April 30, 1997
CCD Imaging Spectrometer
|Submitted to:||Submitted by:|
|George C. Marshall Space Flight Center
National Aeronautics and Space Administration
Marshall Space Flight Center, AL 35812
|Center for Space Research
Massachusetts Institute of Technology
Cambridge, MA 02139
This report covers the period March 1997.
No monthly status review for ACIS was conducted in March. A review had been planned for mid-March as part of a MSFC visit to MIT for a pre-ship review of the ACIS experiment. However, noise problems during the Thermal Vacuum test at Lincoln caused us to delay delivery of the instrument so the face-to-face review was cancelled. In its place, a telecon review was conducted on March 19.
ACIS participated in the weekly AXAF telecons on March 4, 11, 18, and 25.
ACIS participated in the FPSI telecon on March 12. The telecon normally scheduled for March 26 was cancelled due to the monthly review the previous week (see above).
At Lincoln Lab, progress continued on the CCD front. The contamination problem described in last month's report was solved by a vacuum bakeout for several days at 30°C. The four imagers were cleaned in this fashion by March 7 and installed on the flight focal plane; the spectrometers were cleaned by March 15 and then also installed. After measurements of the CCD locations, bakeout, and 1238 certification, the flight focal plane was delivered to CSR on March 27.
The following is a brief summary of the status of the other ACIS elements:
The flight set of OBFs was successfully acoustic-tested at LMA in mid-March and delivered to MIT on March 18.
The T-V test of the ACIS instrument at Lincoln Laboratory was completed by February 25. No anomalies developed during the eight cycles of T-V testing. This was immediately followed by a 1238 bakeout and certification in the same chamber. ACIS passed the 1238 certification on March 2.
Notwithstanding the above, ACIS has been subject to excessive noise throughout the verification activities. Rather than take the ACIS experiment to MSFC for XRCF, it was decided to remain in the T-V chamber at Lincoln to investigate the noise problem. This troubleshooting began on March 2. In the meantime, LMA personnel (Larry Campbell plus tech) came to MIT and worked on the engineering unit PSMC/DEA/DPA. A miswiring in the PSMC was found by analyzing the system level drawings. On March 8, the LL T-V chamber was repressurized, and the mod made to the flight PSMC. Unfortunately, this did not fix the ACIS problem.
At this point, the flight hardware was returned to MIT and additional tests were performed. It was found that the preponderance of the noise was DPA to DEA. A fix was found by connecting the signal ground of the DEA boards to chassis ground (CIC layers of the PCBs) at four places on each board. This 'fix' was implemented on each of the ten analog boards of the DEA and all boards in the DPA.
Preliminary tests of some modified flight boards showed that the DPA to DEA noise was gone, but one noise source remained - 2 kHz coming from the PSMC. LMA was contacted again and a total of four LMA personnel spent the week of March 23 at MIT analyzing the situation (via the engineering unit DEA/DPA/ PSMC). Although the LMA personnel were not able to suppress the 2 kHz coming from the PSMC, they did point out that the on-board regulators in the DEA did nothing to attenuate the noise before passing the regulated voltages to the on-board circuitry. This was due to a low frequency band pass that stopped at 300 Hz.
By modifying the compensation network for the LM101 op-amp of the on-board regulator, MIT was able to extend the pass band to well beyond 2 kHz. Starting on March 29, the four regulators on all ten analog boards of the DEA were modified with this change. The unit was reassembled during the first week of April and the noise level was well within specification.
During the first week of April, the flight detector assembly was put together with the flight focal plane, radioactive source, flight OBFs, and proton shield parts.
During the weekend of April 5-6, the entire flight ACIS experiment was assembled and reinstalled in the T-V chamber at Lincoln. Thermal Vacuum testing and 1238 bakeout and recertification were completed during the second week of April.
The overall ACIS schedule can be expressed in one statement:
Due to the positive status of the ACIS instrument and schedule, layoffs are in progress:
|Joanne Vining||Test tech||April 18|
|Mary Briggs||R&QA tech||June 5|
|Bob Blozie||S/W Verif Eng||June 5|
At the time of the preparation of this report, the entire science team was at MSFC for ACIS/HRMA testing.
One week of science testing, following the first ACIS Thermal Vacuum Test, was completed in the LL thermal vacuum chamber on March 8. During the science testing, the DEA/DPA/SS and PSMC temperatures were set according to the scientists' requests, as opposed to setting the standard hot and cold soak extremes of a thermal vacuum test.
During the science testing, one 8-hour cold condition was maintained while powering the Support Structure heaters. (This was different from most of the cold testing because usually the DEA/DPA/SS was heated and cooled by adjusting the temperatures of their surrounding SIMSIM heater panels.) When the Support Structure heaters were powered, they were heated to their trim heater set-point temperatures (approximately +10°C/+12°C) to simulate the temperatures of the DEA/DPA/SS which will be typical during on-orbit cold operating conditions.
Data from the 8-hour study was compared with the pre-test predictions. Preliminary results indicate that the Support Structure heaters consumed approximately 13% more heater power than predicted. This information was FAX'ed to TRW, MSFC and BASD engineers with the intention of refining temperature predictions for XRCF testing and on-orbit operations. The responses from TRW and MSFC engineers are that a 13% difference is not sufficient to warrant changing their thermal models at this time. Presumably, after ISIM Thermal Balance Testing in September, the ACIS portion of the ISIM thermal model will be updated.
During March, some studies were performed to predict the ACIS Focal Plane temperature on-orbit. Hot and cold predictions indicate the FP will cool below -40°C within the first 12 hours after opening the payload bay doors.
Completed, at XRCF.
Completed, at XRCF.
Completed, at XRCF.
The following software ECOs have been reviewed this month:
They relate to Release 1.2 of the Flight Software, which was burned into the flight instrument during the first period of Thermal Vacuum testing at Lincoln Lab. In addition, the following ECO was prepared to describe the changes to be implemented in Release 1.3:
Revision 1.29 of the IP&CL structures table (36-53204.0204 Rev J) has been released. It describes Release 1.2 of the flight software. This release fixes a number of small bugs uncovered during thermal vacuum testing.
Release 1.2 of the Flight Software has been burned into the flight and engineering units, and is accompanied by release notes and building instructions. Default command blocks, bad pixel lists, etc., were supplied by the ACIS calibration team. Release 1.3, which contains the analog set points corresponding to the flight focal plane, is being prepared.
All BEP and FEP flight software modules continue to be subjected to unit and coverage tests.
High-level testing of Flight Software in FEP and BEP hardware continues, accompanied by tests using the software simulators. The following ECOs related to verification testing were reviewed during the month:
9 new software problem reports have been filed, of which 6 have been closed out. A total of 5 problem reports are outstanding, 1 of which refers to the flight software and will be closed out in Release 1.3.
The status may be inspected at the ACIS web server: "http://acis.mit.edu/axaf/spr/" .
Data sets from the Lincoln Lab tests have been translated from LRCTU to CTUE format and the BEP and IRIG-B time-stamps reconstructed. The resulting data sets have been delivered to PSU and ASC to assist them to prepare for XRCF data processing.
Fifteen (15) Alerts from NASA/MSFC were received over the report period. These items are listed below. Each Alert was compared with the available MIT parts lists. None of the Alerts impact the MIT ACIS Flight Hardware.
|Alert #||MSFC #||Part Number and Manufacturer||Part or Material Name|
Diodes and Transistors
|F4-A-96-01||6924||CV-2960 & CV-2946
Nusil Silicone Technology
|Adhesive, RTV Silicone,
Morpac Industries Inc.
|Logic Control Cards|
AI Technology Inc
|VV-P-97-01||7019||SD6529 et. al.
Advanced Photonix Inc.
|7021||SCT-323 & SCT-327
Daniels Manufacturing Corp
|MSFC TWX||7028||P/N N/A
(4 Meg Video RAM)
|P&W TWX||7032||ABS Polymer||ABS Polymer|
Special tests have been performed on the seven (7) fasteners types used in the Support Structure Assembly. These fasteners were tested for chemical and physical properties at Altran Materials Engineering Inc. A formal report from Altran indicates that all fasteners passed.
All remaining flight parts have been consolidated and reorganized for easier storage and retrieval.
MIT document 36-02030 has been prepared as a process specification to cover packaging, packing, handling, marking, storage and transportation of the ACIS. Copies of this document were sent to MSFC for information.
Waivers 36-001 through 36-004, 36-006, 36-009 and 36-011 have been approved by MSFC. Waiver 36-005 is not used. Listed below is the status of the remaining MIT waivers at this time. Waiver Request 36-016, which pertains to use of over-stressed electrical wire in ACIS Flight Cables, was prepared and submitted to MSFC.
|36-007||3% Reflectance loss on OWS for MSFC-SPEC-1238 testing||MIT||2/8/96||OPEN|
|36-008||AWG26 nickel wire from DA to DEA||MIT||2/7/96||WITHDRAWN|
|36-010||Continuity, IR, and DWV test after harness/cable installation||MIT||7/16/96||IN PROCESS|
|36-011||Use of over-stressed electrical wire in ACIS Flight Cables||MIT||3/28/97||IN PROCESS|
Waiver 36-007 is being revisited by MSFC in light of the decision not to bake-out the optical bench.
NSPAR Status: MIT NSPARs 36-001 through 36-030 have been approved by MSFC. MIT NSPAR 36-024 has been canceled/withdrawn. Lockheed Martin Astronautics (LMA) NSPARs MMA/ACIS-012b through MMA/ACIS-047 have been approved by MSFC. In addition, LMA is incorporating comments on NSPARs otherwise approved.
Specification 36-02352 for external radioactive sources has been changed. These are targeted sources with the radioactive element Fe55. The nickel target was changed to copper. Isotope Products Inc. will be ready for MIT source inspection on 4/22/97.
Prepared and submitted a letter to MSFC, detailing cautions to be observed at XRCF which are unique to the ACIS Flight Instrument.
No Activity this month.
Test Procedures: A total of 14 have been completed. Two test procedures were released this month (SysConfig, Overflow). One area of the Software Requirements (TrickleBias) was covered by Test Procedure MSFC 9902. Another area (DiagnosticMode) was covered by the Short Form test. Four tests are in the review process (RunFromSlot, Threshold, RawModeTest, GradedThreshold). Updated the Verification Run Procedure (36-02407) to include file naming conventions and PASS/FAIL tractability conventions.
Test Scripts: A total of 6 scripts sets have been completed. A script set of 7 scripts for (LoadCommand) has been completed and run on the Flight 1.0 version of the ACIS software. In addition, the test script file structure has been reorganized to conform to the Verification Run Procedure (36-02497).
CEI Requirements: Updated Overflow Test Procedure to include the Traceability to CEI requirements. Updated the VRSD to indicate Software Verification Test Procedures that satisfy various CEI requirements.
There have been 9 new problem reports identified this reporting period.
There now are 105 problem reports identified. Of those:
There has been no activity on the Performance Assurance and Safety (PAS) Plan. The PAS Plan in effect is Revision B.
Oversaw the removal of ACIS from the Vacuum chamber to ensure contamination was not induced. Helped separate the DEA/DPA electronics from the DA for modifications. Packaged the DEA/DPA for shipment to MIT.
Cleaned and inspected the PWAs after all modifications were completed. After final assembly, the instrument was cleaned and double-bagged for shipment and testing at Lincoln Labs.
Helped install the ACIS back into the Lincoln Labs chamber for further testing and 1238 certification.
Certified the Flight Focal Plane to MSFC-SPEC 1238.
Cleaned and vacuum-baked one of the CCD calibration chambers. Started monitoring and developing testing methods to determine cleanliness of the CCD calibration chambers.
Integration of the individual detectors into the Flight Detector Assembly has been completed. Electrical shorts and opens testing of each detector along with dark current measurements made at -40°C confirm that no damage occurred to any detector during assembly. Detector positions were measured after each step in the process and no movements were seen as a result of adhesive curing, dark current testing, or the vacuum bakeout performed for the MSFC 1238 certification. Lateral positions of the detectors easily meet the ±0.004-inch requirement. The out-of- plane errors are contained within a 0.0023-inch band compared to a 0.0020-inch goal. The majority of the out-of-plane errors are within a 0.001-inch band. No tip or tilt correction to the detector assembly is employed to minimize errors. Frame store shields have also been installed and location measurements indicate they are correctly located.
As previously reported, some of the flight detectors had inadvertently been contaminated with droplets of a hydrocarbon oil. Extensive testing of engineering detectors established that the best way to remove these droplets is with a low temperature vacuum bake. Each flight detector was vacuum-baked and functionally tested prior to installation in the Flight Detector Assembly. No anomalies were detected.
The flight array was delivered to CSR on 27 March 1997. Also, four reflexed individual detectors were delivered in March.
A replacement detector for the ACIS-2C assembly was MSFC 1238-certified to support testing at the XRCF.
The three flexprints undergoing a long-term thermal soak at -120°C were evaluated after an additional exposure of 57 days. This brings the total exposure time to 96 days. No anomalies were found.
Flexprints from Speedy Circuits' Lot 6 have successfully completed their thermal cycling tests. No failures in the flexprint vias or the connections between the flexprints and the alumina were seen after 200 cycles from -150 to +60°C. This completes the acceptance testing of this lot of flexprints. All available flexprints have been assembled and cleaned for flight use. This lot yielded 21 flexprints suitable for flight use. These flexprints will be used during the assembly of flight back-up detectors.
Graphics Research Inc. (GRI) has delivered a set of flexprints built with the conventional configuration (has vias at the cold end). These flexprints were ordered July 1997 as a second source of flexprints in case the other source failed to deliver. This delivery includes 65 flexprints that GRI feels are flight quality and 23 pieces that may be suitable for engineering tests. Coupon testing at Hi-Rel Laboratories and Lincoln Laboratory indicate that the parts are acceptable except for a few pieces with out-of-tolerance plating thickness. Visual inspection of the parts indicates that there may be problems with the gold plating. Additional evaluation will be performed in the coming weeks.
Campus confirmed last month that the contamination of samples is coming from their chambers. They observed, in situ, that contaminants adsorbed on samples can be desorbed under vacuum at 30°C. SIMS work at Penn State indicated that Na contamination on samples from various test chambers is below levels of concern to us.
A letter of intent for Change Order 67 was received early this month and the formal Change Order was received late in the month. This change order added several technical tasks and delayed the date of the ACIS Acceptance Review from 3/15/97 to 5/15/97 and delayed the associated work by two months. Since this new effort was defined and coordinated at the February Technical Interchange Meeting (TIM) and an engineering estimate was provided last month, the firm proposal for this change will be prepared quickly and submitted in early April. Also, Change Order 58 was definitized this month so all submitted change orders have been negotiated and Change Order 64 is the only one remaining to be definitized.
No ACIS NASA/MIT Monthly Status Review nor MIT/LMA Technical Interchange Meetings were conducted this month. Technical coordination was achieved by program telecons and LMA technical personnel supporting hardware integration, test and checkout activities at MIT.
Major LMA accomplishments for March included successful 1238 re-certification and delivery (DD250) to MIT/CSR of the Flight Detector Housing, the Flight Venting Subsystem, and the Vacuum Ground Support Equipment (VGSE) #2. The Detector Housing/Venting Subsystem Lifting Fixture and the GFP ACIS Drill Template were also provided to MIT/CSR to support hardware assembly and integration onto the SIMSim and alignment verification activities. LMA performed an alignment verification analysis following the alignment check performed by MIT which showed that proper alignment was maintained and no adjustments are required. The acoustics testing of the "first choice for flight" set of Flight Optical Blocking Filters was successfully completed at LMA and the filters we sent to Luxel Corporation for post-test inspection. A minor modification was made to both the EU and the Flight PSMC units to reduce the ACIS System EMI susceptibility and significant effort was expended in understanding ACIS system noise concerns and determining the cause. The noise concerns were corrected by MIT/CSR through a modification in the DEA and the System was reassembled for verification T-Vac testing at MIT/Lincoln Labs. LMA personnel supported the MIT assembly and integration of the ACIS Flight Hardware at MIT by performing the assembly of the LMA built hardware elements and providing test hardware and components to support assembly and test activities.
The program continued to review internal company Mission Success Bulletins and GIDEP ALERTS received during the month. None of these ALERTS were judged to be applicable to any of the parts or components used by LMA on the ACIS program. There have been no items defined during the month that warranted generating a Contractor-Initiated ALERT.
The program continued to place priority and primary emphasis on completion of the LMA-fabricated flight and ground support hardware assembly, integration and test prior to delivery to MIT; and supporting the test and integration of the ACIS hardware at MIT/CSR and MIT/LL. Efforts are also continuing on the preparation of the final deliverable CDRL documentation and verification reports.
Problems encountered during the month at LMA were limited to a suspected infant mortality failure of a venting subsystem absolute pressure transducer during pre-delivery testing. This transducer is used only by the VGSE. Therefore, it was replaced and necessary testing was performed. Failure analysis will be performed on the failed transducer.
The Flight Unit PSMC and EU2 PSMC continue to be jointly used at CSR in support of ACIS Flight Instrument integration testing. The Flight Instrument thermal vacuum test was completed, with some system-level noise issues requiring post-test attention. Overall system noise performance was evaluated in both Flight Instrument and Engineering Unit testbed configurations.
Initial investigations by MIT yielded grounding changes inside the MIT Flight DEA and DPA, required to correct image noise concerns. While significantly improved, flight hardware retest revealed an unacceptably large 2 kHz noise component still present in the CCD image data. LMA personnel traveled to Cambridge to assist with additional troubleshooting activities involving the PSMC. Systematic troubleshooting of the Engineering Unit Instrument yielded a finding that the series post-regulator/current limiter circuitry in the DEA was not attenuating PSMC noise and ripple at greater than 300 Hz. This was puzzling since the PSMC output voltages met the specified < 100 mV p-p noise and ripple requirement in a stand-alone configuration. When in a system-level configuration, there was approximately 100 mV p-p of 2 kHz ripple on the PSMC power supply outputs, with a demonstrated correlation for change in the 2 kHz ripple component relative to +6 VDC DEA load changes. Additional investigation noted the DEA +6 VDC regulator toggling in/out of a nonlinear current limit foldback condition at approximately 1/10 Hz.
LMA's best engineering judgment concluded that re-compensating the PSMC power supply control loop might be successful in reducing the 2 kHZ ripple amplitude from ~100 mV to ~20 mV p-p (best case), or it might just alter the frequency. However, even in the best case, this would still leave a DEA sensitivity of roughly 10 dB above noise floor to power supply noise. Based on the low corner frequency of the DEA series post regulators (allowing the control loop to see load reactance of greater than 300 Hz), and unknown PSMC loop response to the toggling regulator current limit foldback condition, LMA recommended piece part changes in the DEA to improve the system architecture noise immunity. Therefore, MIT selected a new sense resistor value to keep the +6 VDC regulator out of current limit during nominal operation. At the close of this reporting period, initial Engineering Unit results showed this change should eliminate or significantly reduce the noise concern. With the above recommended changes, the DEA will be more compatible with PSMC power output noise and ripple specified to < 100 mV p-p. Should any systematic noise signature still remain, PSMC power supply loop response can be re-compensated in situ with the new characteristics to minimize overall image noise signature.
The Flight PSMC build and test documentation data package was completed this month, routed through reproduction and delivered to MIT to complete the data package associated with the PSMC delivery.
The LMA technician staff continued to support critical path flight hardware activities in Cambridge, on an as-needed basis. Therefore, assembly of the flight spare PSMC boards continued on a non-interference basis. The thermal control board is complete, with final QA inspections and MAP sign-off planned prior to beginning the board-level test. Work on the IO/EMI Cavity resumed after technician support of the Flight Detector Housing and Venting Subsystem testing was completed. The IO/EMI Cavity is nearly complete. The Vent Valve & Mechanism Control board assembly is also nearing completion. EEE piece part kits were completed for the remaining spare board builds. One piece part shortage remains regarding block capacitors needed to complete the DEA Power Supply Board. This parts shortage is being corrected through completion of MRB action which will make flight parts available, whose leads were inadvertently lead tinned in a manner not prescribed by LMA Standard Manufacturing Processes. These parts have been screened and demonstrated acceptable for flight use. However, the MRB action necessary to complete clearing them for flight use has not been completed.
During the previous reporting period, MSFC completed 1500 volt Dielectric Withstanding Voltage (DWV) testing on the LMA PTS flight cable harness. Since the 1500 volt DWV test exceeds the harness 600 volt wire rating, NASA/MSFC has agreed to provide LMA with documentation granting an exception to the MIL-STD-975 EEE part voltage rating criteria. This should allow formal cable harness verification to complete without issue. MIT has submitted a waiver to MSFC regarding the issue of DWV testing at voltages that exceed flight wire ratings (waiver # 36-016). LMA will hold the PTS flight cable harness verification open pending receipt of the MSFC memo and/or MSFC waiver approval. The harness is still "in-the-queue" for 1238 certification at MSFC. The certification temperature of +46°C was communicated to MSFC during the last reporting period.
At the end of this reporting period, RCTU interface questions still remain regarding the EU2 PSMC. Command interfaces seem acceptable, with some open items involving telemetry interfaces. After the conclusion of ACIS thermal vacuum testing, and when a "known good" RCTU is available at CSR, LMA personnel will travel to MIT to resolve these open telemetry interface issues.
There are no changes to the MIT load table during this reporting period.
The Flight Detector Housing passed 1238 certification and was delivered to MIT during this reporting period. Fitchecks with the flight hardware were completed and the focal plane was installed late in the month.
Modification to the straps will occur prior to Flight Thermal Vacuum Systems test to occur early next month. This will eliminate a potential interference with the flight support structure. This will allow -120°C temperatures on the focal plane in the thermal vacuum test.
The fracture analysis is continuing and the projected completion date supports Acceptance Data Package delivery dates.
The two "first choice for flight" set of Flight Optical Blocking Filters were installed into the CAMSIM and an acoustic test of the filters was completed this month. Post-test inspections at Luxel revealed no anomalies. These filters will complete their pre-installation tests and are due to be installed into the Flight Detector in early April.
Since all flight hardware except the MLI blankets has been built and weighed, there are no updates to the weight summaries from the previous reporting period. The weight data are shown below:
|Assembly||Weight, lb.||Uncertainty, lb.|
|Thermal Control & Isolation||5.4||+0.1|
|Sun & Telescope Shades||16.0||+0.1|
|Power Supply & Mechanisms Controller||32.7**||+0.2|
|Cables & Connectors||9.1||+0.1|
|Total Basic Weight||102.9||+0.9 -0.0|
** Includes Survival Heaters, Thermistors, connectors, and bracket which are not part of ACIS budget. Mark Kilpatrick's (BECD) worksheet dated 12/8/95 assumed 1 pound for these components. LMA does not have an actual breakdown.
1238 certification was completed on the venting subsystem this month. A failure of one of the GSE pressure transducers delayed completion of the final performance testing. A new 1238-certified transducer was installed and final performance testing was successfully completed. The hardware was hand-carried to MIT/CSR and delivered via form DD250 to MIT on the last day of this reporting period.
The lifting fixture modification part fabrication was nearly complete and will finish early next month. The lifting fixture was shipped as-is to MIT for use in MIT and NASA/XRCF hardware handling and test support. Incorporation of the modifications for use of the lifting fixture with the HRC will be made later this year prior to shipping ACIS to BASD.
The stand-alone VGSE #2 final performance, and acceptance tests of the VGSE #2 with the Flight Venting Subsystem, were successfully completed this month. LMA pre-ship reviews were conducted, the hardware was accepted via form DD250 by DCMC and shipped to MIT/CSR. VGSE #2 was shipped by dedicated van and it will be arrive at MIT early in the next reporting period.
During this month, the systems engineering group continued preparation of verification assessment and test reports for the ACIS compliance verification activities and maintained program requirements documents. Engineering specialties activities focused on EMI/EMC test exceedance investigations, collection of fastener data for MSFC, and the Ground Safety Review at KSC. Additionally, the group continued planning and preparation for delivery of the ACIS Acceptance Data Package (ADP) and CDRL update coordination.
Updating the final CDRL/SDRL submittals in support of the Acceptance Data Package continued. The ACIS Wire List was not updated during March as expected and reported last month. That update will follow receipt of a PIRN for ground wire referencing and ground lug designations for the RCTU to PSMC interfaces and collection of final wiring changes, if any, resulting from the hardware verification activities.
Preparation of a Special Consideration Item Drawing (SCID) is nearing completion. This book-form drawing will identify the "Remove Before Flight" red tag items, "Install Before Flight" green tag items, and those items of special consideration; such as, warnings and cautions to be included in procedures that operationally protect the instrument. This drawing is scheduled for completion in time to support the Acceptance Data Package.
System-level overview, support of program scheduling, and update of ground processing flows for ACIS instrument flight hardware testing continued this month. Review of ACIS Verification Requirements and Specification Document SVR02 via incremental telecons was completed during March. It is anticipated that the comments will be incorporated into the VRSD and it will be released as final during the next reporting period. ACIS program support and MIT and NASA/MSFC liaison was maintained.
Review of program activities and scheduling of the PTS and ACIS verification events continued throughout March. This activity, along with satisfactorily completing scheduled events, will confirm that the ACIS instrument meets requirements and will be ready for delivery to NASA/MSFC. Continued support of testing being conducted at Lincoln Labs.
MSFC-SPEC-1238 bakeout activities continued throughout this reporting period. Instrument-level certification is planned to be performed during the Lincoln Labs ACIS performance testing. The Contamination Control Plan was updated and released in final form in support of the Acceptance Data Package during this reporting period.
Testing of the ACIS Engineering Unit hardware for CS01 and CS06 at MIT yielded a fix to the Flight Unit PSMC that essentially assures that ,when future testing of the ACIS Instrument for CS01 and CS06 is performed, the result will be satisfactory. The fix incorporated into the PSMC was to re-pin two internal connectors so that the voltage sense point return lead is directly connected to the feedback sense amplifier. Previously, the return current for the feedback circuit was being conducted through the PSMC case. There was virtually no common mode noise rejection afforded by the wiring. This change allows the twisted pair wires to aid in rejection of coupled common mode noise thus alleviating the conducted interference observed during the ACIS Instrument EMI/EMC testing reported in previous monthly status reports.
System Safety supported the Ground Safety Data Review with a presentation at KSC during this reporting period. One Action Item resulted from this review. LMA is to "Provide Verification Data for Hazard Report 16, Leakage or Rupture of ACIS Vacuum-Backfill GSE." This action item is expected to be resolved during the next reporting period.
Another set of comments was received from MSFC for the Failure Modes and Effects Analysis (FMEA) completed in January and reviewed in real time during the February Technical Interchange Meeting at Cambridge. These MSFC comments were expected early in the March reporting period; however, the comments were not received until 3/27/97. Changes to the FMEA caused by these comments will cause the FINAL release of this document to be extended until late in the next reporting period or to early May. The FMEA changes will require the Critical Items List (CIL) to be updated.
The process of collecting fastener data per direction from MIT was started in response to MSFC letter TA61 (97-003). To maximize task efficiency, LMA developed a logic flow diagram from the information provided in the letter that is guiding the efforts to collect the needed data and make judgments with respect to containment, fail-safe, and any added testing needed. The flow diagram is shown below. Initial efforts show that the majority of the fasteners used in LMA-provided hardware are smaller than #10 screws and the great majority of fasteners are in fact contained, i.e., inside the PSMC. It is anticipated that this effort will be completed in April.
Figure 1. Fastener Data Flow Diagram
The Power Summary Tables that summarize the power requirements have not changed since the June 1996 Progress Report. For current Power Summary date refer to Progress Reports for June or July 1996.
Electrical power requirements (Watts) are summarized in the following table:
|Peak power distribution
in Standby Mode
|Peak power distribution
in Max. Operating Mode
|Peak power distribution
in Bakeout Mode
|Peak power distribution in
Normal Operating Mode*
Note: Normal operating mode refers to the ACIS operating with six analog chains at full power, six front-end processors at full power, one back-end processor at full power and the focal plane temperature being maintained at -120°C.