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 August 1996.
A monthly review for ACIS was conducted at MIT on August 20. Since the recovery from the CCD assemblies is driving the ACIS schedule, and Al Pillsbury was on vacation, Lincoln Lab supported this review with Jim Gregory and Bernie Kosicki; PSU supported this review with John Nousek, and Lockheed Martin attended with Ed Sedivy and Pat Roberts. The MSFC staff in attendance were Nes Cummings, Max Rosenthal, Tony Lavoie, Ken Reed and Buddy Randolph. Paul Plucinsky represented the SAO ASC. Since Mark Bautz was also on vacation, Steve Kissel presented a report on the MIT/ACIS science team activities. The next review will be on October 3 at LMA.
The technical and schedule data presented at this review were still consistent with the project plan agreed to by MSFC in July. This plan is as follows: MIT will proceed to LMA in late October with the flight DEA, DPA, and Support Structure, but with the Engineering Unit Detector Assembly. At LMA, experiment integration would be conducted, EMI/EMC testing performed, and finally 1238 bakeout and certification at BASD in December/January. In the meantime, the flight focal plane would be integrated into the detector assembly in mid December, vibration tests conducted in late December, integration with the rest of the flight hardware (upon return from Denver) in late January, and finally a full up Thermal Vacuum test of the entire ACIS experiment at Lincoln Lab in February. The ACIS experiment would be delivered to XRCF by March 15, 1997. This schedule is still holding although there has been some slippage in individual completion dates. The driving element is still the replacement of the flexprints on the CCDs and the re-calibration of the refurbished units.
MIT participated in the AXAF project level telecons on August 6, 13, and 27. MIT did not participate in the telecon on August 20 due to the monthly review on that date (see above).
MIT participated in an ACIS bi-weekly status review on August 7 The review normally scheduled on August 21 was not held due to the monthly review the day before.
The ACIS schedule is still dominated by the refurbishment of the CCDs, which in turn is predicated on obtaining flexprints that can undergo the thermal cycling expected on orbit. As discussed below, the first set of units was received in early August and are under test. However, some deterioration of the schedule occurred due to the need for Speedy Circuits to make a second lot of flexprints in order to meet the delivery quantity.
The CCD failures has been confirmed to be due to the design and workmanship of the Flex Technology units. In early August, new units were received from Speedy Circuits. A total of 56 units from six panels were received from lot 2 and 9 units from several panels from lot 1. However, since the agreed upon flexprint Verification plan requires the sacrifice of two units from each panel (one for thermal vacuum testing and one for destructive analysis), the lot 1 delivery is not useful as flight candidates. By the end of August, coupons from each of the six panels from lot 2 had been tested by both Lincoln Lab and High Rel with no rejections. One flexprint from each panel was cut in half, with testing done on each half at Lincoln and High Rel. As a result of this testing, two panels were rejected for delamination of the gold coating and two panels were rejected for the presence of an extra layer in the flex portion of the flexprint. The net result is that we have about 18 units still available as flight candidates. In addition to this coupon and flexprint dissection, one unit from each panel (plus three from lot 1 to increase the statistics) were loaded and began thermal vacuum cycling from -150°C to +60°C. At the end of August no units had failed with about 75 cycles on the lot 2 units.
In addition to these flexprints from Speedy Circuits (which are similar to the old design but lack acrylic adhesive and a back cover sheet), a parallel order for the same design is in place at Graphics Research but these are not due until September. In addition, the "via-less" design approved at the workshop at MIT on July 31, is on order at both Speedy Circuits and Graphic Research. The first of these units is due in late September.
Once reliable flexprints are obtained and tested, the next task is to replace the flexprints on the CCD assemblies that have already been calibrated. With this in mind, the ACIS science team has completed a partial calibration of all CCDs at CSR. A total of 28 units are available for re-flexing.
The following is a brief summary of the status of the other ACIS elements:
A test was performed on non-flight CCDs with new (Speedy Circuits) flexprints to assure that the new units are acceptable from a science point of view. It was successful.
The DEA Analog Boards are at Lockheed Sanders for conformal coating.
The DPA printed circuit boards have been loaded. The FPGAs were programmed and loaded on both the FEPs and BEPs at Lincoln Lab. These units are now under test at MIT.
The specification for new Optical Blocking Filters was completed and a new set of flight units is under fabrication at Luxel, Inc.
The Rev B PCBs for the DEA Interface and Thermal Control were received in late August. However, testing at High Rel revealed that all coupons had a fatal problem and were rejected. Another lot of these boards is now being fabricated at Speedy Circuits.
Scheduled `end of project' layoffs for August 30 were postponed due to the re-planning described above. In particular, an R&QA technician was retained and the bond-room parts technician was reassigned to the CCD calibration activity. As far as contractor support is concerned, layoff plans for draftsmen were left intact - one at the end of September and one at the end of October. Finally, Bob Renshaw will be leaving the ACIS project on about September 15, at the conclusion of the fourth cable TIM at BASD.
No CCDs were received.
After calibration measurements were completed on all of the flight devices delivered in May and June, an abbreviated calibration was performed on one device (w129c2) to support a test of re-attachment of flexprints. As of the end of August, 14 Front-illuminated and 3 Back-illuminated devices were fully calibrated available for flight.
All available flight iron55 calibration sources were characterized.
Significant upgrades of the calibration facilities were begun in order to allow more rapid calibration of re-flexed devices during the Autumn. We increased the flux of the high-energy sources in the quantum efficiency measurement chambers. We equipped the low-energy sources with shutters to improve the efficiency of bias acquisition. We ordered additional computers to speed the analysis of data. We modified the HIREFS detector chamber so it can accommodate two CCDs. We also improved control of the initial detector cool down rate to assure that the 3°C/minute limit is not exceeded.
A team of six calibration facility operators was hired (on a temporary basis) to replace the summer student workers. Training was nearly complete at month's end.
Five papers were presented at the 1996 SPIE conference on Instrumentation for EUV-, X-ray and Gamma-ray Astronomy. These papers describe various aspects of the the CCD subassembly calibration and illustrate sample results. The papers are accessible via the ACIS home page.
Fred Baganoff joined the team on 1 August. He will focus on flight software testing.
Considerable effort was devoted to final checkout of ACIS 2C. Several novel readout modes were developed for use in the calibration rehearsal.
The ACIS Contamination Monitor (Door Source) flight unit has successfully completed its tests and is at LMA and MSFC for bake- out and 1238 certification. The External Calibration Source flight unit was at BASD for a fit check. It is now 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 were fit checked on the flight Collimator at LMA. Some pieces required additional chamfers or grooves to clear wiring on the flight Collimator. These were returned to MIT for rework. This is complete and the parts are at LMA for bake-out and 1238 certification.
The Flight Unit +Y and -Y Panels are having the EMI gasket grooves machined and all panels need cleaning and painting.
The flight unit is being assembled. A modification has been made to better control the location of the wire bundle as it leaves the Assembly.
The unit is available for electrical testing with the DEA and DPA. It will be up-graded to a more flight like configuration (heaters and thermistors) in mid October.
A hoist has been received and is being modified for use with ACIS. A Tipper Cart and a X-Ray Cart have been received and are being made ready to support the thermal vacuum testing at Lincoln Labs.
The Heater Control and Interface A and B Circuit Card Assemblies has been updated to show the additional wire jumpers.
Tantalum shields for the Detector Electronic Assembly -X Cover and +Z panel have been redesigned for attachment with loose hardware. The shields were thermally cycled from -40 to +80°C. The shields did not adhere to the panel with the epoxy because of the differential expansion of the tantalum and aluminum. The Panels have been reworked and the shields have been remade. All the parts are at the painting vendor for final finishing.
Cable drawings for DPA, DEA and Support Structure has been drawn. The drawings are now in the release cycle.
Support of the assembly of the DPA and DEA is continuing with ECO activity.
The PSMC was added to the thermal models for the ACIS TV Test. Options studied included several locations within the chamber, with and without a metal or MLI enclosure. The best thermal location is in the rear of the chamber, lower than the SIMSIM assembly. No PSMC enclosure is recommended because it prevents the PSMC from attaining its cold soak temperature of -30°C. The PSMC temperature can be controlled with a temperature-controlled black baseplate and the survival heater on the PSMC lid. MIT participated in the Thermal Operations TIM at SAO on August 13. TRW's presentation showed better hot case predictions for DEA and DPA. PSMC hot case prediction increased to its limit of 35°C without margin. Accordingly, the PSMC protoflight test temperature was increased from 40°C to 46°C, to increase the test margin from 5°C to 11°C, per the judgment of MIT and LMA thermal engineers. On August 14, thermal engineers from MSFC and SAO visited MIT to view hardware and review ACIS thermal models. An analysis of DEA A/D converter temperatures during a latchup failure mode was completed and sent to MSFC investigators. MIT participated in the Thermal TOP Telecon on August 29.
The DEA system as a whole has been fully integrated with the DPA system. All of its commands have been fully exercised. Further, both the DEA and the DPA are now under flight software directive via a Sparc platform.
For the next reporting period, the the DEA and DPA systems will interface with the PSMC. Image performance will be analyzed to ensure noise integrity. Total power consumption will also be tabulated.
Eight engineering FEPs, all loaded with the latest Actels are up and running in the lab. Two complete "software" systems consist of a BEP, FEP, LRCTU and Buffer Box. The eight flight FEPs have all been powered up and testing has proceeded with varying degrees of success. Two boards, which now pass diagnostics, exhibited intermittents during initial testing. One intermittent showed the symptoms of an "open" which is quite worrisome. This FEP has been temperature cycled, but the intermittent never reappeared. Another FEP had some shorts which were fixed, and the board now appears good. Finally, one flight FEP appeared to have a bad CPU, which was removed with some effort. The three flight BEPs have all passed testing, with a fallout of only one oscillator. The engineering DPA has been integrated with the engineering DEA and PSMC. We have been using this system regularly to take images from the DEA and are about to connect in an engineering CCD. The Gulton RCTU emulator, CTUE has just arrived and we are beginning to test it with the engineering DPA. A suite of system level diagnostics (which runs using the flight software, without the debug board) are being generated by Jim Littlefield. We have rudimentary tests available for the BEP; FEP system tests are in the works.
Design and fabrication of a RCTU-to-DPA harness to support integration tests has been completed.
Modification to wire lists for the PSMC-to-(L)RCTU thermal vacuum test harnesses is in progress. Some modification to cables already fabricated and MIT's BTU/FLCA test point box will be required.
Supported testing of the modified RCTU engineering unit prior to integration with the DPA and the PSMC.
Published revision F of the Software Requirements Specifications document (MIT 36-01103). It may be downloaded from the ACIS public internet site ("ftp://acis.mit.edu/pub/acis.sreq.revF.ps.Z") or from the ACIS Web site at "http://acis.mit.edu/sreqf/".
Reviewed ECOs relating to the following module:
As a result of ECO 36-730, several C++ and C header files have been merged into a single "interface.h" whose contents are documented in the ACIS IP&CL Structure Release Notes.
Work continues on BEP code to verify the PRAM/SRAM loads, guarding against a possible overload of the CCD driver circuitry.
Updated IP&CL Structures and Release Notes (MIT 36-53204.0204 Rev. E) to reflect ECO-730. They may be viewed on the ACIS Web site at "http://acis.mit.edu/ipcl/".
Updated flight software and UNIX simulator code to reflect ECO 36-730.
All BEP and FEP flight software modules continue to be subjected to unit and coverage tests.
Flight software has been successfully loaded into the BEP and FEP engineering units, low-level testing has been successfully completed, and high-level testing has begun. Testing also continues with the UNIX software that simulates BEP and FEP.
3 new software problem reports have been filed. A total of 9 problem reports are outstanding. All software test tools have been updated to reflect the changes in ECO 36-730.
Five (5) Alerts from NASA/MSFC, were received over the report period. These items are listed below. These Alerts were compared with the available MIT parts lists. None of the Alerts listed below impact the MIT ACIS design at this time.
|ALERT #||MSFC #||Part Number and Manufacturer||Part or Material Name|
PHILLIPS SEMI (82S137)
|MICROCIRCUIT, DIGITAL MEMORY|
Updated the following complete kits:
|Thermal Control Board (A)||(36-20202)||kit Serial #3, #4|
|Thermal Control Board (B)||(36-20262)||kit Serial #2, #3|
Flight Optical Blocking Filters (OBFs) have been ordered from Luxel. They are due by October 1. The new OBFs will be polyimid instead of lexan.
|Waiver #||Description||LMA/LL/ MIT||Submittal||Approval|
|36-001||printed circuit annular ring||LL||6/28/95||7/26/95|
|36-002||NHB5300.4 (3A-!) Soldering||LMA||11/17/95||1/30/96|
|36-003||NHB5300.4 (3J) Conformal Coating||LMA||11/17/95||1/30/96|
|36-004||NHB5300.4 (3G Cable, Harness, and Wiring NHB5300.4(3H) Crimping and Wirewrap||LMA||11/17/95||1/30/96|
|36-006||NHB5300.4 (3K) Printed Wiring Boards||LMA||11/17/95||1/30/96|
|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||OPEN|
|36-009||jumper wires to part leads||MIT||7/16/96||8/20/96|
|36-010||Continuity, IR, and DWV test after harness/cable installation||MIT, LL, and LMA||7/16/96||OPEN|
|36-002||A to D Converter
|36-003||CA Memory Module
|36-004||FB Memory Module
|36-005||Programmable Supply current
Op Amp 36-02304
Only Memory 36-02306
|36-008||Electrical Connectors, PCB
Mount SND Type
|36-009||Electrical Connectors, PCB
Mount KA Type
|36-012||Junction Field Effect Transistor
|36-013||Dual Surface Mount Diode
|36-014||Dual Operational Amplifier
|36-015||8000 Gate Anti-fuse Field
Programmable Gate Array
|36-017A||Charge Coupled Device
|36-018||Microcircuit, Octal Buffer
|36-019||Microcircuit, Octal Bus
Transceiver (Harris HCS245)
Flip-Flop (Harris HCS374)
Line Driver (Harris HS26C31)
Differential Line Receiver
Q-Tech part type
WIMA P/N FKP2 (36-02312)
|36-025||Wire, Electrical, Nickel
Wirecraft P/N E267U9N
|36-027||Wire, Electrical, Nickel
Specialty Cable AWG26
WIMA P/N FKP2 per
CECC 31 800
(3M-20 pin Connector/Header)
|Microcircuit, Rad Hard
|Relay, Latching, DPDT, 5A||4/4/96||4/22/96|
|Microcircuit, Logic, HC||4/4/96||4/22/96*|
|Diode, Rectifier, Schottky||4/4/96||4/22/96*|
|Transistor, Power Switching||4/4/96||4/22/96*|
|Resistor, Precision, Low TC||4/4/96||4/22/96|
|Magnetic Devices -
Transformers and Inductors
Radiation testing has been completed at Space Electronics Inc. (SEI) on twenty-four (24) device types. Results of these tests are listed below.
|Manufacturer||Part Number||Radiation Test
|Analog Devices||DAC8800BR/883||<2K Rads|
|Com Linear||CLC505A8D||>100K Rads|
|Harris (Chip Supply)||36-02305 (CA 3080)||<100K Rads|
|Analog Devices||OP220AJ/883 (TO-5 can)
|< 20K Rads|
|Texas Instruments||TL082/883B||>100K Rads|
|Analog Devices||REF43BZ/883||>200 K Rads|
|> 100K Rads|
|> 100K Rads|
Devices which have not passed 100K Rads of Cobalt60 testing will be shielded or design work-arounds will be implemented.
Have received TRW HR G16 which involves the LMA MGSE. The GN2 bottle results in 18 verification procedures. TRW also has sent a copy to L. Oldham at LMA. TRW needs updates by Sept. 13.
The MIT license to handle radioactive sources is limited as to the quantity of Cm244. The ACIS order with Isotope Products will exceed this limit. ACIS/CSR has requested that MIT update this license (or obtain a new one) so that the ACIS can be received and then forwarded to MSFC for 1238 certification. In the meantime, the sources are in quarantine at Isotope Products due to a radiation spill in their alpha source lab.
The following items were produced or worked on during the reporting period:
Developed 2 additional test procedures "Windows (2D) Verification' and 'Telemetry/Performance Behavior'. In addition a third procedure 'System Configuration Verification Procedure' is in progress and waiting for more DEA information from the developers.
Test programs are running on a second set of hardware . Alan Braver is in the process of debugging prototype test tools.
There were three new Software Problems Reports generated.
Fred Baganoff has developed images for use in (2d) windowing, and Graded Event Mode. He has run these images using the UNIX version of the software with no reported bugs.
There has been no activity on the Performance Assurance and Safety (PAS) Plan. The PAS Plan in effect is revision B.
Completed the installation of the shroud into the thermal vacuum chamber at ATC. Completed the cleanliness verification and the chamber is now usable. This chamber is dedicated for vacuum conditioning the conformal coating on PWAs.
Performed a vacuum pre-bake on seven partially completed flight FEPs, 2 populated flight Power Distribution Boards, and 1 unpopulated flight DPA Backplane.
The thermal vacuum test cables were cleaned and vacuum baked.
Working with Lincoln Labs on another thermal vacuum chamber that is available. The chamber is up and running and is being monitored with an RGA for cleanliness.
Received DPA and DEA side panels that were painted black by Boyd Coatings. The panels had tape residue left over from the masking. The residue was removed as much as possible and the panels were vacuum conditioned. There was yellow residue left on the chamber walls after the bake of these panels. The paint had passed 1443; however the leftover tape residue was probably what caused the contamination. The panels will be vacuum baked again prior to assembly of the DEA or DPA. Boyd Coatings will use flat washers secured with screws for future masking.
Eleven DEA video boards were put into the NTS chamber. The chamber developed an internal leak and the boards were removed, cleaned, and placed in Lincoln Labs' vacuum bake chamber. The boards completed the vacuum conditioning and were sent to Lockheed Martin Sanders for conformal coating.
Inserts were installed in all of the support structure panels, except for the two that are having the EMI gasket groove machined. Completed the Assembly Work Orders (AWOs) for the assembly of the support structure.
The turbo pump failed in a small vacuum chamber at MIT during the flight DPA internal harness pre-bake. There were signs of mechanical pump oil on the ion gage. The cables were cleaned and placed in the vacuum chamber at Lincoln. The RGA showed small peaks of mechanical pump oil, and the cables were recleaned. The cables have since been completed and are now in the final vacuum bake. The screws on the backshells were spot bonded with Epon 828, Versamid 140, and Aluminum Oxide. This material has since come back from 1443 testing and failed. The sample that was sent to MSFC will be retested.
Sent 5 Fe55 X-ray sources to MSFC for cleaning and 1238 certification.
Sent two shipments of material to LMA for cleaning and 1238 certification. There are five more items that need to be sent. These items are the LED assembly and 4 screws that are on order. The OBFs will be sent at a later date.
Replacement flexprint circuits fabricated by Speedy Circuits (Huntington Beach, CA) were received August 12, 1996. These flexprints have the same design as the original ones that had failed but were fabricated with different materials and with several process enhancements. A total of 56 flexprints were shipped from six panels. Two panels were rejected due to incorrect layer fabrication of the flexible portion of the circuit. Two additional panels were rejected due to delamination of the gold/nickel plating from the barrel of several vias. This second problem was discovered with the sectioning performed on representative flexprints from each panel. The two remaining panels yielded 23 flexprints. Eighteen pieces will be available for flight assembly after sectioning and thermal cycle testing.
Speedy Circuits has begun an additional lot of flexprints to make up for the low yield. Delivery is expected Sept. 26, 1996.
One flexprint from each panel (even those that were rejected) was mounted to an alumina in a flight-like fashion and subjected to qualification level thermal cycling from -150°C to 60°C. This qualification cycling represents the expected conditions during pre-flight device testing and in-orbit operation. As of the end of August, 57 of the planned 200 cycles have been successfully completed on the 6 samples. Thermal cycling of these parts will continue and be completed during September.
One flexprint was subjected to an accelerated thermal cycle test as a quick check of the via ruggedness. One end of the flexprint was alternately dunked in liquid nitrogen and placed in a hot air stream to warm the part to approximately 60°C. No failures were found after 400 such cycles. Multiple failures developed after approximately 100 cycles when original style flexprints were subjected to this test.
Qualification thermal cycling has continued on a prototype of the alternate design flexprint which has the vias moved to the warm end of the flexprint (described in last month's progress report). This test is intended to verify the flexprint to alumina attachment process and has completed 115 of the required 200 cycles to date. Thermal cycling of this alternate design will continue during September.
Speedy Circuits has been awarded a contract for the fabrication of the alternate design flexprints. This design is being pursued as a contingency in case the vias in the standard design experience a failure during qualification thermal cycling. Delivery was expected by the end of August. However, the vendor has been experiencing problems with poor adhesion of the copper traces on the Kapton sheet. The material vendor (Sheldahl) is being consulted and various tests are being performed to determine the cause of this problem.
An alternate flexprint vendor (Graphics Research of Chatsworth, CA) has also been awarded a contract for this alternate design and is expected to deliver November 15, 1996. Graphics Research had previously been awarded a contract for the original configuration and are expected to deliver those parts October 8, 1996.
Previous flexprints (those that had via failures) had low emissivity coatings sputtered on to the flexible portion of the circuit to limit thermal losses to the camera housing. This process was slow, costly, and had some yield difficulties. The replacement flexprints (including those that are undergoing thermal cycle testing) have a low emissivity Kapton tape applied to the flexible portion. During the past month a process was developed to allow electrical grounding of the tape's outer surface.
Four detectors had been installed in the flight detector assembly prior to the discovery of the weak vias (as reported last month). A process has been developed that allows removal of these four detectors (which have been adhesively bonded into place) which should allow their reuse after replacement of the suspect flexprints.
Two parts, 129C2 and 193C1, have had their flexprints removed and replaced with Speedy Circuits parts; unfortunately, 129C2 was mechanically damaged during re-flexing and 193C1 had pre- existing electrical problems, but examination at CSR indicated that the noise levels met the stringent requirements of ACIS. This is the first electrical test in the certification of replacement flexprint parts. Work will continue in September on the replacement and evaluation of previously calibrated flight parts.
During this month negotiations were completed for Change Orders 48 and 28 and Change Order 46 was definitized. Based on these actions, all of the current Change Orders to the LMA contract have been negotiated and all but three have been definitized. It is recognized that the change in the program plans due to the delay in the planned delivery of the ACIS Instrument will result in a new change order to the contract. Discussions of the impact of this change on LMA activities were conducted, additional tasks activities needed to be performed by LMA were defined and a draft set of assumption and changed task descriptions were prepared and provided to MIT/CSR. It is anticipated that the change order will be initiated in early September 1996.
LMA supported the ACIS NASA/MIT Monthly Status Review at MIT/CSR and provided technical and programmatic status. The primary focus of the LMA portion of the review was a discussion of the PSMC schedule status and the causes of the schedule erosion over the past month. The events that resulted in this concern were reviewed and the recovery plan to hold the PSMC completion date was presented and discussed. The replan supports delivery of the flight ACIS instrument delivery by a promise date of 15 March 1997.
Major accomplishments for July included; completion of the GSE Lifting Fixture proof testing, Detector Housing alignment, vibration testing of engineering units (EU) OBFs, 1238 Certification bake of the Flight Radiator, SIMsim assembly and heater installation, design update of the PSMC mechanical details and delivery of the last of the NSPARs. In addition, one of the two EEE parts on the critical path for the PSMC were received so printed wiring board (PWB) assembly could continue.
The program reviewed 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. In addition, there have been no items defined during the month nor during the course of the contract, to date, that have warranted generating a Contractor-Initiated ALERT.
The program continues to focus on flight hardware fabrication and testing, with emphasis on the PSMC, and on resolving day to day situations to maintain schedule. Problems encountered during the month were primarily the result of difficulty in getting flight parts from outside vendors to enable timely completion of the flight hardware. To assure the timely receipt of these parts, a senior member of the LMA ACIS staff has been tracking each outstanding part, expediting dock to stock, taking steps to expedite delivery of the parts to the program and facilitating assembly of the parts into the flight hardware.
IAs reported last month, two lots of 1N6689 diodes were over stressed and/or burned up during Group A electrical screening burn-in at an outside vendor (DPA Labs). Replacement 1N6689 diodes were located and expedited screening was completed during August. These parts were received and loaded into the flight printed wiring boards. This screening failure has incurred an approximate 3 week schedule impact on the flight PSMC PWBs that use these piece parts.
DPA Labs has initiated screening of the 15CGQ100 diodes, now that the IN6689 Group A electrical testing has been completed. A higher than expected fallout of the "CGQs" has occurred, prompting LMA to send all remaining 15CGQ100 diodes to DPA Labs for upscreening. Timely completion of the 15CGQ100 Group A electrical screening is necessary to avoid further delays in final assembly and test of the remaining PSMC flight PWBs.
The flexure mount induced mechanical redesign of the PSMC is completed. Stress analysis shows the 4-point flexure mount can be made fail-safe, while staying within the estimated weight growth to implement this change. In addition to base modifications, the PSMC sides also had to be beefed up to carry higher loads. All PSMC mechanical detail drawings have been released. Expedited procurement is in place to allow machined detail availability to meet PSMC Flight Unit mechanical assembly schedule dates, with one exception. The front connector panel is needed to complete motherboard assembly. All reasonable efforts are being applied to pull in this delivery date. All finished machined details are expected in the next reporting period.
In spite of the progress made this month, the box mechanical part machining activities may still represent the schedule limiting element enabling box-level assembly and testing of the fight PSMC. The Front Panel is needed to fully assemble the motherboard. No meaningful box level assembly and testing can occur without the motherboard, although some preliminary testing can begin using the EU #1 motherboard. This continues to represent a concern as of the end of this reporting period.
Delays in receiving the final EEE parts have delayed final assembly, test, conformal coating and bake out of the flight PWBs planned for earliest completion. This is causing all of the flight electronics to complete board-level activities at approximately the same time, rather than a waterfall completion schedule. Because each board is planned to receive a pre and post conformal coat bake out, properly instrumented vacuum chamber availability will likely be the ultimate limiting factor in determining PSMC assembly and test completion dates.
Other progress includes:
The fabrication of the Detector Housing Thermal Controller (DHTC) is now complete with the receipt of the 1N6689 diodes.
The Serial Digital telemetry circuit card assemblies are complete, tested and in prebake.
The Vent Valve and Mechanism Controller PWB assembly was completed. These boards will be tested early in the next reporting period.
The IO/EMI assembly is nearly complete. Final component installation is nearing completion. This assembly should go into prebake early in the next reporting period.
The DEA Power Supply PWB assembly was initiated. Board assembly completion is expected early in the next reporting period, pending receipt of the 15CGQ100 diodes.
The DPA Power Supply PWBs are on order, with delivery expected early in the next reporting period, due to delays at the vendor. The DPA assembly drawing was completed. The manufacturing process plan has been approved by Quality.
The Motherboard projected delivery is scheduled for early September due to delays at the vendor. This late date is a problem and work-arounds are being investigated, including using the EU1 motherboard for initial electrical integration testing. Delays in delivery of the front panel machined detail would prevent final assembly of the motherboard, even if it were already delivered.
There are no changes to the MIT load table during this reporting period.
The completed piece part radiation test data is now being folded into final radiation analysis verification reports.
Final grinding and match drilling of the shims to the Ball supplied drill template was completed. A post-grinding alignment verification revealed an error in the shim thickness calculations. Therefore, a spare set of shims was ground to the corrected thickness plus 26 mils and was rechecked on the Zeiss coordinate measuring machine. Shim thickness was verified so that the final match drill and shim grind could occur. The final machining of the shims will occur in September and has not held up the 1238 certification of the Detector. 1238 pre-bake and certification is scheduled for September.
The radiators, mounting hardware, thermal straps, and sun shade support posts have been 1238 certified. The sun shade and telescope shades are ready to be shipped to Ball for 1238 certification pending chamber availability.
No progress to report.
The PSMC baseplate analysis was completed this month so that fabrication of the flight mechanical details could start. The SIMsim proof test analysis was completed. The post-proof test analysis was completed on the sun and telescope shades so that the test procedure and build logs could be closed out. With most of the hardware fabrication and testing now complete, full attention has been concentrated on completing the final documentation of the stress analyses.
The SIMsim final assembly was competed this month. Proof test and final cleaning is scheduled in early September. Afterwards the SIMsim can be delivered to MIT for fit checks with the engineering unit hardware.
The suspect actuator was removed from the S/N 005 Starsys mechanism so that it could be disassembled to determine the cause of the gap between the primary O-ring and the backup ring which showed up in the X-rays. The inspection revealed that indeed the backup o-ring was not properly seated over about a 90 degree section. The improperly seated O-ring was caused by excessive Bray lubricant from the initial installation of the heater subassembly into the actuator body. The corrective action to prevent this from occurring again is to add steps in their processes to limit the amount of Bray lubricant used in the assembly process. The suspect actuator from S/ N 005 has been rebuilt and is due to go into final acceptance test in early September. The actuator will then be reinstalled on the actuator mechanism for final performance testing prior to delivery back to LMA. X-rays will occur after assembly and after testing to confirm that the O-rings are properly seated. The MARS will remain open on this actuator pending a final disposition from Starsys. The X-ray of the actuators has turned out to be a valuable verification of proper O-ring seating.
The flow restrictors for the venting subsystem have been fabricated and measured. The flow restrictors prevent an inrush of air from breaking the optical blocking filters during pumpdown and vent up. The connectors installed on the venting subsystem were also replaced with vacuum preconditioned connectors. Once a flow restrictor has been installed, the entire venting subsystem, along with spare flow restrictors and assembly hardware, will be baked for 1238 certification. This is now scheduled to begin during September.
The assembly of the VGSE is nearing completion. A few cable details and the RS232 isolation board are all that remain before final installation and test of the VGSE. These efforts will be complete early next month so that final acceptance may be performed.
The ACIS detector and venting subsystem lifting fixture is complete and proof tested. Although this GSE was designed to handle the detector and venting subsystem for LMA and MIT handling and test support, BASD plans to use this fixture for installation onto the SIM. Therefore, a simulator has been developed based on the current design and will be used in a fit check at BASD in September. There are concerns about possible interference when used for this application which may require some modification. These concerns will have to be addressed after the mockup fit check.
Prebake and coordination of contamination control and 1238 bakeout continued throughout this reporting period. This included monitoring drawing notes and processes to identify specific points in the manufacturing flows for vacuum baking of hardware. Baking of the TCS hardware, except for the Sun and Telescope shades, was completed this month. These two items are awaiting chamber availability at Ball Aerospace.
Vacuum baking of the Detector Housing and Venting Subsystem in preparation for MSFC-SPEC-1238 certification is imminent and is expected to be completed during the next reporting period.
The on-project reviews of the EU#2 EMI test report were completed. Incorporation of comments and release to the program is expected during the next reporting period.
Planning efforts were initiated for the upcoming instrument level system EMI/EMC testing. Currently these tests are planned to commence in November of this year. The tests are expected to take 10 to 14 days to complete on a two 10 hour shift basis. Based on telephone conversations with MSFC and MIT during this reporting period it is anticipated that some of the required tests may be reduced or limited in scope to accommodate the addition of a ESD radiated susceptibility test with the detector housing door open.
Continued to support the ACIS program during this reporting period. Provided guidance for ground handling safety of GSE.
PMP engineering provided drawing review and redlines in support of drawings release. Attended table top and drawing signature reviews. Continued tracking of parts, materials and processes identification on MIT drawings.
The preparation and submittal of Program MUA's and support of MSFC-SPEC-1443 testing continued through this period. In accordance with a verbal agreement between MSFC and MIT obtained during a weekly telecon, a single MUA will be prepared during the next reporting period that will address all materials remaining to be submitted for approval and have unknown flammability ratings.
Incorporation of the final comments into the ACIS FMEA is nearing completion. This document update is expected to be released in final form during the next reporting period.
The systems engineering group continued its support of the ACIS program throughout this reporting period. Requirements were updated and baselined; monitoring the systems design for compatibility with interfacing hardware continued; and engineering specialties activities continued in support of the flight engineering release schedule.
Support of flight hardware fabrication and assembly remains the primary focus for this group. The flight Detector Housing, Venting Subsystem and Thermal Control System assembly and test are nearing completion. These hardware items will be partially disassembled and MSFC-SPEC-1238 certified during the next reporting period. Preparation of verification reports has started.
Compatibility analyses of PSMC to the Detector Housing and Venting Subsystem is completed. Proper operation and pin-to-pin compatibility of these interfaces are assured.
The ACIS PTS Specification, PTS to DPS ICD, and Focal Plane to Detector Housing ICD were signed and baselined during this reporting period. Additionally, the GSE Specification was signed and baselined during this reporting period.
Update of the GSE to ACIS and Facilities ICD process continued during this reporting period. A draft version of this ICD release was released. This effort is projected for completion on or about in early September.
ACIS System Schematics development continues during this reporting period. This is a significant task and is projected for completion in September.
Compatibility analysis continued during this month. Interfaces between the PSMC and Detector Housing/Venting Subsystem were analyzed. All incompatibilities were identified and corrected. The interface schematics developed from this analysis effort were provided to TRW for their on-going ESD analyses tasks.
Continued surveillance of program scheduling and update of the ground processing flows for testing of ACIS instrument flight hardware throughout August. LMA continues to maintain the ACIS component and system level test flows as a matter of normal business. An update of the ACIS Verification Requirements and Specification Document SVR02 is planned for release during the next performance period.
Supported on-project reviews and provided liaison with MIT and NASA/MSFC for review, comment incorporation, and approval of formal verification test procedures.
Review of program activities and scheduling of the PTS and ACIS verification events continued throughout August. This activity confirms that the instrument meets requirements and will be ready for delivery to NASA/MSFC at the completion of design, build, and test. LMA continues to perform this activity as a matter of normal business.
Schedule remains the most significant management problem.
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.