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 November 1996.
At the request of Harvey Tananbaum from SAO, an ACIS delivery schedule meeting was conducted on November 19 at MIT. Various options were evaluated and a preferred plan selected which involves the assembly of an "XRCF" focal plane containing calibrated, but not reflexed, CCDs which would be installed in the EU Detector Assembly and delivered to MSFC for XRCF calibration along with the flight units of the DEA, DPA, and PSMC. The preliminary estimate of the MIT/ ACIS project is that this delivery could be made in early March, with the flight Detector Assembly following in mid May.
A monthly status review for ACIS was conducted on November 21 at MIT. The AXAF Project Office was represented by Buddy Randolph, Ken Reed and Tony Lavoie (Max Rosenthal participated via telecon). Gordon Garmire attended from PSU, and Lloyd Oldham presented the LMA portion of the review. Both Al Pillsbury and Jim Gregory attended from Lincoln Lab and presented the CCD and flexprint status. At the conclusion of this review, the schedule discussion of November 19 was continued with the AXAF Project Office. Subsequent to this review, a list of objections was presented by the Project Office and these were successfully answered by the MIT/ACIS project. The end result of this activity is that MSFC has given preliminary approval for MIT to try to meet this two-phase delivery scheme.
On November 20, as part of the LMA visit to MIT for the Monthly Review, a one- day TIM was conducted between MIT and LMA. LMA presented the detailed performance measurements obtained on the flight PSMC for MIT evaluation. A few anomalies were noted and discussed. The main portion of the TIM was devoted to the detailed planning for the delivery and testing of the flight DEA/DPA/SS to LMA at the end of the month.
ACIS participated in the weekly AXAF telecons on November 5, 12, 19, and 26. ACIS participated in the FPSI telecons on November 13 and 27.
The CCD/flexprint problem finally seems to be in hand. Adequate flexprints were in hand at the start of November so that attention could focus on the CCDs themselves. As previously reported, initial attempts at re-flexing were plagued with ESD failures. Efforts were initiated to find the cause of these failures and the TRW experts on this subject visited the Lincoln facility on November 19-21. This activity to alleviate ESD has paid off. By the end of November, LL had successfully packaged five (out of six) new CCDs with new flexprints. [In the first few weeks of December, they successfully re-flexed five previously calibrated CCDs in five attempts.] Therefore, the ACIS project is now in receipt of sufficient flight-quality CCDs to populate a (all Front Illuminated) flight focal plane-a major milestone. Lincoln will now begin 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.
However, additional flexprints are needed to complete 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 approved for use, but Speedy began the fabrication of a Lot 5. Al Pillsbury traveled to Speedy Circuits at the end of the month for the final processes of this lot in hopes of assuring success. Unfortunately, he was not able to accomplish this task and yet another problem (gold-plating nodules) eliminated this lot from consideration. We will use the best of Lot 4 for the remaining CCD packaging and re-flexing activities.
The following is a brief summary of the status of the other ACIS elements:
The "ACIS-2C" CCDs were calibrated during the month. In order to facilitate the calibration activity, MSFC imposed an alignment requirement on the "2C" instrument. The CCD installation was measured in the flight focal plane facility in NE80. Unfortunately, both CCDs experienced some problem (ESD?) at final checkout on December 11. The nature and cause of this problem is under investigation.
All DEA and DPA electronic boards were conformally coated. At final test, two FEPs failed one of the tests. Engineering units were substituted in the DPA being prepared for delivery to LMA.
A total of four sets of OBFs have been fabricated. The units were sent to the synchrotron at Wisconsin for uniformity testing in early December by PSU.
The DEA Interface and Thermal Control flight boards were loaded at Sanders. However, just after arrival at MIT, an Alert was received which hit the 2N2222A transistors on these boards. The HRC project at SAO lent us sufficient units to replace these parts on the two boards. They are back at Sanders for this substitution.
By the end of the month, both electronics boxes had been assembled and mated to the Support Structure. The flight instrument was installed on the SIM-SIM and Functional testing was conducted on December 1 and 2.
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.
With the successful assembly of sufficient CCDs, the ACIS schedule has stopped slipping. The two-phase plan discussed above will result in the delivery of the flight DEA, DPA, SS, and PSMC, but with an "XRCF" focal plane in an EU Detector Assembly, on about March 15. The flight Detector Assembly and Vent Valve Assembly will complete its verification activities by mid-May and be delivered separately to the XRCF.
The personnel status of the ACIS project has held firm. In fact, due to the receipt of PIRNs 0015A and 0036, MIT was forced to re-hire Marty Furey (via the subcontract to PSI) to re-do the structural analysis of the DEA/DPA and calculate the reaction forces on the translation table. He rejoined the project on November 25 for a period of six months.
Calibration was completed on two devices intended for ACIS2C: w97c1, a front- illuminated device, and w148c4, a back-illuminated device.
Three front-illuminated devices with flight-qualified flexprints were received from Lincoln and screened: w193c2, w461c4 and w457c4. None of these devices were "re-flexed". The latter two devices were produced in the latest ACIS lot (MIT Lincoln Lot 14). The screening results show that flight-quality devices can be produced from this lot.
The effects of latchup on the performance of the CS5012 analog-to-digital converter (used in the flight video board) were determined via x-ray test. Gain and spectral resolution at 5.9 keV were measured before and after latchup for latchup periods of less than one hour and more than 3 days, respectively. No gross performance changes were observed. A full report will be prepared in December.
We hosted an ACIS Science team meeting on 7 and 8 November. We attended the calibration workshop at MSFC on 13-15 November, and presented results of the CCD subassembly calibration.
The ACIS Contamination Monitor (Door Source) flight unit parts are at LMA and MSFC for bake-out and 1238 certification. The External Calibration Source flight unit parts are at LMA for bake-out and 1238 certification.
Two of the Flight BPAs are at LMA for bake-out and 1238 certification. The third unit is being used to assist in flight cable assembly.
The parts of the Proton Shield parts are at LMA for bake-out and 1238 certification.
All drilling for pins is complete. The Support Structure is assembled and supporting the DEA and DPA for the EMI testing at LMA. Procurement of satisfactory pins for the Flexure to Support Structure interface is waiting for a suitable specification. Difficulty was encountered during assembly with the +Z Panel mating with the Y Panels. This will be addressed when the unit returns to MIT.
The new cable clamp has been completed and the unit assembled It is at LMA for bake-out and 1238 certification.
The EU DA is at LMA undergoing EMI testing.
The fitcheck of the SIM-Sim at Lincoln Labs was completed successfully with only a few minor changes required. The chiller assembly has been modified and tested with the EU DA. The Focal Plane does reach the low temperature intended.
The DPA and DEA drawing package has been completed. Work is continuing on Support Structure and top-level ACIS assembly drawing.
Both the DPA and DEA have been assembled in the flight configuration for the EMI test. Two interferences in the DEA were encountered: a screw head with the Tantalum shield, and two transistors on the tenth Video board with the Interface Board. The screw interference was solved by ordering buttonhead screws and the board interference was solved by new lead bending of Q2 and Q28 on the tenth Video Board.
The mechanical fitcheck at LL to prepare for the ACIS TV Test was completed on November 1.
Several tests were run to cool the EU FP with a Neslab Cryo-Cooler. The aluminum GSE straps were insufficient to cool the FP to the target temperature of -40°C or cooler. Sections of copper braid were added to improve the cooling capability of the straps. The FP was cooled to -46°C with the Detector Housing at room temperature. New copper straps were also fabricated and showed further improvement in a preliminary test.
Modifications to the x-ray cart to be used in the TV Test are underway. The cart will be returned before 31 December.
An updated list of the 1238 bake-out test temperatures for ACIS hardware was issued. Temperatures for DEA and DPA are approximately 15°C cooler than previous predictions because of improved cooling in the ISIM thermal design by Ball.
ACIS thermal models are being updated to reflect the latest boundary conditions from the October "Delta CDA" and final design details.
MIT participated in the November 7 and November 21 Thermal TOP Telecons.
The DEA flight system is completely operational. Total system integration has begun. Functionality testing commences with the DPA flight system and the engineering PSMC. Final integration with the engineering focal plane assembly is underway.
The DEA engineering system is currently being configured to be placed into its assembly housing. The full-up system will be integrated with the engineering DPA. Upgrades to flight configuration will be finished soon.
DPA Status: November 1996-December 1996
After loading the complete set of DPA boards into the flight backplane, two were removed due to failures. The flight DPA continued to undergo testing using two engineering FEPs. Now at the LMA EMI test facility, it appears to be functioning successfully.
The two failing flight FEPs were debugged last week. Both flight FEPs were determined to have failed due to opens. One open developed after initial test and involved a corner pin of an Actel (SEI packaged) device. Another open most probably was always present and involved a defective etch on the printed circuit board.
The ACIS electrical ground support equipment was brought on-line in early November. This EGSE was then used to support the testing of the flight hardware during final assembly at the end of the reporting period.
In order to avoid any schedule impacts due to hardware failures, a second EGSE was configured and both units were packed and shipped to LMA on December 3, along with the flight hardware, to support integration and EMI/EMC testing.
The main EGSE activity left at MIT is preparing for the thermal vacuum testing of the full-up instrument at Lincoln Lab in early February. All cables have been designed and are in fabrication at LMA, Lincoln Lab, or MIT, and are scheduled to be completed by the end of December. The cable assemblies will be baked out in January.
The following software ECOs were generated this month:
These design changes are described in "http://acis.mit.edu/axaf/eco".
Version 1.20 of the IP&CL structures table (36-53204.0204 Rev. F) was subjected to internal review and then delivered to TRW. It describes the Beta release 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.
The Beta version of the Flight Software was delivered on November 15, accompanied by release notes and building instructions. Default command blocks, bad pixel lists, etc., were 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.
14 new software problem reports have been filed, of which 10 have been closed out. A total of 11 problem reports are outstanding. These may be inspected at "http://acis.mit.edu/axaf/spr/".
The psci test tool now replaces processScience in all verification tests. The status of verification testing was discussed in a telecon between Peter Ford and Bob Blozie (MIT) and Tim Crumbley and Steve Purinton (MSFC) on November 20.
Twenty (20) 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. One of the Alerts listed below impacts the MIT ACIS design at this time. JSC TWX A-96-08, MSFC Alert number 6996, reported that 10.3% of the lots of MIL-W-22759 wire were rejectable. The rejectable wire was fabricated by seven (7) different manufacturers, but none of those manufacturers were named. MIL-W-22759 wire is used extensively in the DPA, DEA, and interconnecting cables and harnesses. All MIL-W-22759/33 wire used by MIT was fabricated by Tensolite. Due to the general nature of this Alert, MIT does not have any action to recommend at this time.
|ALERT #||MSFC #||Part Number and Manufacturer||Part or Material Name|
|9Q-P-97-01||6978||MS51832 (Generic)||Screw thread inserts|
|QB-A-96-02||6985||988 A-10PN & 588 D-10CN
(Norman Filter Co.)
87014, 87015, 87016,
|R4-A-97-01||6988||XXXRTDh-A (Tonichi America Corp.)||Screwdriver, torque|
|ZW-A-97-01||6989||JANTX2N6796 (Siliconix Inc.)||MOSFET, N-Channel|
|XS2-A-97-01||6990||MS28889-2 (Hydro Fitting Mfg. Corp)||Valve,pheumatic,
|SM-A-97-02||6991||41006056-101 HR (Textron Inc.)||Valve, linear,|
|BP6-P-97-01||6992||Various customer SCDs (Harris Corp.)||Microcircuit marking|
|GD-P-97-01||6993||HS5214 (Sipex Corp.)||Microcircuit,
|9Q-A-97-01||6979||261-0328-XXX (Langley Corp.)||Seals, metallic flange|
|JSC TWX-A- 96-08||6996||MIL-C-27500,
|TWX-A-97- 03||6998||MIL-R-11 (RC), &
|MSFC TWX||6999||NDBC-TFE-22-2SJ-75 (Bay Assoc.)||Cable, electrical|
(Buckeye Rubber Products)
|Hose, rubber, fuel,
oil, cool ant
(Eagle-Pitcher Ind. Inc.)
|IB8-P-97-01||7004||Various part numbers
Shipped two Thermal Control/Interface kits to Lockheed Sanders for assembly.
One hundred-fifty (150) JANTXV2N2222A Motorola transistors were purchased, received, and sent to ATC for PIND, X-Ray, and DPA to replace the JANTXV2N2222A New England Semiconductor (NES) transistors identified in an Alert last month.
Waivers 36-001 through 36-004, 36-006 and 36-009 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|
|36-011||RCTU serial interface circuit resistor||MIT||11/7/96||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 cancelled/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 locations 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).
An additional new flight Spectrometer Optical Blocking Filter (OBF) has been ordered from Luxel. This OBF is of such superior quality that it may replace one of the flight OBFs previously tested.
Materials:MIT received approvals of 11 MUAs from MSFC. This leaves 12 MUAs still open.
No Activity this month.
For ACIS SW verification, a test procedure describes what requirements are to be tested. This may result in many test scripts, but for purposes of reporting, we track the completion of all scripts produced as a result of a procedure as a single entity.
Currently, MIT has developed 14 of 36 test procedures. During this reporting period, FepPowerTest was generated but needs to be redesigned because of review comments. Of the 14 Test Procedures, 11 were checked against the Software Verification Requirements Matrix and updated. All are in the review process.
Six (6) test script sets have thus far been developed and run on engineering hardware. During this reporting period, 3 were generated but not reviewed. These are Graded, Reset, and Overflow.
Changed over from processScience to psci. This required a major change to the software test environment, as well as minor changes to some test scripts.
There have been 11 new problem reports identified this reporting period.
There now are a total of 76 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.
Supported the assembly of the ACIS electronic boxes, which were required for completion for EMI testing at LMA in late November. All available Flight material was cleaned and vacuum conditioned as planned and any miscellaneous hardware was cleaned as needed. The contamination engineer was present during major assembly processes to ensure proper handling. Even though the electronics and support structures will require additional work, contamination prevention was an important part of the assembly process. After the EMI test at LMA, final assembly, cleaning, and vacuum conditioning will pose interesting challenges during the next few months.
Calibration of the OBFs is planned for December at the Synchrotron Radiation Center in Wisconsin. PSU sent MIT the required holding fixtures, which were cleaned and vacuum baked. Witness samples were developed to monitor the contamination levels during the OBF calibration.
Testing of reflex candidates 157C2 and 189C2 has confirmed they were damaged by ESD while being repackaged in the month of October. Progress has been made in several areas to improve control of ESD in the packaging operations. These changes have included installation of a humidifier that can control in the 40 % RH range, installation of a conductive floor, testing of the air ionizers in the room, and testing of clean-room gowns. The most important factor, however, was the visit by Melissa and Harry Jolliff of TRW; they are very well-schooled in ESD control and were able to identify problem areas (non-functional air ionizers, non-dissipative gowns), and give valuable advice on how to reduce our ESD risks while packaging. Following their advice, we have introduced more dissipative surfaces into the lab and removed triboelectrical materials. We have also ordered dissipative chairs and the meters necessary to monitor and calibrate our equipment. We are having discussions with the gowning vendor regarding the fact that the gowns, although purchased as being static-dissipative, are not sufficiently conductive to meet the current standards; it may be necessary to switch vendors to resolve this point satisfactorily. Since we implemented these changes, we have successfully installed flexprints on 3 of 4 flight CCDs; this is comparable to our historic yield of 67%. In December, we will attempt to reflex calibrated parts; we are confident the yield will continue to increase as more of the equipment mentioned above is installed.
Additional evaluation of the flexprints from Speedy Circuits' Lot 3B has been performed. Coupons prepared by both Hi-Rel Laboratories and Lincoln Laboratory have been evaluated by MSFC and found to be acceptable despite the presence of some minor folds and voids. Since thermal cycling of these parts (and some that have similar but more severe defects) does not cause failure, all of the available Lot 3B flexprints will be used. This makes eight more flexprints available for flight detectors.
Slow thermal cycling of two flexprints from Lot 3B has been completed successfully. These samples included the redundant back junction wires previously described. Thermal cycling was between -150°C and +60°C for 200 cycles. This concludes the acceptance testing of Lot 3B flexprints. Additional evaluation of Speedy Circuits' Lot 4 has also been performed.
As for Lot 3B, micro-sectioned coupons from Lot 4 were sent to MSFC for evaluation of the hole quality problems that were described in the previous report. MSFC accepted 7 of the 8 panels that were evaluated. These panels will receive additional evaluation during December. This will include micro-sections of real flexprints from each panel as well as slow thermal cycle testing of flexprints from each panel. Previously 2 of the worst flexprints from this lot (from the panel MSFC rejected) were subjected to 400 rapid thermal cycles without any via failures as determined by continuity testing. During November, the vias with the worst fabrication flaws (burrs and nodules) were micro-sectioned to see if there were any cracks or De-laminations that had been initiated. No thermally induced defects were seen when examined at 1000 X. Because of the concern about the hole quality in the Lot 4 parts, an additional lot is being started at Speedy Circuits. It is expected that Lot 5 will be completed during December, 1996. Al Pillsbury will be present at Speedy Circuits from December 1 until this lot is completed to monitor its progress.
Additional evaluation of the "via-less" flexprints from Speedy Circuits has been performed. Nine via-less flexprints representing the 9 panels containing flight candidates were bonded to alumina substrates. These samples then began the 200 slow thermal cycle acceptance test. Within 42 cycles, 7 of the 9 samples had developed open back junction connections. This style flexprint does not allow the use of the redundant back junction connection utilized on conventional flexprints. A failure analysis indicates that there was much better wetting of the conducting silver epoxy on boards that had previously been prepared and successfully subjected to testing. The epoxy-starved connections found on the failed pieces may be the result of poor workmanship or variations in the prepreg sheets of epoxy used for mounting flexprints. In either case, the back junction experience of the via-less flexprints does not apply to the conventional design attachment. Additional work needs to be done to pinpoint the cause of failure and to verify corrective actions before the via-less flexprints are qualified for use on flight devices. Use of the via-less design remains a contingency plan at the current time. Graphics Research, our second flexprint vendor, delivered 65 conventional design flexprints during November. However, close visual examination indicated that there were adhesion problems with the gold plating. MIL specification tape peel tests were performed on flexprints with cosmetic defects revealing that there was significant De-lamination of the gold plating. Graphics Research performed adhesion testing on their gold-plated coupons and concurred that the plating was unacceptable. They have agreed to make a replacement lot with delivery expected 23 December 1996.
Graphics Research has experienced delays in fabricating via-less flexprints. They are not reporting any defects at this time but delivery is not expected until the beginning of December 1996.
During this month Change Order 58 was negotiated. The negotiations were conducted at MIT/CSR contiguous with the monthly ACIS NASA/MIT Monthly Status Review and MIT/LMA Technical Interchange meetings to minimize travel cost. This Change Order modified the program plan due to the delay in the planned delivery of the ACIS Instrument to 3/15/97 and added several other specific tasks to the contract. It also updated the ACIS post-delivery support to be consistent with the 3/15/97 ACIS Experiment delivery date to NASA as identified in the Change Order. Change Order 62, which definitized Change Order 48, was also received. Based on this action, Change Order 58 is the only change order to the LMA subcontract remaining to be definitized.
LMA supported the ACIS NASA/MIT Monthly Status Review and MIT/LMA Technical Interchange meeting conducted at MIT/CSR this month. The MIT/LMA Technical Interchange meeting placed specific emphasis on the upcoming ACIS System EMC Test to be performed at LMA, the status of the Flight PSMC, and the interface between the PSMC and the RCTU. Following the ACIS NASA/MIT Monthly Status Review, LMA supported technical discussions and a telecon between MIT/CSR and NASA/MSFC on providing an ACIS XRCF test unit with a fully populated and calibrated focal plane array for testing in the March 1997 time frame. This new option appears to be feasible and will allow much more meaningful ACIS testing at XRCF.
Major accomplishments for November included completion of NASA-SPEC-1238 bake of the Flight TCS Shades, completion of the functional refurbishment of VGSE #1 to the VGSE #2 configuration and shipping to MIT/CSR, and completion of the acoustics testing of the second set of Flight OBFs and initiated NASA-SPEC-1238 bake. The OBF bake had to be cut short to provide the OBFs to Penn State for calibration/irradiation. Therefore, additional baking is still required to meet NASA-SPEC-1238. The flight cable harness fabricated by LMA completed merger and acceptance testing and was shipped to MIT and the Engineering Unit (EU) Venting Subsystem was completed and shipped to MIT. Random vibration, thermal cycle, and post-environments performance tests were completed for the Flight PSMC. As a result of these tests, the PSMC design and hardware were upgraded to improve performance margins in two areas identified during thermal cycle testing. Additional vibration testing will be performed on the PSMC after the system EMC test to assure quality workmanship in implementing these improvements.
The program continued to review inter-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 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 of flight hardware testing and preparation for the System EMC test to be conducted at LMA in December. This required continued emphasis on performing to the PSMC schedule, and on resolving day to day situations to maintain that schedule. Problems encountered during the month were primarily 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 was restarted. No interim results are available as of 1 December.
Assembly of survival heaters and thermistors to the flight PSMC lid has been completed, allowing final box-level assembly and testing to be completed.
All flight printed wiring board assembly and testing were completed, with all PWBs except DPA/DEA Power Supplies receiving a post-conformal coat bake-out. The flight unit was fully assembled and tested in an "open box" configuration. The flight unit was subsequently closed and formal verification testing initiated.
Proto-flight vibration testing was successfully performed on the flight unit in X/Y/ Z axes using the Ball provided flexures. Pre- and post-Performance Tests were run, with between-axis functional testing. All of these tests were successfully completed using the PSMC test rack. Test results are summarized in the mechanical section of this monthly report.
One item of note occurred during the functional test run between Y and Z axes: The PSMC test harness, that mates with the LMA built test rack, was included in the vibration test to simulate cable harness loads at the ISIM level. After the first PSMC axis (Y) was vibrated, the functional test was stopped to investigate loss of serial digital telemetry. The problem was traced to a broken coax cable wire within the test harness. Evidently, the small-gauge coax center conductor used for the serial digital synch signal broke during the first 60-second vibration test. While this does not constitute a PSMC failure, it does underscore the fragile nature of these coax cables, where the center conductor dielectric has been removed.
The flight PSMC was subjected to a thermal cycle test, with the average box wall temperature held between + 46°C and -36°C, and functional tests performed during hot/cold soak for each cycle. A cold start/functional test was also performed at -40°C to demonstrate PSMC functionality at the cold survival limit. Two anomalies occurred during this test.
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 prebake was initiated at +100°C.
During the next reporting period, the prebake 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 Detector Housing assembly is complete, ready for ACIS integration, and is being maintained in storage until it is required by MIT for focal plane installation.
The Engineering Unit Venting Subsystem was upgraded to the flight configuration this month. All thermistors, connectors, vent valves, and pressure transducers were assembled and delivered to MIT. Both the EU Detector Housing and the Venting Subsystem were installed onto the SIM Sim in preparation for the upcoming integration with the flight DPA and DEA. VGSE # 1 was used to pump down and re-pressurize the detector prior to installation of the OBFs. A few bugs were found in the VGSE firmware. These will be fixed prior to the EMI test in December.
After delivery of the EU radiator assembly to MIT for fitchecks, the radiator shipping fixture was returned so the FU radiators could be placed into storage. The EU Radiator Assembly was installed onto the SIM Sim and will be left on the SIM Sim until after EMI testing. The Sun Shade and Telescope Shade were 1238 certified this month and have also been returned to LMA for storage until needed for installation.
No activity to report.
Stress analysis updates will be completed by the end of December with the completion of the fracture analysis to follow. The PSMC Vibration Test procedure was approved after addressing some MSFC concerns. All parties agreed that the PSMC should be tested on flexures if there was adequate separation between board frequencies and flexure frequencies. If there was not adequate separation, then a hard-mounted test spectrum was derived.
PSMC vibration testing was successfully completed for all three axes on 11/15/96. The low-level vibration data did show adequate separation between the boards and the flexures so all testing was completed with the PSMC mounted on the flight-like flexures. The first mode for the flexures in both the Y and Z axis was around 90 Hertz with the boards resonating around 200 Hertz. The first mode in the X axis was around 400 Hertz.
The 8-cycle thermal cycle test was completed on the PSMC on 11/29/96. Details of the test will be provided in the Electrical Section of this report. In normal operating mode, the PWM chips on the DEA run about 18°C above the box wall temperatures using the PRTs which are bonded to the components. This will be compared to the flight predictions so new 1238 bake-out temperatures can be determined. Preliminary data shows that the 1238 certification temperatures can be reduced to around 75°C.
The G-10 spacers (to replace the nylon spacers) were delivered and installed onto the SIM Sim. They will be baked out along with the rest of the SIM Sim hardware after the EMI test is complete at LMA.
Two more filters were damaged after the CAMSIM was evacuated and just prior to acoustic testing. This occurred when a NW16 clamp came loose as the UUT was placed into the shipping tote. This rapidly re-pressurized the camera, destroying the Imaging OBF. Initially, the Spectrometer OBF appeared to be undamaged but inspection at Luxel showed a new pinhole and some cracks along the edge of the frame. After this anomaly, all clamps were redundantly fastened with string ties to prevent a re-occurrence of this failure. Flight OBF acoustic testing was completed on 4 sets of the new Polyimide filters and were shipped back to Luxel for post-test inspections after 1238 prebakes. New filters were purchased by MIT to replace the damaged filters. There are 4 imagers and 3 spectrometers which passed the acoustic test without damage. The new filters (2 spectrometers and 1 imager), may be qualified by similarity which will eliminate the unnecessary risk of another acoustic test. There is a lot of handling of the OBFs which must take place in performing these acoustic tests and this puts the filters at extreme risk. Justification of a Qual- by-similarity is warranted since a total of 5 imagers (1 EU, 4 FU) and 4 spectrometers (1 EU, 3 FU) have been acoustic tested at proto-flight levels (all of the new Polyimide design). Pre- and post-test inspections were performed on all of these filters by Luxel and no acoustic damage was ever recorded.
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 (+.60)**||+0.2|
|Cables & Connectors||9.1 (-0.4)||+0.1|
|Total Basic Weight||102.9||±0.9|
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 in December or early January.
VGSE #1 was shipped to MIT 11-21-96 and was received by MIT 11-26-96. VGSE #1 will be used to support final assembly of the engineering unit detector and EMC testing.
VGSE #2 final assembly and test will commence in December with an expected completion date in January 1997.
The systems engineering group continued with the preparation of verification assessment and test reports, maintaining program requirements documents, and providing engineering specialties support of the flight hardware fabrication and verification activities during the November reporting period.
Revision F of 36-03020.02 ACIS Wire List was completed and published during this reporting period. This revision contains no impact to spacecraft interfaces; therefore, no PIRN was needed.
Systems Engineering personnel continued to monitor the spacecraft charging test and analyses conducted at TRW during this reporting period.
Development of ACIS System Schematics continues.
System-level overview and support of program scheduling and update of the ground processing flows for testing of ACIS instrument flight hardware continued throughout this reporting period. The ACIS component and system-level test flows are continuing to be maintained. A final update of the ACIS Verification Requirements and Specification Document SVR02 was not completed as planned and is now scheduled for completion during the next performance period. 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. A significant effort was expended during this reporting period in planning and coordinating the instrument-level EMI/EMC Test activities within LMA and with MIT.
Review of program activities and scheduling of the PTS and ACIS verification events continued throughout November. 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. The last of the verification procedures from LMA will be completed during the next reporting period.
Prebake and coordination of contamination control and MSFC-SPEC-1238 bake-out activities continued throughout this reporting period. MSFC-SPEC-1238 certification of the telescope and sun shades was completed during November. Baking of the connectors for Lincoln Labs test harnesses was also completed during November.
Tests for interface compatibility between the PSMC and the RCTU were continued during the November reporting. Support of system electrical checkouts with ACIS hardware occurred at MIT.
The ACIS Instrument EMI/EMC Test Plan/Procedure was completed during November. This document is out for review by MIT and MSFC, with comments due early in December. The test is scheduled to commence on December 4, 1996.
System Safety continued to support and monitor the program during 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.