Contract End Item Specification

Advanced X-ray           AXAF - I
Astrophysics Facility    CCD Imaging Spectrometer
Document No.36-01101-07
DPD 727 DR SCM02
Contract # NAS8-37716
April 20, 1995
Submitted to:

    George C. Marshall Space Flight Center
    National Aeronautics and Space Administration
    Marshall Space Flight Center, AL 35812

Submitted by:

    Center for Space Research
    Massachusetts Institute of Technology
    Cambridge, MA 02139


    Gordon P. Garmire                  Philip J. Gray
    Instrument Principal Investigator  Project Manager
    Pennsylvania State University      Massachusetts Institute of Technology

Table of Contents

Revision Table

REVISION     TITLE:                                   DOC.NO.
     LOG          Contract End Item Specification          36-01101
Revision Date
Reason Approval
01 5/7/93 N/A All Requirements Review
02 10/18/93 N/A Append A RID Num. AXSI-0312
10/18/93 N/A Append A RID Num. AXSI-0313
10/18/93 N/A Page 27 RID Num. AXSI-0314
10/18/93 N/A Page 17 RID Num. AXSI-0323
10/18/93 N/A Page 37 RID Num. AXSI-0335
10/18/93 N/A Page 37
Page 1
RID Num. AXSI-0336
10/18/93 N/A Append A RID Num. AXSI-0348
10/18/93 N/A Append A RID Num. AXSI-0353
10/18/93 N/A Page 28 RID Num. AXSI-0358
10/18/93 N/A Append A RID Num. AXSI-0364
10/18/93 N/A Page 21 RID Num. AXSI-0376
10/18/93 N/A Page 17 RID Num. AXSI-0380
10/18/93 N/A Page 21 RID Num. AXSI-0398
10/18/93 N/A Page 37 RID Num. AXSI-0405
10/18/93 N/A Page 36 RID Num. AXSI-0408
10/18/93 N/A Page 18 RID Num. AXSI-0455
10/18/93 N/A Append A RID Num. AXSI-0465
10/18/93 N/A Page 24 RID Num. AXSI-0469
10/18/93 N/A Page 16 RID Num. AXSI-0470
10/18/93 N/A Page 10 RID Num. AXSI-0500
10/18/93 N/A Page 28 RID Num. AXSI-0503
10/18/93 N/A Page 17 RID Num. AXSI-0509
10/18/93 N/A Page 7 RID Num. AXSI-0545
10/18/93 N/A Page 10 RID Num. AXSI-0549
10/18/93 N/A Page 15 RID Num. AXSI-0552
10/18/93 N/A Page 9 RID Num. AXSI-0561
10/18/93 N/A Page 32 RID Num. AXSI-0554
10/18/93 N/A Page 35 RID Num. AXSI-0581
10/18/93 N/A Page 10 RID Num. AXSI-0567
03 11/2/93 N/A Page 11 RID Num. AXSI-550
11/2/93 N/A Page 6 RID Num. AXSI-544
11/2/93 N/A Page 15 RID Num. AXSI-501
11/2/93 N/A Page 35 RID Num. AXSI-404
N/A 10 RID Num. AXSI-0548
3-7-94 N/A All PRD to CEI flow down

RID Num. AXSI-0320; Change "AXAF-I to Science Instrument ICD" to "Observatory to Science Instrument ICD" global

N/A 9 RID Num AXSI-0546
3-8-94 N/A 39 RID Num AXSI-0330
3-8-94 N/A 7 RID Num AXSI-0441, 0442, 0443, 0444
3-8-94 N/A 38 RID Num AXSI-0504
3-8-94 N/A 32 RID Num AXSI-0466
3-8-94 N/A 3, 32 Change of applicable document to MM8075.1
3-8-94 N/A 33 RID Num AXSI-0337
3-14-94 N/A 30 RID Num AXSI-0372
3-21-94 N/A 16 RID Num AXSI-0502
3-21-94 N/A 16,17 RID Num AXSI-0553
05 3-21-94 N/A 5 Add NASA TM 100351
5-10-94 N/A 5 Add HDBK-KSTSM-14.1
5-10-94 N/A 37 Define Verification Phases
5-10-94 N/A 5 Add FED-STD-209B
5-10-94 N/A 23 Add Section 3.2.8
5-10-94 N/A 40 Modify section 4.6.9
5-10-94 N/A 31 Modify section
5-10-94 N/A 16 RID Num AXSI-0553
5-10-94 N/A 21 Add section
5-10-94 N/A 21 Add Section
5-10-94 N/A 16,17 Change Alignment and Stability Specifications
5-10-94 N/A 37,38 Redefine Verification Phases
5-10-94 N/A 42-46 Modify Verification Matrix
06 5-17-94 N/A 15 Change Omega x from 4 to 10 arc min
5-17-94 N/A Appendix A Change Ver Matrix
07 9-19-29 N/A 14 RID # IPDR 1103
9-19-94 N/A Appendix A RID # IPDR 1135
9-19-94 N/A 20 RID # IPDR 1143
9-19-94 N/A 12 RID # IPDR 1133
9-20-94 N/A 28 Comment #PDR-18
1-6-95 N/A 30 Revise Elect. Power Requirements
4-11-95 N/A 12 Update quantum efficiencies
5-1-95 N/A 6 Para. 2.5 Remove-For reference only
5-1-95 N/A 23 Add Para.
5-1-95 N/A Appendix B Remove
5-1-95 N/A Most Update ICD references
5-1-95 N/A 18 Add Doc.NSTS 13130B
5-1-95 N/A 20 Para. Added door reference
5-1-95 N/A 31 AXAF supply voltage +22 to +35
5-1-95 N/A 35 Added post acceptance by Observatory Contractor


This document defines the performance, design, development and verification requirements for the AXAF-I CCD Imaging Spectrometer (ACIS).


The following documents form a part of this requirement to the extent specified herein. In the event of conflict between documents referenced below and other project documentation, the requirements specified herein shall govern. Safety documents shall be an exception and shall take precedence. Reference to the documents contained herein is by basic number only; for the applicable revision, refer to the section below. Specifications developed by the instrument supplier which satisfy the intent of the documents listed below may be used if approved by MSFC.

2.1 NASA Documents

Document No. Title Para. Ref.
NHB 5300.4 (1D-2) Safety, Reliability, Maintainability and Quality Provisions for the Space Shuttle Program. 5.2
NHB 5300.4(3A-1) Requirements for Soldering Electrical Connections
NHB 5300.4(3G) Requirements for Inter-connecting Cables, Harnesses, and Wiring
NHB 5300.4(3H)
(change 1)
Requirements for Crimping and Wire Wrapping
NHB 5300.4(3I)
(Change 1)
Requirements for Printed Wiring Boards
NHB 5300.4 (1B) Electrical, Electronic and Electromechanical(EEE) Parts Management and Control Requirements
NHB 5300.4(3J) Requirements for Conformal Coating and Staking of Printed Wiring Boards and Electrical Assemblies
NHB 5300.4 (3K) Design Requirements for Rigid Printed Wiring Board Design
NHB 6000.1C Requirements for Packaging, Handling, and Transportation for Aeronautical and Space Systems, Equipment and Associated Components
NHB-8060.1B Flammability, Odor and Outgassing Requirements and Test Procedures for Materials in Environments that Support Combustion
NASA TM-86538 Design and Verification Guidelines for Vibroacoustic and Transient Environments
NMI 2410.6 NASA Software Management Requirements for Flight Projects
NMI 8010.1A Classification of NASA Payloads 3.1.8

2.2 MSFC Documents

Document No. Title Para. Ref.
MSFC-STD-126E Inspection, Proof Testing and Certification of Handling Equipment
MSFC-STD-156 Riveting, Fabrication and Inspection Amendment 1
MSFC-SPEC-250A Protective Finishes for Space Vehicles Structures and Associated Flight Equipment, General Specifications
MSFC-STD-486A Torque Limits for Threaded Fasteners
MSFC-SPEC-494A Installation of Electrical Wiring Harness Assemblies
MSFC-HDBK-505A Structural Strength Design and Verification Requirements
MSFC-STD-506B Materials and Process Control
MSFC-SPEC-522B Design Criteria for Controlling Stress Corrosion Cracking
MSFC-HDBK-527E Materials Selection List for Space Hardware Systems
MSFC-STD-531 High Voltage Design Criteria
MSFC-STD-557 Threaded Fasteners, 6AL-4V Titanium Alloy, Usage Criteria for Spacecraft Applications
MSFC-STD-561 Threaded Fastener, Securing of Safety Critical Flight Hardware
MSFC-STD-655 Weld Filler Metal, Control of
MSFC-STD-781 Standard for Electrical Contacts, Retention Criteria
MSFC-SPEC-1238 Thermal Vacuum Bakeout Specification for Contamination Sensitive Hardware
MSFC-STD-1249 Standard, NDE Guidelines and Requirements for Fracture Control Programs
MSFC-SPEC-1443 Outgassing Test for Non-Metallic Materials Associated with Sensitive Optical Surfaces in a Space Environment
MSFC-HDBK-1453 Fracture Control Program Requirements
MSFC-SPEC-1839 Advanced X-Ray Astrophysics Facility (AXAF) Science Instruments Calibration Requirements
MM-8075.1 MSFC Software Management and Development Requirements
CQ-5330.1 Software Quality Assurance Requirements for MSFC Projects
CR-5320.9 Payload and Experiment Failure Mode and Effects Analysis and Critical Items List Groundrules
MM 8040.12A MSFC Standard Contractor Configuration Management Requirements 4.3
MM 8070.2L Specifications and Standards, Approved Baseline List 3.3.2
MMI 1860.4B Reporting Requirements for Minor Radioactive Sources
MMI-6400.2A Packaging, Handling and Moving Program Critical Hardware
(89-0782) 10/17/89
Electrical Wire Insulation Guidelines for the AXAF and AFE Projects
Observatory to Science Instrument 14 February 1995 Rev 1F1-20 Entire
TBD The Charged Particle Radiation Environment for AXAF-I
AXAF-I EMC Control
TBD AXAF-I Contamination Environment and Control

2.3 Other NASA Documents

Document No. Title Para. Ref.
GP-1098F KSC Ground Operations Safety Plan, Launch Complex 39 and KSC Industrial Area, Volume 1
JSC SP-R-0022A General Specifications, Vacuum Stability Requirements of Polymeric Materials for Spacecraft Applications
KHB 1700.7A Shuttle Transportation System Payload Ground Safety Handbook
NSTS 1700.7B Safety Policy and Requirements for Payloads Using the National Space Transportation System (NSTS)
NSTS 07700, Vol.XIV,
Rev.J, Attachment 1
Space Shuttle System, Payload Accommodations (ICD 2-19001)
NASA TM 100351 Materials Selection Guidelines to Limit Atomic Oxygen Effects on Spacecraft Surfaces
FED STD-209B(1) Clean Room and Work Station Requirements, Controled Environments
HDBK-KSTSM-14.1 Launch Site Accomodations Handbook
SD77-SH-0214A STS Models Configuration Management Control Systems and Standards Analyses for Payload Load Cycle

2.4 Military Documents

Document No. Title Para. Ref.
MIL-HDBK-5E Metallic Materials and Elements for Aerospace Vehicle Structures
Amendment 1
Cables, RF, Coaxial, Dual Coaxial, Twin conductors, and Twin Lead
MIL-STD-454L General Requirements for Electronic Equipment 3.3.9
MIL-STD-461B Electromagnetic Emission and Susceptibility Requirements for Control of Electromagnetic Interference
MIL-STD-883D Military Standard Test Methods and Procedures for Microelectronics
MIL-STD-975G Standard parts List for Flight and Mission Essential Ground Support Equipment
MIL-STD-1285A Marking of Electrical and Electronic Parts 3.3.8
MIL-STD-1686A Electrostatic Discharge Control Program for Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices)
Amendment 3
Amend Bonding, Electrical, and Lightning Protection for Aerospace Systems
Amendment 1
Electromagnetic Compatibility, Systems Requirements
MIL-B-7883C Brazing of Steel, Copper, Copper Alloys, and Nickel Alloys
Amendment 1
Wire, Electric, Fluoropolymer-Insulated, Copper or Copper Alloy
MIL-M-38510F Military Specification for Microcircuits
Supplement 1
Connectors, Electrical, Miniature, High D, Quick Disconnect, Environment Resistant, Removable Crimp Contacts, General Specs for
Supp. 1b
Connectors, Coaxial Cable, General
MIL-W-81381A Wire, Electric, Polyimide-Insulated Copper or Copper Alloy

2.5 Reference Documents

Document No. Title Para. Ref.
AXAF-101 Advanced X-ray Astrophysics Facility Program Policy and Requirements Document Level I 3.1.2
(Draft, dtd 8/3/92)
Advanced X-ray Astrophysics Facility (AXAF-I) Level II Project Requirements Document (PRD) 3.1.5


3.1 Definition

The science instrument program includes the definition, design, development, verification, calibration,launch, operation and data analysis as part of a free-flying observatory called the Advanced X-ray Astrophysics Facility - Imaging, hereafter referred to as AXAF-I. AXAF-I is designed to collect X-ray imaging and spectroscopic data from celestial sources in the energy range of 0.2 to 10 keV. AXAF-I is planned to operate for 5 years.

The instrument program includes, in addition to the hardware and software, all unique ground support equipment and associated software required to develop, test, calibrate, handle and maintain the instrument during all operational phases.

3.1.1 ACIS Description

The AXAF-I CCD Imaging Spectrometer (ACIS) is a focal plane Science Instrument on the Advanced X-ray Astrophysics Facility - Imaging (AXAF-I). ACIS has two Charge-Coupled Device (CCD) arrays: one for imaging and one for spectroscopy. ACIS detects faint X-ray sources over the range of 0.2 to 10 keV. The pixel size shall be no greater than 24 microns; the field of view of one pixel during integration shall not exceed 0.5 arcsec. This field of view should be used for reference only.

Primary assemblies comprising ACIS are shown in Figure 3.1-1. These assemblies are separated into two groups: the Detector & Processor Subsystem (DPS) and the Power & Thermal-Control Structure (PTS). The Detector Assembly (DA) houses the CCD arrays, fiducial lights and an X-ray calibration source. Signals from the CCD's are amplified and digitized in the Detector Electronics Assembly (DEA). The Digital Processing Assembly (DPA) controls instrument operation, extracts valid X-ray events, and processes the data for downlink. The Remote Command and Telemetry Unit (RCTU) provides the interface between ACIS and the Observatory data management system. The Power Supply (PS) supplies conditioned power to all assemblies. The Thermal Control system provides thermal control for the DA allowing operation of the focal plane at a nominal temperature of -120 deg C. Heaters provided by the Science Instrument Module (SIM), will maintain minimum temperature levels on ACIS electronic assemblies.

3.1.2 Science Objectives

The objectives of the ACIS instrument include, but are not limited to:

a) Accurately measure the contribution of discrete sources to the X-ray background.

b) Map the temperature and elemental distribution, especially of iron, in clusters of galaxies.

c) Determine cluster evolution in clusters of galaxies to a red shift between 1 to 2.

d) Detect and determine the distribution and types of X-ray sources in galaxies out to the distance of the Virgo cluster.

e) Determine the emission mechanisms in quasars and active galaxies by distinguishing between thermal and non-thermal spectra.

f) Test Compton models of quasars and active galaxies by studying time variability as a function of energy.

Figure 3.1-1 ACIS Assemblies Allocated Between

DPS & PTS Subsystems.

g) Classify emission from normal galaxies out to 800 Mpc and beyond.

h) Clarify the origin of X-ray emission from starburst galaxies.

i) Determine the structure and spectra of jets and lobes in active galaxies and quasars.

j) Determine the abundance and distribution of iron in supernova remnants (SNRs) in order to ascertain the composition of the presupernova star and verify models of nucleosynthesis.

k) Determine the temperature of neutron stars in SNRs to test cooling theories.

l) Detect and identify SNRs and Crab-like pulsars out to M31.

m) Measure the temperature and elemental abundance of the hot plasma in stellar X-ray emission.

n) Conduct phase-resolved spectroscopic studies of line emission in accreting compact objects to determine details of the disc geometry.

o) Determine the contribution of stars to the soft X-ray background.

p) Measure the abundance of elements in the interstellar medium.

q) Evaluate the role of X-ray ionization in regulating star formation in molecular clouds.

r) Determine important physical properties of interstellar dust.

3.1.3 Science Modes CCD Readout Modes

The ACIS electronics (DEA) shall be capable of simultaneously reading a minimum of six data streams from any combination of CCDs in the imaging or TGS array. Each channel shall collect data from each of the CCDs in the array at a maximum rate of 166,666 12-bit words per second. Through the control of the parallel and serial clocks, and the selection of the output amplifier of each CCD (each CCD has four output amplifiers), the following readout modes can be achieved.

a) Timed Exposure Mode

In a timed exposure mode, the CCD exposure time shall vary as commanded between 0.1 (TBR) and 10 seconds. The imaging-to-framestore operation shall be executed in no more than 60 msec (TBR). ACIS shall be capable of reading out the framestore in less than 6.5 sec., and shall be capable of reading less than a full frame, whereby a TBD rectangular subarray within a chip can be read out at normal clocking rates, with the rest of the array being skipped over as fast as possible.

b) Continuous Readout Mode

During continuous exposure mode, ACIS shall be capable of reading a data stream from a maximum of two CCDs with a full-line readout time (including parallel transfer) of no more than 6.2 msec. To produce the highest possible time resolution, it shall be possible to sum a commandable number of lines (in the detector output register) prior to each line readout.

c) Diagnostic Clocking Mode

ACIS shall have the capability to clock each CCD's serial register in the reverse direction to obtain diagnostic noise measurements on the processing electronics. Data Processing Modes

ACIS shall contain a digital processing system which is capable of several modes of operation.

a). Event Modes

The processing system shall identify candidate X-ray events, remove detector bias and dark current artefacts, extract information on event location in the focal plane, event time, and X-ray energy, and format this information for telemetry to the ground. This information shall be extracted in such a way as to preserve the position, time and spectral resolution inherent in the input data stream. In particular, pixels with bias-corrected amplitudes exceeding a commandable event threshold, and which are local maxima, relative to the eight nearest neighboring pixels, shall be deemed centers of candidate events.

The bias and dark current removal processing shall accommodate frame-to-frame variation of detector bias level.

ACIS shall be capable of two event telemetry submodes. In faint submode, all available information (event location and nine pixel amplitudes and the bias correction amplitude) shall be telemetered. In bright submode, event amplitude and position information shall be telemetered, but fewer bits shall be assigned to each event. Some loss of information about spatial distribution and amplitude of events may occur in bright telemetry submode. In faint submode, information about all candidate events shall be telemetered. In bright submode, data processing algorithms shall be used to assign grades to candidate events. The grade of an event shall be a function of the amplitude and spatial distribution of charge in that event. Grades shall be defined so as to facilitate discrimination between valid X-ray events and background events. In bright telemetry mode, it shall be possible to select events for telemetry on the basis of grade. The grade selection criteria shall be adjustable via command, and it shall be possible to include all event grades in the bright submode telemetry stream.

Event timing information shall be relatible to the AXAF-I clock with an accuracy of one period of the AXAF-I central clock as defined in paragraph 3.6.3 of the Observatory to Science Instrument ICD. Paragraph 3.6.3 of the Observatory to Science Instrument ICD states that the clock resolution is 1us.

The digital processing system shall be capable of continuous operation in event mode with any input data stream with all of the following characteristics:

i) containing at least 1000 pixels above threshold per second per CCD data stream (due to valid x-ray events, background events, and hot pixels); and ii) containing a total valid X-ray event rate (in all six CCD data streams) of a rate of at least 750 events per second.

b) Timing Mode

This mode shall be used to process data obtained in continuous readout mode. Event amplitude and position information will be compressed to a level commensurate with the telemetry limit. The data stream shall be time-stamped with the AXAF-I central clock time at least every (TBR) major frame.

c). Bright Source Imaging Mode

Data rate control involving loss of temporal, spatial or spectral resolution shall be provided if required to accommodate the telemetry bandwidth constraints. Where these measures are inadequate to reduce the output data rate below 24 kbps, data processing shall be terminated for the duration necessary to eliminate data buffer overflow. The data buffer size is TBD and the action(s) of the data system on data buffer overflow are TBD.

d). Bright Source Spectroscopy Mode

This mode shall provide specialized data compression for TGS observations of bright sources. The data compression shall preserve information on X-ray intensity as a function of position along the grating dispersion axes inherent in the input data streams.

e). Calibration and Diagnostic Modes

All calibration and diagnostic modes shall function both when ACIS is at the HRMA focus and when ACIS is next in line, making full use of the telemetry capacity available in either state. These modes shall provide information on system performance including system noise, CCD charge transfer efficiency, CCD dark current, spectral resolution, energy-to-pulse-height gain, CCD quantum efficiency and background event rates. For diagnostic purposes, there shall be the capability of transmitting a full frame

3.1.4 Organizational and Management Relationships

The AXAF-I Program Requirements are defined in AXAF-101, AXAF Program Policy and Requirements Document, Level I. NASA Headquarters is responsible for Level I documents. The AXAF-I project requirements are defined in MSFC-SPEC-1836, Advanced X-ray Astrophysics Facility Level II Project Requirements Document (PRD).

The Observatory to Science Instrument ICDs are Level II documents. Instrument and GSE CEI specifications and instrument subsystem VRSD's are Level III documents. Instrument subsystem and non-flight software requirements and specifications are Level IV documents. MSFC is responsible for Level II and Level III documents. The instrument organization is responsible for Level IV documents. The instrument organization may be required to provide inputs to MSFC for Level I, II, or III documents. The instrument organization shall be required to provide informal inputs to the AXAF-I Integration Contractor for preparation of the observatory-to instrument ICD's and observatory level specifications and procedures.

Documents numbered AXAF-101 and MSFC-SPEC-1836 are incorporated into this CEI specification for information only, and are not intended to be used as a source for the design and performance requirements, unless specifically specified.

3.1.5 Systems Engineering Requirements

The ACIS Project Work Breakdown Structure is contained in ACIS 36-00103. This document defines the effort to design,develop, and produce the ACIS instrument for AXAF-I. A specification tree indicating the relationships among the specifications governing the ACIS program is illustrated in Figure 3.1-2. The systems engineering effort will insure compliance between the specifications governing the ACIS program and the requirements for the AXAF-I. In addition this effort supports design, fabrication, assembly, procurement and testing of the ACIS instrument to insure successful integration, calibration, and operation of the ACIS instrument

3.1.6 Government Furnished Equipment (GFE)

Government Furnished Equipment (GFE) required for development of this instrument is identified in the Contract Statement of Work, Attachment J-8, of Contract NAS 8-37716.

3.1.7 Payload Classification

The instrument shall be designed as a Class B Payload in accordance with NMI-8010.1.

3.2 Characteristics

3.2.1 Performance

The ACIS instrument shall have the following performance characteristics when installed in the AXAF-I:

a) Imaging with a multi-CCD array located on the HRMA focal surface. Spectroscopy with a second multi-CCD linear array positioned at the HETG Rowland Circle.

b) Each CCD shall be a framestore device, with pixel size in the imaging array of no larger than 24 microns square (subtending no more than 0.5 arcsec at the telescope focus.)

c) The field of view for imaging shall be at least 285 square arc minutes. The Transmission Grating Spectrometer (TGS) array shall be at least 24.58 mm wide and 149 mm long.

d) The CCDs shall be capable of detecting individual X-ray photons, with quantum efficiencies of at least 5% between 0.4 and 0.7 keV, at least 85% at 4 KEV. The CCD quantum efficiency shall nominally exceed 50% between 0.7 and 8 KEV. The CCDs shall be deemed to have met the nominal specification if the specified quantum, efficiency is exceeded over at least 75 % of the specified passband.

e) Energy resolution in the imaging mode shall be no worse than 100 eV (full-width at half-maximum) at 1 keV and no worse than 150 eV at 5.9 keV.

f) System noise measured for each CCD shall not exceed 4 electrons RMS (TBR).

g) The mean (pixel averaged) quantum efficiency of each CCD, measured at wavelengths between 400 and 1100 nm, shall not exceed 10E-6 TBR when the optical blocking filter is in place. This efficiency specification will be updated after further evaluation of the CCD devices.

3.2.2 Physical Weight

The ACIS weight, excluding GFE components, shall not exceed 260 pounds. Center of Gravity

The instrument configuration shall be designed so as to be consistent with CG constraints specified in the Observatory to Science Instrument ICD paragraph Envelope Dimensions

The instrument envelope outer dimensions shall not exceed the static and dynamic envelopes as defined in the Observatory to Science Instrument ICD paragraph Mounting

The instrument shall be mounted to the spacecraft in accordance with paragraph of the Observatory to Science Instrument ICD. The detector assembly shall be capable of removal and subsequent remounting without loss of alignment

The instrument shall be equipped with GFE provided fiducial lights and located as shown in paragraph of the Observatory to Science Instrument ICD.

The stability of the fiducial light locations, relative to the positions of the ACIS detectors, shall be such that errors in knowledge of the fiducial light locations relative to the ACIS detectors contributes no more than 0.12 TBR arcsec (in quadrature) to total RMS image location error, and no more than 0.23 TBR arcsec to the RMS diameter of the reconstructed image of a point source. This specification on the location and orientation of the fiducial lights relative to that of the detectors limits cumulative errors arising at any time between successive Observatory boresight operations. The times and conditions of Observatory boresight operations are specified in TBD.

The long term stability of the fiducial light locations shall be sufficient that the fiducial lights are always within the field of view of the Observatory aspect system, as specified in paragraph of the Observatory to Science Instrument ICD., for all nominal SIM positions placing ACIS in the HRMA beam. Stray Light

Light reflected from or emitted, including internally generated, by the instrument shall not exceed the limits specified in paragraph 3.1.2 of the Observatory to Science Instrument ICD SI Induced Disturbances

SI induced disturbances shall meet the requirements of paragraph of the Observatory to Science Instrument ICD . Alignment

Given that the position of the focal-plane relative to the ACIS-SIM interface is nominal, immediately after focusing operations the initial position of the detector surface shall not deviate from the nominal prescribed surface for receipt of best-focused X-ray energy by more than:

Delta x =  0.025 in.
Delta y =  0.008 in.
Delta z =  0.025 in.
Omega x =  10 arcmin
Omega y &Omega z = 1.5 arcmin

The alignment of the ACIS focal plane relative to its alignment reference will be bias corrected to account for the alignment at the nominal operating temperature of the focal plane ( -120 deg C )

The rotation and lateral dimensions in this section refer to the spacecraft coordinate system. ACIS will incorporate alingment references in accordance with paragraph of the Observatory to Science Instrument ICD (TBR) Long-Term Stability

Given that the position of the focal-plane relative to the ACIS-SIM interface is nominal, the RMS amplitude of long-term ACIS detector motion, relative to the nominal prescribed surface of receipt of best-focused X-ray energy shall not exceed the following, over the temporal frequency ranges indicated: and as shown in paragraph of the Observatory to Science Instrument ICD (TBR)

Delta x = 0.0015 in  (all frequencies)    TBR
Delta y = 0.002 in.  (0 < f < 0.05 Hz)
Delta z = 0.002 in.  (0 < f < 0.05 Hz)
Omega x = 150 arcsec  (0 < f < 0.05 Hz)
Omega y = 14 arcsec  (all frequencies)    TBR
Omega z = 3.5 arcsec  (all frequencies) Short-Term Stability

Given that the position of the focal-plane relative to the ACIS-SIM interface is nominal, the peak-to-peak amplitude of ACIS short-term detector motion, relative to the nominal prescribed surface of receipt of best-focused X-ray energy shall not exceed the following, over the temporal frequency ranges indicated: and as shown in paragraph of the Observatory to Science Instrument ICD (TBR)

Translation        Rotation
Delta x =   0.0005 in                Omega x = 5 arcsec(>0.05 Hz)
Delta y =  0.00009 in.(>0.05 Hz)    Omega y = 3.5 arcsec
Delta z =  0.00009 in.(>0.05 Hz)    Omega z = 3.5 arcsec Detector Assembly Purge

The detector assembly shall be designed to accommodate a gaseous purge for contamination abatement purposes. The DA shall meet all performance requirements with the purge removed 61 hours prior to launch (not including contingency), and after purging in accordance with all applicable procedures during ground operations and processing. The DA shall employ a vent pipe to allow venting of the assembly to space and to serve as a means of pressurization or evacuation of the assembly. The vent pipe will be designed to prevent the back flow of outside air into the detector assembly.

3.2.3 Reliability Operational Life

The instrument shall contain no design features which preclude an overall lifetime of eleven (11) years, including ground and on-orbit life. Ground Life

The instrument shall be designed for a ground lifetime of six (6) years, beginning with application of electrical power to the instrument, and includes: instrument test and verification; instrument storage; AXAF-I test, verification, observatory storage and launch. On-Orbit Life

The instrument shall be designed for an minimum on-orbit life of five (5) years. The ACIS instrument shall be capable of performance as specified herein under a combination of all worst-case environmental (except for on orbit irradiation environment which for purposes of this paragraph is nominal only) and operational conditions. Electrical, Electronic, and Electromechanical (EEE) Parts Standard

EEE parts shall meet the intent of NHB 5300.4 (1F), tailored for the SI as follows:

a. A Parts Control Board is optional. (ref.1F201)

b. EEE parts shall be selected in accordance with MIL-STD-975. EEE parts shall be of a quality level no lower than Grade 2.

c. Rescreening of JANTXV devices is not required.

d. For applications deemed criticality 1, 1R, 2R. 2P or 2PR per MSFC CR-5320.9, Grade 1 parts or parts upgraded to Grade 1 shall be used. Upgrading shall conform to the requirements of MIL-STD-975, Appendix B.

e. Microcircuits and semiconductors shall be subjected to radiographic (X-ray) inspection and Particle Impact Noise Detection (PIND) appropriate to construction. Microcircuits per MIL-M-38510 are preferred. However, microcircuits which are fully compliant with para. 1.2.1 of MIL-STD-883 may be used with MSFC approval (NSPAR required). If a microcircuit is not a QPL class B part or purchased from a QML manufacturer, then it requires a NSPAR.

f. Custom devices shall include DPA (Destructive Physical Analysis) on a sample basis. DPA shall not be required on other devices. (ref. 1F313)

g. Data required under NHB5300.4 (1F) shall be satisfied by the submissions of DRs SPA01, SPA02, SPA03, SPA05, SCM05,SCM10 AND SHF03 of the SI DPD. (ref. 1F201, 1F202, 1F204, 1F205L, 1F300, 1F301, 1F304 AND 1F308)

h. Requirements for a coordinated parts procurement do not apply. (ref. 1F203)

i. EEE parts shall be retested prior to installation if the time prescribed in the controlling specification or 5 years have elapsed since the part successfully completed inspection lot test. (ref. 1F310)

j. The SI contractor shall review ALERTS, notices and advisories and respond to MSFC in accordance with DR SPA07.

k. The SI contractor shall ensure that the results of receiving inspection, parts tests, material review boards and parts problems reported from system testing are documented and periodically reviewed. (ref. 1F307) Parts

Nonstandard parts may be used where standard parts do not exist or are not available. Nonstandard parts must be of a quality equal to that of standard parts and must be approved by MSFC via NSPAR. (ref. 1F301 and DR SPA03) Parts

Used EEE parts shall not be incorporated into the instrument hardware. Parts removed shall be replaced with new components. Critical Components

Components having failures in categories 1, 1R that are less than two fault tolerant, 2 or 2P, as defined in MSFC CR-5320.9, shall not be used.

3.2.4 Safety

The SI and its support equipment shall be designed to be in compliance with MSFC and NASA safety requirements as specified below. Flight Safety

The SI and its airborne support equipment shall be designed to comply with NSTS-07700, Vol. XIV, Attachment 1 and NSTS 1700.7. Launch Site Safety

The SI and its ground support equipment for KSC shall be designed to comply with KHB 1700.7 and GP-1098. Other Safety Requirements

Other safety requirements which shall be incorporated into the SI safety design are contained in MMI 6400.2, MSFC-STD-126 and NHB 6000.l Radiation Safety

Any material, component, or subsystem containing natural or man-made sources of nuclear radiation shall be avoided unless prior approval by waiver is obtained from NASA and unless the item(s) are in compliance with MMI 1860.4, NSTS 1700.7 and NSTS 13830B.

3.2.5 Environmental Conditions Natural

ACIS shall be designed to withstand the natural environments in accordance with paragraph of the Observatory to Science Instrument ICD. Radiation

Electronic subsystems subjected to environments defined in (document number SE29), shall be designed so that the instrument performance is not degraded to values below those specified in the CEI Instrument Performance Characteristics (para 3.2.1). This will be in accordance with paragraph of the Observatory to Science Instrument ICD. Thermal

The SI shall be designed to meet the thermal requirements to be encountered in the mission, including safe mode survival temperatures. These extremes consist of two types:

(a) steady state -- "hot and cold case"

(b) on-orbit thermal transient

The SI shall perform satisfactorily following exposure to the on-orbit safemode thermal environment. The thermal environments are identified in paragraphs and 3.3.2 of the Observatory to Science Instrument ICD Steady State Extremes

Steady state extremes, which affect temperature level, shall include the ground processing environment, the launch environment and the on-orbit environment. On-Orbit Extremes

The on-orbit extremes shall be based upon worst case combinations of the space environment thermal parameters and the spacecraft parameters, i.e., surface thermo-optical properties, insulation performance, power level, Beta angle, altitude, and attitude. Magnetic Susceptibility

The SI shall meet the performance requirements stated herein during exposure to magnetic field limits defined in paragraph of the Observatory to Science Instrument ICD Induced Environment

The SI shall meet the performance requirements stated herein following exposure to any environment or combination of environments specified in the Observatory to Science Instrument ICD for ground handling, launch and abort landing. The detail requirements of NSTS 1700.7 (structural, pressure, fault tolerance, etc) shall be satisfied under the worst-case STS environments, including abort and emergency landing conditions as specified in paragraph of the Observatory to Science Instrument ICD. The instrument shall be certifiable as safe in these environments. Acoustics

The SI shall meet the performance requirements stated herein following exposure to the acoustic levels specified in paragraph of the Observatory to Science Instrument ICD Random Vibration

The SI shall meet the performance requirements stated herein following exposure to the random vibration levels specified in paragraph of the Observatory to Science Instrument ICD Design Loads

The SI shall meet the performance requirements stated herein following exposure to the combined loads derived from the acoustics, random vibration, thermal, vehicle transients (including launch, aborts, and landing with the SSE), and quasistatic loads. The SI is a non-returnable payload as defined in NSTS-07700, Vol XIV, Attachment 1. Component and Subsystem Loads

Final design loads shall be the appropriate combination of the analytically derived component, subsystem and system loads. System Load Factors

The SI shall meet the performance requirements of the Launch and Landing loads specified in paragraph of the Observatory to Science Instrument ICD Magnetic Environment Magnetic Field Intensity

The instrument shall be designed for magnetic cleanliness, wiring control, and minimal dc magnetic fields. The magnetic field generated by the instrument shall not degrade its performance below the performance requirements stated herein and shall comply with paragraph of the Observatory to Science Instrument ICD. Magnetic Moment

The residual plus induced magnetic moment in an arbitrary orientation in the Earth's magnetic field shall not degrade its performance below the performance requirements stated herein and shall comply with paragraph of the Observatory to Science Instrument ICD. Meteroid and Orbital Debris Impact

The SI shall provide protection against loss of functional capability of the radiator when subjected to the meteoroid flux as defined in paragraph of the Observatory to Science Instrument ICD The probability of SI functional capability shall be at least 0.92 for 5 years. Orbiter Cargo Bay Environment

The ACIS radiators (thermal control system) shall be designed with enough pre launch margin to be compatible with the Orbiter Cargo Bay cleanliness and contamination requirements as stated in paragraph of TRW SE28 Contamination Control and Implementation Plan. In addition the ACIS detector housing shall be designed with a door assembly that will remain closed and sealed when the AXAF is in the Orbiter Cargo Bay. Atomic Oxygen

The AXAF-I Observatory will be placed into a high altitude orbit (10,000 to 100,000 kilometer ) for its operational life. AXAF-I will spend a short duration in a low altitude parking orbit before being placed into its final high altitude orbit. The short duration ( TBD ) that AXAF-I will spend in a low earth orbit reduces the effects of Atomic Oxygen on the ACIS to a negligible level. Also the selection of materials shall be compatible with this short term exposure (during the low earth parking orbit period) to the effects of orbital atomic oxygen.

3.2.6 Transportability and Transportation

The SI shall be transported using equipment specifically designed to protect the flight hardware during ground or air transportation. Vibration, shock, temperature, pressure, humidity, electrostatic potential, and contamination shall be controlled during transportation to not exceed flight hardware design levels. All handling and transportation equipment used shall be compatible with the structural and environmental limits. Transportation and handling of the SI shall comply with the requirements of MMI 6400.2, MSFC-STD-126 and NHB 6000.1. Ground Handling

The SI shall have provisions for the attachment of handling fixtures to permit transportation and horizontal installation and removal from AXAF-I in accordance with paragraph of the Observatory to Science Instrument ICD.. Transportation Equipment Shipping Container

The SI shipping container shall be provided by the instrument supplier, and shall be compatible with the structural and environmental limits specified herein and in accordance with paragraph of the Observatory to Science Instrument ICD.. Vibration and Shock

During transportation and handling of SI flight hardware, ground support equipment shall impose no more than 80 percent of the dynamic loads specified in paragraphs and of the Observatory to Science Instrument ICD. Environmental Control Humidity

The transportation equipment shall maintain the relative humidity between 40% and 60% under protective covers such that changes of temperature during transportation shall not result in the condensation of moisture. Temperature

The temperature during transportation shall be maintained between -20 deg C and 40 deg C. Pressure

The pressure inside the shipping container during transportation shall be maintained such that the SI's performance not be degraded below the performance requirements stated herein. Contamination

The contamination levels inside the shipping container during transportation shall not degrade the SI performance below the performance requirements stated herein. Instrumentation

Instrumentation for measuring acceleration, temperature, humidity, contamination, and pressure shall be provided to measure and record the conditions experienced during transportation. SI Monitoring

The transportation equipment shall accommodate monitoring and maintenance of critical instrument parameters such as DA pressure Unique Instrument monitoring and maintenance equipment shall be provided by the instrument supplier for integration into the AXAF-I transportation system.

3.2.7 Storage

The ACIS shall be stored using equipment specifically designed to protect the flight hardware. Temperature, pressure, humidity, and contamination shall be controlled during storage so as not to exceed flight hardware design levels. Instrument Storage

The instrument shall be capable of storage in its shipping container. AXAF-I Storage

The instrument shall be capable of storage in the SIM and the AXAF-I system.

3.2.8 Safe Modes

The ACIS instrument shall be capable of entering a safe mode that will have its survival temperature maintained by the SIM and have its subsystems configured into a low power mode, by command, to conserve spacecraft power while at the same time retaining its SRAM data tables. This mode once initiated will not require ground intervention for 72 hours or more and will be implemented in such way as to minimize the impact on the DSN and mission timeline when transitioning from safe mode back to normal operating mode. Also ACIS will be capable of having all power turned off by command, and the survival temperature limits of ACIS maintained by SIM controled heaters. This mode once initiated has no time limit, however once power is reinstated, by command, to the ACIS instrument a default system configuration only (ie. parameter, mode tables) will be available until new table configurations can be loaded via. the space craft command system.

3.3 Design and Construction

3.3.1 General

All material and parts shall be procured to an approved specification or an approved part drawing. Approved process specifications shall be used to control critical manufacturing and assembly operations.

3.3.2 Selection of Specifications, Standards and Processes

All materials, parts and processes shall be defined by standards, specifications and processes selected from MM 8070.2 and MSFC-HDBK 527E. Selection of experimenter specifications and standards over existing higher order of precedence standards, specifications, and procedures must have prior MSFC approval. Rationale for this selection shall include an identification of each higher order of precedence specification, standard or process examined and state why each was unacceptable. For purposes of this order of precedence, commercial materials, parts and processes shall be considered equivalent to experimenter standards. Approved MSFC specifications and standards shall be selected in accordance with MM 8070.2, paragraph 7.

3.3.3 Electrical Electrical Networks Wiring Harnesses

Wiring installation shall consist of cable harnesses where required. Electrical wiring harness assemblies shall be in accordance with NHB 5300.4(3G) and MSFC letter EH02 (89-0782), and shall be installed per MSFC-SPEC-494.

To the extent practical, redundant wiring shall be routed through separate bundles and harness in-line interface connectors. All safety critical functions shall be routed through separate connectors. Wires

Wire used in cable harnesses shall conform to Specifications MIL-C-l7, MIL-W-22759, and MIL-W-81381. Cable Shielding

All ACIS electrical wiring not contained within an electricaly conductive enclosure shall be shielded in accordance with paragraph of the Observatory to Science Instrument ICD where possible. Interconnections Connectors

Connectors shall be in accordance with MIL-C-38999 and MIL-C-390l2. Electrical contact retention shall comply with MSFC-STD-781. Splices

Splices are not allowed without prior MSFC approval. Crimping and Wire Wrap

Crimping and wire wrap shall be in accordance with NHB 5300.4(3H). Soldering

Soldering shall be in accordance with NHB 5300.4 (3A-1). Brazing

Brazing shall be in accordance with specification MIL-B-7883. Printed Circuits Boards

Printed circuit boards shall be designed in accordance with NHB 5300.4(3K) and fabricated in accordance with NHB 5300.4(3I). Conformal Coating

Conformal coating shall be in accordance with NHB 5300.4(3J). Continuity and Insulation

Continuity, insulation resistance, and dielectric withstanding voltage shall be in accordance with NHB 5300.4(3G). Analog Circuit Routing

Analog circuits which require remote signal conditioning shall be routed on a twisted-wire pair or co-ax and shall not use structure as return. Electromagnetic Compatibility Electromagnetic Radiation Self Compatibility

The instrument shall be electromagnetically compatible within itself and shall meet the requirements of MIL-E-6051. Orbiter Compatibility

The instrument shall be compatible with the STS electromagnetic characteristics as defined in NSTS 07700, Volume XIV, Attachment 1. Electronic Equipment

Electronic equipment shall meet the requirements of MIL-STD-461 and MIL-E-6051. The requirements of MIL-STD-46l shall be modified as necessary to assure compliance with MIL-E-6051 and be in accordance with paragraph of the Observatory to Science Instrument ICD. Corona Suppression

Electrical and electronic subsystems and components shall be designed in accordance with MSFC-STD-53l, such that their proper performance shall not be impaired by corona discharge in normal operating environments and shall not be a source of interference which adversely affects the operation of other equipment. RF Components

Any RF component shall be designed to avoid the occurrence of multipaction and/or corona RF breakdown during all phases of mission operations. Sealed Components

Where adverse corona effects are avoided by pressurizing or evacuating a component, the seals used shall be capable of maintaining the required internal pressure throughout the established useful life of the hardware. Unsealed Components

Where adverse corona effects are avoided in unsealed components by restricting operation to space-vacuum conditions, the equipment shall be capable of reaching the required vacuum level of 10E-5 torr, within 10 days after deployment from the Orbiter. Lightning Protection Component Protection

Electrical and electronic components shall be adequately protected from high currents induced by lightning in accordance with the bonding specification MIL-B-5087. Lightning Induced Failure Protection

ACIS shall be designed such that a lightning induced failure in ACIS shall not propagate into an AXAF-I or Orbiter catastrophic failure.

3.3.4 Mechanical Factors of Safety

The instrument shall be designed using the "A" values of MIL-HDBK-5 to a factor of safety on all structural components, subsystems and systems equal to or greater than those shown in the following. This stipulation includes nonmetallic structures for which "A" values shall be developed using the statistical methods contained in MIL-HDBK-5. AXAF-I structural elements shall be designed to the factor of safety defined in MSFC-HDBK-505 for manned flight structures. Structural elements are defined as those structural parts, including fasteners, brackets and light shields, that experience loads during ground operations, launch, ascent, on-orbit operations and return to Earth. Emergency Landing

The SI shall be designed such that it will not create an STS hazard when subjected to the emergency landing loads specified in paragraph of the Observatory to Science Instrument ICD. Following exposure to these loads, the instrument shall not be required to operate satisfactorily. The structure may yield but not fracture. Control of Weld Filler Material

Control of weld filler material shall be in accordance with MSFC-STD-655. Strength

The instrument structure shall be designed to have sufficient strength to withstand the yield and the ultimate loads with other accompanying environmental phenomena for each design condition. Nonmetallic Materials

With MSFC approval, certain nonmetallic materials may be required to meet the ultimate loads criterion only. Fasteners

Fastener allowable strength shall be in accordance with MIL-HDBK-5. Threaded Fasteners

Installation torque values for threaded fasteners shall be in accordance with MSFC-STD-486 and MSFC-STD-557, and secured in accordance with MSFC-STD-561. Rivet Type Fasteners

Rivets and rivet type fasteners shall be installed in accordance with MSFC-STD-156. Fatigue and Fracture Mechanics

The structural elements shall be designed to withstand the effects of repeated loads and pressure cycles caused by all SI ground handling, transportation and testing, AXAF-I transportation to the launch site, two launches (neither followed by an emergency landing), two returns to Earth. Requirements of MSFC-HDBK-1453 shall be implemented, and all required nondestructive evaluation shall be performed per MSFC-STD-1249. Pyrotechnic Devices

Pyrotechnic devices shall not be used.

3.3.5 Materials Materials and Processes

Materials and Processes shall comply with MSFC-STD-506 . The materials selection list MSFC-HDBK-527 shall be used during design. Outgassing and Volatile Condensable Materials

All materials shall meet the thermal vacuum stability and volatile condensable requirements of JSC-SP-R-0022. Any nonmetallic material which has the potential for contaminating the HRMA optical surface and for which adequate test data is not available shall be tested per the requirements of MSFC-SPEC-1443. Castings

Castings shall not be used without specific MSFC approval. Corrosion of Metal Parts

Metal parts shall be protected from corrosion by stress relieving, plating, anodizing, chemical coatings, organic finishes, or combination thereof, provided that such protection is compatible with the operating and space environmental requirements. Metallic materials used in construction of the instrument shall meet the stress corrosion requirements of MSFC-SPEC-522. Dissimilar Metals

The use of dissimilar metals (as defined in MSFC-SPEC-250) in direct contact is discouraged. When dissimilar metals are required to be joined, their facing surfaces shall be adequately insulated, preferably by an approved sealing compound to assure protection from electrolytic corrosion. Additional organic finishing or barrier tapes may be used, subject to requirements and restrictions of MSFC-SPEC-250. Finish

The finish shall be in accordance with MSFC-SPEC-250, except for special thermal and baffle finishes. Flammability

All nonmetallic materials shall meet the flammability requirements of NHB-8060.1. Corrosion

Metals in contact with fluid media shall be corrosion resistant and shall be compatible with the media to which they are exposed.

3.3.6 Contamination Control Environment

The instrument shall be designed to be compatible with the AXAF-I contamination requirements as specified in the ACIS contamination control plan, and in accordance with the paragraphs of section of the Observatory to Science Instrument ICD Bakeout

All cables, connectors, and other potentially contaminating equipment shall be baked out as required by MSFC-SPEC-1238 in accordance with paragraph of the Observatory to Science Instrument ICD..

3.3.7 Coordinate Systems

The coordinate system shall be in accordance with the paragraphs of 2.3.3 of the Observatory to Science Instrument ICD.

3.3.8 Identification and Marking

The instrument shall comply with identification and marking requirements as specified in MIL-STD-1285.

3.3.9 Workmanship

Workmanship standards shall comply with MIL-STD-454L.

3.3.10 Software Compatibility

The SI software shall comply with the AXAF-I to Science Instrument ICD.

3.4 Logistics

A spare for each circuit board configuration shall be fabricated and tested with the flight unit boards.

3.4.1 Maintenance

The ACIS instrument shall be designed for ease of maintenance,accessibility,and for reduction of maintenance needs and life cycle costs. The ACIS electronics, PSMC and detector assembly will be removable from the SIM.

3.4.2 Supply


3.4.3 Facilities and Facility Equipment Ground Support Equipment (GSE)

The instrument shall utilize facilities and facility equipment, such as cranes, transporters, and lifting devices provided by the integration and launch site organizations as common payload processing equipment. The instrument design shall comply with the launch site safety and processing requirements defined in GP-1098 and KHB 1700.7. Unique GSE

Unique GSE required for instrument handling and functions, such as checkout equipment and slings, shall be provided by the instrument supplier. This GSE shall comply with safety requirements specified in MSFC-STD-126.

3.5 Personnel and Training

Personnel and training shall be in accordance with NHB5300.4 (1D-2).

3.6 Interface Requirements

3.6.1 Observatory to Science Instrument Interfaces

Observatory to Science Instrument Interface characteristics and values are defined in the paragraphs of section 3.0 of the Observatory to Science Instrument ICD . The instrument design shall be consistent with these requirements.

3.6.2 Instrument-to-Instrument Interfaces

The instrument shall be designed to comply with the instrument-to-instrument interfaces as defined in APPENDIX A of the Observatory to Science Instrument ICD .

3.7 Subsystems

Each instrument subsystem shall be designed to meet the performance requirements specified herein when subjected to the environments and interfaces defined in the Observatory to Science Instrument ICD.

3.7.1 Structures and Mechanical Subsystem Structures and Mechanisms Instrument Mounting

The instrument shall provide mounting provisions for all components and subsystems in accordance with paragraph the Observatory to Science Instrument ICD . Attach Points

The instrument shall make provisions for suitable tiedown and lift attach points. Attach points shall not interfere with the assembly, checkout, or integration functions. Mechanisms

All mechanisms shall use redundancy where necessary to improve reliability. All mechanisms shall operate in a one g environment in any orientation, using counter balancing, if required. The detector housing will have an on orbit remotely actuated aperture cover.

The aperture cover shall be designed for the following cycle life:

a . Ground test, checkout and calibration operations, 100 open and close cycles.

b. on orbit, 1 open cycle.

The ACIS instrument will have mechanicely operated vented valves these valves shall be designed for the folowing cycle life.

a . Ground test, checkout and calibration operations, 100 open and close cycles.

b. on orbit, 1 open cycle. Dynamic Characteristics

Documents NASA TM-86538 and SD77-SH-0214 shall be utilized for defining and analyzing instrument dynamic characteristics. Stiffness

The instrument shall have stiffness which results in modal frequencies that satisfy the criteria listed in paragraph of the Observatory to Science Instrument ICD. Subsystem Induced Disturbances

To the extent practical, the instrument shall be designed to decouple frequent subsystem-induced disturbances from the SIM andAXAF-I. The instrument shall not exceed the levels specified in paragraph of the Observatory to Science Instrument ICD.

3.7.2 Thermal Control Subsystem (TCS) Heaters

The instrument TCS shall be primarily passive. However, heaters may be used where it can be demonstrated that thermal requirements cannot be totally met by passive techniques alone. Controlled Elements

The instrument TCS shall provide thermal control for all thermally sensitive components. Thermal Isolation
The instrument shall be thermally isolated from the observatory and from other SI's by use of low emissivity surfaces and low conductivity standoffs.

3.7.3 Venting Subsystem Ascent and Re-Entry

The instrument design shall provide ascent and re-entry venting between the instrument internal volume and the AXAF-I in accordance with profiles specifiedin paragraph of the Observatory to Science Instrument ICD. Pressure Differentials

The instrument venting design shall be such that ascent and descent pressure differentials shall be compatible with instrument structural design limits. Orbital Venting

Orbital venting shall be provided to reduce the internal volume pressure to required levels prior to activating pressure-sensitive equipment.(Ref. para.

3.7.4 Electrical and Power Subsystem (EPS) Electrical Power Requirements

The Peak Nominal Operating Mode Power shall not exceed 145 watts.

( Peak Nominal Operating Mode Power refers to ACIS operating with six active CCDs and the ACIS focal-plane being maintained at -120 deg C with both the voltages and currents at their maximum values.). The ACIS power interface shall be compatible with the AXAF supplied voltage of between +22 and +35 Vdc and ACIS shall be designed to operate over this voltage range. Bus Protection

The instrument shall provide internal bus control and protection in accordance with the paragraphs of of the Observatory to Science Instrument ICD.. EPS Interfaces

The EPS shall interface with the AXAF-I in accordance with the paragraphs of 3.5.1 of the Observatory to Science Instrument ICD. Power Isolation

All circuits receiving primary power from the AXAF-I shall be isolated from structure by a minimum of one megohm DC. When secondary (transformer isolated) power is generated within the SI, each secondary power return shall be grounded to structure as close to the source as possible. Loads receiving secondary power shall be isolated from structure by at least one megohm DC before connection to the Single Point Ground (SPG). Electrical Return Paths

Supply current shall not be returned through structure. Bonding

Instrument structure and equipment mounting shall be electrically bonded in accordance with MIL-B-5087. System Reliability Failure Propagation

No electrical failure shall cause propagation beyond the instrument-to-observatory interface. Redundant Paths

Redundant wiring shall be routed through separate bundles and connectors, to the greatest extent possible. Electrostatic Discharge Sensitive Parts

All electrical components utilizing electrostatic discharge sensitive parts shall provide adequate protection to preclude part failure resulting from handling, shipment, or storage situation, in accordance with MIL STD 1686A Cross Strap of Redundant Systems

The instrument shall be designed so that activation of redundant internal systems shall not require reconfiguration of observatory electrical and/or data systems.

3.7.5 Flight Software Subsystem General

Instrument flight software shall conform to the standards and requirements specified in CQ-5330.1, MM-8075.1 and NMI-2410.6, and shall provide the data processing necessary to implement such items as science instrument control and redundancy management. On-orbit changes capability and memory dump capability shall be provided. In addition the instrument flight software shall provide the data processing necessary to implement the CCD readout modes and the data processing modes of section 3.1.3 of this CEI specification. Observatory Interfaces

Observatory interfaces with the instrument flight software shall be in accordance with the paragraphs of 3.6 of the Observatory to Science Instrument ICD. This Observatory interface shall include a spacecraft generated time stamp (time stamp format TBD), the ability to accept commands for ACIS configuration and memory uplink, in addition to interfacing ACIS housekeeping and science data to the spacecraft onboard data system. Functions

The flight software is an integral part of the instrument and shall accomplish at least the following functions:

(a)  Executive
     (1)  Interrupt service
     (2)  Power-on/initialization
     (3)  Scheduler
     (4)  Mode control
     (5)  Service routine
     (6)  Utility.

(b)  Communication
     (1)   Command processing
     (2)   Telemetry control processing.

(c)  Redundancy Management
     (1)   Fault detection and isolation
     (2)   Periodic self-test
     (3)   Hardware reconfiguration Fault Management

The instrument flight software shall include the capability to detect and isolate faults, reconfigure to redundant units, report status and provide sufficient engineering data to the observatory telemetry system to verify instrument operation and support the ground controller in critical decisions. Periodic Self-Test

In addition to component fault detection and isolation, the flight software shall provide periodic self-test of the computational elements.

3.7.6 Data and Command Subsystem

The instrument data and command formats shall be compatible with paragraph 3.6 of the Observatory to Science Instrument ICD.


4.1 General

Verification of instrument design, construction, and performance shall assure that the hardware and software conform to the requirements stated herein. Environmental verification of the instrument shall be accomplished using the protoflight approach. The protoflight approach to verification means that a test program will be structured to combine the elements of qualification and acceptance testing into a joint qualification/acceptance test. The elements for accomplishing this test program are to apply controled environment test levels that generally exceed the predicted flight values and limit the test duration to those defined for flight acceptance testing. The protoflight levels will be chosen using MSFC-HDBK-670 as a guide. For the purpose of this CEI specification "the protoflight approach" test levels (chosen using MSFC-HDBK-670 as a guide and the environmental levels found in the Observatory to Science Instrument ICD ) will be used during the instrument environmental qualification phase.

4.1.1 Responsibility for Verification

The instrument team, including quality assurance, has responsibility for the verification of the SI; however, MSFC reserves the right to witness test performance, separately perform tests, and review or otherwise verify the results of all verifications accomplished.

4.1.2 Relationships to Management Review

(a) Development verification shall be reviewed at the Instrument PDR and CDR.

(b) All qualification verification shall be satisfactorily completed and reviewed prior to acceptance verification.

(c) Satisfactory completion of acceptance verifications shall be a prerequisite of the Instrument Acceptance Review.

4.1.3 Test and Equipment Failures

(a) Hardware and software failures (during testing) due to design errors during test shall disqualify all hardware and software made to the same specifications and intended for the same applications the hardware undergoing test (excluding limited life or "one-shot" items).

(b) When a failure occurs, necessary hardware or procedural or software changes shall be made and the non conformance shall be documented, understood, and dispositioned prior to continuing operations. In addition MSFC will be notified within 24 hours of a failure occurance.

(c) MSFC concurrence shall be required of qualification or acceptance test failure dispositions.

(d) A failure shall be defined as any condition which results in a performance parameter which is outside the required tolerance or may cause damage other than cosmetic.

4.1.4 Verification of Unplanned Equipment Uses


4.2 Verification Requirements

Verification of the instrument design and performance requirements and interfaces shall be accomplished by one or more of the verification methods and phases listed below. Also listed below are the associated codes to be used to complete the Verification Cross Reference Matrix (see paragraph 4.3).

Code Verification Methods       Code Verification Phases
  1  Similarity                   A. Development
  2  Analysis                     B. Qualification/Acceptance
  3  Inspection                   C. Post Acceptance
  4  Validation of Records        D. Prelaunch
  5  Demonstration, Measurement   E. Predeployment
  6  Simulation                   F. Flight/Mission
  7  Test
  8  Review of Design Doc
  9  System Environmental Test

A zero shall be entered into N/A column in the matrix when no verification is required.

4.2.1 Development

The development test phase objective is to assure that testing of critical items at all levels of assembly is sufficient to validate the design approach. This generally requires the use of a development unit, and thus, this phase is included in this document for information and comparison to the two phases which are used in protoflight hardware development. Verifications in this phase are not used as formal verification of requirements but as early evidence that the development or prototype unit will prove the feasibility of the design approach. It will demonstrate the capability of the selected configuration to satisfy performance requirements under ambient and environmental test conditions. This phase will develop confidence in the ability of hardware to accomplish the mission objectives. Development tests are used in the confirmation of performance margins, manufacturability, testability, maintainability, reliability, life expectancy, and compatibility with system safety requirements. While the use of system level development tests is generally not applicable in a protoflight program, development testing on critical components, when possible, is recommended.

4.2.2 Qualification/Acceptance

A Qualification/Acceptance test program will be implemented at the protoflight component level. This is accomplished, in most cases, by applying controlled environment tests levels that generally exceed predicted flight level extremes but do not exceed the design values. The test duration's are limited to those defined for flight acceptance testing. This type of program:

For the protoflight integrated hardware this phase will demonstrate that the assembled protoflight hardware will meet the performance specifications when subjected to environments generally equal to the maximum expected flight levels. This phase includes all ACIS verification activities up to ACIS integration into the SIM. For convenience this phase is also used for all formal analysis submittals, document releases and records validation since they are used to show requirement compliance as justification for "acceptance" of the hardware. Note formal analysis can be performed and submitted much earlier in time than acceptance or joint qualification/ acceptance testing and still fall under this phase.

4.2.3 Post Acceptance

This phase is used to indicate testing after ACIS integration into the SIM, and includes any verification testing related to the ISIM, observatory interfaces, XRCF or end to end testing that is required for ACIS. This phase ends with AXAF-I shipment to the launch site. Post Acceptance testing is the responsibility of the system contractor in accordance with paragraph of the Observatory to Science Instrument ICD..

4.3 Verification Cross Reference Matrix

An instrument Verification Cross Reference Matrix is attached as Appendix A, which describes how each specification requirement defined herein is verified by phase and verification method.

4.4 Verification Support Requirements

The following verification support requirements shall be satisfied.

4.4.1 Facilities and Equipment

(a) Facilities and equipment existing at the instrument supplier, subcontractors, and NASA shall be used to the maximum practical extent.

(b) Activation and operation plans shall be established involving test facilities/equipment, personnel, procedures and safety requirements.

(c) Test facilities/equipment used to test an item of hardware at more than one location shall be integrated to assure uniformity of test results.

(d) All test equipment shall be qualified or certified and verified prior to it's interfacing with flight or flight type hardware to ensure that no damage or degradation shall be introduced into the hardware being tested and that the test results shall not include test equipment error.

4.4.2 Test Articles

(a) Test articles (flight hardware or special GSE) required to support the instrument test program are as follows:

(a) ACIS Flight Unit

(b) TBD, To the extent feasible, designated test articles shall be minimized.

4.4.3 Software

Existing test automation and requirements traceability software shall be utilized to the maximum practical extent in support of verification. Test software interfacing with flight hardware shall be verified prior to verification tests.

4.4.4 Interfaces

When verification requires interfacing of the instrument CEI to other CEI's facilities/equipment, the interface verification shall be in accordance with verification procedures, specifications, and/or drawings. External interfaces shall meet the requirements specified in the Observatory to Science Instrument ICD.

4.4.5 This paragraph has been deleted, per RID #AXSI-0404 .

4.5 Verification Documentation

All verification documentation shall be available to inspection, test and assessment personnel. Applicable verification drawings, specifications and procedures shall be physically located at the verification site at the time of the verification event.

When each verification event is complete, the information required to validate compliance to each requirement shall be entered into the verification/compliance data base for completion of the matrix in the Verification Requirements Compliance Document.

4.6 Verification Methods

4.6.1 Similarity

Verification by similarity is a method of verification that verifies a requirement based on previously existing results from components and assemblies of like kind and includes a review of prior relevant hardware configurations and applications. Hardware of similar design and manufacturing process that have been qualified to equivalent or more stringent specifications also apply to this method.

4.6.2 Analysis

A method of verification, taking the form of the processing and accumulated results and conclusions, intended to provide proof that verification of a requirement(s) has been accomplished. The analytical results may be based on engineering study, compilation or interpretation of existing information, similarity to previously verified requirements, or derived from lower level examinations, tests, demonstrations, or analyses.

4.6.3 Inspection

An element of verification consisting of investigation, without the use of special laboratory appliances or procedures, to determine compliance with requirements. Examination is nondestructive and includes (but is not limited to) visual inspection, simple physical manipulation, gauging and measurement.

4.6.4 Validation of Records

Validation of Records is a method of verification that consists of a systematic review of all relevent records to demonstrate compliance with a requirement

4.6.5 Demonstration/Measurement

A method of verification that is limited to readily observable functional operation to determine compliance with requirements. This method will not require the use of special equipment or sophisticated instrumentation.

4.6.6 Simulation

Verification by simulation is a process of verifying a requirement through the use of a representative device or system that emulates the behavior of a device or system to be verified. This method is often used when direct measurements is not possible.

4.6.7 Test

A method of verification that employs technical means, including (but not limited to) the evaluation of functional operation by use of special equipment or instrumentation, simulation techniques and the application of established principles and procedures, to determine compliance with requirements. The analysis of data derived from test is an integral part of this verification method.

4.6.8 Review of Design Documentation

Verification by the review of design documentation is a method of verification that consists of a systematic review of design documentation to determine compliance with a requirement

4.6.9 System Environmental Test

System environmental tests are tests conducted after the ACIS has been integrated as a system and under the environmental conditions that the system will be subjected to during its life. These environments shall include but not be limited to thermal vacuum, and EMI.

5.0 Preparation For Delivery

5.1 General

Preservation and packaging materials shall be compatible with the environmental conditions and electrostatic discharge sensitive device requirements specified herein.

5.2 Specification Requirements

In addition to the general requirements of NHB 5300.4 (1B), the following specific requirements shall apply.

5.2.1 Shipping Container

The ACIS shipping container shall be designed to allow for at least one inch of protective padding material between the sides of the item and the inner walls of the case.Provisions shall be made for maintaining a purge for the detector housing during shipment, and provisions shall also be made for inclusion of the instrument log to accompany the item in shipment.

5.2.2 Preservation and Packaging

Preservation and packaging shall conform to MIL-P-9024 and the following:

a). Protection from electrostatic discharge shall be in accordance with MIL-STD-1686.

b).Machined surfaces and mounting holes shall be protected.

c). As a minimum, the item shall be wrapped and sealed in a polyethylene or equivalent bag, with whatever additional provisions as required for contamination control.

d).The item shall be cushioned using polystyrene or equivalent material.

e). A non contaminating film meeting the low outgassing requirements of JSC-SP-R- 0022A shall be used for the inner film bags. ( the film material will be selected from a list of films supplied by the spacecraft contractor )

5.2.3 Packing

The shipping container shall meet applicable carrier regulations and be of sufficient strength to safely ship the item without further packing or special provisions.

5.2.4 Marking for Shipment

Marking for shipment shall be in accordance with MIL-STD-129. Additional marking for electrostatic discharge sensitive items shall be in accordance with MIL-STD-1686.

The ACIS shipping container shall be marked or labeled with clear identification along with any special instructions needed for safe handling. A "FRAGILE-SENSITIVE SCIENTIFIC EQUIPMENT" label should be affixed to the shipping container. The label shall be clearly marked with the following information:

(a) Instrument identification number
(b) Instrument nomenclature
(c) Applicable NASA contract number
(d) Designation:  "ACIS"
(e) Contractor's name and address
(f) Destination name and address
(g) X-Ray not allowed

5.3 Transportation

5.3.1 Method

The ACIS instrument shall be transported using equipment specifically designed to protect the flight hardware during ground or air transportation. During transportation, vibration and shock shall not exceed 80 percent of those specified for flight operations. Temperature, pressure, humidity, static charge, and contamination, shall be controlled not to exceed flight hardware design levels. All handling and transportation equipment used shall be compatible with the applicable structural and environmental limits. The ACIS instrument will be escorted by ACIS personnel at all times during transportation. The transportation and handling of ACIS critical hardware shall be in compliance with the requirements of MMI 6400.2 and NHB 6000.1.

5.3.1 Destination

The destination of the shipped ACIS shall be the SIM contractor facility.

3.1 Definition

Provided For Information Only
3.1.1 ACIS Description

7 CCD Read out Modes


Data Processing Modes


3.2 Characteristics

3.2.1 Performance


3.2.2 Physical

Title Weight

2,5 Center of Gravity

2.5 Envelope Dimensions

2,5 Mounting

2,5 Fiducial Lights

2,5 Stray Light *

7 SI Induced Disturbances

9 Alignment

2,5 Long Term Stability
8 2 Short Term Stability
8 2 Detector Assembly Purge


3.2.3 Reliability

Title Operational Life

2 Ground Life
8 On Orbit Life

2 EEE Parts

Title Selection Standard

2,4 Nonstandard Parts
8 2,7 Used Parts

3,4 Critical Components


3.2.4 Safety

Title Flight Safety
8 2,4 Launch Site Safety
8 2,4 Other Safety Requirements

2 Radiation Safety
8 2

3.2.5 Environmental Conditions

Title Natural

2 Radiation

2 Thermal

2,7 Steady State Extremes

2 On Orbit Extremes

2 Magnetic Susceptibility
8 2,7 Induced Environment

2 Acoustics

7 Random Vibration

7 Design Loads
8 2 Component and Subsystem Loads System Load Factors

2 Magnetic Environment

Title Magnetic Field Intensity

2,7 Magnetic Moment

2,7 Meteoroid and Orbital Debris Impact


3.2.6 Transportability and Transportation

Title Ground Handling

Description Transportation Equipment

Title Shipping Container

2 Vibration and Shock

2 Environmental Control

Title Humidity

5 Temperature

5 Pressure

5 Contamination

5 Instrumentation


Description SI Monitoring


3.2.7 Storage


Title Instrument Storage

5 AXAF-I Storage


3.3 Design and Construction

3.3.1 General


3.3.2 Selection and Specifications of Standards and Processes

3.3.3 Electrical

Title Electrical Networks

Title Wiring

Title Harnessers

3,4 Wires

3,4 Interconnections Connectors

3,4 Splices

3,4 Crimping and Wire Wrap

3,4 Soldering

3,4 Brazing

2,4 Printed Circuits

Title Boards

2,4 Conformal Coating

4 Continuity and Insulation

2,7 Analog Circuit Routing
8 Electromagnetic Radiation

Title Electromagnetic Compatibility Self Compatibility

7 Orbiter Compatibility

7 Electronic Equipment

7 Corona Suppression

2 RF Components Sealed Components

2 Unsealed Components

2 Lightening Protection

Title Component Protection
8 2 Lightening Induced Failure Protection
8 2

3.3.4 Mechanical

Title Factor of Safety
8 2 Emergency Landing
8 2 Control of Weld Filler Material

3 Strength
8 2 Nonmetallic Materials
8 2 Fasteners
8 4 Threaded Fasteners
8 4 Rivet Type Fasteners
8 4 Fatigue and Fracture Mechanics
8 2 Pyrotechnic Devices

3.3.5 Materials

Title Materials and Processes

4 Outgassing and Volatile Condensible Materials

2,7 Castings

4 Corrosion of metal parts

4 Dissimilar Metals

2,4 Finish

3,4 Flammability

4 Corrosion


3.3.6 Contamination Control

Title Environment

2 Bakeout


3.3.7 Coordinate Systems

3.3.8 Identification and Marking


3.3.9 Workmanship


3.3.10 Software Compatibility *

7 7

3.4 Logistics


3.4.1 Maintenance

3.4.2 Supply

3.4.3 Facilities and Facility Equipment

Title Ground Support Equipment (GSE)
8 Unique GSE
8 2,7

3.5 Personal and Training


3.6 Interface Requirements

3.6.1 Observatory to Instrument Interfaces *

7 7

3.6.2 Instrument to Instrument Interfaces

7 7

3.7 Subsystems

3.7.1 Structures and Mechanical Subsystems

Title Structures and Mechanisms

Title Instrument Mounting

5 Attach Points

2,3 Mechanisms

2,5 5 Dynamic Characteristics
8 Stiffness

2 Subsystem Induced Disturbances


3.7.2 Thermal Control Subsystems *

2,9 2,9

Title Heaters *

2,9 2,9 Control Elements *

2,9 2,9 Thermal Isolation *

2,9 2,9

3.7.3 Venting Subsystem

Title Ascent and Re-Entry

2 Pressure Differentials

2 Orbital Venting


3.7.4 Electrical and Power Subsystems (EPS)

Title Electrical Power Requirements

7 7 Bus Protection

2,7 EPS Interfaces

7 7 Power Isolation

2,7 Electrical Return Paths

2,7 Bonding

3,7 Reliability

Title Failure Propagation
8 2 Redundant Paths
8 2 Electrostatic Discharge Sensitive Parts
8 2 Cross Strap of Redundant Systems
8 2

3.7.5 Flight Software Subsystems

Title General *

2,7 7 Observatory Interfaces *

7 7 Functions *

7 7 Fault Management *

2,7 7 Periodic Selftest


3.7.6 Data and Command Subsystems *

7 7

* Post Acceptance testing is required


ACIS    AXAf-I CCD Imaging Spectrometer
AFD     Aft Flight Deck
ATP     Authority to Proceed
AXAF    Advanced X-ray Astrophysics Facility
AXAF-I  Advanced X-ray Astrophysics Facility-Imaging Mission
BER     Bit Error Rate
BOD     Bright Object Detector
BOE     Basis of Estimate
C&DM    Configuration and Data Management
CCCB    Contractor Configuration Control Board
CCD     Charge Coupled Device
CDM     Command and Data Management
CDR     Critical Design Review
CDS     CCD Detector Subsystem
CEI     Contract End Item
CEIS    Contract End Item Specification
CFE     Contractor Furnished Equipment
CI      Configuration Item/Inspection
cm      Centimeter
CMS     Command Management System
COD     Change Order Directive
CPA     Change Proposal Authorization
CPU     Central Processing Unit
CSR     Center for Space Research
CTD     Charge Transfer Device
DA      Detector Assembly
DASS    Detector Assembly Support Structure
db      decibel
dc      direct current
DDT&E   Design, Develop, Test & Evaluate
DEA     Detector Electronics Assembly
DH      Detector Housing
DPA     Digital Processing Assembly
DPS     Detector and Processor Subsystem
DR      Data Requirements
ECM     Engineering Change Manager
ECP     Engineering Change Proposal
EEE     Electrical, Electronic and Electromagnetic
EGSE    Electrical Ground Support Equipment
EMC     Electromagnetic Compatibility
EMI     Electromagnetic Interference
EPD     Engineering Procedures Directive
EPS     Electrical Power Subsystem
ETR     Eastern Test Range
EU      Engineering Unit
eV      Electron Volt
EVA     Extravehicular Activity
FLCA    Fiducial Light Controller Assembly
FMEA    Failure Mode Effects Analysis
FOV     Field of View
FPA     Focal Plane Array
FPSI    Focal Plane Science Instrument
FRACAS  Failure Reporting and Corrective Action System
FU      Flight Unit
FWHM    Full Width Half Maximum
g       Gravity
GESS    Grating Element Support Structure
GFE     Government Furnished Equipment
GSE     Ground Support Equipment
GSFC    Goddard Space Flight Center
HEAO    High Energy Astronomical Observatory
HEG     High Energy Grating
HETG    High Energy Transmission Grating
HMSS    HRMA Module Support Structure
HRC     High Resolution Camera
HRMA    High Resolution Mirror Assembly
Hz      Hertz
I/F     Interface
IC      Integrated Circuit
ICD     Interface Control Document
ICS/E   Item Change Schedule/Estimate
ID      Identification
IEP     Instrument Engineering Plan
IPI     Instrument Principal Investigator
IRD     Interface Requirements Document
IS      Integrating Structure
JSC     Johnson Space Center
JU      Job Unit
kbps    kilobits per second
keV     kilo electron Volt
km      kilometer
KSC     Kennedy Space Center
LETG    Low Energy Transmission Grating
LOS     Line of Sight
LSB     Least Significant Bit
       micro (10-6)
MA      milliamp
MEL     Master Equipment List
MGSE    Mechnical Ground Support Equipment
min     minimum
MIT     Massachusetts Institute of Technology
MLI     Multi-Layer Insulation
MMAG    Martin Marietta Astronautics Group
MP      Master Plan
MSB     Most Significant Bit
MSFC    Marshall Space Flight Center
MSOCC   Multi-Satellite Operations Control Center
mV      millivolt
NA      Not Applicable/Available
NASA    National Aeronautics and Space Administration
NSTS    National Space Transportation System
OBA     Optical Bench Assembly
OBC     On-Board computer
OCC     Payload Operations Control Center
OD      Operations Directive
OGM     Objective Grating Mechanism
ORU     Orbital Replaceable Unit
OTG     Objective Transmission Grating
PCAD    Pointing Control and Aspect Determination
PCM     Program Change Manager
PDIS    Power, Digital & Integrating Structure
PDR     Preliminary Design Review
PMP     Parts Materials & Processes
PRD     Program Requirements Document
PRR     Preliminary Requirements Review
PS      Power Supply
PSF     Point Spread Function
PTS     Power and Thermal-Control Structure
QA      Quality Assurance
RAM     Random Access Memory
RCTU    Remote Command and Telemetry Unit
RFC     Request for Change
RFI     Radio Frequency Interference
RID     Review Item Discrepancy
ROM     Read Only Memory
RWA     Reaction Wheel Assembly
SAAD    South Atlantic Anomaly Detector
SEDB    Systems Engineering Data Base
SEMP    Systems Engineering Management Plan
SI      Science Instrument
SIAH    Science Instrument Accommodation Housing
SIM     Science Instrument Module
SOW     Statement of Work
SPL     Sound Pressure Level
SRM&QA  Safety, Reliability, Maintenance & Quality Assurance
SSE     Space Support Equipment
STE     Special Test Equipment
STS     Space Transportation System
TBD     To Be Determined
TBR     To Be Revised
TBS     To Be Supplied
TCS     Thermal Control System
TDRSS   Tracking and Data Relay Satellite System
TEC     Thermoelectric Cooler
TGS     Transmission Grating Spectrometer
TS      Telescope System
vdc     volts direct current
WBS     Work Breakdown Structure
WIP     Work In Progress
XRCF    X-Ray Calibration Facility
XRS     X-ray Spectrometer