The following is taken from the spacecraft incident report:
April 30, 2002 [J120]
At AOS of the 1250 UT pass, red high limit violations were observed for
the +/- 5V and the +/- 13V power supplies in the MICS instrument. The
values were +/- 6.3V and +/-14.98V, respectively. The FOT notified the
Instrument Scientist and the Instrument Engineer. The FOT Instrument
Engineer made the decision based on a pre-approved contingency response to
execute the MICS pre-maneuver sequence which involves ramping down the
high voltages and turning off the MICS Data Processing Unit (MDPU). The
Instrument Engineer concurred with the decision. During ramp down of the
microchannel plate power supplies, the instrument failed to respond to
commands with the appropriate telemetry and appeared to be "hung." The
decision was made to turn off the MDPU, meaning the main power to the
instrument was turned off. The keep-alive power remained on.
May 3, 2002 [J123]
Preliminary examination of the data file from the anomaly period showed no
indication of high voltage problems. It was determined that a stuck bit
or latch in the serial interface could have caused the observed incorrect
(full scale) data values for the +/- 5V and the +/- 13V power supplies.
On May 3 the MICS Data Processing Unit (MDPU) was powered on in an attempt
to clear the latchup, with no success. The standard procedures check all
housekeeping and stop the process if data values are out of range. Since
the power supply voltages were still at full scale, the procedure could
not continue.
May 17, 2002 [J137]
A second test was performed on May 17 to verify the MICS serial science
data stream was functional. Procedures were modified to ignore the full
scale data values for the power supplies. The timing of this test was
such that the spacecraft was in a portion of the orbit that ensured
measured particle fluxes were well above background levels (ensuring valid
science data would be present when the MDPU was powered on and the
voltages ramped up). This test also failed. The MDPU was powered up and
the voltages ramped up nominally, however, no science data was observed.
The voltages were ramped down and the MDPU turned off. The keep-alive
power remains on.
June 10, 2002 [J161]
An Anomaly Review Team was convened to discuss the MICS anomaly and
recommend any further course of action. The failure was localized to the
portion of the telemetry circuit between the optocouplers in the MICS high
voltage "bubble" and the MDPU. The exact cause is unknown and cannot be
absolutely determined from the available housekeeping data. One final
test was recommended since it had not been tried: turn off the "keep
alive" power, let the instrument sit for 15 minutes (clearing all memory),
power up the MDPU and see if data is retrieved (i.e. full reboot of the
MDPU).
June 26, 2002 [J177]
The final test (full MDPU reboot) was performed with negative results.
All power to MICS has been turned off. The MICS portion of the CAMMICE
instrument is no longer operational.