of the isoplanatic field or the field specified in 515, whichever is less.

532c-1 Spectral Direction with Integral Field Unit

Requirements/Goals: TBD

532c-2 Spatial Direction with Integral Field Unit

Requirements/Goals: TBD
 
 
 

540 OIWFS Feed

The GNIRS shall provide an optical feed compatible with the operation of the On-Instrument Wavefront Sensor module supplied by Gemini.
 
 

541 Beam Characteristics

(TBD) with a plate scale corresponding to 0.2" pixels. The optics inside the GNIRS in the path to the OIWFS shall distort the beam fed to the GNIRS by the Gemini telescope no more than 60 nm rms.
 
 

542 Field Curvature

The beam feed optics shall be designed assuming the telescope is providing the GNIRS its normal curved field uncorrected by adaptive optics.
 
 

543 Wavelength Sensitivity

The OIWFS beam shall contain as much of the energy from the telescope beam in the wavelength range of 1 m m to 2.5 m m as it is practical to provide.
 
 

1. The purpose of the OIWFS is to provide feedback to the fast tip/tilt and focus correction control loops. The OIWFS will always provide telescope flexure correction. It may provide a fast tilt source for adaptive optics.

550 Target Acquisition

The GNIRS shall provide a means for simple target acquisition.
 
 

551 Target Complexity

The GNIRS shall provide a means for locating the slit on single stars, specific features, and complex fields.
 
 

552 Target Wavelength

The GNIRS shall provide a means for locating the slit on targets not detectable in the visible band of the electromagnetic spectrum, but detectable in the wavelength range of the science detector.
 
 

1. Examples of complex targets include crowded star fields, the core of a galaxy, and an emission region in a nebula. This may require an imaging mode for locating the slit on targets, but other designs may be acceptable.
 
 

560 Baffling

The GNIRS shall be properly baffled to minimize stray radiation.
 
 

561 Thermal Baffling

The GNIRS shall contain sufficient thermal baffling to minimize heat loading on the cryogenic systems.
 
 

562 Optical Baffling

The GNIRS shall contain proper optical baffling to reduce stray radiation to levels below that detectable by the science detector.
 
 

570 Internal Instrument Background

The GNIRS 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.
 
 

580 Throughput

The GNIRS shall be designed to maximize throughput to take maximum advantage of the Gemini telescope performance.
 
 

581 Vignetting

The GNIRS design shall minimize vignetting, including diffraction effects.
 
 

582 Signal-to-Noise Ratio

The GNIRS shall be designed to maximize throughput and signal-to-noise ratio.
 
 
 
 

590 General Optical Requirements

The GNIRS shall meet the general optical requirements listed below.
 
 

591 Lyot Stop

The GNIRS shall provide a cold Lyot stop at an image of the telescope pupil (the secondary mirror). Any field stop before this cold Lyot stop shall be at least 100 arcseconds in diameter. The Lyot stop shall be capable of being changed when the instrument is off the telescope and warmed up.
 
 

592 Coatings

The following characteristics of all optical coatings shall be specified in design documentation:

Transmission (for transmissive coatings) or reflection (for reflective coatings) over the

entire wavelength range

Transmission (for transmissive coatings) or reflection (for reflective coatings) within

each atmospheric window

Maximum allowed reflection (for transmissive coatings) or transmission (for reflective

coatings)

Environmental testing

Hardness or equivalent ISO standard

Adherence or equivalent ISO standard

Abrasion or equivalent ISO standard

Humidity

Cleanability

Water solubility

Surface appearance (flaking, peeling, finger prints, etc.)

All coatings shall be unaffected by repeated thermal cycling over the operating, storage, and transportation temperature ranges.
 
 

593 Vacuum Environment

All optical components and coatings shall meet all performance requirements when operated in a vacuum of less than 10^-5 Torr at operational temperatures.
 
 

594 Thermal Cycling

All optical components and coatings shall meet all performance requirements when thermally cycled at a maximum rate of temperature change of 0.25 K/minute.

610 Rigidity and Repeatability

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

611 Alignment of the Instrument to the Telescope Optics

The alignment of the GNIRS cold stop with the secondary mirror shall be set and maintained to better than 1% of the apparent secondary mirror diameter.
 
 

611 Tracking with the OIWFS

Tracking performance when using the GNIRS OIWFS shall hold motion of the image on the slit to at most 10 microns in one hour of observation.
 
 

612 Tracking with the Peripheral Wavefront Sensor

Tracking performance when using the peripheral wavefront sensor is (TBD - flexure to be with respect to ISS).

613 Motion of Slit Image on Detector

The maximum image motion of the slit on the detector in one hour of observation shall be no more than 0.1 pixel (2.7 m m).

614 Mechanism repeatability

All mechanisms shall return to a normal position with repeatability that limit motion of the slit image on the detector to 0.1 pixel and of the object image on the slit to 10 microns. This is a goal and not a requirement for the camera turret.

620 Mechanical and Thermal Tolerances

2. Thermal transient effects during cool-down or warm-up shall be considered in the design of the GNIRS.

640 Space Requirements

644 Electronic Enclosures

All GNIRS electronic enclosures mounted on the ISS shall be counted in the space requirements given above.

645 Access to Electronic Enclosures

The electronic enclosures shall be accessible without removing the GNIRS from the ISS.

646 Access to Vacuum Ports

Vacuum ports on the GNIRS shall be accessible without removing the instrument from the ISS.

646 Access to Liquid Nitrogen Ports

The GNIRS does not use liquid nitrogen.

647 Access to Helium Ports

Helium ports on the GNIRS shall be accessible without removing the instrument from the ISS.

648 Mechanical Connections

All mechanical connections on the GNIRS shall be accessible without removing the instrument from the ISS and while mounted with other instruments.
 
 

1. Space requirements are specified in ICD 1.1.1/1.9 and the ICD for the ISS (/1.9).

650 Mass and Center of Gravity Requirements

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

651 Total Mass

The GNIRS shall have a mass of 2100 kg or less.

652 Center of Gravity

The GNIRS shall have a center of gravity on the port axis 1000 mm mm from the mechanical interface on the ISS. The tolerance is as specified in ICD XXXX
 
 

653 Balance Tolerance

The out-of-balance during operation due to moving elements, fixtures, (including LN₂ boiloff) etc. within the GNIRS shall be less than 400 N-m.
 
 

654 Ballast Weight

A ballast weight and its supporting structure shall be supplied as required to meet the above requirements.
 
 

655 Electronic Enclosures

All GNIRS electronic enclosures mounted on the ISS shall count in the mass and center of gravity requirements given above.
 
 

660 Cooling System

The GNIRS shall meet all cooling system requirements listed below.
 
 

661 Cooldown Time

The GNIRS cooling system shall have the capability to cool the instrument from room temperature to operating conditions, with a goal of 72 hours. Cryogenic closed cycle coolers shall be used to maintain the operating temperature once it has been achieved.
 
 

662 Warmup Time

The GNIRS shall not require more than 24 hours to warm up the entire instrument from operating conditions to room temperature.
 
 

663 Thermal Stability

The GNIRS detector assembly shall have an active temperature control system providing a variable accuracy to be set at the optimum temperature for the detector between 30 K and 40 K, and a stability of +/- 0.1 K.

664 Vibration

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.
 
 

670 Vacuum System

671 Staging and Holding Areas

(TBD)

672 Vacuum Pump Capacity and Selection

(TBD)

673 Operating Procedure and Set-Up

(TBD)

674 Test Set-Up

(TBD)

680 Operational Requirements for Mechanisms

GNIRS mechanisms shall meet the requirements listed below.
 
 

681 Safety

No mechanism shall be back-driveable in the event of loss of electrical power.
 
 

682 Time to Function

The goal for all individual mechanisms is to take no more than 60 seconds to operate from any position to any other position. The maximum allowable time is 180 seconds. The time to re-zero or "home" any mechanism from an unknown position shall not exceed 210 seconds.
 
 

690 Instrument Handling

The GNIRS shall be delivered with an instrument handling rig that can hold the GNIRS during installation on the ISS. The instrument handling rig shall also hold the GNIRS during storage and will provide assistance during assembly and disassembly.
 
 

1. The handling rig is intended to be used for instrument storage, safe movement around the instrument preparation and assembly areas, and for assembly and disassembly assistance. Consult the Instrumentation Control Document, Section 3.2.

2. Instruments are mounted on the ISS using the Cassegrain handling rig (supplied by Gemini). An instrument will be moved from the storage/preparation area in the facility to the observing floor via the service lift of the large lifting platform. Once on the observing floor, the instrument will be transferred from its handling rig to the Cassegrain handling rig. Depending upon the ISS port that the GNIRS is to occupy (side- or up-looking port), the GNIRS handling rig will orient the instrument in the proper configuration before transfer to the Cassegrain rig, which is a maneuverable lifting platform. The GNIRS will then be maneuvered to the intended port by the Cassegrain handling rig, positioned, and the GNIRS load bearing fasteners will be engaged (dowels or expanding bolts), followed by the load bearing clamping fasteners (clearance bolts). The position of location and load bearing fasteners is outlined in the Critical Design for the Cassegrain Assembly. Each consists of a circular raised boss with an annular flat surface. At the center of the surface is a locating counterbore with a tapped hole further in. More guidance regarding the Cassegrain handling rig and the general scheme for mounting instruments can be found in the Instrumentation Control Document, Section 8.1.

3. A handling rig usable in all telescope orientations is likely to be very large, complex and extremely expensive. It is anticipated that the GNIRS will be installed in the zenith pointing position of the telescope.
 
 
 
 

6A0 Metric Dimensioning

Metric dimensions shall be used in the GNIRS.
 
 

6A1 Metric Dimensions on Drawings

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

6A2 Metric Fasteners

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

1. This requirement permits the use of "soft metric" design, in which, e.g., two holes are spaced 4 inches apart by the designer. The fabrication drawings may show dimensions in inches to reduce confusion and retooling costs, but the as-built drawings will be converted before delivery to metric dimensions, e.g., 4 inches will be shown as 101.60 mm.
 
 

710 Electronic Design Requirements

The GNIRS shall be designed in accordance with modern electronics engineering practice for astronomical instruments.
 
 

711 Grounding and Shielding

Separate ground returns shall be provided for low level signals, noisy components such as relays and motors, and hardware components such as mechanical enclosures, chassis, and racks.
 
 

712 Electrostatic Discharge

The GNIRS design shall protect sensitive components from electrostatic discharge.
 
 

1. Good grounding practice is discussed in Ott, Henry W., Noise Reduction Techniques in Electronic Systems, Second Edition, AT&T Bell Laboratories, 1988, Chapter 3.

2. Ott (above) discusses electrostatic discharge on page 332.
 
 
 
 

720 Cassegrain Cable Wrap Interfaces
 
 

1. Cassegrain cable wrap interfaces are provided by the break out panels on the ISS, and should be defined by the ICD 1.5.2/1.9.

730 Temperature Monitoring

Thermocouples (or gas thermometers) are required to monitor the cryo environment within the dewar and the detectors

731 Temperature Sensor Locations

(TBD)

732 Sensor Interfaces

The temperature sensor read-out interface shall be part of the Engineering Interface as described in section 234.
 
 

1. The GNIRS will have a variety of temperature sensors inside the dewar and between the radiation shields. Normal NOAO practice is to provide a total of 24 such sensors.

2. The GNIRS detector will be provided with temperature sensors, at least 2 for the mount and 2 for the detector.

3. The GNIRS electronics temperature is monitored by the Gemini thermal enclosure system.

800 Software Requirements

810 Software Design Requirements

The GNIRS shall be a "conforming" instrument, in that it shall use EPICS and conform to Gemini software and control system standards and the requirements listed below.
 
 

811 Use of EPICS

The GNIRS shall use a standard Gemini configuration of a workstation for the operator interface, connected to an EPICS based system used for controlling motors, coolers, and heaters and for receiving status information from sensors.

812 EPICS System

The EPICS system shall be a standard Gemini unit (VME crate, 68040 CPU, VxWorks operating system.

813 Use of the Core Instrument Control System Software Package

The GNIRS software engineers shall use the Gemini-furnished Core Instrument Control System Software Package to develop the Instrument Control System (ICS).
 
 

1. The Gemini Software Design Description contains guidelines for developing Gemini-compatible software.

2. Gemini will provide the GNIRS team with a Core Instrument Controller Software Package to aid in the development of an ICS that conforms to Gemini requirements and standards.

814 Functionality

The following capabilities shall be provided by the GNIRS software:

1. Respond to commands issued from the OCS;
2. Provide command completion information;
3. Provide and maintain status and health information for the instrument and mechanisms;
4. Provide and maintain instrument header information;
5. Accumulate and log data for specified sensors;
6. Produce trend line for specified sensors;
7. Raise alarm conditions of appropriate severity;
8. Operate in Gemini-prescribed simulation and debug modes;
9. Log and display meaningful messages when in debug mode or in the event of an error;
10. Coordinate activities between the GNIRS components controller and the Gemini-furnished array controller software;
11. Provide and Engineering Interface with diagnostic tests.

1. Allow for complete configuration changes in 3 minutes or less;
2. Allow simultaneous motion of all mechanisms. However, the grating selection and tilt must be sequential, and the available power may not be sufficient to drive all mechanisms at once. The maximum number of mechanisms for which power is available is TBD.
3. Share CPU and other resources with the OIWFS components controller.

The GNIRS software will not:

1. Connect to the Gemini Interlock System
2. Prohibit combinations of mechanism configurations (any achievable configuration shall be allowed);
3. Interlock any jump-start or warm-up system or configuration.

1. Refer to section 230 for additional software requirements regarding the Engineering Interface.

820 EPICS Compatibility

The GNIRS software shall be based on and use an EPICS system as required

by 810.

821 Interfaces to the Gemini System

Interfaces to the Gemini system shall conform to the descriptions

presented in the Core ICS documentation. In particular, all OCS

commands to, and responses from, the GNIRS shall be by CAD, CAR and SIR

EPICS records as described in the Core ICS documentation. Interfaces

to other Gemini subsystems shall conform to the relevant Interface

Control Documents.
 
 

1. Low level software in the GNIRS will be a mixture of EPICS code and C-coded tasks, both running directly on VxWorks.
 
 
 
 

830 Gemini Furnished Software

Gemini shall furnish a complete and final set of all Interface Control Documents not later than the GNIRS PDR.

Gemini shall furnish to the GNIRS software engineers a functional CICS (see 813) as soon as practical, and shall provide updates as they become available. The first release of the CICS should be by GNIRS PDR with general information available before then.

Gemini shall furnish a complete interface description of the detector sub-system as soon as practical.

Gemini shall furnish a complete interface description of the OIWFS sub-system as soon as practical.

Gemini shall furnish a DHS (or a simulation thereof) when the detector subsystem is delivered.

Gemini shall furnish a prototype of the OIWFS components controller software as soon as practical. This software must simulate operation of the OIWFS in a stand-alone mode.

Gemini shall furnish software for obtaining accurate time information when the detector sub-system is delivered.

910 Documentation

The GNIRS shall be delivered with adequate documentation to facilitate the operation, maintenance, and repair of the instrument.
 
 

911 User’s Manual

The User’s Manual shall be written to enable a new user of the GNIRS to easily get acquainted with the operation of the instrument.
 
 

912 Service and Calibration Manual
 
 

913 Software Maintenance Manual

This document described the software at a level of detail sufficient for a competent programmer not initially familiar with the software can maintain it properly. It includes detailed verbal descriptions of all software systems and subsystems written by NOAO at a high level, including purpose, organization, and interaction with any other software systems and subsystems. Included are any systems analyses, data flow diagrams, data dictionaries, structure charts, and mini-specs developed during the software design process, updated to reflect as-built conditions. Also included are listings of all software delivered as part of the GNIRS, including firmware in ROM’s, PROM’s and DSP’s. All software source code modules shall include a standard header documenting the module contents, and each module shall contain a sufficient number of comments explaining the purpose and function of each section of code that a programmer unfamiliar with the software can understand it. Any systems engineering analyses that led to the allocation of functions between hardware and software or the software design used are included.

914 As-Built Drawings

The as-built drawings shall show all dimensions in millimeters, down to 0.01 mm. All fasteners specified in these drawings shall be standard metric sizes. All drawings shall otherwise be to NOAO standards used in instruments of similar size, function, and complexity.

915 Drawing Standards

(TBD)

916 Drawing Numbering System

(TBD)

917 Drawing Filing System

(TBD)

2. Final released drawings will be maintained by IGPO.

920 Training

The GNIRS development team shall provide training documentation and a training course to Gemini operations personnel on the operation, maintenance, and repair of the GNIRS.

930 Reliability

The GNIRS shall be designed and built to be reliable.
 
 

931 Downtime

The GNIRS shall have a total downtime of 2%, with 1% as a goal. Where possible, component failure shall result in gradual performance degradation. Single point failures that may result in significant downtime shall be determined and, where necessary, critical spares shall be identified.
 
 

932 Continuous Duty

The GNIRS shall be designed and built for continuous operation. Modules containing moving parts, e.g., cryocooler cold heads, shall be designed or selected to meet Requirement 931 assuming continuous operation.

940 Maintainability and Serviceability

The GNIRS shall meet the requirements for maintainability in the Instrumentation Control Document, Section 2.2.
 
 

941 Standard Components

Wherever possible, the GNIRS shall use unmodified commercially available standard components.
 
 

942 Modularity

To the extent possible, the GNIRS shall be designed to be modular.
 
 

943 Access

Access to components and subassemblies shall be considered in the GNIRS design, particularly for those elements that are accessed frequently. Tool and hand clearances shall be considered, as well as space required to remove modules, visual access to components (or a means to feel their correct position and alignment, e.g., for electronic connectors).
 
 

944 Alignment

Alignment of optical components shall be achieved to the extent possible by accurate machining of locating fixtures.
 
 

945 Relative Equipment Arrangements

Equipment shall be located with due consideration of the sequence of operations involved in maintenance procedures. To the extent possible, the most accessible locations shall be reserved for the items requiring most frequent access.
 
 

946 Subassemblies

Subassemblies of the equipment that require more frequent service (inspection, adjustment, repair, or replacement) shall be configured as plug-in modules or, if in racks, as drawers that can be withdrawn easily.
 
 

947 Handling

Modules greater than 20 kg in mass shall have suitable handles for use in removing, replacing, and carrying them. Handles shall be located such that the vector sum of resultant handling forces shall pass close to the center of gravity of the unit.
 
 

 948 Revisability

Multilayer electronic boards shall not be used unless they are replaceable as a module. Backplane interconnections between custom boards is discouraged.
 
 

1. Requirement 944 can be achieved by machining captive thick shims to achieve the assembled tolerances, but the intention is to avoid an involved re-alignment procedure on assembly or re-assembly.
 
 

950 Lifetime

The GNIRS shall be designed for an operational lifetime of 10 years without a major overhaul. Components likely to affect the lifetime requirement shall be identified.
 
 

1. Battery back-up systems will require replacement at intervals of less than 10 years.
 
 

960 Safety
 

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