ACE Weekly 06/21-27/02

All ACE spacecraft subsystems are performing nominally.
An attitude maneuver was executed on 06/26/02. The next
attitude maneuver is tentatively scheduled for 07/12/02.

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Ongoing Activity:
The engineering test to determine the new HGA constraint is continuing.
The current constraint (as of 6/3/02) is 6.0 degrees, with current tests
reaching 6.5 degrees.  On 6/26/02, the spacecraft drifted to -6.4 degrees
and the attitude maneuver reached +5.9 degrees. The spacecraft is expected
to drift to -6.5 degrees.  The attitude maneuver on 7/12/02 is expected
to target +6.5 degrees.

The spacecraft is currently near the peak earth-spacecraft range (1592458
km on 6/26/02).  The FOT has been monitoring the Signal Strength, the MFR
AGC levels, and the Signal-to-Noise Ratios(SNR). The drop in RF levels from
an HGA angle of 0 degrees to 6 degrees has been approximately 3dB. There has
been no loss of telemetry due to the increased HGA angles.  Once all analysis
has been completed, the new HGA constraint will be determined.

The following HGA angles and range values are from FDF.
Man Date Pre Man Post Man Earth-ACE Range
03/28/02 -4.58 deg +4.38 deg 1408287 km
04/04/02 -4.35 +4.50 1414808
04/11/01 -5.09 +3.79 1428491
04/18/02 -5.16 +3.85 1440512
04/26/02 -5.77 +5.56 1455949
05/06/02 -5.72 +5.43 1493008
05/17/02 -5.81 +5.31 1527979
05/28/02 -4.34 +4.88 1550263
06/06/02 -2.38 +5.96 1576064
06/20/02 -6.57 -3.66 1590405
06/26/02 -6.43 +5.94 1592458
07/12/02 -6.5 +6.5 (expected)

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ACE Lissajous Orbit Status from FDF:
The ACE Lissajous orbit crossed into the old 4.75 deg Solar Exclusion
Zone(SEZ) on June 18th and will emerge early on July 4th after an
approximately 14-day transit. During this period the minimum Sun-Earth-ACE
angle will be about 4 degrees (3.96 to be exact), and that minimum will be
reached at 11:30Z on June 26th.
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Anomalies:

06/21/02 DOY 172 - ACE Anomaly #G02-0074 - 12 minute drop in telemetry
14:53-15:03, lost telemetry. D66 reported a loss of Receiver 1. After
switching to Receiver 2, experienced problems with Exciter 2. D66 switched
to Exciter 1. Playback data was redumped. DR#M100815

06/22/02 DOY 173 - ACE Anomaly #G02-0075 - No monitor data at AOS
D66 performed a reconfiguration of the SCP. DR#M100820

06/26/02 DOY 177 - ACE Anomaly #G02-0076 - 3 minute drop in telemetry
15:37-15:40, lost telemetry. DR#M100833