ACE Weekly Report:  07-19-00

All ACE spacecraft subsystems are performing nominally. An Attitude 
maneuver was successfully executed on 07-18-00.  The next attitude 
maneuver is scheduled for 07-28-00.

DSN has placed its plans to transfer its overseas sites to the 26 
Meter Automated System on hold until the various Projects have 
verified the equipment.  ACE scheduled a test support for Day 195 
with Station 66 (Madrid).  The station used the 26 Meter Automated 
System for the support.  The legacy equipment was available in the 
event of any problems;  its data was recorded on the CDR.  During the 
support two instances of corrupted data of ~1 second duration were 
seen.  As a result numerous critical flags were triggered in the MOC. 
The FOT has examined the legacy system CDR file and the critical 
flags are not set;  only with the data from the 26m automated system 
are the critical parameters flagged.  Further investigation is 
on-going.

Two major solar flares occurred last week: an X1.9 on July 12 at 
10:18 UT and an X5.7 on July 14 at 10:03 UT. As a result, the SIS 
instrument reached saturation and had to be commanded to raise its 
thresholds. This action brought the detector out of saturation. Also, 
the CRIS instrument's safeguarding kicked in to protect it. Both 
these instruments will be commanded this week to return them to a 
nominal state.  On 07-17-00 SSR B's telemetry sections were scrolled 
through;  no Single Bit Errors (SBE) were found.

On 07-14-00 the SEPICA instrument was automatically ramped down by 
the S3DPU. The solar storms are not suspected to have caused this 
since this particular anomaly has happened in the past and during 
quiet solar periods. The anomaly can be explained by the fact that 
SEPICA is, "...operating at the edge of its performance capability" 
according to Mark Popecki of the Instrument team.  The instrument was 
slowly ramped up during the next several days and is back at its 
pre-ramp down state.  Plans to redirect data to spare memory have 
still not been scheduled.

On 07-16-00 Station D66 transmitter went red for ~54 minutes during 
the support.  The Ops Chief extended the support and all commanding 
was successfully completed;  all SSR data was recovered [DR# L04545].

While DSN has placed its plans to transfer its overseas sites to the 
26 Meter Automated System on hold, the Goldstone site [D16] 26 Meter 
automated system has been made operational.  ACE's first support on 
the operational automated system at D16 was scheduled for 07-18-00. 
While telemetry was being received, the MOC was unable to send 
commands to the s/c at BOT.  While the station attempted various 
solutions, including an exciter failover and a TCP reboot,  the 
problem continued.  At BOT + 1 hour the s/c automatically 
reconfigured itself for the low (434 bps) data rate;  telemetry went 
static.  The FOT informed the station of the reconfiguration and 
requested they reconfigure for the low rate data.    At that time the 
stationed informed the FOT that they did not have ACE's low data rate 
in their 'desktop'.  The FOT then requested D16 configure to the 
legacy system.  After ~36 minutes telemetry was again received in the 
MOC.  After an additional 22 minutes D16 informed the FOT that ACE 
was go for commanding on the legacy system.  The Ops Chief extended 
the support by one hour.  The FOT began the nominal ACE activities; 
an attitude maneuver was successfully executed.  Due to the problems 
at D16, there was insufficient time to complete the SSR dump.  The 
remaining portion of the SSR was dumped during the following support, 
prior to commencing the nominal SSR activities.  During the debrief 
at the end of activities the station informed ACE that a DC voltage 
offset on the command line between station 16 and the ground antenna 
is believed to be the cause of the command problems.