January 8, 1998
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 from October 1 to December 31, 1997.
Since ACIS was delivered to MSFC on April 14, standard Monthly Status Reviews have ceased. The last review was on August 4 at LMA.
ACIS participated in the weekly AXAF telecons on Oct 7, 14, 21, and 28 and Nov 4, 18, and 25. There was no telecon on Nov 11 due to the holiday. The FPSI telecons that were conducted on alternate Wednesday mornings have ceased, since both the HRC and the ACIS have been delivered to MSFC.
The following is a brief summary of the status of the main ACIS elements:
The CCD status at MIT is unchanged. All remaining flight-quality CCDs (for the spare flight focal plane) are at MIT awaiting calibration. Two of the calibration chambers have been disassembled, cleaned, and reassembled. Calibration is underway. We estimate completion by December 24.
During this reporting period, MIT, MSFC, and LL negotiated a reduction in the LL SOW concerning the spare focal plane. Only six CCDs will be mounted and the extra activities that are needed for flight status will be postponed. If no problems are detected during the TRW thermal vacuum test, the six-CCD focal plane will be delivered to MIT and used as the detector complement for the ACIS engineering unit system. With this agreement for a reduction in the SOW and costs at LL, MIT was able to submit a revision to the Cost-to-Complete proposal to MSFC at the end of November.
The flight detector assembly continues to be checked for leaks at every opportunity. During this reporting period, the BASD ISIM Thermal Balance test was conducted and this provided the chance to accurately determine the detector housing pressure. Later in the reporting period, the VGSE was attached to the detector housing so that the unit could be pressurized and the door opened. In both cases, the answer appears to be less than one torr per week (specification is 10 torr per week).
The main event of the reporting period was the thermal balance test of the ISIM at BASD. During this two week period, ACIS was operated extensively and no instrument problems were detected. The only "ACIS" issue that arose was the inability to reach -120°C on the focal plane during this test. The focal plane did reach -122°C during the ACIS TV test at LL, so the design of the instrument is proven. However, our ability to reach the lowest temperature depends on the details of the radiator mounting and the local environment inside the TV chamber. It is the contention of the ACIS project that BASD must model the TV chamber environment and produce a documented prediction of the radiator temperature. If this prediction is attained during the thermal balance test, then the ACIS/ISIM interface is verified. At the moment, no such modeling has been produced.
Shades. At the beginning of the reporting period, tests on the engineering unit shade at MSFC showed that the VDA on Gold Kapton would provide acceptable results. When BASD broke vacuum after the thermal vacuum test on the ISIM and found the tantalum delamination problem, we used this opportunity to remove the flight shades from the ISIM on Nov 4 and ship them to LMA for incorporation of the vent holes. The flight units were then shipped to Thin Films Inc in California on Nov 11 and the aluminum and SiO2 were deposited later in that week. The coupons were tested at LMA on Nov 15 (and passed) and the shades were then shipped back to BASD on Nov 17 and arrived in Boulder on the 18th. They were installed back on the ISIM at the end of the reporting period.
PSMC. We used the same break in activity on the ISIM after the thermal balance test to remove the flight PSMC from the ISIM, shipped it to LMA, and began the change-out of the chip capacitors. This activity is discussed in detail in the LMA portion of this report, but a brief summary is that LMA was well prepared, had few if any problems, and was able to deliver the unit back to BASD by December 11 (including a 1238 recertification of the modified PSMC). The flight PSMC was reinstalled on the ISIM on December 13. A functional test of the ACIS instrument (including the modified PSMC) was successfully completed on December 22, thus ending this activity.
Items (e) and (f) are discussed further in the LMA portion of this report.
As of the successful test on Dec 22, ACIS is ready for launch. The only tasks remaining are to assist BASD and TRW with AXAF integration activities.
Due to the continued positive status of the ACIS instrument and schedule, the following layoffs have been made:
|Dorothy Gordon||Electrical Engineer||Jan. 1, 1998|
|Gordon Gong||Electrical Engineer||Jan. 1, 1998|
Calibration of CCDs for the backup focal plane is nearly complete; status is listed below. As of this writing (19 Dec 97), calibration is complete on 13 of 15 available devices, and the final two devices will be calibrated by 24 Dec. One of the 15 available devices (w200c1) shows peculiar behavior under continuous clocking and probably should not be used for flight.
The HIREFS chamber was successfully recertified and has been in regular use. The second large QE chamber (Butthead) was tested with a TQCM and found to be clean (<0.3 Hz/hour) over 48 hours.
15 candidate devices for ACIS backup focal plane.
All devices are front-illuminated.
|Device||QE calibration status
|Low-energy resolution calibration
|w198c1||done 20jan97||done 19dec96|
|w461c4||done 27nov96||done 01dec96|
|w200c1||done 03oct97||est. 22dec97|
|w215c1||done 13oct97||done 10nov97|
|w216c3||done 20oct97||done 10nov97|
|w163c3r||done 16dec97||done 09dec97|
|w459c1||done 28oct97||done 17nov97|
|w467c4||done 03nov97||done 17nov97|
|w163c1r||done 18nov97||done 30nov97|
|w168c2r||done 10dec97||done 22nov97|
|w185c3r||done 11nov97||done 30nov97|
|w192c1r||done 04dec97||done 23nov97|
|w78c1r||done 24nov97||done 08dec97|
|w210c3r||done 05apr97||done 11apr97|
|w202c3r||est. 24dec97||done 16dec97|
We supported the following science-related tests at Ball:
ACIS alignment measurements: Positions of ACIS reference mirrors looked good. Relative tilts of the two ACIS mirrors differ from values measured at MIT. The matter is under investigation, but is probably related, in part, to differential pressure across the camera housing during measurements at Ball.
During Thermal Balance:
ACIS dark current/focal plane cold survival test: ACIS dark current/focal plane cold survival test: We measured dark current at -60°C and -90°C. For FI devices, dark current is typically 1 electron/pixel/s at -60°, and less than 0.1 el/pix/s at -90°C; dark current for BI devices is higher than for FI devices. Bob Goeke pointed out that we can therefore use dark current at -90°C as a diagnostic for mechanical integrity of the focal plane. If a CCD-to-paddle bond is damaged, the CCD temperature will rise to the housing temperature of -60°C even if the focal plane is -90°C. The resulting dark current change is easily measurable. We used this technique to verify that the focal plane survived a cold soak to approx. -135°C.
External Source Calibration: We verified that the external source produced the expected flux of 145 ct/s/CCD (as of 10/97) and that we could detect Mn L and K lines, as well as K lines of Al and Ti.
Gain shifts: Some of the devices appear to have exhibited gain shifts as large as 1% between XRCF testing and Ball thermal balance testing. The gain measurement error is of order 0.2%, and lab reproducibility of detector gain is at this (0.2%) level. Not all detectors show gain shift at the 1% level, so the effect is probably not the result of detector electronics temperature differences.
We presented 6 poster papers at this meeting, and flogged the AXAF General Observer program with relentless enthusiasm.
Following a request from the ACIS science team, a software patch has been developed to perform "graded event histogramming", i.e., using the back-end processor to form event histograms after bias subtraction and filtering. No other changes have been made to the software design.
Additions are being prepared to the ACIS IP&CL Structures document to describe the Graded Event Histogram mode and to correct the description of the fatalMessage.fatalCode and fatalMessage.fatalValue telemetry fields. The following deliverable is still under review:
ECO 36-957 -- ACIS Software Users' Guide
Release 1.5 of the Flight Software (ECO 36-940) was burned into the flight and engineering units immediately prior to SIM integration at Ball Aerospace. It was decided that any remaining software problems will be fixed via patches.
Unit testing of BEP and FEP flight software modules is now complete. No additional anomalies have been noted.
High-level testing of flight software in FEP and BEP hardware continues, accompanied by tests at MIT and MSFC using the software and hardware simulators.
A problem arose when running 6 FEPS simultaneously on the hardware simulator. It was traced to a timing problem on the engineering version of the FEPs which does not appear to affect the flight FEPs.
The current status of ACIS software verification is detailed on an ACIS Web page.
No new flight software problems have been found and no reports have been filed. One prior software problem report has been closed and patches have been tested that correct the remaining 3 problems:
SPR-113 (M97071101) Incorrect PBlock Selection when Desired Block is Corrupted.
SPR-115 (M97080401) Bad varianceOverclockLow values in Raw Histogram Mode exposure packets.
SPR-116 (M97101301) Incorrect reporting of corrupted bias pixels.
A list of software problem reports may be accessed via the ACIS Web server
The following software performance tests were performed during the SIM integration:
|ECO 36-962||-- Jitter DAC Test Procedure
-- AC/BD Histogram test Procedure
-- FEP Ring Buffer Reset Test Procedure
-- FEP Hardware Stress Test Procedure
-- Clocking Mode Survey Test Procedure
Ten (10) Alerts from NASA/MSFC, were received over the report period. These items are listed below. Each ALERT was compared with the ACIS Parts and Materials lists. None of the listed ALERTS affect ACIS flight hardware.
|ALERT #||MSFC #||Part Number and Manufacturer||Part or Material Name|
SILICON GRAPHICS INC.
DIFF. LINE RECEIVER
KEMET ELECTRONICS CORP.
AND RIGID FLEX
|LP-P-97-01||7097||FSC 9630||CHROME PLATING
|E4-A-97-01||7098||4213400-1 (MODEL 3100)
MIT waiver request 36-005, Multiple Point Secondary Power Return, and 36-018, Weld Filler Material, were approved by MSFC. Listed below are the open MIT waivers at this time. All other waivers have been approved or withdrawn.
|36-007||OBF VISIBLE LIGHT EFFICIENCY||MIT||8/6/96||OPEN|
|36-016||USE OF OVERSTRESSED WIRE||MIT/LMA||3/28/97||Disapproved|
|36-020||CRIMP CONNECTOR TESTING||MIT||10/1/97||OPEN|
Provided support at Ball Aerospace for Thermal Balance and Thermal Vacuum Testing of the ISIM.
Delivered the PSMC-EU2 to Ball Aerospace. Temporarily installed PSMC-EU2 on the ISIM.
Supported Ball Aerospace during Failure Analysis and Corrective Action of the AXAF ISIM. Monitored ACIS during FA.
Witnessed VDA cleaning and coating of the ACIS Telescope and Sun Shades. Inspected same after coating.
Removed ACIS PSMC-EU2 from the flight AXAF ISIM. Installed the new flight telescope and sun shades as well as the flight PSMC on the flight AXAF ISIM.
Supported alignment testing of ACIS and the AXAF ISIM.
All forty-six (46) ACIS Nonstandard Parts Approval Requests (NSPARs), data requirement SPA 03, have been submitted to and approved by MSFC.
All thirty-nine (39) ACIS Material Usage Agreements (MUAs), data requirement SHF04, have been submitted to and approved by MSFC. MSFC comments have been incorporated into the FMEA and CIL. The final version of the FMEA and CIL were submitted to MSFC.
There has been no additional activity during the report period.
See Software Quality Assurance under paragraph 1.1.3 above.
There has been no activity on the Performance Assurance and Safety (PAS) Plan. The PAS Plan in effect is revision B.
Performed wipe test of the ACIS collimator and detector door for possible contaminants.
Completed MSFC-SPEC-1238 certification of the ACIS PSMC-EU2.
The flexprints undergoing Thermal Soak had to be removed (and tested) from the Bell Jar because of a mechanical problem with the cold plate. The temperature dropped from its normal temp to -148°C for about an hour. In theory, this should not have harmed the flexprints since we were cycling them to -160°C during the thermal cycling tests. The tests show that there are no new (unexplained) problems with the flexprints. All the problems found are due to a bad product originally or bond wire problems. The vias appear to be fine.
Latest Thermal Soak Results:
|Flex #||Days of Soak||Test Results(Change)|
|9632-3I||323||Video "A" Return is now open along with Video "A" Output. Visual inspection shows that bond wires are missing from both of these. Hand probing finds the vias to be fine.|
|9632-4D||323||Video "B" Return and Video "A" Return are both open. Hand probing and manipulating shows that all traces between BJ, "A" Return and "B" Return are no longer conducting. Since they are all on Layer 4, we can conclude that this is being caused by the slice made by the vendor (Speedy) when removing the cover sheet. This Flex Print was known to have this problem.|
Upon request from CSR, W202C3 (former XRCF Paddle Device) was Keithley-tested again with good results and returned to campus.
LMA received authorization to commence activities in support of the proposed Change Order 72 tasks. These tasks include: (1) delay to SIM integration, (2) "Hot Shade" issues and support activities, and (3) Johanson DESC SPEC-87106 capacitor issues and support activities.
LMA personnel continued post-ACIS Acceptance Review support activity. LMA continued to maintained a level of Systems Verification personnel through 10/15/97, to respond to MSFC-raised issues or Action Items generated regarding formal ACIS verification.
The flight PSMC was returned to LMA on 11/04/97 for removal of Johanson DESC SPEC-87106 capacitors and replacement with upscreened DESC SPEC-87106 capacitors from a variety of manufacturers. The identified activity for R & R of the capacitors was scheduled for approximately 8 weeks. By the end of this reporting period, the schedule had been reduced by two weeks, primarily because of upfront preparatory work.
Upscreening activities for DESC SPEC-87106 capacitors continues. Remaining testing is now limited to completion of life testing at AVX. All other upscreening efforts and tests have been successful.
The flight shades were also returned to LMA during this reporting period to incorporate modifications to the reflective "goldized Kapton" surface preparation. Following modifications, the flight shades were transported to Thin Film Technologies in California for application of Vacuum Deposited Aluminum. This entire activity was completed during this reporting period and the flight shades have been returned to Ball Aerospace and reintegrated onto the Integrated Science Instrument Module (ISIM) in preparation for Thermal and Vacuum retesting of the ISIM.
The program continues to review internal company Mission Success Bulletins and GIDEP ALERTS received during the month.
The program continued to place priority and emphasis on completion of the ACIS flight and ground support hardware assembly, integration ,and test at BASD. All planned hardware activities have been completed except for: completion of spare board assembly and test, vibration testing, and MSFC-SPEC-1238 certification of the PSMC, and final assembly and testing of VGSE #1.
Major LMA technical accomplishments for October and November are summarized in the following sections.
The removal and replacement process development was an early focus during this reporting period. Two candidate processes were identified previously as (a) hot plate used in combination with a custom machined fixture (similar to how the parts were initially installed) and (b) a method involving the use of a solder fountain. The solder fountain process was chosen to be the process for use.
Detailed procedures were developed for removal of the Johanson DESC SPEC-87106 capacitors and subsequent replacement with upscreened DESC SPEC-87106 capacitors. These processes were documented and circulated to MSFC, MIT, and internally for review and comment. Following many telephone conversations to work off issues and comments, the final process was written and approved.
To date, three lots of 87106 capacitors have been received from Union Technologies Corp. (UTC). A second lot of each of four part numbers was also ordered from AVX-Olean and received. AVX has performed Group A and Group B testing, meaning the parts are ready for use. The UTC parts, on the other hand, have been subjected to lot qualification and 100% screening at LMA and are complete. Two lots of UTC parts have passed and are ready to use. One lot is acceptable, but not desirable for use (87106-091) and is being held as possible replacement parts should they be needed.
The flight PSMC was received at LMA on 11/04/97 for removal of the Johanson DESC SPEC-87106 capacitors and replacement with upscreened DESC SPEC-87106 capacitors from the lots identified above. Upon receipt of the PSMC, performance was measured and documented to establish a baseline. Following the successful performance tests, the PSMC was disassembled and the process to remove and replace DESC SPEC-87106 capacitors was started and completed.
The Johanson DESC SPEC-87106 capacitors were removed from spare boards and replaced with upscreened DESC SPEC-87106 capacitors at the same time flight boards were being R & R'd.
Each board was vacuum-baked for a period (between 48 and 100 hours) after reinstallation of the capacitors in preparation for conformal coating application. Conformal coating was applied using the brush application technique. The PSMC was reassembled and vacuum-baked for 100 hours with the lid ajar to facilitate removal of volatile fluids used in the soldering, conformal coating, and cleaning processes. After vacuum baking, the PSMC was completely reassembled and all fasteners were torqued to specification. The PSMC was thermal-cycled for 4 cycles with functional tests being performed at each extreme temperature and at ambient temperatures for cycle 1 and 4. The next test is Vibration scheduled to commence on 1 December 1997 followed by MSFC-SPEC-1238 certification.
PSMC EU#2 passed it's MSFC-SPEC-1238 certification so that it can temporarily be used in place of the Flight PSMC in a clean thermal vacuum environment should it be needed.
LMA has no option but to continue to hold open the final PTS flight cable harness verification indefinitely because MSFC has rejected the submitted waiver request (Waiver # 36-016) and has stated that no other action is needed. MIT submitted a waiver to MSFC regarding the issue of DWV testing at voltages that exceed flight wire ratings (Waiver # 36-016). This testing is required by MSFC specification that is in direct conflict with MIL-STD-975, also an MSFC specification. The Request for Waiver was rejected, and a subsequent CCCB meeting at MSFC results stated that no other action is required. Because of this issue, the ACIS cables will remain under suspicion for the duration of the AXAF-I mission.
There are no changes to the MIT load table during this reporting period.
There has been no change in power dissipation since the last reporting period.
The Flight Detector Housing and Venting Subsystem were delivered and installed onto the ISIM in September where they remain. There were no significant problems, and installation was successful.
The flight shades were returned to LMA during this reporting period for modification to mitigate the "Hot Shades" issue. The chosen modifications were crosscut vents and Vacuum Deposited Aluminum (VDA). The crosscut vents were implemented onto each shade's surface where "goldized Kapton" was attached to the shades. After making the crosscut vents, the shades were transported to Thin Film Technologies in Buellton, California, by Roberts "White Glove" Express for application of VDA.
VDA was applied to the same surfaces that required crosscut vents and inspected by Brian Klatt and Neil Tice. Inspection included visual inspection using a laser and the results showed that the VDA is acceptable. The shades were shipped, again by Roberts "White Glove" Express, directly to Ball Aerospace in Boulder, Colorado, and reintegrated onto the ISIM.
No new issues to report.
No new issues to report.
Since all flight hardware has been built and weighed, there are no updates to the weight summaries from the previous reporting period. The weight data is shown below:
Assembly Weight, lb Uncertainty, lb Detector Housing 20.8 +0.2 Venting Subsystem 8.7 +0.1 Thermal Control & Isolation 5.4 +0.1 Radiators 10.2 +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.
** Includes Survival Heaters, Thermistors, connectors, and Bracket, which are not part of the ACIS budget. Mark Kilpatrick's (BASD) worksheet dated 12/8/95 assumed 1 pound for these components. LMA does not have the actual breakdown.
The ACIS Detector Housing and Venting Subsystems have been successfully integrated onto the ISIM where they remain. The electrical interface bracket was delivered to BASD and installed on the ISIM along with the ACIS venting subsystem.
Performance and functional testing of VGSE #1 remains an open item.
During this period of performance, ACIS Systems Engineering supported post-Acceptance Data Review activities and next-level assembly integration activities. ACIS Systems Engineering supported the review, release, and submittal of various engineering drawings revised to reflect as-built hardware and the incorporation of Acceptance Data Review comments.
The Material Identification and Utilization List, MIUL, has been updated and submitted in this period. The revision was performed in compliance with MIT direction in response to MSFC concerns raised during the ADP.
Supported new process development to remove and replace the existing suspect capacitors during this period. Significant coordination has taken place to support the receipt of the PSMC from NASA/MSFC (at BASD for ISIM integration) for the removal, replacement, and re-acceptance activities. All efforts are being made to minimize the impact to the program and AXAF launch schedule.
MSFC-SPEC-1238 bake-out activities were reinstituted during this reporting period in preparation for the upcoming certification of the PSMC.
EMI/EMC activities were slowed during this reporting period. The final effort remains to close out open test procedures now that the approved waivers have been received.
No activity during this reporting period.