ACE Weekly Report:  06-06-01

All ACE spacecraft subsystems are performing nominally.  An attitude
maneuver was successfully performed on 06-01-01.  The next attitude
maneuver is scheduled for 06-08-01.

Total Percentage Data Capture May:  99.986%

The SEPICA Instrument team continues to investigate the autonomous
ramp down of the instrument by its DPU on 05-27-01 (DOY 147).

OCR ULEIS-048 was executed on 06-04-01 (DOY 155) as part of the ULEIS
Instrument team's on-going investigation of their Motor Error Flag
anomaly.  Commands were included to keep the ULEIS motor powered
instead of turning it off after each movement to a new shutter
position as with previous OCRs.  The expected result was not seen;
the motor error flag was set.  The Instrument team will continue
investigating the anomaly.

Anomalies:
S01-0006:  Reset of ULEIS Instrument's DPU
While completing OCR ULEIS-049 on 06-06-01 (DOY 157), the ULEIS DPU
crashed and the instrument reset.  OCR ULEIS-049 is part of an
ongoing investigation by the instrument team to diagnose shutter
motion problems.  This OCR implemented a delay between stopping the
shutter motor phase lines and reading the fiducials (which indicate
the shutter position).  As with OCR ULEIS-48 commands were included
in OCR ULEIS-049 to keep the ULEIS motor powered during the command
sequence.
The last instructions of OCR ULEIS-049, are to command the shutter
between the 6% (closed) and the 100% (open) positions, every 2
minutes as instructed by the instrumenter.  While moving the shutter
between the two positions, the ULEIS instrumenter notified the FOT at
15:12:00 that the ULEIS instrument had reset.  The reset occurred
between S/C Ticks 119316285 & 119316301 (approximately 15:11:05 -
15:11:21 S/C time).
The reset seems to have occurred after the shutter had moved 4 times
and occurred during the 5th movement (while the shutter was moving
from the 100% position to the 6% position).   At the time, 2 more
commands had already been sent to the spacecraft moving the shutter
to the 100% position and then to the 6% position. These commands were
not completed by the instrument.
The ULEIS team submitted OCR ULEIS-050 to reconfigure the instrument
for nominal operations.  The tracking pass with D66 was extended one
hour and these procedures were successfully completed.  "ULEIS is
currently operating as it has been over the last year, with all
operating parameters restored."  The ULEIS team is investigating the
cause of the DPU crash.



 ================================================
 Jacqueline Maldonado Snell
 Honeywell Technology Solutions Incorporated (HTSI)
 Goddard Space Flight Center
 Bldg. 3 Rm N135C, Code 428.2
 Greenbelt, MD 20771
 Phone: (301) 286-7072
 Fax:   (301) 286-0218
 E-mail:   Jacqueline.Snell.1@gsfc.nasa.gov