Monthly Newsletter

July 2001

SORCE July 2001 Project Summary
The SORCE Program is on schedule and within budget. Launch is scheduled for July 31, 2002. SORCE recently received high praise from the administration of GSFC (Goddard Space Flight Center). SORCE is the only Principal Investigator mode mission that has maintained schedule for 3 years. Highly deserved thanks to all of the SORCE team members and their continuing efforts to meet schedule.
Much progress was made on the SORCE mission during the past month. At LASP the XPS and TIM instruments were integrated onto the satellite observatory. The integration of the MU (microprocessor unit) to the satellite observatory was also completed. At Orbital the CEU (central electronics unit), fuse box and harnesses were integrated on the spacecraft bus. The SIM and SOLSTICE instrument flight configuration builds were finished. XPS calibrations and environmental test are now complete. The TIM pre-environmental characterizations are complete and the SOLSTICE SURF (Synchrotron Ultraviolet Radiation Facility) pre-environmental calibration is complete. The SOLSTICE solar verification has been done. The first solar spectrum through the SOLSTICE flight instrument was obtained. Scattered light testing has been done and light leak testing is complete.
SORCE is not planning any descopes but removal of the FOG "gyros" ACS component from the SORCE spacecraft is still under consideration. A review was held June 28, 2001 at Orbital to evaluate the potential descope. Orbital has submitted an ECP (engineering change proposal) for the removal of the gyros from the SORCE spacecraft along with a plan for optimization of the ACS control system for to increase performance. The ECP to remove the gyros has been assessed. GSFC Code 570 has prepared a position paper expressing concern on the gyroless flight mode for the SORCE spacecraft. SORCE is currently studying the resulting issues with the Aerospace Corporation to ensure the robustness of the SORCE satellite without the gyros. SORCE and the Aerospace Corporation will present the results of their study at a PMC (program management council)

meeting at GSFC September 13, 2001 to evaluate mission impact. Until then, SORCE continues to proceed in a gyroless mode.
The top concerns facing the SORCE program include diminishing schedule slack, a late flight MU (microprocessor unit) build, dwindling budget contingency, tight test schedules, and possible launch conflicts with ICESat. All concerns face constant review and solutions evolve day by day. As always, instrument build and test schedules are carefully monitored to meet the priorities of the SORCE program.
Last month, anomalies were found in the Interpoint power converters used on the SORCE instruments. Due to a problem of transient over voltage spikes, experienced on the power H-Bridge boards at turn on, new Interpoint +5volt converters were installed on all the boards. The new converters are from date code lots that do not exhibit the transient over voltage problem. Engineering ±15volt converters (from Advanced Analog) were installed on all of the power H-bridge boards to allow integration and test activities to continue. The Advanced Analog converters will be replaced with Interpoint converters and a soft-start turn-on transient limiting circuit will be added. The new circuit has been designed, simulated and is in prototype testing. Each board will require about ½ day of testing once the converters and the soft-start circuits are installed. All flight hardware will be burned in for >72 continuous hours at +50degrees C during the IM (instrument module) thermal vacuum testing. This will qualify all hardware, which was formerly powered by the faulty converters. Additional investigation continues.
On the business side of the program, SORCE contracts enjoy excellent status. SORCE deliverable products have been distributed on time and billed accounts have been paid to date. Several subcontract modifications are in negotiation regarding Mission Operations support, PWB (printed wire board) coupon testing, insight meetings proposals, thermal blanket proposals, and IV and V, (independent validation and verification). Test plan comments for the ACS (attitude control system) have

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