January 16, 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 December 1996.
No monthly status review for ACIS was conducted in December. The last review was held on November 21 at MIT and was reported in the November report. The next review is scheduled for January 29.
ACIS participated in the weekly AXAF telecons on December 3, 10, and 17. The telecons normally scheduled for the 24th and 31st were cancelled due to the holidays.
ACIS participated in the FPSI telecon on December 11. There was no telecon on the 25th.
Thanks to the assistance of Harry and Melissa Jolliff from TRW in solving the ESD problems associated with CCDs, Lincoln Lab, in the first few weeks of December, successfully re-flexed five, previously calibrated, CCDs in five attempts. Combined with the new units delivered in late November, the ACIS project is now in receipt of 11 flight-quality CCDs to populate a (all Front-Illuminated) flight focal plane -- a major milestone. Lincoln then began the attempt to re-flex the three flight-quality Back-Illuminated CCDs that were originally planned for positions S3, S4, and S5 of the flight focal plane. The first BI unit was delivered to Lincoln on December 18. Unfortunately, the main LL technician (Pete Daniels) was out sick at the time. What initially was thought to be the flu turned out to be a gall bladder problem and major surgery was performed just before Christmas. Pete returned to work, part-time, on January 6. The end of December was spent training several new technicians in reflexing, packaging new devices ,and mounting CCDs to focal planes. In the meantime, calibration of the FI devices at CSR has proceeded quite well and five units had been completed by the end of December. The first BI device could have been installed in the calibration facility as early as January 13, but it will be delayed a few days due to the personnel problem at Lincoln.
Additional flexprints are needed to process the CCDs for the spare flight focal plane. Lot 4 from Speedy Circuits was received in early November, but the quality was only marginally acceptable. The coupons were sent to MSFC for evaluation and all but one panel was approved for use. These flexprints were prepared for vacuum bakeout by the end of December, but the vacuum chamber was then reassigned to the ACIS-2C 1238 certification.
The following is a brief summary of the status of the other ACIS elements:
The CCD installation on ACIS-2C was measured in the flight focal plane facility in NE80 in early December. Unfortunately, both CCDs appeared to be bad at final checkout on December 11. The units were removed and sent to Lincoln for testing. Unexpectedly, they were both found to be operating correctly. The problem has been traced to the fact that the RTDs installed in the ACIS-2C were being over-driven by the (external) MIT thermal controller and were emitting some light. The CCDs were reinstalled in ACIS-2C, the RTDs were covered, the unit was tested, and the entire assembly was installed in the Lincoln Lab chamber for 1238 bakeout and certification on December 23. This certification was completed on January 3 and the unit is undergoing a final test prior to delivery to MSFC (expected on January 14).
Two FEPs failed functional testing in November. One was found to have a broken lead on an ACTEL. The device was removed and sent to MSFC for analysis. A new ACTEL was installed at Sanders. The second board was found to have a missing trace on an infrequently used reset line. A jumper wire was installed to replace the missing trace. Both boards have been successfully tested, conformal coating re-applied to the modified areas, and a thermal bakeout performed.
All four sets of flight OBFs have been calibrated at the Wisconsin synchrotron and were beginning 1238 certification at LMA at the end of the month.
The DEA Interface and Thermal Control flight boards were loaded with the replacement 2N2222A transistors at Sanders. The units were successfully tested at CSR by December 27 and then spot-bonding and cleanup were performed by the end of the month. Both units were installed in the thermal vacuum chamber at Lincoln Lab for pre-conformal coat bakeout as soon as the ACIS-2C was removed on January 3.
The DEA/DPA/SS, on the SIM-SIM, along with the MIT EGSE and MGSE, was shipped to LMA on December 3 for integration with the flight PSMC and the start of EMI/EMC testing. This testing was successfully completed by December 16 and the SIM-SIM, with the MIT flight hardware, was shipped from LMA on December 17 and arrived at MIT on the afternoon of December 19. Cold tests with the EU Detector Assembly were completed by December 30, and functional test procedure generation continued through the end of the month. In parallel with this activity at MIT, the flight PSMC was shipped from LMA to BASD for 1238 bakeout and certification over the Christmas/New Year holidays.
With the successful assembly of sufficient flight-quality CCDs, the ACIS schedule has held firm. The two-stage completion/testing plan, in place since mid-November, currently shows a delivery of the flight DEA, DPA, SS, and PSMC, but with an "XRCF" focal plane in an EU Detector Assembly, on March 10. The flight Detector Assembly and Vent Valve Assembly is projected to complete its verification activities by early May and be delivered separately to the XRCF on May 13.
The personnel status of the ACIS project has held relatively stable.
As reported last month, Marty Furey rejoined the project on November 25 for a period of six months in order to redo the structural analysis as a result of the new translation table spring rates.
On December 1, Gordon Gong, the DEA analog engineer, began working half-time on the Cell Culture Unit experiment for Space Station (PI is Bob Langer of the MIT Chemical Engineering Department.).
The subcontract to PSI which provides the services of Peter Tappan, the Detector Assembly mechanical engineer, has been extended to the end of March 1997.
ACIS 2C devices were installed in the ACIS2C top plate. Relative location and orientation of the two detectors was established using the alignment facilities in the NE80 mechanical lab/cleanroom. During post-alignment testing, we found that the ACIS 2C temperature sensors (which differ both from those used in flight device calibration and on the flight focal plane) appear to emit detectable radiation when the excitation current is too high. We do not understand this rather surprising phenomenon, but it will not affect ACIS 2C operation at XRCF. At XRCF, the excitation current is always within the rated limits of the RTDs.
Six front-illuminated devices with flight-qualified flexprints were received from Lincoln and screened. Two of these, w198c1 and w194c1, are newly-packaged devices judged by Lincoln to be "A-" grade, which we had never calibrated. The other four, w168c4r, w201c3r, w203c4r, and w215c2r are previously calibrated "re-flexed" devices. (The "r" suffix indicates that the flexprint on the device has been replaced.). As of the end of December, a total of 11 flight-quality CCDs (all front-illuminated) with flight-quality flexprints had been delivered to CSR.
Calibration results for w201c3r show significant changes in gain, (attributable to the reflexing operation), acceptable spectral resolution and quantum efficiency, and no discernible change (at the 1.5% level on 0.75mm boxcar-smoothed images) in spatial variation of quantum efficiency. We believe that, in future, re-calibration of "re-flexed" front-illuminated devices can be completed in about half the time required for the initial calibration. The recalibration is required for re-tuning of operating parameters, re-measurement of the gain, verification of the quantum efficiency at coarse spatial scales, and checking the temperature dependence of the response.
At the end of the month, calibration had been completed on five flight candidate devices.
We used the new wavelength shifter beam-line at PTB/Bessy to extend the spectral range of the absolute quantum efficiency calibration of reference devices to 12 keV. Previous measurements on the old "white light" beam-line provided data at energies no higher than 4 keV. These data will be essential in constraining the CCD depletion depth.
Measurements were made at the Advanced Light Source in Berkeley to determine the near-edge transmission characteristics of the ACIS CCD gate structure. Transmission of thin films of gate oxide and nitride (prepared at Lincoln using the same techniques used to fabricate flight detectors) was determined from below the silicon L-edge to above the oxygen K-edge. The data appear to be of very high quality, and initial analysis confirms that the near-edge absorption features seen in the thin-film data correspond well with features observed in previous detector quantum efficiency measurements.
One of us attended an ACIS Science team meeting on 17 December at Penn State. The same one of us met at MIT with Nousek (Penn State) and McNamara (ASC) to plan phase II XRCF measurements with ACIS2C.
The ACIS Contamination Monitor (Door Source) flight unit parts have completed bake-out and 1238 certification at LMA and MSFC. The External Calibration Source flight unit parts have completed bake-out and 1238 certification at LMA.
Two of the Flight BPAs have completed bake-out and 1238 certification at LMA.
The parts of the Proton Shield parts have completed bake-out and 1238 certification at LMA.
Pins for the Flexure to Support Structure interface have been received. Work is proceeding to correct the difficulty that was encountered during assembly with the +Z Panel mating with the Y Panels. Survival heaters and thermistors are being fitted to the Support Structure./P>
The LED Assembly has completed bake-out and 1238 certification at LMA.
The EU DA is being vacuum-baked in preparation for thermal vacuum testing at Lincoln Labs.
The SIM-Sim is being vacuum-baked in preparation for thermal vacuum testing at Lincoln Labs. Lifting fixtures and vibration test fixtures are being completed.
The Support Structure Assembly drawing has been completed and is in engineering review. Work is continuing on the top-level ACIS assembly drawing.
The last two cable assembly drawings, Support Structure Survival Heaters and Thermistors, are in engineering review.
Reviewed and provided input to the ACIS Vibration Test Procedure. Generated necessary modification and fabrication drawings.
Updated the ACIS interconnection diagram to show the chassis ground connections on the Detector Assembly, Power Supply and Mechanism Controller, and the Digital Processing Assembly.
Extensive updates were made to the ACIS thermal models to refine temperature predictions for the ACIS Thermal Vacuum Test. Updates included the revised location of the SIM-SIM within the chamber (10-inch translation), the detailed conductors among SIM-SIM panels and isolators, the DPA area modifications to account for blockage from the survival heater harness, the revised (black replaced white) paint on the DPA, and the Support Structure heater set-points presented at the Delta SIM CDA.
An updated MIT/LMA personnel list for the ACIS TV Test was sent to LL personnel to provide badges and size information for cleanroom suits.
MIT participated in the Thermal TOP Telecon on 19 December.
Many hours of analysis and word processing were spent on the preparation of Rev. A of the ACIS TV Test Procedure, scheduled for release on 2 January 1997.
The EMC/EMI testing at Martin has been completed. For this test, the DEA assembly contained two Interface engineering cards and 10 flight video cards. The Flight Interface boards are currently being conformal-coated and will be integrated into the flight assembly when this is done. Final functional testing will then commence.
We are still awaiting news of failure analysis for the two defective FEPs:the broken corner pin of an ACTEL (SEI packaged) device and the defective etch on the printed circuit board. (See last month's progress report and associated memo.) In the meantime, these FEPs have been repaired and re-tested.
The engineering DPA has been instrumented for performance analysis, which is an ongoing activity. The flight DPA is being used in-house for system test and characterization.
Supported EMI test of the ACIS instrument at Lockheed Martin Astronautics.
Machine shop work on the "FLCA/SS/DH/PSMC Test Box" (used to test the fiducial lights, read thermistor and heater circuits, and distribute the thermistors to a data logger) has been completed and is currently being wired.
Machine shop work and assembly of the "PSMC Serial Data Mux" box (used in conjunction with the "Littlefield PSMC RCTU") has been completed.
Fabrication of the "SIM-SIM Heater Panel Power Distribution" box is in progress.
Developed software that reads ACIS DEA housekeeping packets and ACIS engineering pseudo-packets and writes mnemonic-value lines that list, in ASCII, the data that the packets contain. Bob Goeke developed a GUI that displays these data. Prepared two workstations to function away from the MIT network and set them up at Lockheed Martin Astronautics in Denver, Colorado. Supported EMI/EMC testing at LMA. Reinstalled the workstations on the MIT network after returning from LMA.
The following software ECOs were reviewed this month:
These design changes are described in "http://acis.mit.edu/axaf/eco".
While ECO 36-823 merely resulted in a small change to the Software Requirements Specification, ECO 36-822 has necessitated substantial changes to flight software. It was decided not to include them in Release 1.0.
Version 1.24 of the IP&CL structures table (36-53204.0204, Rev. G) is being subjected to internal review. It describes Release 1.0 of flight software.
Peter Ford met with Joel Kastner and Eric Schlegel (ASC) on November 18 to discuss ACIS parameter classes and OR user options.
Release 1.0 of the Flight Software is being prepared for January 1997 to be accompanied by release notes and building instructions. Default command blocks, bad pixel lists, etc., are being supplied by the ACIS calibration team.
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. Jim Francis helped develop Short Form ACIS test procedures and traveled to Lockheed-Martin Astronautics, Denver, to assist with ACIS EMI testing.Revision 3 of the Software Tools Document has been released. It includes all changes required to support Flight Software Release 1.0.
Six new software problem reports have been filed, of which 5 have been closed out. A total of 9 problem reports are outstanding. These may be inspected at "http://acis.mit.edu/axaf/spr/".
No Alerts or problem notices were received from MSFC during the report period.
Produced 2 cable termination kits.
Shipped two Front End Processor (FEP) kits (flight spares) to Lockheed Sanders for assembly.
Although no requirement has been imposed on MIT, a listing of all flight fasteners is being compiled. This list includes the name of the fastener manufacturer, Certificate of Conformance (C of C) status, chemical and physical test report status, and contained or not contained application. Included in the fastener list are screws, nuts, inserts, shear pins, and stand-offs. Additional chemical and physical testing is being performed on fasteners in the structural load path on the support structure.
One hundred-fifty (150) JANTXV2N2222A Motorola transistors were received from ATC after PIND, Xray, and DPA. These parts were manufactured by Motorola and purchased to replace the JANTXV2N2222A New England Semiconductor (NES) transistors identified in an Alert in November.
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.
|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, LL, and LMA||7/16/96||IN PROCESS|
Waiver 36-007 is being revisited by MSFC in light of the decision not to bake-out the optical bench.
MIT NSPARs 36-001 through 36-029 have been approved by MSFC. MIT NSPAR 36-024 has been canceled/withdrawn. Lockheed Martin Astronautics (LMA) NSPARs MMA/ACIS-014a through MMA/ACIS-047 have been approved by MSFC. Below is a listing of NSPARs still in process. In addition, LMA is incorporating comments on NSPARs otherwise approved.
|36-030||Transistor, Silicon, NPN,
Low Power (JANTX2N930)
|Microcircuit, High Voltage
Radiation testing has been completed at Space Electronics Inc. (SEI) on twenty-four (24) device types. Results of these tests have been submitted to Dr. Jim Howard at MSFC. Jim has evaluated each part and its location in the ACIS. Tantalum shielding has been added to the outside of the DEA; .080-inch on the -X panel and .040-inch on the +Z panel. In addition, four (4) parts have been spot-shielded. Twenty thousandths (.020) of tantalum were added to the top of the A to D Converter (CS5012A), Dual Operational Amplifier (OP220), and CMOS Switch (IH5143). The OP220 and IH5143 have .020-inch tantalum shields on the bottom as well. Eighty thousandths (.080) of tantalum were added to the top of the Octal D to A Converter (DAC8800).
Materials: MIT received approvals of 11 MUAs from MSFC. This leaves 12 MUAs still open.
No Activity this month.
Developed a schedule that covers verification activities through May 1997. MIT has identified 32 Test Procedures which can be developed. It is projected that 24 Test Procedures and 20 Test Scripts can be completed. In all likelihood, these numbers will improve as the software verification process progresses.
Test Procedures: Last month it was reported that 14 of 36 test procedures were developed but only 1 procedure (Reset) was released. Since then, 2 more (Window2D and BadPixel) have completed the review/release process and 4 (MemBep, LoadFromRom, Overflow, and Graded Threshold) are in the review process. The remaining 7 are still in prerelease.
Test Scripts: Incorporated review comments into Reset, Window2D, and Bad Pixels. Changed test environment software to use all engineering-supported test tools.
There have been 4 new problem reports identified this reporting period.
A total of 80 problem reports have been documented. Of those, 71 have been fixed and 9 are open. Of those 9, 4 are flight software-related, 1 is test tool-related, and 4 are IP&CL or SRS-related.
There has been no activity on the Performance Assurance and Safety (PAS) Plan. The PAS Plan in effect is Revision B.
Preparations are being made for the Thermal Vacuum Test at Lincoln. People were measured for their garments which have been ordered by Lincoln Laboratory. Many of the cables that will be used have been completed and vacuum-conditioned. The SIM/SIM, with the Engineering Detector Assembly and Vent Valve Assembly, was put into the vacuum chamber at NTS. Its bakeout temperature is +60 C.
Picked up the PSMC mounting plate from Boyd coatings. It still needs to be cleaned and vacuum-baked.
Preparations were made to perform the 1238 certification for ACIS 2C. Wrote a procedure for this test and performed a dry run. The test started on Tuesday ,Dec. 24 and completed on Friday, Jan. 3, 1997. The TQCM final results measured 0.1 Hz/hr. The OWSs have not yet been measured.
Cleaned all of the clean tents before the flight hardware arrived. Cleaned and vacuum-baked the heaters and the thermistors for the support structure.
The external Flight Cables were vacuum-baked and then sent to MSFC for IR and DWV testing. Wrote a specification for the handling of the external flight cables during the IR and DWV testing at MSFC.
The LED Assembly for the Detector Housing failed the 1238 test at LMA. The reflectance was 8.8% and 5.8% for the two OWS samples. LMA will repeat the test after the OBFs are completed.
Measured the witness samples used by Leisa Townsley, during the OBF calibration at the Synchrotron in Wisconsin. All samples showed no measurable amounts of NVR and minuscule amounts of particulate accumulation.
The improvements made during November to lessen ESD damage appear to have had a large positive effect. Two virgin flight chips were successfully packaged, as were five flight reflexes; there were also two practice chips reflexed in this period and there were zero failures, bringing our current score to 12/13 packaged without damage after the ESD improvements were made. Work is proceeding on introducing floor mats and Faraday cages into the outer cleanroom to improve the yield of the wafer-cutting process.
There are six FI and three BI parts to reflex, seven FI sawn parts to package, and twelve FI parts to saw and package.
Additional flexprints (Lot 5) have been fabricated by Speedy Circuits. Several workmanship problems were eliminated or reduced with this lot but there were difficulties during the gold-plating operation that make the parts unusable for ACIS. There are many small (0.00025 to 0.0005-inch diameter) gold nodules on the gold-plated surfaces. These nodules are easily displaced and could cause shorts on the circuits or contaminate the detector area.
Assembly of thermal cycle samples has begun for the flexprints designated Lot 4 from Speedy Circuits. Samples from this lot are also being prepared for micro-sectioning.
Graphics Research has delivered 50 via-less flexprints. External visual inspection indicates that the vast majority of these parts meet workmanship standards. Hi-Rel Laboratories has analyzed the coupons and found all but one panel to be acceptable.
Three flexprints of the type that are being used on the flight focal plane assembly have started a long-term thermal soak test. This test will have the flexprints maintained at -120°C for many months to determine if there are any additional failure modes that are not detected by the thermal cycling qualification testing that is performed on a sample from each panel of flexprints.
To support system testing at the XRCF, Lincoln Laboratory has agreed to put together an ACIS detector assembly using available detectors and other components. Preparations have begun for this work. This unit is expected to be shipped during January 1997.
Change Order activity this month included receiving Change Order 64 to fabricate a new GSE Electrical Interface Bracket and new MLI Blankets to meet new requirements defined by PIRNs. Schedule critical parts of this work had been initiated earlier based on a letter of intent from MIT/CSR. Change Order 62, which definitized Change Order 48, was also received early in the month and reported in the November Report. Change Order 58 is currently the only change order waiting to be definitized.
No ACIS NASA/MIT Monthly Status Review nor MIT/LMA Technical Interchange meetings were conducted this month. However, MIT/LMA face-to-face technical coordination was enabled through the MIT team that were at LMA for the ACIS System EMC Test.
Major accomplishments for December included receipt of the EMC test hardware from MIT, setup and early completion of the ACIS System EMC Test, and successful transport of the hardware back to MIT. Elective testing with the EMC test hardware was performed to investigate and understand specification exceedences. The EMC test resulted in one unexplained narrow-band exceedance on CSO6. This exceedance will most likely be treated as a waiver request. The PSMC completed thermal-cycle testing and minor modifications were made to improve the design for areas with lower than desired thermal margin and correction of a wiring error. Following these modifications, the PSMC received additional open-box pre-bake, random vibration testing to verify workmanship, successful completion of performance testing, and the NASA-SPEC-1238 bake was initiated at Ball Aerospace. VGSE #1 was shipped from MIT/CSR to LMA with the EMC test hardware and verification of a new EPROM was completed before the hardware was returned to MIT. The Flight OBFs NASA-SPEC-1238 bake was re-initiated and bake continued through the LMA holiday shutdown. The ACIS Lifting Fixture drawing modification and the Table Top Review were completed. Fabrication of parts is planned to start after the first of January 1997. The Engineering Unit (EU) Thermal Radiators, Shades ,and MIL were shipped to BASD before Christmas, per MIT request, to support testing at BASD.
The program continued to review intercompany 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 being 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 focus this month was on completion the PSMC tests with associated modifications and completing the System EMC test. Problems encountered during the month were associated with correction of minor anomalies identified as a part of normal test and checkout. Schedule critical milestones were met this month so there was no critical path schedule erosion.
Group B and C electrical testing of the 1N6689s and 15CGQ100s is nearing completion. Interim results indicate no difficulties. Group B and C testing is planned for completion early in the next reporting period.
The flight unit PSMC closed-box formal verification testing was completed.
The open-box pre-bake at +100°C (which was initiated during the last reporting period) was completed. This pre-bake was performed since the DPA/DEA Power Supplies did not receive a post-conformal coat bake-out. After pre-bake completion, the PSMC lid was reinstalled and post-thermal cycle performance testing was completed in preparation for ACIS System-Level EMC Testing.
A systems schematic review has been proceeding concurrent with other PSMC build and test activities. This schematic review yielded one issue relevant to the PSMC that required a hardware configuration modification. The "A" and "B" side control relays within the PSMC were wired to primary spacecraft input power in a manner that applied "B" spacecraft power to both the "A" and "B" side relays. This issue was identified during the ACIS System-Level EMC Test. After EMC testing was completed, the PSMC was returned to the ACIS electronics lab where the lid was removed and a single "jumper" wire was moved to a different "E-Terminal" on the EMI Cavity PWB to correct the problem. The PSMC was reassembled and tested to verify the "A" side relays received only "A" spacecraft power and the "B" side relays received only "B" spacecraft power. This modification restores A/B block redundancy within the PSMC.
An acceptance vibration "retest" was successfully completed on the flight PSMC. Proto-flight vibration levels were run in the Y axis only, using the Ball-provided flexures. This axis was selected since Y axis random vibration puts higher energies into the PWBs, thereby validating EEE part modifications made as a result of the anomalies identified during the PSMC Thermal Cycle Test. Pre- and Post-Functional Tests were run. All of these tests were successfully completed using the PSMC test rack. Test results are summarized in the mechanical section of this monthly report.
The Flight PSMC was present for all system-level EMC testing. The EMC test results are summarized in the Systems Engineering section of this report.
After EMC testing was completed, a set of engineering tests were conducted with the ACIS Flight Instrument at AVL, using TRW-provided RCTU/CTU test hardware/software. These tests were run to validate end-to-end telemetry interfaces between ACIS and the spacecraft C&DH system. These tests yielded a complete set of telemetry calibration equations for the PSMC, and revealed a wiring error in the TRW-provided interface cable affecting PSMC serial digital telemetry. A cable "patch" was employed to complete the testing. A set of system power dissipation tests were also performed to validate power dissipation predictions for the ACIS Flight Instrument.
The PSMC exterior was re-cleaned to remove particulates, bagged, and shipped to Ball for MSFC-SPEC-1238 certification bake. A conservative set of analyses and assumptions were used to arrive at a PSMC certification temperature of +73°C.
If QCM data projects difficulty passing 1238 at +73°C, actual measured flight PSMC power dissipation data will be used as part of a PSMC 1238 certification temperature reevaluation. The PSMC began 1238 bake on December 20, 1996.
There are no changes to the MIT load table during this reporting period.
At hot soak, the "B" side temp controller executed the "Bake-out Disable" command concurrently with the "Bake-out Off" command. The "Bake-out Disable" command should not execute until specifically commanded to do so.
At cold soak, the "A" side DEA power supply would not respond to its "On" command at low line (+22VDC).
After 2 thermal cycles, the flight unit was partially disassembled and both boards in question, Temperature Control and DEA Power Supply, were separately monitored to isolate the anomalies. Conclusive data were obtained to identify and correct both anomalies with minor piece part value changes to correct the "marginal" operation and improve the operating margins at temperature extremes. The flight PSMC was subsequently reassembled and the remaining 6 thermal cycles were completed with no further anomalies.
After thermal cycle test completion, the PSMC lid was removed, and an open box pre-bake was initiated at +100°C.
During the next reporting period, the pre-bake will be completed, lid reinstalled, and post-thermal cycle performance testing completed in preparation for ACIS System-Level EMC Testing.
There are no changes to the MIT load table during this reporting period.
The FU Detector Housing Assembly is being maintained in storage until it is required by MIT for focal plane installation. The CAMSIM will be shipped to Ball as soon as all testing is complete.
The Engineering Unit Venting Subsystem was tested with the flight electronics in the EMI test at LMA. The venting subsystem performed as designed with the exception of a possible miss-wire on one of the low conductance vent valves. The valve functioned properly but the polarity shown on the EGSE was reversed. The anomaly could also have been a software problem and will require further debug in January. The VGSE in combination with the Venting Subsystem functioned normally and did not have any problems.
The EU detector housing door functioned normally when opening the door for the first time. During the first closing operation, full rotation occurred on the door mechanism assembly and the two bar linkage appeared to go over-center and lock. However, the door close actuator continued to receive power from the PSMC which could only occur if the limit switches were not closing properly and therefore the operation was aborted after 1-2 minutes. Subsequent door open and close operations repeated this anomaly and some limited debug with the connector readout panel indicated that the limit switches were not operating properly. In addition, the door was not latched even though the linkage was over-center and appeared to be fully closed. This gave the indication that the Starsys actuator had been damaged prior to the EMI test. Therefore, the actuator was sent to the manufacturer, Starsys, for test and repair. Starsys performed full mechanical and electrical checkout on the actuator and could not find anything wrong. Based on this result, additional testing will be performed at MIT in late January. Three possibilities exist for this anomaly and all will be investigated prior to the Lincoln Labs thermal vacuum test. The possible problems include: 1) wiring problem on flight harness, 2) not waiting long enough for door to fully close and latch, or 3) the tight fit between the actuator output shaft and the mechanism drive shaft could have caused some deformation in the actuator covers which would not allow the latches and limit switches to fully engage. The first two possibilities can be resolved with further debug and testing.
Possibility 3 will require minor rework of the output shaft so it fits better into the square hole in the drive shaft prior to re-installation on the EU detector. Currently it is not installed since the EU detector and Venting Subsystem are in pre-bake. This actuator (S/N 001) was originally installed on the CAMSIM for life cycle testing and was fully flight-like including internal limit switches. In over 300 cycles of testing at LMA, this problem was never encountered with this actuator mechanism prior to being installed on the EU detector. After installation in October `96, it was tested with the EU#2 PSMC and EU cable and did not have any problems. It should be noted that the original EU actuator (S/ N 002), which was delivered back in February `95, did not have all the flight design enhancements and, therefore, was swapped out in October. Regardless, this situation should be resolvable with a day's worth of testing prior to the Lincoln Labs test. There are no concerns with the flight PSMC or flight Detector Housing.
All TCS hardware has been 1238-certified and is in storage. The flight radiators, straps, and MLI will be delivered to MIT as required for use in the Lincoln Labs Thermal Vacuum Test. EU radiators, straps, and MLI were delivered to Ball in preparation for thermal testing to occur in June 1997.
No activity to report.
Stress analysis updates have continued with a promised completion of the end of January. The completion of the fracture analysis will follow. The stress analyst is scheduled to go part-time into February so the Fracture Analysis will not be completed until March. This will support the Acceptance Data Package delivery dates.
A single Y axis workmanship test (Proto-flight level) was performed after some minor rework was required after thermal cycle testing on the Flight PSMC. All flexure resonant frequencies were similar to previous testing; however ,Y axis measured responses were higher in this test than in the previous test and the Z axis responses were lower. Previous testing showed responses which were nearly identical in Y to the cross-talk axis in Z. However, the total measured PSD energy, if you combine the Y and Z axis responses, was similar in the two tests. The latest test is more in line with what we would have expected (i.e., the test axis had the higher overall levels and PSD energy). The only explanation is that flexure clocking was slightly different in the two tests. Stress analysis will be performed to the higher of the two tests and in both cases we passed, so there are no real concerns with the data discrepancies.
The SIM Sim is in vacuum pre-bake in preparation for the Lincoln Labs Thermal Vacuum Test. The pre-bake is scheduled to be completed in January.
All flight Optical Blocking Filters are in vacuum bake for 1238 certification. Pre-bake continued through the holiday with OWS exposure to occur in early January 1997. As of the end of this reporting period, TQCM and pressure data showed that the filters were almost ready for OWS exposure. All filters will be shipped back to MIT after certification is complete.
PTS Weight Summary is shown in Table 1. These values are the measured weights of all LMA supplied components. Uncertainty margins have been reduced as measured data becomes available.
|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|
Note: Numbers in bold indicate actual measurements. Numbers in parentheses indicate changes from last month.
** 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.
The Venting Subsystem is complete except for flow restrictor sizing. During tests of the engineering unit ,it was discovered that the current size restrictor is too large. The flow restrictor will be sized during January 1997.
GSE #1 was shipped to LMA for EMI testing in December. The VGSE was received and functioned correctly at LMA. A bug in a diagnostic loop was fixed, this bug did not affect normal GSE performance. MIT will continue alpha testing on VGSE #1 so that any bugs or missing functionality may be added to VGSE #2.
VGSE #2 final assembly was completed in December. With EMI testing, completion of final debug was delayed until January 1997. Debug will complete in January and engineering functional tests followed by acceptance testing will commence. After testing and acceptance, the VGSE #2 will be connected to the flight venting subsystem and detector housing to size the flow restrictor. This will conclude the requisite testing for VGSE #2 to be ready for delivery to MIT.
During December, the systems engineering group continued preparation of verification assessment and test reports, maintaining program requirements documents, and performing engineering specialties activities in support of the flight hardware fabrication and verification. Of specific importance during this reporting period was completion of the ACIS instrument level EMI/EMC testing.
Identification of requirements for updating the final CDRL/SDRL submittals in support of the Acceptance Data Package was started during this month. The ACIS Wire List will be updated in January to accommodate needed wiring changes for the RCTU to PSMC interfaces.
Development of ACIS System Schematics continues. It is anticipated that the System Schematics will be completed during the next reporting period.
System level overview and support of program scheduling and update of the ground processing flows for testing of ACIS instrument flight hardware continued this month. ACIS component- and system-level test flows maintenance continues. Final update of the ACIS Verification Requirements and Specification Document SVR02 was rescheduled for January completion. On-project reviews were supported and a liaison with MIT and NASA/MSFC for review, comment incorporation, and approval of formal verification test procedures was maintained.
Review of program activities and scheduling of the PTS and ACIS verification events continued throughout December. 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 when needed.
Pre-bake, contamination control coordination, and MSFC-SPEC-1238 bakeout activities continued throughout this reporting period.
The Power Summary Tables that summarize our current understanding of the power requirements have not changed since the June 1996 progress report. Therefore, these tables have been deleted from this 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.