ACE Weekly Report (05/24/02  05/30/02)

All ACE spacecraft subsystems are performing nominally. An attitude 
maneuver was successfully performed on 05/28/02.  The next attitude 
maneuver is scheduled for 06/6/02.

An engineering test is in progress to determine a new HGA constraint. The 
current constraint is 5.5 degrees, however the FOT has been given 
authorization to drift to as much as 6.0 degrees prior to maneuvers. The 
constraint was increased on 26 April, as part of a several step process 
that will continue over the next month with the maximum constraint being 
reached by late June, when the spacecraft will be at its maximum 
range.  This approach allows the spacecraft to drift until the new 
constraint is violated, at which time an attitude maneuver is executed.

Date: HGA angle reached prior to Attitude Maneuver (degrees):

03/28/02 ~4.8
04/04/02 ~4.8
04/11/01 ~5.1
04/18/02 ~5.2
04/26/02 ~5.6
05/06/02 ~5.8
05/17/02 ~5.9
05/28/02 ~4.2  (maneuvered on this day due to the sun constraint)
06/06/02 ~2.3  (expected)(sun angle constraint)

Analysis is ongoing, though no degradation in signal strength has been seen.

Anomalies:

5/24/02 DOY 144 - ACE Anomaly #G02-0061   There was a delayed AOS of 
approximately 2 hours due to problems with the Complex software at 
D16.  Started the pass with D16 in the low bit rate of 498 bps.  Switched 
to the high bit rate of 87648 bps ~2 minutes later.  A resweep of the 
spacecraft was required due to the B receiver on the spacecraft going out 
of lock when the first poke command was sent to C&DH B.  Extra time was 
found on D66 to extend the pass to 18:55.  The station handover took place 
at 17:25. All data was recovered. (DR#G101177)

5/24/2002 DOY 144 - ACE Anomaly #G02-0062    After the station handover 
from D16 to D66, D66 was unable to put monitor blocks online.  A reboot of 
the SCP was required to put the monitor blocks online.  The FOT gave the go 
ahead to reboot the SCP and monitor blocks were back online at 17:42:27. As 
a result of the SCP reboot, data was offline from 17:41:30 through 
17:42:26.  All data was recovered.

5/27/02 DOY 147 - ACE Anomaly #G02-0063  At 16:31:00, (1 minute after AOS) 
the FOT noticed duplicate VC2 data from D16.  At 16:31:39, the FOT informed 
D16 of the duplicate data.  At 16:33:45, the duplicate VC2 data problem was 
corrected.  At 16:40:00, the FOT started receiving duplicate VC1 data hits 
(once every 30 seconds) and notified D16.  At 16:45:12, the duplicate VC1 
data hits were corrected. Later analysis showed that all VC1 data was 
duplicated from 16:31:39 - 16:45:12.  During this time frame the FOT 
received invalid CHRIS, SIS, and S3DPU limit violations which were a result 
of the duplicate telemetry.

5/28/02 DOY 148 - ACE Anomaly #G02-0064  At 16:51, the FOT stopped 
receiving data from D24.  At 16:52, the FOT contacted D24 to find out the 
cause of the drop-out. At 16:54, D24 confirmed the problem was on their end 
and it was affecting the entire complex.  At 1711, telemetry was back 
online. All data was recovered. (DR#N100445)