February 19, 1997

Advanced X-ray
Astrophysics Facility

CCD Imaging Spectrometer

ACIS Monthly Progress Report


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

1.0 General

This report covers the period January 1997.

1.1 Accomplishments

1.1.1 Program Management


No monthly status review for ACIS was conducted in January. A review was conducted on February 4, and will be reported in the February report The previous review was held on November 21 at MIT and was reported in the November report.


ACIS participated in the weekly AXAF telecons on January 7, 14, 21, and 28, and in the FPSI telecon on January 15 and 29.

ACIS Hardware

Lincoln Lab continued to have great success in re-flexing CCDs. Pete Daniels recovered from gall bladder surgery and returned to work, part-time, on January 6. A new technician at Lincoln, working under Pete's supervision, successfully re- flexed the remaining three flight BI CCDs and these units were delivered to CSR by mid-January. In the meantime, calibration of the FI devices at CSR has proceeded quite well and all previously received units were completed by January 13. One new FI device was received in January. The first BI device was installed in the calibration facility in mid-January and the calibration activity for the flight focal plane is now expected to be completed by February 10.

Additional flexprints are needed to process the CCDs for the spare flight focal plane. Lot 4 from Speedy Circuits was received in early November, but careful examination of the gold plating on the flexprints showed these to be unacceptable. Lot 5 had the same type of problem as reported last month and has been rejected. Lot 6 was ordered in late December and received in January. Inspection of this lot shows about 35 useful devices. Processing of these units is underway.

The following is a brief summary of the status of the other ACIS elements:

  1. ACIS-2C was 1238 certified at Lincoln Lab and delivered to MSFC on January 14. A cold test confirmed that an unacceptably large leak was present in the LN2 lines. The unit was repaired at MSFC in late January. It is now ready for installation in the XRCF system during the next re-pressurization cycle (Feb 10-20) of the XRCF chamber.

  2. All four sets of flight OBFs had been calibrated at the Wisconsin synchrotron and successfully completed 1238 certification at LMA in January.

  3. The Flight DEA/DPA/SS was assembled and successfully tested by the last week in January. Vibration testing was conducted at the C. S. Draper Lab on January 30 to February 3. The natural frequencies measured for the first two axes were generally lower than predicted, but within the 20% tolerance allowed by the procedure. For the third axis (Z), the frequency was about 40% less than expected which caused a cessation of the test. The unit was returned to CSR and the torque on all structural fasteners was checked - no problems were found. We concluded that the problem was caused by the lack of shear pins in the mounting of the flexures to the shake fixture and insufficient torque in the mounting fasteners. Unfortunately, the ICD does not specify the fasteners to be used or the torque values. Therefore, due to the lack of shear pins, we substituted high-strength fasteners for this attachment and increased the torque by 60%. Upon retest, the natural frequency increased significantly, and although still low, the vibration test was completed on February 3. Functional testing after vibration showed no anomalies.

Schedule Status

In spite of several minor problems, the overall ACIS schedule has remained intact for the last month. The two-stage completion/testing plan, in place since mid- November, currently shows a delivery of the flight DEA, DPA, SS, and PSMC, but with an "XRCF" focal plane in an EU Detector Assembly, on or about March 10. The flight Detector Assembly and Vent Valve Assembly is projected to complete its vibration test activities by mid-April. Due to the fact that the Detector Assembly is actively thermally controlled (irrespective of the thermal condition of AXAF), MSFC has agreed that the `thermal vac' test of the flight Detector Assembly will be conducted in the XRCF chamber at MSFC in May after mating with the rest of the ACIS flight hardware. This allows the delivery of the flight Detector Assembly to be moved forward from the previous May 10 date to now coincide with the removal of the HRMA from the XRCF in late April. However, LMA has noted that, in order to verify the CEI alignment specification, the flight Detector Assembly needs to visit the LMA facility one last time before installation in the SIM at BASD. We currently have the option of performing this alignment verification before or after the XRCF activities. The final decision will probably depend on how the overall XRCF schedule plays out.

Personnel Status

The personnel status of the ACIS project has held relatively stable.

The subcontract to PSI which provides the services of Peter Tappan, the Detector Assembly mechanical engineer, had been extended to the end of March. MIT has informed us that, due to IRS regulations, this subcontract cannot be extended. At the moment, this restriction is just consistent with the schedule for the flight Detector Assembly.

Due to the positive status of the ACIS instrument and schedule, `end of project' layoffs, which had been on hold for several months, will begin again in February.

1.1.2 Science

CCD Testing and Calibration

ACIS2C CCDs were installed and aligned at MSFC. A leak in the liquid nitrogen supply system (caused by a defective gasket) was found and repaired.

Calibration was completed on four front-illuminated devices with flight-quality flexprints (w182c4r, w203c4r, w215c2r, and w198c1), bringing the total number of calibrated, flight-candidate front-illuminated detectors to ten. A single front- illuminated flight candidate, w210c3r, remains in calibration. The three flight- quality back-illuminated CCDs (w147c3r, w134c4r, and w140c4r), now equipped with flight-quality flexprints, were received. Calibration was nearly complete on these three detectors at month's end.

It was discovered that one of the back-illuminated detectors, w147c3r, had developed a crack at the edge of the imaging area. It appears that this crack developed some time during the flexprint replacement operation. Re-inspection of the crack at Lincoln, and evaluation by Lincoln, suggest that the crack is likely to grow, and that it would be unwise to attempt to fly this device. Just before the final stage of calibration, this device was found to have been contaminated. The cause of the contamination is under investigation.

Calibration results for the front-illuminated devices were summarized. These devices are remarkably similar to one another; most performance parameters (quantum efficiency, spectral resolution, gain and noise) vary by less than 10% from detector to detector.

1.1.3 Hardware Design Detector Assembly / Integrating Structure

Calibration Sources

The External Calibration Source flight unit parts have not completed bake-out and 1238 certification at LMA as previously reported. It is planned to do this operation at MSFC at the same time as the sources are certified.

Back Plate Assembly

Two of the Flight BPAs are available for flight assembly.

Proton Shield

The parts of the Proton Shield are available for flight assembly.

Support Structure

Pins for the Flexure to Support Structure interface have been installed. Work is complete to correct the difficulty that was encountered during assembly with the +Z Panel mating with the Y Panels. Survival heaters and thermistors have been fitted to the Support Structure. The fasteners have been changed out for NAS fasteners where possible. The Support Structure, along with the DEA and DPA, are undergoing vibration testing at Draper Lab.

LED Assembly

The LED Assembly is available for flight assembly.

EU Detector Assembly

The EU DA has been vacuum-baked in preparation for thermal vacuum testing at Lincoln Labs. The unit has been disassembled in preparation for the installation of the XRCF Focal Plane.

Mechanical GSE

The SIM-Sim has been vacuum-baked in preparation for thermal vacuum testing at Lincoln Labs. Lifting fixtures and vibration test fixtures are complete. Electronics Packaging

The DEA/DPA Assembly drawing, 36-30000, has been completed and released.

The ACIS Vibration Test of the DEA/DPA Assembly has been completed. The unit successfully passed the test. There was no mechanical damage and the assembly passed the pre- and post-vibration long form functional test. Thermal

Revision A of the ACIS TV Test Procedure was reviewed by MIT engineers and released. Revision B is planned for ECO review before Feb. 10.

Contingency plans in the event of an electrical power outage during the LL TV Test were discussed with MIT and LL personnel. Backup batteries and an AC generator at the LL were located, and will be available during the Test.

MIT participated in the Thermal TOP Telecon of January 30.

The MIT thermal models were exercised to predict the temperature transients during transitions from hot to cold soaks. Analog Electronics

For this period, the ACIS Detector Electronics Assembly has been fully integrated with the flight interface cards. The system as a whole is now fully functional and has undergone extensive testing with the DPA, PSMC, and the Detector Assembly. Preparation is underway for shake and temperature testing. Digital Processor

The flight DPA is integrated with the PSMC and flight DEA. Vibration testing was performed last week. Ongoing support continues for the engineering DPA and software development DPA. Ground Support Equipment

Prepared the EGSE for support of thermal vacuum testing at Lincoln Lab. Developed software that reads PSMC serial digital telemetry received from a Littlefield RCTU. The EGSE is now able to read at run time a file that specifies the locations of this and other ACIS engineering telemetry in the AXAF-I major frame. Previous versions of the engineering telemetry programs contained this information as constants. Installed software developed by others that reads output from the data logger that ACIS will use at Lincoln Lab. Reviewed the IP&CL update sent to TRW.

1.1.4 Software

Detailed Software Design

The following software ECOs were reviewed this month:

They relate to Release 1.1 of the Flight Software, to be burned into the flight instrument during Thermal/Vacuum testing next month.

External Interfaces

Version 1.24 of the IP&CL structures table (36-53204.0204, Rev. G) has been released. It describes Release 1.0 of the Flight Software.

Software Delivery

Release 1.0 of the Flight Software has been burned into the flight and engineering units, and is accompanied by release notes and building instructions. Default command blocks, bad pixel lists, etc., were supplied by the ACIS calibration team.

Unit Testing

All BEP and FEP flight software modules continue to be subjected to unit and coverage tests.

Integration Testing

High-level testing of flight software in FEP and BEP hardware continues, accompanied by tests using the software simulators.

Jim Francis has helped develop the Short and Long Form ACIS test procedures for use during Thermal/Vacuum testing at Lincoln Lab.

10 new software problem reports have been filed, of which 6 have been closed out, including all those relating to the flight software. A total of 7 problem reports are outstanding, 2 of which refer to the flight software and both will be closed out in Release 1.1. The status may be inspected at "http://acis.mit.edu/axaf/spr/" .

1.1.5 Performance Assurance Quality Assurance


No Alerts or problem notices were received from MSFC during the report period.


Although no requirement has been imposed on MIT, a listing of all flight fasteners has been prepared and submitted to Tony Lavoie at MSFC. This list includes the name of the fastener manufacturer, Certificate of Conformance (C of C) status, chemical and physical test report status, and contained or not contained application. Included in the fastener list are screws, nuts, inserts, shear pins, and standoffs. In addition, all screws and shear pins in the support structure, regardless of size, are being tested for chemical and physical properties at Altran Materials Engineering Inc.

Waiver/Deviation Status

Waivers 36-001 through 36-004, 36-006, 36-009 and 36-011 have been approved by MSFC. Waiver 36-005 is not used. Listed below is the status of the remaining MIT waivers at this time.

Waiver # Description LMA/LL/MIT Submittal Approval
36-007 3% Reflectance loss on OWS for MSFC-SPEC-1238 testing MIT 2/8/96 OPEN
36-008 AWG26 nickel wire from DA to DEA MIT 2/7/96 WITHDRAWN
36-010 Continuity, IR, and DWV test after harness/cable installation MIT 7/16/96 IN PROCESS

Waiver 36-007 is being revisited by MSFC in light of the decision not to bake-out the optical bench. Parts Engineering

NSPAR Status

MIT NSPARs 36-001 through 36-029 have been approved by MSFC. MIT NSPAR 36-024 has been canceled/withdrawn. Lockheed Martin Astronautics (LMA) NSPARs MMA/ACIS-014a through MMA/ACIS-047 have been approved by MSFC. Below is a listing of NSPARs still in process. In addition, LMA is incorporating comments on NSPARs otherwise approved.

NSPAR # Part Submittal Approval
36-030 Transistor, Silicon, NPN,
Low Power (JANTX2N930)
11/25/96 OPEN
Microcircuit, High Voltage
Regulator (849AC410850-63)
(Linear Technology
on 1/23/97
OPEN Reliability Engineering

Radiation testing has been completed at Space Electronics Inc. (SEI) on twenty- four (24) device types. Results of these tests have been submitted to Dr. Jim Howard at MSFC. Jim has evaluated each part and its location in the ACIS. Tantalum shielding has been added to the outside of the DEA;.080-inch on the -X panel and 0.040-inch on the +Z panel. In addition, four (4) parts have been spot- shielded. Twenty thousandths (.020) of tantalum were added to the top of the A to D Converter (CS5012A), Dual Operational Amplifier (OP220), and CMOS Switch (IH5143). The OP220 and IH5143 have 0.020-inch tantalum shields on the bottom as well. Eighty thousandths (.080) of tantalum were added to the top of the Octal D to A Converter (DAC8800).

The DAC8800 was retested by SEI at a dose rate of 113 Rads/min. (Si) with a bias voltage of 5 volts, to more closely simulate the application and space environment. Performance testing was done at 500 Rad intervals out to 2.5 KRads without failure. An extrapolation of the data indicates the DAC8800 should stay within specification beyond 15 KRads. It was also determined that annealing at room temperature for 24 hours completely restores the DAC8800. The original radiation susceptibility tests on this part were done at a dose rate of 1800 Rad/min. (Si) with a bias voltage of 12 volts, and resulted in an out-of-spec failure at 1.2 KRads.

Materials: MIT received approvals of the last 2 MUAs from MSFC. System Safety

No Activity this month. Software Quality Assurance


Test Procedures: A total of 6 have been released. Two test procedures were released this month (MemBep, Overflow), and one was developed (LoadFromRom) but replaced by the short form test of R. Goeke. Four tests are in the review process (MemFep, LoadCommand, MemPatch, and IgnoreBadPixel).

Test Scripts: A total of 4 scripts have been completed. Two scripts (Overflow, Threshold) have been completed and run on the Flight 1.0 version of the ACIS software. Modification to the test environment was necessary to support both 500 and 24000 LRCTU baud rates.

Problem Reports

There have been 8 new problem reports identified this reporting period.

There are a total of (88) problem reports identified. Of those: Performance Assurance and Safety Plan

There has been no activity on the Performance Assurance and Safety (PAS) Plan. The PAS Plan in effect is Revision B. Cleaning/Vacuum Conditioning and Contamination Control

Thermal Vacuum Test

Preparations are being made for the Thermal Vacuum test at Lincoln Laboratory.

The SIM/SIM, with the Engineering Detector Assembly and the Vent Valve Assembly, passed 1238 certification.

Vacuum-baked the flight support structure, the PSMC mounting plate, and test cables W1 and W2 at NTS.

Delivered the X-ray cart to Lincoln Laboratory for a fitcheck and cleaning. After some modifications, the X-ray cart was attached to the vacuum chamber and is currently under vacuum.

Vacuum-baked the Starsys Actuator at Lincoln Laboratory.

Cleaned and vacuum-baked two connector plates, side rails, and other miscellaneous material that will be inside the Thermal Vacuum Chamber at Lincoln Laboratory.

Other Bakeouts

The XRCF Focal Plane passed 1238 certification.

The ACIS 2C passed 1238 certification.

The six external ACIS Flight Cables were vacuum-baked, bagged, and sent to MSFC for IR and DWV testing.

Conformal-coated and vacuum-baked the 11th and 12th Flight boards for the DEA.

Vacuum-baked strips of 3M 427 thermal adhesive tape for the heaters on the support structure.

Installed new Humidity and Temperature recorders in five cleanrooms

1.1.6 CCD Development and Packaging

Reflexing the FI and BI chips proceeded this month, with five flight detectors, including the three flight BI devices, delivered to CSR during January. All were devices that had their original flexprints replaced with new ones. We have now completed reflexing all the remaining FI flight reflex candidates (a total of twelve), aside from those in the XRCF detector array. Since restarting the packaging process in November after improving the laboratory ESD environment, we have successfully reflexed 19/20 devices. There remain seven FI sawn parts to package, and twelve FI parts to saw and package. We will be able to proceed with these when additional flexprints have passed inspection and are assigned to these flight devices.

Apparently, the edge of BI 147C3 (the best BI part) developed a crack; the cause of this tragedy is not understood. We are not certain if this crack will propagate, so it has been removed from the flight inventory even though it still operates well. When this device was inspected at Lincoln at the end of the month, it appeared to be contaminated with oil-like droplets. Work is in progress to learn what this contaminant is, where it came from, and how to remove it.

The XRCF detector assembly was delivered to CSR on 23 January, 1997. This unit was assembled at an accelerated rate to support programmatic requirements. One detector (S2) shifted out-of-plane as a result of dark current testing at -40°C and the MSFC 1238 certification process. Steps will be taken to prevent this from happening on the flight assembly but the cause of the shift cannot be established. No detectors were damaged during assembly.

Devices are being collected at Lincoln in anticipation of start of assembly of the flight detector array. These candidates will be inspected carefully to assure that they don't suffer contamination that was seen on the BI device. Based on experience with the XRCF array, we are currently on schedule to complete the flight array on time if no delay due to unforeseen problems, such as this contamination, arises.

Microsectioning results from Speedy Circuits' Lot 4 indicate additional problems. Previously, only the coupons had been examined. Microsectioning samples from real flexprints show that there are problems with the gold plating. These problems include delamination and small gold nodules of the type seen on Lot 5. Thermal cycling samples have been made from Lot 4 and they have successfully completed 57 cycles.

The three flexprints (from Speedy Circuits' Lot 2) undergoing a long-term thermal soak at -120°C were evaluated after 6 weeks of exposure. No anomalies were found.

An new lot (designated Lot 6) of conventional design flexprints from Speedy Circuits has been received. Of seven panels received, 2 have been rejected. One was rejected for poor registration of internal layers (no annular rings) and one panel was rejected due to delamination of the gold/nickel plating from the copper traces and vias. Microsectioning of flexprints and the assembly of thermal cycle samples will continue into February.

1.1.7 Lockheed Martin Activities


Change Order activity this month included firm proposal submittal and completing negotiations for Change Order 64. This change order directs fabrication of a new GSE Electrical Interface Bracket and new MLI Blankets to meet new requirements defined by PIRNs. Change Order 58 and Change Order 64 are currently the only change orders waiting to be definitized.

No ACIS NASA/MIT Monthly Status Review nor MIT/LMA Technical Interchange Meetings were conducted this month. Technical coordination was achieved by program telecons and LMA technical personnel supporting hardware test and checkout activities at MIT.

Major accomplishments for December included completion of Group B & C testing of two diodes which were the remaining PSMC parts being carried on open MARS (MARS closure was completed). PSMC activities included: completion of testing, NASA-SPEC-1238 bake/certification and delivery of the flight PSMC to MIT. LMA also supported the integration of the PSMC with the DEA and DPA and the "Long Form" system performance test at MIT. The EMC test results were compiled, the test report completed, draft waivers prepared for exceedances, and both are in review before formal submittal to MIT. The Lincoln Labs (LL) T-Vac cables were also completed and shipped to MIT. Prior to shipping the PSMC, integrated functional testing of the Flight Detector Assembly, Venting Subsystem, and the PSMC was performed and correct operation demonstrated. The Flight OBFs NASA-SPEC-1238 bake was completed and the filters were returned to MIT. Other activities performed during this month included initiating fabrication/ modification of the ACIS Lifting Fixture parts; repair of the PSMC EU2 at MIT; pin assignment reverification, cleanup and vapor degrease of the flight W1/W2 cable harness; and, completion of minor modification and demonstration tests to improve the performance of the Starsys actuators thermistor over-temp cutoff attachment and readout. The thermistor modifications were also incorporated into the EU actuators and tested at MIT.

The program continued to review inter-company Mission Success Bulletins and GIDEP ALERTS received during the month. None of these ALERTS were judged to be applicable to any of the parts or components being used by LMA on the ACIS program. There have been no items defined during the month that warranted generating a Contractor-Initiated ALERT.

The program focus this month was on completion of the LMA-fabricated flight hardware assembly, integration and test prior to delivery to MIT, and support of the MIT test and integration of the XRCF test ACIS in preparation for the T-Vac testing planned during February. Problems encountered during the month were associated with correction of minor anomalies identified as part of normal test and checkout. Schedule-critical milestones were met this month, so there was no critical path schedule erosion. Power Supply & Mechanisms Controller

LMA performed diagnosis and anomalies repair associated with EU2 PSMC operation at MIT. Problems noted involved DEA A and B Power Supply operation. Several hardware issues were addressed, resulting in correction of the anomalies. The conclusions drawn from the repair activity was that several piece parts, that were added after release of EU2 engineering, primarily to accommodate requirement-driven design changes, had moved from their original mounting locations/positions. This led to intermittent DEA Power Supply operation and loss of chassis power isolation. Although proper fabrication techniques were employed, the EU2 PSMC was not intended to withstand "launch-like" nor truck transport vibration environments. It is recommended that any future cross-country shipment of this unit be by hand-carry rather than truck freight.

At the end of this reporting period, RCTU interface questions still remained regarding the EU2 PSMC. The EU RCTU is known to have problems associated with its PSMC interface cable harness, as well as suspected deficiencies with the "B" side serial digital telemetry. After these RCTU problems are corrected, any EU2 problems that may remain will be corrected.

Group B and C electrical testing of the 1N6689s and 15CGQ100s is complete. Final results indicate no difficulties. The open MARS associated with the lot/date codes in ACIS flight hardware are all closed. These parts are now considered qualified for flight.

Actual measured flight PSMC power dissipation data and temperatures were used, in conjunction with PWB thermal modeling, to arrive at a PSMC 1238 certification temperature of +65°C. The PSMC successfully completed its 1238 bake on January 20, 1997.

Immediately after 1238 certification, a post-environment full performance test was conducted on the PSMC, with no anomalies reported during the test. This test concluded formal verification activities associated with the PSMC at Denver.

After the post-1238 performance test was completed, a set of engineering tests were conducted with the ACIS PTS Flight Instrument in the RDL Class 100 clean room. These tests were conducted using the flight Detector Housing (DH), Venting Subsystem (VSS), Cable Harness, and PSMC to validate end-to-end functionality of the PTS Flight hardware. Some modifications were made to the flight DA and VSS to correct Starsys Actuator thermistor readout temperatures, and are discussed further in the mechanical section of this monthly report. Testing yielded a complete demonstration of PTS functionality.

Vacuum tests using the Flight PSMC and Cable Harness with the CAMSIM, were also performed. These tests validated the Starsys Actuator high temperature safety shutoff circuitry. High temp shutoff operated at +137°C and +135°C for door mechanism close and open operation, respectively. Also, Detector Housing closed- loop thermal control (at -60°C) was demonstrated for both A and B sides of the PSMC. The CAMSIM Housing was controlled within the -60°C ± 1°C requirement. This requirement will be formally verified during LL T-Vac testing.

LMA internal Product Integrity Engineer (PIE) and Preship Reviews were held for the PSMC. LMA Flight Systems Central Systems Engineering, Quality Assurance, and Mission Success personnel were among those in attendance. No action items were assigned, and the flight PSMC was deemed ready for delivery to MIT.

The flight PSMC was hand-carried to MIT on January 27. LMA personnel remained in Cambridge to support post-delivery test and checkout of the PSMC. At the end of this reporting period, all tests and checkouts involving the Flight Unit PSMC were proceeding without incident.

There are no changes to the MIT load table during this reporting period. Thermal/Mechanical Design and Testing

Flight Detector Housing Fabrication/Test Status

A modification was required on the FU Detector Housing Assembly to solve a concern with the performance of the Starsys Actuator thermal protection thermistors. These performance concerns were resolved by adding a 150 ohm parallel resistor across the leads of the thermistors. This change allows temperature telemetry through the RCTU down to 0°C and up to 150°C. This enables verification that heat has been applied to the actuators once the command is sent to open or close the door. The second concern, which was also resolved with the parallel resistor, was to guarantee that the thermistor resistance was 53 ohms at the upper temperature limit for the actuators with margin. The PSMC monitors the resistance of the thermistors and in the event of a limit switch failure or other anomaly, automatically shuts off power to the actuators. Prior to the change, the PSMC may not have shut off power to the actuators in time to prevent a shear disk rupture due to the thermal lag of the thermistor in comparison to a thermocouple which defined the upper temperature limit.

A new adhesive was also required between the actuator and the thermistor. The original EA9394 bond was very brittle, and several EU and CAMSIM thermistors had come loose during test and/or handling. The EA9394 was replaced with Pressure Sensitive Adhesive (PSA) 3M Part #468 after several different thermal vacuum tests were conducted. This adhesive survived 60 thermal cycles between -35°C and +120°C on the CAMSIM actuators in actual operation. In several of these cycles, the limit switches were purposely disabled to test the high temperature shutoff and functioned as designed with the flight PSMC. The other adhesives (EA9394 and EC2216) did not consistently survive this environment. Additional protection from a bond failure was provided with an aluminum overtape and a Tefzel wire tie. Testing was conducted that demonstrated this to be a very reliable technique in guaranteeing that the thermistors perform as designed even in a degraded mode. Additional tests were performed with failed bonds to determine whether the aluminum tape provided enough conduction for the thermistor to reach 53 ohms in the event that the limit switches did not function properly. The testing confirmed that the resistance would be low enough to protect the actuators from a shear disk rupture.

The modifications discussed above were made for both the flight and the engineering unit detector housing and venting subsystem actuator thermistors. As a result of these modifications, 1238 certification of the flight units will be reverified in early February. Schedule analysis shows that these hardware modifications and tests should not compromise meeting the delivery dates required to support the flight detector assembly schedule.

Engineering Venting Subsystem/Detector Housing

During the EMI test at LMA, an apparent anomaly occurred where the door did not appear to close and latch properly. However, this concern was resolved this month through additional tests performed on the same unit at MIT. Tests showed that the operators did not wait long enough for the door to latch properly and removed power before the door close operation was complete. This left all limit switches in an open state and made it difficult for the PSMC and GSE to get back to a known condition. The reason the power was prematurely removed from the actuators was that there was no temperature data available, as discussed above, to determine when power should be removed, and it would have been very undesirable to rupture a shear disk in the actuator. The apparent anomaly was repeated at MIT when thermocouples were removed as was the case in the EMI test. The only protection for the actuators was to monitor the time it takes for the door to close and compare it to previous data. The problem is, the time required is a function of the bus voltage (i.e., 24 to 32 volts), the starting temperature, and whether the door is opening or closing. The closing operation takes longer since the door must fully compress the O-ring before the door latches; while the opening operation has virtually no-load and it occurs faster. Bus voltage is a big variable since the power in the actuator heaters varies with the square of the voltage. The new bonding adhesive and the parallel resistor across the thermistors have provided the confidence that this situation will not occur again. Conclusion: Be more patient and watch the temperature of the actuators and not the duration of the operation in deciding whether or not to remove power from the actuators.

TCS Fabrication/Test Status

All TCS hardware, with the exception of some of the MLI blankets, has been NASA-SPEC-1238 certified and is in storage. The flight radiators, straps, and test MLI will be delivered to MIT as required for use in the Lincoln Labs Thermal Vacuum Test in early February.

Stress/Dynamic Analysis

Stress analysis updates have continued with a promised completion in early February. The analysis completed to date has been waterfalled to MSFC as it is completed to enable timely review. The fracture analysis will continue into March on a part-time basis and supports Acceptance Data Package delivery dates.

Science Instrument Module Simulator (SIMsim) Status

The SIM Sim was pre-baked at 60°C and passed 1238 certification in preparation for the Lincoln Labs Thermal Vacuum Test.

OBF Test Status

All flight Optical Blocking Filters passed 1238 certification and have been shipped back to MIT. Weight Summary

PTS Weight Summary is shown in Table 1. Values are the measured weights of all LMA-supplied components. Uncertainty margins have been reduced as the measured data becomes available.

Assembly Weight, lb. Uncertainty, lb.
Detector Housing 20.8 +0.2
Venting Subsystem 8.7 +0.1
Thermal Control & Isolation 5.4 +0.1
Radiators 10.2 +0.1
Sun & Telescope Shades 16.0 +0.1
Power Supply & Mechanisms Controller 32.7** +0.2
Cables & Connectors 9.1 +0.1
Total Basic Weight 102.9 +0.9 -0.0

** Includes Survival Heaters, Thermistors, connectors, and bracket which are not part of ACIS budget. Mark Kilpatrick's (BECD) worksheet dated 12/8/95 assumed 1 pound for these components. LMA does not have an actual breakdown. Mechanical Ground Support Equipment
Venting Subsystem

The flow restrictor will be sized early in February. The modifications to the thermistors on the venting subsystem have begun and will be completed in February as well.

Mechanical Ground Support Equipment

The lifting fixture modifications are underway. Parts required for this modification are being made and should be complete by the middle of February.

A set of shipping cases that allow shipping of the venting subsystem and detector housing have been procured with expected delivery in early February. These containers have been especially sized to allow hand-carry shipment onboard commercial jet aircraft.

VGSE #2 was essentially completed this month. Some firmware modifications are required to provide more detailed diagnostic information. Acceptance testing of the VGSE has been postponed until after completion of the flight detector housing. Testing will commence in the latter part of February.

Diagnostic equipment was delivered to MIT for isolating the anomalous behavior of the GSE low conductance vent valve. The valve failed to open during VGSE operation. Tests showed that both engineering unit, PSMC- controlled valves operated as expected. The GSE valve, when manually pulsed with a power supply, operated as expected and has continued to do so when commanded from the VGSE. It is currently thought that a defective wire or connector in the GSE cables is the most likely cause of this intermittent behavior. Both engineering unit venting subsystem and VGSE #1 have undergone extensive testing and reworking not performed on VGSE #2 or the flight GSE valve. The anomaly is intermittent and has not been made to repeat. Work on this will continue into the next months. Systems Engineering

During January, the systems engineering group continued preparation of verification assessment and test reports for the ACIS compliance verification activities, maintaining program requirements documents, and engineering specialties activities in support of flight hardware verification. Additionally, the group began preliminary planning for preparation and delivery of the Acceptance Data Package (ADP) and CDRL update coordination for ACIS.

Requirements Identification and Tracking

Identification of requirements for updating the final CDRL/SDRL submittals in support of the Acceptance Data Package continued during this month. The ACIS Wire List will be updated during February, following receipt of PIRNs, to accommodate needed wiring changes for the RCTU-to-PSMC interfaces.

System Design

The ACIS System Schematic was completed during this reporting period. It is expected that this schematic will be released during the next reporting period. The preparation of a Special Consideration Item Drawing (SCID) is planned to begin in the near future. This book form drawing will identify the "Remove Before Flight" red tag and "Install Before Flight" green tag items and those items of special consideration such as; warnings and cautions to be included in procedures that operationally protect the instrument, and specific handling requirements.

Test Planning and Coordination

System-level overview and support of program scheduling and update of the ground processing flows for testing of ACIS instrument flight hardware continued this month. Final update of the ACIS Verification Requirements and Specification Document SVR02 was completed during this reporting period. This version of the VRSD will be used to support the NASA/MIT Monthly Review scheduled for the first week in February. Following the monthly review in Cambridge, comments will be incorporated into the VRSD, and it will be released for the final time. Continued support of the ACIS program and liaison with MIT and NASA/MSFC was maintained.


Review of program activities and scheduling of the PTS and ACIS verification events continued throughout January. This activity, along with satisfactorily completing scheduled events, will confirm that the ACIS instrument meets requirements and will be ready for delivery to NASA/MSFC when needed. The VRSD verification matrix is scheduled for review by MSFC/ MIT and LMA personnel at the ACIS Monthly Meeting during the next reporting period. Engineering Specialties

Contamination Control

Prebake, contamination control coordination, and MSFC-SPEC-1238 bakeout activities continued throughout this reporting period. This activity is nearing completion. Instrument-level MSFC-SPEC-1238 certification is planned to be performed during the Lincoln Labs ACIS performance testing.


The data for ACIS Instrument EMI/EMC tests, performed during the month of December 1996, were compiled, and analyses of the data were performed during this reporting period. The following is the Quick Look EMI/EMC test results:

Inrush Current:
Amplitude - DHTC-B Enable @ 35 vdc = 7.6 Amps
Integrated Amplitude-Duration Product - DHTC-B Enable @ 35 vdc = 0.0095A-s Pass
Rise/Fall Time - Power Application A or B = 0.065A/usec Pass
Transient Voltage Exceeded
Emissions Conducted Emissions (CE01,03) Pass
Magnetic Field Radiated Emissions (RE01T) Pass
Electric Field Radiated Emissions (RE02) Pass
Susceptibility Low Frequency Conducted Susceptibility (CS01) Exceeded
Radio Frequency Conducted Susceptibility (CS02) Pass
Transient Conducted Susceptibility - SPIKE (CS06) Exceeded
Magnetic Field Radiated Susceptibility (RS01) Pass
Electric Field Radiated Susceptibility (RS03) Pass
Transient Radiated Susceptibility (ESD) Pass

The initial ACIS Instrument EMI/EMC Test Report has been completed by test laboratory personnel. The report is in review by ACIS personnel and will be published and distributed during the next reporting period. Four Requests for Waiver were prepared to accompany the report to accommodate the exceedances encountered during testing.

System Safety

System Safety continued to support and monitor the program during this reporting period. Current planning and data coordination for the Ground Safety Data Review is underway.

Reliability Engineering

The Failure Modes and Effects Analysis (FMEA) was updated during this reporting period. This update will be reviewed in real time during next month's Technical Interchange Meeting at Cambridge. These changes also require that the Critical Items List (CIL) be updated. This activity is expected to be completed during the next reporting period.

2.0 ACIS Power Summary

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.

3.0 Mass Properties

4.0 Electrical Power

Electrical power requirements (Watts) are summarized in the following table:

ACIS Power Distribution

Peak power distribution
in Standby Mode
28.86 7.45 0 15.58 51.89
Peak power distribution
in Max. Operating Mode
53.54 49.72 6.7 46.37 156.33
Peak power distribution
in Bakeout Mode
43.96 7.45 57.6 48.7 157.71
Peak power distribution in
Normal Operating Mode*
41.79 49.72 6.7 46.37 144.58
* Peak Nominal Operating Mode power to be entered into the CEI Spec.

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.

5.0 Software Schedule Status

Reported separately.

6.0 Non conformance Summary


Last modified: Thu Feb 20 20:19:47 EST