CCD Imaging Spectrometer
George C. Marshall Space Flight Center
National Aeronautics and Space Administration
Marshall Space Flight Center, AL 35812
Center for Space Research
Massachusetts Institute of Technology
Cambridge, MA 02139
This report covers the period December 1995.
Due to timing of the November review (Nov. 30) and the end of the year holidays, there was no monthly status meeting for ACIS in December. The next monthly review is scheduled for January 17 at NE80. This date is still tentative until the MSFC project returns from furlough and an overall AXAF project review schedule is determined.
For the same reason, there was no monthly Technical Interface Meeting with LMA in December. The next review is scheduled at LMA for January 25 and 26.
During the review on November 30, MSFC requested an ACIS Verification and Test meeting at MIT during the Jan.-Feb. time frame. The main purpose of this meeting is to discuss the constantly evolving ACIS test plans, including the latest plan for separate thermal vacuum testing of the DEA/DPA and the PSMC. The date for this review is still open pending the government return to work.
MIT participated in the AXAF project level telecons on December 5, and 12. There were no AXAF telecons after this date due to the shutdown of the Federal Government.
MIT participated in the ACIS bi-weekly status review on December 13. The SI telecons normally scheduled for December 20 through January 3 were also canceled due to the government furlough.
During the month of December, the ACIS schedule continued to be plagued by slow vendor delivery. The activities for the loading and testing of the calibration PCBs had to be re-programmed due to the severe delays at Lockheed Sanders and their planned shutdown from Christmas to New Year. It had been planned that MIT would load and test the first PCB. After this unit was successfully operated, Sanders would load the five PCBs to be used for the CCD calibration activities. Testing of the first board was completed and five kits of boards and parts were sent to Sanders on December 16. Unfortunately, due to a heavy workload and the planned shutdown, they would not promise delivery of the first board until January 5 and delivery of the remainder at a rate of two per week. Since this schedule would directly impact the critical path, MIT went into a two-shift operation (including the Christmas and New Year weekends) and proceeded to load three of these boards. By January 5, four boards had been loaded by MIT and three had completed all functional tests. Sanders has promised delivery of two boards by January 9 and, assuming at least one is delivered by this date, all calibration test sets will be delivered to the science team by the scheduled date of January 12, thus holding the critical path.
With respect to the flight hardware, the Analog Boards tested above exceed ed all specifications by a wide margin. Therefore, the flight design for the CCD drive and readout is solid. The remaining issue is the presence of single point failures on the Analog Boards. The PSMC has redundant power supplies (six regulated voltages) for the DEA. These redundant voltages are diode-ORed on each Analog Board. This results in six single-point failures on each of the ten Analog Boards in the DEA. Although the probability of a short at any one of these points is very low, the fact that there are sixty such points is very worrisome. A fair amount of effort was expended in December to try to develop an alternative approach to dealing with the DEA power distribution (e.g., dividing the DEA into sides A and B with each powered by one of the PSMC set of supplies, adding fuses to the Analog Boards, re-designing the input power limiting/regulation circuitry on each Analog Board). A decision on the resolution of this problem is scheduled for January 5, so that the preparation of the final flight schematics can begin on January 8.
The significant step towards the performance of the DEA/DPA/Detector Assembly thermal vacuum testing at Lincoln Lab, as part of the existing System Level test, was accomplished in December. A problem had developed in finding the necessary technician support at Lincoln Lab to support round-the-clock operation of the thermal vacuum facility for approximately thirty straight days in July-August. A meeting was held with the heads of Division 7 and 9 at Lincoln, and the necessary support was re-programmed from other projects. Implementation of this plan will shorten the critical path by about two weeks and increase the slack on the delivery date of December 15. The down side of this option is that the flight PSMC would not be available to participate in this combined test program. As mentioned above, MSFC is worried about this plan and has requested an ACIS Verification and Test meeting. Until approval is received from MSFC, the official ACIS schedule still has the thermal vacuum test at BASD after delivery of the MIT hardware to LMA in early September of 1996.
On the down side, as a result of detailed planning for the Detector Assembly alignment operation, LMA reported that this activity will take on the order of thirty days. The ACIS schedule allows about 14 days before the critical path is impacted. MIT will work with LMA to try to accelerate the alignment activities, or, if necessary, reduce the alignment requirements so that the 14 day schedule allocation can be met.
As of the end of December, we are still showing an eight week slack with respect to the delivery of the ACIS experiment to BASD on December 15.
As discussed above, the ACIS project remains in relatively good shape from a schedule point of view. The main technical driver in November was weight. As a result of a Mass Audit by MSFC in late November, and the completion of a series of recommendations from the review team, the ACIS weight is now estimated at 293 lbs. This weight was maintained through December.
As part of the effort to minimize weight, MIT requested a radiation dose mapping of the inside of the DEA/DPA electronic boxes from TRW. This report was received at the end of December and, coupled with the radiation hardness test data on MIT parts obtained from SEI, the shielding requirements for the EEE parts for the DEA and DPA were determined. The weight of this shielding was within the allocation made by MIT for the 293 lb. ACIS.
During December, no personnel changes were made to the ACIS staff at either MIT or LMA. However, the MIT project has decided to hire a contractor software test engineer (for about seven months) in order to keep the flight software effort on track. The coding of the flight software has basically been completed, but due to its complexity the remaining test effort is quite significant. In addition, at the end of the month, David Voutour, the design engineer for the Backend Processor of the DPA, informed the ACIS project that he had accepted another position and will be leaving MIT on January 19. Due to the short term nature of this position (the job was scheduled to end in May), the ACIS project management is in an awkward position and we are evaluating possible options (perhaps augmenting the SOW of Jim Littlefield - a contractor already working on the testing of the FEP and BEP).
Six devices were received in December; all of these were front-illuminated flight candidates, and all passed the screening test. There are now 13 devices at CSR which have passed screening tests, and are available for use in the flight Focal Plane. They are itemized below.
|Device||(FI/BI)||Date Rec'd||Date Screened
|w147c3||BI||10 Aug||11 Aug|
|w129c2||FI||15 Sep||15 Sep||Shows "D noise"|
|w87c4||FI||3 Nov||3 Nov|
|w78c1||FI||7 Nov||8 Nov|
|w97c1||FI||17 Nov||17 Nov||Shows "D noise"|
|w157c1||FI||24 Nov||24 Nov|
|w157c2||FI||24 Nov||27 Nov||Shows "D noise"|
|w158c2||FI||4 Dec||4 Dec||Shows "D noise"|
|w158c4||FI||4 Dec||5 Dec|
|w159c1||FI||14 Dec||15 Dec||Marg. spectral resol. at OK|
|w163c3||FI||14 Dec||19 Dec||Shows "D noise"|
|w168c2||FI||19 Dec||22 Dec|
|w168c4||FI||19 Dec||26 Dec|
Performance data for these devices is available on the ACIS web site.
In order to increase the flux available from the tritium calibration source, a significant modification of the quantum efficiency chambers was undertaken. The modification will allow the source to be placed closer to the devices under test. This modification was completed in December, and the chambers were re-cleaned by the contamination control engineer.
The sensitivity of CCD gain to CCD temperature was measured. For both front- and back-illuminated devices, the gain was found to change approximately 100 parts-per-million per degree C. The measured temperature stability of the calibration test sets (+-1.50C) is easily sufficient to maintain gain stability at the required level of 1 part per thousand without detailed correction for temperature variations. Furthermore, we are considering changing the calibration plan to perform gain calibrations at only two (rather than 4) off-nominal temperatures.
In preparation for receipt of ACIS engineering model Detector Electronics (DE), a breadboard (Rev A) version of the DE board, together with supporting electronics, was tested successfully in the calibration laboratory in building 37. It was verified that a pixel-to-pixel cross-talk problem identified in this breadboard last month had been solved by the DEA design team. Work began on final specification of DE SRAM and PRAM loads to be used for calibration. A problem concerning the skew of pixel codes relative to data was identified; this problem can be worked around for the calibration, but should be remedied in the flight board design.
An effort to measure the depletion depth of sample devices, and to compare the results with CCD quantum efficiency determined with reference to the Si(Li) Detector, was undertaken.
A training script was prepared to support training of additional people (from ASC and from the engineering team) in the operation of the In-focus Monochromator (IFM) test station. The script was tested on several candidate operators. Additional scripts will be prepared for the other calibration facilities.
The radioactive sources for the ACIS external calibration source were specified. One Fe55 thin-window source (similar in construction to the ACIS internal contamination source) of 90 microcuries, and 3 Cm244 alpha sources will be used. Each of the alpha sources will be equipped with a different target to provide a different set of characteristic X-ray lines. The three alpha sources will be selected from the following four:
|Nominal Photon Output
(ph/s/ster, in line)
|1 mCi||Teflon||0.677 (FlK)||2.4e3|
|1 mCi||Al||1.486 (AlK)||2.6e3|
|4 mCi||Ti||4.511 (TiK)||670|
|4 mCi||Cu||8.048 (CuK)||80|
Each Focal Plane CCD subtends approximately 2.4e-3 ster when viewed from the sources. Both the Ti and Cu sources are to be fitted with 25-micron-thick Be windows to suppress back-scattered alphas, which can damage the CCDs.
The ACIS contamination monitor (Door Source) engineering unit has been built and modified. These refinements will be incorporated into the drawing package for the flight unit.
The External Calibration Source has been defined by the Scientists. The existing drawing package is being checked prior to release.
The flight assemblies have been received and are ready for receiving inspection.
It has been decided that the Proton Shield will not affect the Collimator except to require the addition of some through holes. A design has been started.
Design continues. Details of the structure are nearly complete. The DEA to DPA cable routing has been addressed. ACIS has not been able to contribute to solving the assembly problem without changes which will affect the SIM interface. The detail drawings reflect the existing interface. Discussions with Ball concerning the interface have continued. The latest ideas have included the addition of "outriggers" to minimize the loading on the SIM. The engineering unit will be built to the present design.
No activity during this reporting period.
Mechanical parts for the engineering unit have been received.
Acoustic and vibration testing has been successfully completed at LMA on the thinnest samples. Flight frames are being procured.
The lifting fixture for the Support Structure, DEA, and DPA is being built for the mock-up and the engineering unit.
The DPA Front End Processor circuit card assembly has been updated for the flight layout. The assembly has been sent to the PC layout house for placement and routing. The printed wiring board assembly fixture has been designed and detail drawings are nearly complete. Documentation has been generated to support DEA circuit card assembly at Sanders.
Refinement of the ACIS cable interconnection continues. Particular attention has been given to the DEA power distribution and support structure heater and thermistor wiring.
Participated in Thermal TIM at BASD on 12/8. BASD presented the ISIM thermal design for the outdated 143W ACIS design. At the meeting, TRW directed BASD to proceed with a design for the current ACIS dissipation of 163W.
At the TIM, TRW's thermal representative, Joe Vogrin, said that TRW accepts the placement of the ACIS heaters on the Support Structure, pending modeling confirmation.
Completed the detailed thermal analysis of DPA-BEP (Back End Processor) components. Generated PIRN requests to change DPA -Y wall external coating from black to white paint and to change 2 DEA wall (-X,+Y) external coatings from black paint to irradiate. These changes will accommodate a hole in the SIM wall opposite the DPA, if implemented, and will reduce DEA heater power requirements.
Locations have been selected for the ACIS RCTU thermistors and the internal DEA thermistors.
Engineering effort this month focused on debug and testing of the first two DEA subsystem boards. Both boards are now fully operational and performance evaluations with a flight CCD is exceptional.
The Back End Processor (BEP) debugging continued through the month of December. The test breadboard, which contains the flight EEPROMs, has been debugged and the flight EEPROMs contents can be read by the BEP.
Flight test software has been loaded on the BEP and several minor bugs have been found and fixed.
The BEP schematics, which have gone through the review cycle and had many changes, are nearly complete for the engineering unit PC board layout.
FEP continues to checkout via marathon diagnostics which exercise the various subsystems concurrently. It has also undergone frequency and voltage margining. The frequency margining uncovered a larger than expected turn-off time of the bulk memory modules. A work-around (the addition of another CPU wait-state) was implemented in one of the FPGAs.
The DPA Backplane has been partially tested. It has been used to send a few words back and forth between the FEP and BEP boards, which was enough to verify etch and buffer layout on the three boards.
The PREP and power I/F board schematics have both been released to Rev. A.
The FEP schematics have been revised to incorporate the single power supply and removal of the diode OR, as well as a new and improved power switch. The engineering board layout will occur shortly.
Frame buffer circuit board #1 (configured to generate continuous ramp frames) has not been updated as yet and is still operating with a FEP. Testing of board #2 has been completed and is being installed in a permanent chassis. Testing of board #3 is nearly complete at this time.
A Direct Memory Access (DMA) interface card for a SPARCstation has been received. The card and driver software have been installed and awaiting testing.
Work was begun on a Sun-workstation compatible device driver for use in sending files to the image loader hardware, which will be used to test CCD controllers. Work continued as a member of the test tools group worked on system requirements and architecture for testing major components and ACIS.
Submitted Rev. C of the Software Requirements Specification to MSFC for MSFC baseline review. Submitted to TRW a set of revised IP&CL tables containing a bit-level description of ACIS command and telemetry packets.
Closed one item from the review (merging command and window parameter blocks in downlink telemetry). Three (out of 18) remain open.
Conducted ECO reviews of BEP start-up classes. Work continues on three remaining modules: SRAM library, data compression, and fatal error handling.
Finished low-level testing of the BEP serial command interface. Several firmware problems were identified and fixed. Began testing the BEP-DEA interface -- generally successful, although access to SRAM and PRAM is rather slower than expected. Continued to test the BEP serial telemetry interface, identifying several firmware problems. Continuing to test high-level FEP software, both in a simulated environment (unit and coverage tests) and in a pre-engineering FEP.
The pre-Alpha release was successfully compiled by Q/A.
All flight software is now being subjected to unit and coverage tests.
Work continues on the suite of software test tools described in the Test Tool Specification. The ACIS command builder is 90% complete (it still lacks support for discrete commands), and the pixel loader is written but untested.
Six (6) 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. MSFC Alert #6889 does impact the AXAF however. Two (2) of the connectors covered by the Alert were purchased by MIT and supplied to Ball who is building the interface cables. The connectors in question are MS27505E17F8PA (A1J1) and MS27505E17F8PB (A1J2). These are the Spacecraft power to the PSMC. Mr. Kevin Soranno of TRW has been made aware of the MIT shipment to Ball and was sent a copy of the Alert by MIT.
|ALERT #||MSFC #||Part Number||MFR.||Part or Material Name|
Series 1, 2, 3
Developed kit list for Detector Electronics Assemblies (DEAs) using Copper/Invar/Copper (CIC) boards. Assembled 4 kits.
Assembled and shipped 6 (DEA) kits to Sanders for assembly into engineering printed wiring assemblies (PWAs)
Flight bench stock procedures have been implemented.
Preseal visual examination was done at Teledyne on Frame Buffer Memories and Cache Memories. Parts and data were presented for MIT final source inspection of forty-five (45) flight Cache (CA) Modules and twenty-five (25) flight Frame Buffer (FB) Modules. The final test data for the CA modules was compared with the MIT specification, 36-02302. Data did not support all testing required by the SCD. The parts were not accepted.
One inch OWS holders were redesigned and manufactured to mount onto the CCD framestore covers to monitor the NVR build up during the CCD calibration process.
Received a TQCM.
The OBF mounting plates for the Wisconsin (PENN State) Synchrotron vacuum chamber were redesigned. The drawings were sent to PENN State to manufacture new plates.
Designed and manufactured a 4 inch silicon wafer holder that will be used to monitor the large CCD vacuum chambers during CCD calibration.
Three parts were sent to MSFC in two different shipments for 1443 testing.
Deviation request numbers 36-002, 36-003, 36-004, and 36-006, regarding Lockheed Martin Astronautics (LMA) procedures and processes, were submitted on November 17, 1995 to MSFC. MIT has not received a formal response to these requests.
Prepared SCD 36-02351 for Cm244 calibration sources.
No new NSPARs were submitted for approval during the report period. Approval was received on NSPAR 36-023. No NSPAR approvals are outstanding.
|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
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)||8K Rads|
|Texas Instruments||TL082/883B||>100K Rads|
|Analog Devices||REF43BZ/883||>200 K Rads|
|Chip Supply||OP-220 (DIP)
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.
MIT is implementing a cleaning paragraph that is required on all contracts involving machining of Beryllium parts.
Hazard reports G04, G06 and G16 from TRW were addressed. LMA has been instructed to remove the Ni bottle from the vacuum GSE while it is at KSC.
Reviewed specifications for radiation sources containing Fe55 and Cm244. The door has a maximum quantity of 100 microcuries. The SIM source has a maximum quantity of 7+millicuries.
There has been no activity on the Performance Assurance and Safety (PAS) Plan. The PAS Plan in effect is revision B.
The cleaning requirements, 1238 certifications and certification locations, have been identified for each piece part of the Detector Assembly. Special notes have been added to the Detector Assembly drawings.
Contacted Brian Ramsey, of Marshall, on the methods of cleaning the X-ray source. They have the ability to clean their X-ray source and it is a question of whether or not they can do our internal and external sources.
Procedures continue to be written and updated to reflect the individual processes.
Developing a method for particulate sampling on material using tape test methods per ASTM F 312-69, and NVR sampling using solvent wipe per MIL-STD-1246.
Developing procedure with Lincoln Laboratories for baking out the campus paddle Focal Plane subassembly for 1238 acceptance testing, without using an OWS. We will use the results of this test to 1238 certify the flight Focal Plane subassembly without using an OWS. The chamber, at 70 0C, was monitored using a TQCM, at 100C and maintained a rate of less than 1 Hz/hr for 60 hours.
Continued the monthly monitoring using contamination witness samples for the assembly areas in Buildings 37 and NE80. All areas are maintaining acceptable levels of particulate and NVR. (One clean tent experienced high amounts of particulate fallout due to being turned off for vacuum chamber troubleshooting purposes. The tent was cleaned and no hardware was exposed during this time period.)
Two CCD vacuum chambers were modified and reassembled during the month. Many parts were cleaned individually by hand and then installed into the chambers while in the clean tent. Continued efforts are in process to certify their cleanliness to level 100A per MIL-STD-1246.
Participated in Software ECO CCB: IP&CL. Continued developing Memory access test procedure. Participated in test tools review session with Software developers.
During this month six flight candidate FI chips were shipped to campus. All six of the FI flight candidates were considered acceptable, raising the total number of FI candidates at CSR to twelve, which is more than adequate to populate the first flight paddle. There are sufficient FI candidates at various stages of the packaging process to yield a total of forty FI flight devices. The gating item for packaging is now considered to be flex prints, although an adequate supply is due for delivery at the beginning of January.
The emphasis in packaging will now be switched to delivering BI parts to determine how many can be incorporated in the first flight paddle. Two devices are in the packaging sequence now and will be ready for delivery early in January. There are six more BI candidates besides those produced in BI Lot 4 (which suffer from high dark current and high CTI), suggesting that a total of four BI chips could be available for use in the first flight paddle, or as back ups.
Eddy current testing of the flight back-up structures has been successfully completed. Locating pins and threaded inserts have been installed and locations verified. These parts have been sent out for gold plating which will complete the fabrication process.
All components required for assembly of the flight unit are in hand except for the heater elements used for temperature control and contamination bake-out. These heaters are expected during the first week in February.
Additional components to assemble Detector Assemblies (alumina substrates and beryllium tees) have been ordered, to allow packaging of all available CCD devices. These components are expected to arrive long before existing supplies run out.
Metallization of the flexprint circuits for the low thermal emissivity coatings continues to proceed smoothly. All of the available flexprint circuits have been metallized successfully. Additional flexprint circuits are expected during the second half of January. These should arrive soon enough to prevent an interruption in Detector packaging.
During this month Change Order 43 was received from MIT/CSR and a firm proposal to accomplish the directed work was prepared and submitted. This Change Order was associated with extending the ACIS delivery date to December 1996. Firm proposals were also prepared and submitted to MIT/CSR for Change Orders 39, 41 and 42. Preparation of these proposals was a major program activity for the month.
The ACIS Program Technical Interchange Meeting (TIM) was postponed to January 1996 due to the number of personnel who were on vacations associated with the Christmas holidays.
Major accomplishments for December included successful completion of the PSMC EU#1 EMC/EMI test and the thermal cycle test with no significant anomalies or concerns. Additionally, the vibration/acoustic test were successfully completed for the 2000 Angstrom thick Optical Blocking Filters. The results of this test showed that this thickness filter will survive the dynamic environments imposed during the AXAF mission.
During the month the training and certification of LMA technicians and Quality Assurance inspectors for fabrication, in compliance to NASA Spec-NHB 5300.4 Cable and Plastics, was completed. Soldering training was postponed to January 1996 due to personnel schedules.
Science Instrument Module (SIM) Cabling and Thermal Technical Inter change Meetings (TIMs) held at Ball Aerospace were supported. Date presented and discussed at the Cabling TIM indicated that the cable routing data requested by LMA in April 1995 will not be available in time to support the LMA cable design and fabrication schedule defined as a part of Change Order 43. Work around approaches are being investigated to try to accommodate ate data delivery without impacting the ACIS hardware delivery date.
Bakeout of the 3' x 5' chamber was resumed following chamber rework welding or a leak that developed during the extended high temperature bake out of the chamber in November. Chamber recleaning and bakeout could not be completed in time to enable certification of the chamber during December.
Two major systems tests were completed this month, Thermal Cycle and EMI. Both tests were successful by either meeting or exceeding requirements. The thermal cycle test was begun on Thursday, December 21. The test was conducted in the Materials Test Lab using a temperature chamber capable of reaching -4C. Three thermocouples were placed on the three hottest exterior walls of the box and three more were placed at three of the hottest points in the PSMC. The hot case of 5C (maximum survival temperature) was tested first. The PSMC was allowed to thermally stabilize and the performance test procedure was run. The PSMC was then chilled to -3C (minimum operating temperature), allowed to cold soak and the performance test procedure was repeated. The box was then powered down and further cooled to the survival temperature of -4C and allow to cold soak. The PSMC was powered up to assure startup, but performance was not measured. The PSMC was then heated to the maximum temperature and the performance measured. One ripple anomaly was observed in the DPA PS that showed an out of spec condition. For this test the voltage ripple requirement was not met. However, analysis of the anomaly indicates that the condition was most likely the result of the use of commercial parts within the engineering unit. The anomaly is suspected to have been created by one of these commercial parts drifting out of its specification due to the temperature. The following table highlights the temperature requirements and the PSMC results.
|Max Operating||+46C||+51C||Full Performance|
|Min Operating||-36C||-36C||Full Performance except DPA PS 246 mV pp ripple (200 mV pp req't)|
|Max Survival||+51C||+51C||Full Performance|
|Min Survival||-45C||-45C||Full Startup achieved|
The EMI test was also successful. The suite of EMI tests was structured such that the most important tests were performed first; conducted emissions and conducted susceptibility were performed first, followed by radiated magnetic emissions tests. The details of the EMI test are reported in the Systems section of this report.
Assembly of the second engineering unit (EU#2) continues. Due to heavy emphasis on PSMC testing as well as the Christmas holiday, only minimal progress was made in this area. The current status of the assembly of the PWBs for EU#2 is as follows: the Detector Housing (DH) Thermal Controller is 99% complete, Digital Power Supply is 100% complete with initial testing underway, Analog Power Supply is 95% complete, the Serial Digital Telemetry is 100% complete, Vent Valve and Mechanism Controller is 100% complete, the IO/EMI cavity is 100% complete, and the Motherboard is 100% complete. Individual PWB testing will begin next month and this will be followed by open frame testing.
Individual part types are now being reviewed and analyzed for radiation tolerance. In cases were no radiation data is available, the part will be tested. As part of the current activity, these parts and their associated parameters are being identified. Given that the radiation levels are known within the PSMC and that the radiation tolerance levels are known and understood for a part type, a radiation tolerant PWB layout can now be achieved. For the cases where simple placement is not adequate, additional local shielding will be added. This information will be used in the layout of the flight PWBs.
All Detector Housing piece parts fabrication was completed during this reporting period. Most of the small parts have been precision cleaned. However, a contamination problem with the bagging material for the piece parts held up the transfer of the parts back to the ACIS clean room. A new bagging material has been chosen which will allow the parts to be final bagged. For the large parts (i.e. Collimator, Camera Body, etc.), new material was ordered and will be available in mid-January 1996. This will delay the start of assembly by several weeks. The Detector Housing assembly drawing was released this month. This enabled process plans to be initiated for the final assembly. The survival heater connector bracket drawing was also released.
Fabrication of TCS components is on schedule with no major problems to date. The release of the TCS installation drawing has been delayed since additional notes and sheets will be required for adding thermistors and wiring diagrams. Release of this drawing is expected to occur in January.
Both acoustic and vibration testing was completed on the 2000 Angstrom Lexan filters. The filters survived acoustic qualification levels for 3 minute durations with an internal camera pressure of 20 torr. To demonstrate margin, the test was also performed at 40 torr and 80 torr internal camera pressure for 30 seconds duration. Vibration testing was performed at qualification vibration levels for 3 minutes in each axis with an internal camera pressure of 20 torr. To demonstrate margin, the camera was retested at 40 torr for 30 seconds in the X axis only. Since the 2000 Angstrom Lexan filters survived all testing, the 3000 Angstrom filters were not tested. The test report has been sent to MIT for their review.
The OBF integrity monitor worked well during all phases of the tests. However, for upcoming tests, an additional LED will be added for self testing before and after the test to verify that the electronics are still functioning properly.
The completion of the stress analysis CDRL continues to be delayed as a result of more tasks assigned related to tiger team activities and action items. OBF test activities and design and drawing maintenance tasks on the TCS drawings have also delayed the completion of the stress analysis. There are no stress concerns to note at this time and all components analyzed to date are showing significant positive margins.
Attended thermal TIM at BECD. No additional thermal analysis was performed this month.
The preliminary release of the life cycle test failure report was completed by StarSys. The report was forwarded to MIT for their comments prior to the final release.
The test reports were completed on the mechanism life cycle tests. The reports will be released after all the StarSys anomalies are re solved and the individual actuator life cycle test is completed.
All four of the vent tubes failed X-ray inspection. Two of the tubes had flaws that prevented repair. The other two tubes had flaws that could be repaired. However, to implement this repair introduces substantial risk that requires a major repair process and leaves only a flight tube and a flight spare. Further, with more rework the distortion caused by repeated heating may cause the alignments to go out of the required tolerance. Given the importance of the function that the internal vent tube performs, it has been determined that the cost and schedule impact of remanufacturing the vent tubes must be evaluated before the final course of action is determined. In addition, a different vendor, HPS, was contacted and ask to send comparable weld samples to us for weld certification and approval using the flight hardware inspection tests. Successful completion of these tests will certify this vendor and provide the option of rebuying the tubes. This appears to be the lowest technical risk course of action but causes some schedule and delayed test concerns. The referenced test results and decision data will enable a decision in January.
During this month priority was placed on completing the VGSE schematics. The schematics for VGSE #1 were completed and are being error checked. This process is expected to be complete the first week of January with drawing release in mid January.
Testing is continuing on the VGSE #1, on a low level. Testing of the refurbished turbopump was deferred into January 1996.
Finalization of the firmware for the VGSE subroutines was also delayed this month pending the completion of the VGSE schematics.
As a result of better definition of the changes in the test and integration process associated with the schedule stretch-out the shipping container requirements were better defined. The SIM simulator will be smaller than originally planned and will support only the Detector Assembly, Venting Subsystem, DEA, DPA and Support Structure. However, this is still larger than any of the containers originally planned for which a "right to use" was obtained. Therefore, the build of a special container will be required.
The light shade design was coordinated with Mr. John Sharp of MSFC. After a long conversation it was decided that the worst case scenario is direct illumination by the Earth and has been evaluated. The analysis does not show adequate margins for this condition. However, the additional margin needed can be achieved by painting the inside of the vent tube black chemglaze Z306 paint. This paint is considered acceptable and has passed 1443 screening. Changes in the engineering will be addressed after the first of the new year. This will resolve the Earthshine concerns for all conditions.
Review of the Contamination Control Plan is in process at LMA with an anticipated release on 1/12/96.
The 1238 Chamber vacuum leak was repaired and precertification bake resumed.
The ACIS FMEA/CIL prepared by LMA was in review and updated by MIT during this month to add the data for the MIT developed subsystems. Collection of FMEA and CIL update information for ACIS DPS hardware will be supported by LMA Systems Engineers supporting MIT. Incorporation of all of the collected information is scheduled for late January and early February.
EMI/EMC testing of PSMC #1 was started and completed during this reporting period. Preliminary results indicate that the PSMC met all requirements with margin.
The primary focus of Systems Engineering for the vacation and holiday shortened month of December was support for the Change Order #43 Firm Proposal and completion of EMI/EMC testing of PSMC #2.
Redlines to the ACIS PTS Specification were coordinated during this reporting period and the specification was released.
Update of the GSE CEI Specification is planned for completion next month with a draft out for review be late January, 1996. Comments are due from MIT by the end of January with a final publication by 26 February, 1996.
The Observatory to SI ICD (IF1-20) was released by TRW. This document is in review.
Drafts of the ACIS PTS to DPS ICD and the ACIS FP to DH ICD have been reviewed by MIT. Written comments for incorporation have been received. Final release of both ICDs is scheduled for 15 January 1996.
During this reporting period Systems Design activities continued to support Spacecraft charging requirements being developed by TRW for the AXAF-I mission. The group continued support of the AXAF-I Weekly Action Item Tracking (WAIT) telecon on Wednesdays.
Telecon discussions between MIT and LMA (Cambridge) personnel about test and ground system processing flows for the ACIS instrument hardware continued throughout December. LMA continues to review the ACIS component and system level test flows. The various assembly flows are inter-related and require several more review and update cycles by MIT and LMA technical leads. Ongoing efforts continue for requirements flowdown from the AXAF-IPD PRD to the ICD to ACIS CEI's and eventually to the LMA PTS Specification. This task is nearing completion with an anticipated presentation at the January 1996 MIT/LMA TIM.
|Deliver PSMC EU#1 to MIT||Mid January|
|MIT/LMA TIM @ Denver||Late January|
|Grounding TIM||Mid January|
|Cabling TIM||Mid January|
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.