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.
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.
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.
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.
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
TIM DSP software is ready for test with the complete instrument.
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
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 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
Each month SNS will present mission progress, highlights, and news. If
you have any information to distribute to the SORCE Team, contact Kathy.Lozier@lasp.colorado.edu,
and we will include it in the next month's issue of SNS.