During a routine manouver on 06-05-98, Flight Dynamics Facility (FDF) analysts
observed thrusters firing asynchronously, which could cause excessive
nutation.  A thruster abort was issued. The manouver was aborted on the 14th
of 16 repeat counts and determined to be near the original desired result.

Following the thruster abort, the Attitude Determination System (ADS) software
calculated an incorrect spin rate of 3.75 RPM instead of the nominal 4.99 RPM.
The ACE Flight Ops Team (FOT) and FDF confirmed the 4.99 RPM spin rate and nominal
spacecraft attitude from other telemetry data. Analysis of the telemetry indicated
that parameters related to the sunpulse time tags were not updating. Further
investigation led to the conclusion that the thruster abort had caused a timing
problem in the Command and Data Handling (C&DH) subsystem onboard the spacecraft,
and that a C&DH reset would most likely be necessary to restore the C&DH to its
original state.

Since attitude manouvers use the sunpulse as a referance, it was determined that
attitude manouvers could not be performed without risk until the anomaly was resolved.
A reset of C&DH-A was scheduled for Friday, 06-12-98.

Tuesday, Wednesday and Thursday (08-09-98 to 06-11-98) were spent performing various
actions in an attempt to clear up the problem and to avoid a C&DH reset. In addition,
the science instruments were put in standby mode in preparation for C&DH reset, and a
dump of C&DH memory was performed.

Analysis of the C&DH memory dump by engineers at Johns Hopkins University/Applied
Physics Lab (JHU/APL) indicated that a memory poke to a location in C&DH-A memory
would clear up the problem. On Friday, 06-12-98, the memory poke was executed, and
the C&DH returned to normal operation. Reset of the C&DH was not necessary.

At this time, all indications are that things are back to normal, and the science
instruments are being commanded back into their operational states.