Monthly Newsletter

February 2001

The SOLSTICE instruments are also in the processes of integration, calibration and testing. Instrument mechanical-optical integration is complete. O-ring seals for the coverbench interface require rework. Characterization of the detector head will require three weeks. A hardware fringe counter has been added to the electronics to eliminate grating drive reset caused by external disturbances. Unit level tests of the grating drive provide absolute accuracy, step response and bearing preload on the flight encoder heads before final integration.

XPS Status
The final assembly of the flight unit has been completed. The XPS PER (pre-environmental review) took place January 11, 2001 and XPS in now undergoing environmental test. Mass, power, and vibration tests are complete, EMI-EMC tests and thermal vacuum tests are in progress. Light leaks, shifting of mounting feet, and problems with the "dynamic breaking" command were discovered and fixes are already underway, or nearly complete. FOV (field of view) maps and XPS-MU interfaces should be complete in early March.

SORCE Data System Status
Progress on the Science Data System has been good, with many areas near completion. A planning meeting was held with the Independent Verification and Validation facility personnel at GSFC on February 21, 2001. The purpose of the meeting was to identify a level of IV&V that is appropriate for the SORCE mission. SORCE software requirements, development methodologies, and status were reviewed and a preliminary agreement for the SORCE mission was reached. IV &V facility personnel will perform an assessment of critical instrument and spacecraft flight software functions and a Memorandum of Agreement will be submitted to SORCE as early as mid-March.

Microprocessor Unit Status
The SSI (Science Support Interface) FPGA (field programmable gate array) final design is complete and has been released for software testing. The SSI telemetry FPGA design is in process and scheduled for delivery March 16, 2001. The flight PCB board should be delivered March 12, 2001. The engineering model of the MU power distrubution is nearly done, and full integration into the EM MU is expected soon. The flight unit MU power distribution board parts are in house, build has begun and flight testing should be complete by the end of March. All GCI (generic channel interface) engineering model boards are complete and tested. Flight PCB fabrication has begun with the most progress on the SOLSTICE instrument.

Digital Signal Processor Status
The grating drive control performance on SOLSTICE meets and exceeds requirements. A control loop has been tweaked to add robustness, new PID constants for SOLSTICE are generated by model, refined by hardware test and models are updated with as-run values. Minor algorithm changes have been made to improve SOLSTICE performance for anomolous situations. SIM DSP software is in test with instrument
subsystems. TIM DSP software is ready for test with the complete instrument.

Spacecraft Systems
Spacecraft progress had been good. Instrument harness routing has begun. Instrument module MGSE and EGSE are on schedule for early April delivery. Thermal vacuum cables are also in design. The preliminary FMEA (failure mode and effects analysis) for SOLSTICE, SIM, TIM, and MU has been delivered and is in review. Power, mass, memory and bandwidth margins are in good shape.
However, preliminary trajectory analysis results have determined that northerly trajectory options for the SORCE launch will result in unacceptable performance (mass to orbit) and stage 3 casualty expectations. But there is insufficient ground station coverage for a southerly trajectory option. SORCE and LASP are evaluating the used of additional ground stations (Pretoria and Malindia) for launch and early orbit campaign plus the impacts of a lower orbit inclination. Trajectories incurring performance penalties or high casualty rates are only last resort options.

Orbital News
Orbital spacecraft news follows. The static testing of the bus primary module is complete. The transceiver CDR was completed Feb. 7-8, 2001. The TAMS (tri-axial magnetometers) have been received from Ithaco. The FlatSat (flat satellite testing unit) is complete minus the APE EDU (attitude processing electronics engineering development unit). Orbital assisted in a successful TIM (technical interface meeting) harness integration at LASP. Study continues on the ACS (attitude control system) for a"gyroless" SORCE spacecraft, results look promising, and further gyro options are being explored. All flight cards (except APE LVPS) have been built as far as materials will allow, and parts procurement issues are being pursued. The RFA's Orbital received from the SORCE MCDR November 11, 2000 have been addressed.

Information Submission:
Each month SNS will present mission progress, highlights, and news. If you have any information to distribute to the SORCE Team, contact, and we will include it in the next month's issue of SNS.

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