Monthly Newsletter

September 2001

SORCE September 2001 Project Summary
THE EOS SORCE mission is scheduled for a launch date of July 31, 2002. LASP is currently under contract with NASA GSFC for all the phase C/D/E activities to accomplish the SORCE mission (excluding launch vehicle procurement, which NASA is providing within the cost cap). Orbital Sciences Corporation is under contract with LASP to provide the S/C bus, S/C systems integration and test, and launch services interface and launch support. The launch vehicle has been procured through NASA. A Pegasus, launched in campaign mode, from KSC, is on schedule.
Overall, the SORCE Program is still on schedule, but schedule slips may be imminent due to the replacement, and retesting of diodes and power converters on the SORCE GCIs (generic channel interfaces) and the SORCE instruments. No descopes are required at this time. SORCE managers and engineers attended the SORCE Delta Gyro Review at Goddard Space Flight Center October 1st and 2nd, 2001. SORCE is pleased with the outcome of the review, as SORCE has the "go ahead" to fly in a "gyroless" mode.
Progress made on the SORCE program at LASP during the month of September 2001 includes the completion of the SURF calibration for SOLSTICE A and the completion of the SOLSTICE And TIM Thermal Cycle. The SOLSTICE B was successfully shaken on October 1st and 2nd. The MU (microprocessor unit) bugs continue to be ironed out. Parallel testing efforts for the SORCE instruments have proceeded in a remarkably smooth manner. This is due to the combination of LASP's upgraded class 10000 clean room facilities, the improved and enlarged MOBI thermovac tank, commendable scheduling efforts, and the professional, innovative, and dedicated efforts of the SORCE scientists, engineers and students. The nearly complete instruments can be viewed through the clean room windows, and the work is impressive. Also see our web site, for more information and illustration.
SORCE Red Team activities continue to evolve, and the final detail of the Red Team agreement between SORCE/NASA/Orbital and the Aerospace Corporation are underway. As always, SORCE schedules are monitored on a daily basis to meet the varying needs of the SORCE program. While slack continues to dissipate, new solutions to difficulties are created daily and incorporated into the agenda for SORCE.

The top concerns for SORCE include: 1) Diminishing slack in the instrument integration schedule, 2) Late flight MU delivery resulting in late test of flight software, 3) Reduction of slack for SIM characterization and calibration, 4) Replacement of diodes and Interpoint power converters on the SORCE GCIs and instruments, 5) Decreasing contingency funds. Rescheduling, additional personnel, double shifting, efforts to expedite parts, and rebudgeting have addressed these concerns.

Orbital News
Progress has been good at Orbital Sciences Corporation, manufacturer of the SORCE spacecraft bus. Orbital has verified the full core avionics path and has sent commands from MAESTRO through the CEU and APE to the PRE and has received appropriate telemetry during the process. Orbital also successfully completed the crossstrapping risk mitigation test and the hardware interface verification between the 2 CEUs, (central electronic unit) and the APE (attitude power electronics). Orbital has received both flight star trackers and has received the software update for the EDU(engineering development unit) tracker. The EDU tracker has been tested on the Flat Sat (flat satellite). In addition, Orbital has loaded the flight software build 3.0 to the bus to match the Flat Sat. Three of the four RWA's (reaction wheel assemblies) have been integrated to the bus. Orbital has also completed bench test (actuation) and integration of the solar array pin pullers. In addition, Orbital attended the Xcvr TRR (transceiver test readiness review). Subsequently, one unit had a vibration failure: rework and retest have both been successfully completed, and both units are currently in thermal vacuum test. Orbital has added staff to the I&T (integration and test), Flat Sat and SE (systems engineering) teams, and the development of the BPT (bus performance test) is underway. Planning and scheduling for double shifting begins the first of October 2001.

SORCE Science News
In July, SORCE received news that NASA was going to "turn off" UARS. This decision would have had major negative impact on the SORCE science, and would have severely compromised the relation of the SORCE ultraviolet irradiance to the time period of UARS. If UARS were discontinued the following effects would take place.
1) The long - term record of ozone and ozone change would not have the required continuous and long-term record of solar forcing.

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