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 February 1996.
Due to schedule conflicts and the Spacecraft CDA at MSFC, there was no monthly status review for ACIS in February. The next monthly review is scheduled for March 12. MSFC has requested that the review be at LMA, Denver, since the critical path for ACIS delivery is now gated by the delivery of the flight PSMC and/or the LMA-provided Detector Housing.
For the same reasons given above, there was no monthly TIM between MIT and LMA. Due to the monthly review date and location, the next TIM is also scheduled at LMA for March 13 and 14. The MIT contracting will fly to LMA and this TIM will be followed by negotiations for Change Orders #43 and #25.
MIT participated in the AXAF project level telecons on February 13, 20, and 27. There was no AXAF telecon on February 6 due to on-going S/C CDA at MSFC (and the delayed opening of MSFC due to icy roads).
MIT participated in the ACIS bi-weekly status review on February 21. The ACIS telecon normally scheduled for February 7 was canceled due to the S/C CDA and the bad weather at MSFC.
During the month of February, the ACIS schedule continued to be a struggle. The critical path has broken into two parts. As mentioned last month, the flight PSMC will not be completed until October 10. The overall ACIS plan has been adjusted such that at the time of this delivery the MIT hardware is already at LMA and the only tasks remaining are the overall integration, check-out, and EMI/EMC testing. During this period from October 10 to ACIS delivery on December 15, there is still 20 days of slack.
The big effect on the ACIS schedule relates to the parallel effort at MIT leading up to the delivery to LMA. Last month, this path showed an additional four weeks of slack. This "MIT" slack has basically eroded.
The PERT Chart shows this critical path is driven by the delivery of the Detector Housing from LMA. Due to confusion introduced by the MSFC/AXAF Science Office report that claimed no Proton Shielding was necessary, and the overall weight problems of the ISIM, this area of the ACIS design was ignored throughout the fall. When the report was finally received and refuted, it was too late to incorporate the needed changes in the spare Collimator and make a hardware swap. Therefore, the fully completed flight Collimator is currently being modified with Proton Shield mounting holes, and then has to be re-certified and re-cleaned. About four weeks of schedule time was lost at LMA due to this MIT-requested change in the flight Collimator.
In fact, many other areas of activity at MIT also suffered a schedule slip and would have become the critical path if the Detector Housing were not late. The following is a brief summary of these problem areas:
(a) The CCD calibration got off to a slow start due to normal start-up problems. By the end of February these problems have all been resolved and the calibration is proceeding quite smoothly. The current estimated completion date has about 10 days of slack with respect to the local critical path.
(b) The DEA Analog Board is well off the critical path. However, the "11th" board in the DEA has become a problem. The main cause of this problem is that the function of this board has slowly changed from "Interface and Thermal Control" to "Miscellaneous". The design of this board has been almost completed three times. As the system design for the DEA matured, more and more functions were added to the "11th" board. It now includes an array of 15 relays for power switching the 10 Analog Boards (to eliminate single point failures on the Analog Board), the A/D converter and interface for the housekeeping of the 10 Analog Boards (there was not enough room on the Analog Board to perform this housekeeping on each board), and since the "11th" board now contains a latch-up sensitive A/D converter, power limiting circuitry must now be installed on this board as well. The last change had to do with the realization that this "11th" board now probably had too many components for a single board. Due to the schedule risk of trying to layout a board which had too many components, it was decided to break-up the dual functions of the "11th" board into an "11a" and an "11b" set of boards. The design of this board appears to have been finally completed at the CCB meeting on February 29. Layout of this board is scheduled to begin on March 7. This start date is only four days removed from the critical path (but does include a re-layout of the board for flight since there is a reasonable probability that problems will be encountered on the engineering boards).
(c) The FEP design for the DPA seems to be pretty solid, and the layout of the flight board is just completing. However, the BEP does have some schedule problems. If you recall, Dave Voutour left the project in late January. Dorothy Gordon (FEP designer) has agreed to take over the BEP. At the time of the departure of Dave, the BEP did have some technical problems, so Dorothy is re-designing major portions of the BEP. That process is well under way (and has already led to the deletion of the Prep board in the DPA), but the new design is not expected to be completed until March 15. This completion date is only a few days removed from the critical path.
On the positive side, one should realize that the "MIT" critical path includes 33 days for Detector Housing alignment measurements, shim fabrication, shim installation, and alignment verification. The current plan has all of these activities happening sequentially after delivery of the completed Detector Assembly to LMA. A plan was developed at the LMA/MIT TIM in late January to spread these alignment activities out so that some might be done off-line. LMA is working on the details of this plan. Secondly, after six months of searching, MIT has finally found a PCB vendor for CIC boards who "claims" to be able to make the boards with a delivery time consistent with the current ACIS schedule plans.
As discussed above, the ACIS project is still holding to a delivery date to BASD of December 15 (with positive slack). All of the mechanical parts of the DEA and DPA engineering units have been received and assembled, and the parts for the Support Structure are due momentarily. The Analog Boards for the DEA engineering unit have been fabricated and four of the six have completed testing. Flight layouts are in process for both the FEP and the Analog Board. The DEA Backplane layout is almost completed. Actual flight hardware is accumulating; the first sets of flight Optical Blocking Filters were completed on February 29 and shipped to LMA for bakeout on March 1, the dip-brazed connector panel for the DPA was received and accepted (the DEA was received in January), and the flight Focal Plane is being assembled at Lincoln Lab (heaters and thermistors) in preparation for receipt of the first calibrated CCDs from MIT on March 12.
The high level technical problems of the past few months seem to have all been resolved. Power allocations were maintained through February. The weight allocation was also held but there was an adjustment in the MOI of the DEA/DPA/SS. The DPA went from 9 PCBs to 8, while the DEA went from 11 to 12. The total ACIS weight stayed the same, but the heavier DEA became even more heavy. This will probably require a slight modification in the design of the flight Support Structure.
During February, several personnel changes were made to the ACIS staff at MIT. As anticipated, Bill Ward, the ACIS procurement specialist and expediter, obtained a position at ISAS in Japan and formally left the project on March 1. Bill was temporary staff and his appointment at MIT was scheduled to end on January 11. Due to the ACIS schedules problems, we obtained a six month extension of his appointment until July, but he warned us that he was actively trying to obtain a staff position at an aerospace company in Japan. Since the Japanese fiscal year begins on April 1, if he succeeded his new position would begin on that date. Fortunately for him (and unfortunately for ACIS) he was able to obtain the job he sought. On the other hand, Jim Cook, an ACIS draftsman working for Peter Tappan on the Support Structure, unexpectedly quit on February 27 with no notice. Since our drafting load has peaked (mainly into ECOs), we have decided not to replace Jim, but rather have the other two ACIS draftsmen work overtime to compensate. Both have agreed to do so.
No flight-candidate CCDs were delivered in February.
DEA development continued. Temporal instability in the bias level was observed, particularly after readout mode changes. Kissel ameliorated this problem to some extent by modifying DEA software loaded into SRAM and PRAM. Bias instability is still a problem under some circumstances, and the root of the problem is not understood. The work-arounds developed for lab use may complicate the ACIS flight PRAM generator software. In any event, with these software modifications, the DEA was deemed sufficiently functional to support calibration.
The DEA provides the capability to operate with both high and low phases of the parallel clocks positive potential. This capability, not available in previous laboratory electronics, should provide greater CCD depletion depth. Prigozhin therefore evaluated detector performance at high parallel clock levels. He found that CCD readout noise and spectral resolution were maintained with clock levels as high as +2V on the low phase and +11V on the high phase. At these levels, a depletion depth in excess of 70 microns was achieved. These clock levels were adopted as the baseline ACIS operating levels for front-illuminated CCDs, and will be used for CCD calibration.
CCD subassembly calibration began on 8 Feb. As of 29 Feb., four devices were in various stages of calibration. Calibration of the first pair of devices (w163c1 and w185c3) will be completed on 12 March. These two devices will be installed in Focal Plane locations I0 and I1.
The ACIS Contamination Monitor (Door source) engineering unit parts are in assembly. The radioactive source has been received by MIT Radiation Safety.
The External Calibration Sources are on order. The existing drawing package has been checked prior to release. Minor changes to the collimation of the beam are in process. Materials have been ordered.
Leak checking of the Back Plate Assemblies has been completed with all flight plates failing. They will be returned to the vendor for rework. The EU plate is acceptable.
The details of the Proton Shield are complete and ready for review. Mounting holes are being added to the flight Collimator.
The large parts of the Support Structure are being shipped. The smaller parts are nearly complete. Reinforcement of the Flexure to Support Structure joint is planned for the flight unit. We are concerned by the Ball decision to not fully support the feet of the Flexures. This may require stiffening of the Flexures. Several changes to the Support Structure have developed as the DA to DEA cabling has been designed.
This assembly has been completed.
Flight filters are at LMA.
The lifting fixture for the Support Structure, DEA, and DPA is complete for the mock-up and parts are available for the engineering unit. The vacuum GSE has arrived at MIT and its operation is being checked out.
The Digital Processing Assembly engineering unit enclosure and aluminum PWB mounting frames have been fit checked. No problems have been encountered. The DPA and DEA engineering units are being used to determine the flight cable configuration. Detail design of the flight units continues.
The Heater Control and Interface CCA and DEA Backplane have been sent to Applied CAD Knowledge for design layout. The flight design of the DEA subgroup has been sent out for fabrication.
Participated in Thermal Tiger Team Telecons on 2/8 and 2/21. The thermal problem of hot case temperature predictions for the DPA may be resolving, according to Dave Dooley at Ball. He said the latest SIM thermal design provides a hot case DPA temperature of 410 deg C, less than the limit of 430 deg C. The cold cases also seem to be within cold limits. We await written reports of Dooley's analysis.
Obtained verbal agreement from TRW and Ball thermal personnel that the location of 3 ACIS heaters on 3 walls of the Support Structure is acceptable to them.
Completed the thermal model of the TV Test in the LL chamber. Reviewed results with MIT personnel and Neil Tice of LMA. Ordered heaters for the walls of the SIMSIM.
Analyzed thermal impact of deleting the DPA PREP board. Impact is less than 20 deg C.
Activity this month focused on the design and layout of the DEA interface card and the passive Backplane. Both activities are progressing in parallel and are expecting completion in two weeks. Final design and input/output signal requirements have been established.
Six additional engineering unit subsystems have been received from fabrication and populated. The debug and operational testing of these 6 subsystems are underway with GSE equipment.
The FEP engineering board layout is still in progress.
The BEP engineering board design for the past two weeks has been concentrated into the detailed development of the Actel FPGA. The timestamping logic, telemetry I/F and data transfer have been completed and simulated. An overall chip routing is expected within the next week, which will allow us to generate a BEP engineering board schematic and begin the layout process. The DPA Backplane schematic will be generated in parallel.
Functional testing of all three "Frame Buffer" boxes has been completed using a DEC station platform. A design requirement was that the boxes also operate on SPARCstations. DMA interfaces and cables for 2 additional SPARCstations have been ordered.
The ACIS thermal vacuum test facility and equipment configuration plan and MIT supplied harness design is well underway. Vacuum feedthroughs and mating connectors have been located and ordered and should be in-house shortly.
Developed and tested
SendCmds, software that will put
ACIS commands into AXAF command format. Developed software to read
ACIS-format telemetry packets from an input stream. Tested
putImages software for Sun SPARCstation systems. This will
copy binary image files from the workstation desk to Mike Doucette's
Frame Buffer for FEP testing.
Met with Steve Purinton and Allyn Tennant of MSFC to discuss (a) the response of flight software to radiation alarms, (b) behavior of the serial command interface in the presence of interference, and (c) status of verification and testing. This meeting was particularly useful to us because of Purinton's suggestion that we run our BEP and FEP timers off the internal ACIS clock, rather than the Spacecraft clock as originally intended. We are studying this matter. The meeting resulted in no other action items.
Review of the last outstanding module, the BEP Sequence RAM Classes, has been postponed in order to gather more information from the ACIS Calibration Team regarding workable SRAM and PRAM configurations. These have been the subject of some discussion between us since the DEA boards being used for calibration do not always behave as anticipated. If this condition persists, the flight software design must be changed in one of two ways -- either the PRAM synthesizer must be made more sophisticated or the synthesizer must be by-passed entirely in some situations, which means that provision must be made to uplink PRAM loads in a compressed form.
Continued testing the BEP serial telemetry interface and the BEP-DEA interfaces. We await the redesign of the BEP firmware before further testing of the FEP-BEP interface.
An unofficial delivery of simulated ACIS telemetry packets, and the software used to generate them, has been made to PSU and ASC. Work has begun to document the Huffman tables that are used to compress ACIS bias maps and raw image data, to form a part of the ACIS S/W maintenance document.
All BEP and FEP flight software modules continue to be subjected to unit and coverage tests.
Work continues to integrate the BEP software simulator with the FEP software simulator in a single workstation using POSIX strings and UNIX processes. Work progresses on the set of test suites to be used for verification and validation. These now include a graphical user interface using the TCL language.
Ten (10) Alerts from NASA/MSFC were received over the report period. These items are listed below. They were compared with the available MIT parts lists; none of the Alerts impact the MIT ACIS design at this time.
|ALERT #||MSFC #||Part Number and
|Q9-A-96-01||6899||MS3400 - MS3408
AT & T MICRO.
T2 UNITED CHEMI-CON
|EB7-P-96-03||6909||CLR35 & CLR37
(MIL-C-39006/03 & /04
|JSC TWX-A-96-02||6913||P/N N/A
KAISER FLUID TECH.
Generated 5 supplemental DEA kits. All were issued.
Assisted in developing procedures involving cleaning of parts for Bonded Stock room operation.
Updated Excel Macros to produce Configuration Traceability Lists and labels.
5 component lots were sent to Associated Testing Laboratories (ATL), Inc., Burlington, MA for multi-stage part testing (PIND, X-ray, DPA)
Final source inspection was performed on 2/12/96 at SEI on the 36-02306 (EEPROM).
Pre-seal visual examination was performed on 2/13/96 at Q-Tech on the 36-02311 (38.4 MHz Crystal Oscillator).
Final source inspection was performed at Harris Semiconductor, Melbourne, FL on the ACTS244KMSH, 80 pieces, PO SO-R-547060; HS1-26C31RH-8, 100 pieces, PO SO-R-558265; and HS9-26C31RH-8, 15 pieces, PO SO-R-628278.
Final source inspection was performed at Chip Supply, Orlando, FL. on the OP220, 36-02307, 154 pieces, PO SO-R-581384.
Nitrogen supplies have been delivered and are ready for installation. This will be used for purging of bags for shipping as well as blowing of particles and drying material before admittance into the cleanrooms.
A fifteen foot cable was made for use on the TQCM at Lincoln.
A change in bagging material location was made. Nylon 6, clean to level 50A, will now be used as an inner bag and the Aclar 22C, clean to level 50A, will be used as an outer bag.
Sent the following material to MSFC for 1443 testing: Aeroglaze Z306 Paint with 9924 Primer from Lord Chemical Products, Erie, PA.
Deviation Request number 36-008 was submitted in response to Midterm review action item ELEC-11. This deviation request has been replaced by NSPAR 36-025, for nickel wire.
Speedy Circuits is a manufacturer of printed circuit boards, qualified to MIL-P-55110, and located in Manhattan Beach, CA. A Supplier Capability Survey will be performed by MIT Performance Assurance at Speedy Circuits on 3/15/96, in anticipation of buying CIC printed circuit boards from them.
Prepared SCD 36-02313 for Nickel Wire. See "Deviations/Waivers" above.
NSPAR 36-024 for a Polypropylene Capacitor and NSPAR 36-025 for Nickel Wire were submitted.
|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
MIT has encouraged Lockheed Martin Astronautics (LMA) to submit required NSPARs to MIT. These are in process at LMA.
Radiation testing has been completed at Space Electronics, Inc. (SEI) on fourteen (14) 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)
|Analog Devices||REF43BZ/883||>200 K Rads|
Devices which have not passed 100K Rads of Cobalt 60 testing will be shielded or design work-arounds will be implemented. Eight (8) more device types are planned for radiation testing. These are listed above without results.
Four (4) lots of components were forwarded to Interpoint, Redmond, WA for radiation shielding.
Four engineering and four flight Teledyne Frame Buffer Modules were returned from SEI. They currently have the control engineering unit and one flight frame buffer with the epilayer for radiation testing.
Sent fax to MSFC informing them of Ni2 bottle removal.
Have learned that Ni2 bottle will remain. MIT will write two (2) hazard reports.
There has been no activity on the Performance Assurance and Safety (PAS) Plan. The PAS Plan in effect is revision B.
Four external engineering harnesses, over 100 D38999 type connectors, EMI shield, and expando sleeving material have been sent to LL for cleaning. We are developing the cleaning procedures for these harnesses.
Three platens were received for the flight OBF calibration test by PSU at Wisconsin. These were cleaned at Lincoln Labs. All material necessary to maintain the cleanliness of the OBFs have been shipped to Wisconsin.
Updated the procedure for dressing, behavior and material handling in cleanrooms to include Work Area Preparation, Bagging Material and Special Handling of 1238 hardware.
Generated a procedure that will be used in Wisconsin during the OBF calibration. The procedure consists of instructions for certifying the clean tent, installing the OBF to the platen, installing the platen to the chamber, and removal instructions. Have worked closely with Dr. Leisa Townsley of PSU, who will actually be installing the OBFs.
Completed a draft for cleaning Electronic Boxes.
Have reviewed assembly procedures (AWOs) and supplied comments.
Received the holding fixture from Lorraine Ryan of TRW. Have sent her a 3000A Imager OBF along with returning her fixture, for contamination testing at TRW.
A deviation was written to certify the Focal Plane Subassembly to MSFC-SPEC-1238 using TQCM Data and not an OWS. This is currently being discussed with MSFC.
The cleaning list for the DEA, DPA, Support Structure, and GSE has been generated. The Bonded Stock procedure has been updated to include sending material out that requires cleaning.
Packed and shipped all materials necessary for the OBF calibration testing in Wisconsin.
Sent George Chartas a 2000A Imager, that was from LMA, to perform cold test calibration.
An ACF Imager and Spectrometer Frame was cleaned at LL and sent to Luxel for spares.
Visited Wisconsin to install a clean tent around the beamline for OBF calibration. Certified the tent as acceptable for flight operations.
Received fixtures from George Chartas from PSU, who is performing OBF tests at Brookhaven, NY. The fixtures and safety covers were cleaned at Lincoln Labs and returned. Some modifications are necessary before flight OBFs can be put into these fixtures.
A total of 80 test procedures have been identified which need to be developed to verify the Science Instrument Software. This will probably result in 240 test scripts. All of this will take about 3 man years to develop.
Two test procedures were developed (BEP Memory Access and Post Launch Patch).
Added hyperlinks and table IDs to every table in the Software Requirements Specification (SRS). This resulted in the release of version D of the SRS.
UNIX shell scripts have been developed to boot the BEP, boot RCTU, load BEP, and receive telemetry on the test station in the development lab. In addition, developed shell script to guide operator in running any verification test script and produce a test report.
Reminder: The "Dump Patch" feature of the flight software has not been implemented nor has the test tool necessary to support it.
During this period our efforts were redirected at delivering packaged BI parts, so after mid-month no further FI parts were shipped to campus, but the stock of sawn FI parts has grown to 14, with 17 additional chips in the queue for sawing. We received word from CSR that all seven FI parts delivered in December and early January were acceptable, giving us an overall acceptance at CSR as 19/19 for FI devices. We project a grand total of 38 to 40 packaged FI parts will be available for inclusion in flight paddles.
Two BI parts, 138-1 and 139-4, were lost during packaging, presumably due to ESD damage since they both showed shorts in the output gate and output register regions (these structures have the smallest area and, therefore, the smallest capacitance of any features on the CCD). Similar shorts were also noted on other, non-ACIS BI CCD's going through the packaging process at this time. All packaging was halted pending experiments to resolve this apparent problem. Several changes were implemented, including making a direct connection between electrical ground and the shorting plug inserted in the Positronics connector, bonding from Flexprint to the chip (standard practice had been the reverse order), and general review of all operations to prevent ESD damage. Since these changes have been made, several non-flight devices have been packaged without any loss due to shorting. Packaging efforts have been resumed; this leaves us with a pool of six flight grade BI devices and two more of questionable quality from BI Lot 4.
All of the components required for the build-up of the flight and flight back-up assemblies are now in hand. The temperature control heater elements arrived at the end of last month, one week ahead of schedule. The Beryllium structures have been gold plated and will be thoroughly cleaned prior to heater installation. Prior to the installation of Detectors, the heaters, RTDs, terminal strip, reference alignment mirror, and locating blocks must be installed and inspected. It is expected that the flight assembly will be ready to receive the first Detectors during the first week of March.
The second Focal Plane assembly (engineering unit) has been delivered to CSR. Prior to shipment, two Detectors were replaced to allow development of this procedure. Visual inspection, dark current measurements at -4000C, and automated parametric analyzer results all indicate that no damage occurred to the Detectors replaced or to other Detectors on the assembly. The development and demonstration of this replacement procedure had held up the delivery of the engineering unit to CSR but is an important milestone.
A vacuum bakeout procedure and monitoring techniques have been developed for the Focal Plane assembly. These were used on the engineering unit prior to shipment. The results were within the MSFC-SPEC-1238 guidelines. Although this bakeout was not functionally required for the engineering unit, it did support the contamination control program by verifying the process.
All of the necessary fixtures and supplies required for the build-up of the flight Detector Assembly have been cleaned and assembled.
The Flexprints under fabrication at Flex Technology Inc. had arrived from their drilling vendor and were having holes etched back in preparation for thru-hole plating, along with registration and etching of the outer layers. After this process was completed, the thru-holes were plated and the Flexprints sent out for gold and solder reflow plating. Last month Flex Technology in formed Lincoln that during the solder reflow process, the bottom gold pad accidentally had solder applied to it. Flex technology sent 15 of the circuits for Lincoln to examine. The solder covered the bottom of the back junction pad, along with 2/3 of the height of the inside hole. Normally, epoxy is used to make contact to this pad, but this was not possible now that solder covered the gold. A modified process in which the epoxy would fill the hole and make contact with the uncovered gold at the top pad was proposed to CSR, and was approved for use.
During this month update proposals were prepared for Change Orders 25 and 28, negotiations were completed for Change Orders 18, 39 and 42 and Change Order 31 was definitized. Negotiations for Change Orders 25, 28, 41 and 43 are scheduled for mid March.
No ACIS Program Technical Interchange Meeting (TIM) was scheduled this month; however, both an MIT/LMA TIM and the ACIS/NASA Monthly Status review were scheduled to be held in Denver in March.
The TRW Spacecraft CDR held at NASA/MSFC was supported this month by Systems/EMI/ Spacecraft Grounding and Contamination engineers.
Major accomplishments for February included providing a 3D model of a proposed layout for the ACIS cables on the SIM to Ball Aerospace, completion of PSMC EU #1 testing and shipping EU #1 to MIT, completion and ship of VGSE #1 to MIT, completion of the GFE OBFs and shipping containers precision cleaning, completion of prebake for the first set of flight OBFs, and initiating procurement of the first LMA flight PSMC printed wiring board. In addition, a PSMC reliability prediction was developed and provided to MIT.
During February, a cable fabrication form board for the ACIS flight and T-Vac test cables was designed and fabrication of the form board was initiated. This form board design was based on the proposed cable layout developed by LMA and provided to Ball based on their verbal concurrence with the cable layout.
The anticipated Science Instrument Module (SIM) Cabling routing data from Ball Aerospace was not provided in January. This data was requested by LMA in April 1995 and identified as needed no later than 17 January, 1996 to support the LMA cable design and fabrication schedule. To attempt to accelerate development of this data, LMA prepared an alternative cable routing recommendation and provided it to Ball Aerospace. Work on ACIS flight cables has been delayed pending response to this recommendation and receipt of the cable routing data. Workaround approaches are still being investigated to try to accommodate this late data delivery and avoid impacting the ACIS hardware delivery date.
As a result of the rework, recleaning and bakeout of the 3' x 5' chamber completed in January, the chamber was operated to assure acceptable cleanliness levels and certified in February for future 1238 bakeout activities.
Complete PSMC interface requirements definitization was a key goal for February. The RCTU serial digital interface received significant attention and agreement was reached with no change to the PSMC. All 32 bits (4 ea. 8 bit words) of PSMC serial digital data will be sampled by the RCTUs every major frame.
The revised MIT load table presented at the January TIM caused at least one change. The PSMC over voltage protection (OVP) transient response characteristics and optimization of EU#2 OVP transient response were aggressively worked during February. Open items exist on the DPA and DEA over voltage protection (OVP) limits and were carried over into March in search of final agreement.
Completion of designs and incorporation of changes into the EU #2 and associated test tools has been proceeding. In parallel with these efforts, there has been a real push to get flight schematics completed, PWB layouts completed and PWB orders placed. The temperature control PWB was completed with the PWB engineering out for vendor quotes. The flight thermal control PWB purchase order should be placed early in the next reporting period.
EMI Control PWB layout is nearing completion and should be ready for procurement early in the next reporting period.
The following additional activities were accomplished:
Parts procurement is getting significant attention and is proceeding. Delivery dates on at least two Harris radiation hardened parts have now extended to a point were use of already procured alternate parts will probably be necessary. Request for quotes were prepared on screening/QCI on three SSDI diodes. Due to some of the recent changes, several new parts for procurement have been identified. The remaining new part requests, required to support CO 43 redesign are expected to be given to procurement by mid March.
All Test Plans for radiation testing of electronic parts have been completed and a plan has been implemented for all testing. There are twelve parts to be tested. The first lot is to be completed by March 22 and all tests are scheduled for completion by May 3.
Engineering for the Lincoln Labs cables was initiated. The three dimensional cable form board design was initiated, with drawing release for fabrication expected early in the next reporting period.
All Detector Housing piece parts excluding the Collimator and the Camera Body are complete and precision cleaned. Direction was received on the bolt interface design of the Proton Shielding to be added to the Collimator. The engineering was updated and released to include the mounting holes recommended by MIT. The shop is due to start drilling the holes in early March. Due to late information on the location of the Proton Shield interface holes and the time required to machine, die penetrant inspection, and cleaning the parts; the start of assembly of the Detector Housing and Collimator has been delayed by approximately 6 weeks. Efforts are being made to compress the in-process work to make up time in the current assembly and test schedule. In parallel with the Collimator holes, the Camera Body will also be match drilled to the Collimator to aid in alignment and prevent movement during induced environments. Two high strength alloy steel shear pins are required because of the mismatch in CTE between the titanium Collimator and the aluminum Camera Body and will require a MUA.
Fabrication of TCS components is on schedule with no major problems to date. The cold radiator and thermal straps were completed this month. NDE was completed on the warm radiator with Martin Black application to occur in March. The radiator stand offs (excluding gold coating) are complete with proof testing to occur next month. The support posts passed proof testing this month and are ready for flight. Final machining of the shades will occur in early March. All other small details are complete and precision cleaned. Bulk lay-ups started on the flight MLI blankets. Fabrication of all flight blankets should be complete by the end of March. We are expecting final information on the MLI mounting approach for the +Z panel and sun shade and telescope shade from Ball in early March.
Thermal cycling (5 cycles) between -7 deg C and +4 deg C was completed on the PSU irradiated filters without failure. The CAMSIM Focal Plane was reinstalled into the CAMSIM Detector after a dimensional inspection at Lincoln Labs. The X-axis vibration test which was scheduled to occur on these filters did not occur be cause of an operational error in pumping down the Detector. The Christmas tree pumping station was hooked up incorrectly resulting in a rapid pump down and subsequent failure of the OBFs prior to the test. A second set of irradiated filters will be required to complete this phase of testing.
The completion of the stress analysis CDRL continues to be delayed as a result of more tasks related to tiger team activities and flight hardware support. Heavy ACIS Tiger Team activities have required effort to support the PSMC base plate redesign. A preliminary NTE weight increase of 1.5 pounds is required to support the new 4 flexure-mount design. Analysis was completed on the new shear pins between the Collimator and the Camera Body. In addition, final analysis of the radiator standoffs was completed so that a proof test procedure could be written.
Updates to the PSMC thermal analysis were made in February as the flight release of the Printed Circuit cards has started. Preliminary predictions show some of the components at very near their maximum allowable junction temperature of 12C for a +4C PSMC side wall temperature. Efforts were made to reduce the predicted junction temperatures with additional heatsinking of hot components. Additional copper was added to the boards around the high power axial lead diodes which has helped to reduce the temperatures. If the current Ball prediction of +3C (PSMC side walls) is maintained, all components will be within their derated temperature limits. As each of the boards are reviewed in table-top reviews, reference designators, piece part dissipations, and component locations will be modified in the spreadsheet to reflect the flight configuration.
The StarSys written test report for the life cycle test which qualifies the new Minco heater design was completed this month and closes out all StarSys activities.
The final reports on the Door Actuator and Venting Subsystem life cycle tests will now be completed as time permits.
The new external vent tubes were received and are currently in receiving inspection. These will be sent over for X-ray and dye penetrant inspection as soon as the dimensional checks are complete. The external vent tubes have passed inspections and two will be selected for flight and flight spare based on the results of inspection notes and a visual inspection of sealing surfaces.
VGSE #1 was shipped to MIT on 2-14-96. The manual followed with the set of keys the next week. After several questions regarding initial hookup, there are no expected difficulties getting the VGSE to function as designed.
The VGSE passed a preliminary set of performance tests using the LMA CAMSIM engineering unit. Six complete pump down cycles were performed with a 3000 Angstrom Optical Blocking Filter in place. These tests demonstrated that the VGSE did not damage the filter during any phase of testing including power loss. During these tests the pump down cycle was verified to take about 2 hours while the vent up cycle takes about one hour to complete.
Shipping container design and fabrication will begin next month after the SIM simulator design has progressed a little further. ACIS is evaluating the potential use of the AXAF mirror shipping containers to function as a SIM simulator shipping container. The main question to be resolved is the size required by the SIM simulator.
An OBF was pressure tested to failure as part of the tests performed during February. The tests revealed that a 3000 Angstrom filter will withstand a 4.5 Torr pressure differential before failure. The test was conducted with the CAMSIM engineering unit in flight like configuration. The bypass vent around the OBF was sealed to allow the pressure to build up behind the filter. Both filters broke at the same pressure indicating a sympathetic failure and both were completely destroyed by the failure. The flight filters are to be 2000 Angstroms thick, indicating the extreme care required to maintain OBF health.
Review of the Contamination Control/96 to accommodate incorporation of on-project comments.
A PSMC reliability prediction analysis was performed at the request of MIT to define the change in reliability when both DPA power supplies are operated simultaneously. The ACIS FMEA/CIL is being prepared/planned and will be scheduled to commence during the next reporting period.
EMI/EMC test report continues to be a concern and will be revisited during the Spacecraft CDR.
Systems engineering activities during this reporting period were spread across many disciplines. Requirements documents were being updated, designs for Detector Housing, Thermal Control System, and PSMC hardware were being updated and flight release started. System analyses and schematics were started. Engineering Specialties efforts were increased to perform reliability analyses of the PSMC. The Systems Group supported the AXAF-I CDR held in Huntsville at the request of MSFC.
Systems engineering activities for the month of February were focused on several design and documentation issues including: ACIS specifications and ICD's updates, flight engineering release activities, development of test plan/procedures responsibilities list, and verification reports responsibilities.
The ACIS PTS Specification, PTS to DPS ICD, and Focal Plane to Detector Housing ICD are in process of update to reflect impacts from Change Orders #43 and #46.
Update of the GSE CEI Specification, planned for completion last month, continues to be delayed as a result Mr. Glen Schaff's employment termination from MIT. Coordination with the new EGSE Lead, Demitrios Athens, and information gathering activities continue this month with an update of the GSE CEI Specification for EGSE items planned for early April 1996.
Update of the GSE to ACIS and Facilities ICD process continues during this reporting period. A draft version of this ICD release is scheduled for early April 1996 with a final version to be released on or about 4/15/96.
System design activities focused on supporting discussions about over-voltage and over-current protection within the PSMC, definition of survival heater installation for the PSMC, and establishing the requirements for development, design, fabrication and testing of cabling needed to support thermal-vacuum testing of the ACIS DPS hardware in the Lincoln Labs chamber. The cabling fabrication form-board design, a tool to aid in fabrication of flight cables, was started and completed during this reporting period. This form-board will be used to fabricate the Lincoln Lab chamber cables during the next reporting period.
ACIS System Schematics development was started during this reporting period. This activity is being closely coordinated with MIT to effectively use common software tools and produce a document usable for fault isolation as well as developing an under standing of the design.
Schedule remains the most significant management problem.
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 deg C.