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)
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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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