ACE Weekly Report (05/31/02  06/06/02)

All ACE spacecraft subsystems are performing nominally. An attitude 
maneuver was successfully performed on 06/06/02.  The next attitude 
maneuver is scheduled for 06/20/02.

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OCR SEP-102; executed on 06/05/2002 DOY 156.  The SSD low gain pixels were 
switched to the high gain mode to improve identification of low energy iron.

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An engineering test is in progress to determine a new HGA constraint. The 
current constraint is 6.0 degrees, however the FOT has been given 
authorization to drift to as much as 6.5 degrees prior to maneuvers. The 
constraint was increased on 06/03/2002, as part of a several step process 
that will continue into this month with the maximum constraint being 
reached 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.

As part of the test the FOT has been monitoring the Signal Strength, the 
MFR AGC levels, and the Signal-to-Noise Ratios(SNR) that are obtained 
through the DSN Monitor Blocks for any significant or unexpected degradation.

As of the maneuver on Day 02148 (May 28, 2002), there has been no severe 
degradation to the SNR with respect to the widened HGA angle.  The analysis 
of this data has been on-going since Day 02075 (March 16, 2002).  As 
expected, a slight degradation in signal levels (SNRs) has been seen (~3db 
less).  This is nominal. At an angle of 6 degrees off the antenna boresight 
we expect to see a loss of ~3db. There hasn't been any degradation to 
telemetry due to increasing the HGA.

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  (sun angle constraint)
06/06/02 ~2.3  (sun angle constraint)
06/20/02 ~6.5  (expected)

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ACE Lissajous Orbit Status from FDF:

1. The orbit is in fine shape following April's stationkeeping maneuver.

2. FDF expects we can coast into early August--and perhaps longer--before 
needing to do the next stationkeeping.

3. The Lissajous will cross into the old 4.75 deg Solar Exclusion Zone(SEZ) 
late on June 18th and emerge early on July 4th after an approximately 
14-day transit. During that 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.

*** NOTE on the orbit geometry: The Sun-Earth-ACE angle is an orbital
geometry measure, the angle between the Sun and ACE directions as subtended
at the Earth.  It is entirely different from, and independent of, the 
HGA  boresight-to-Earth angle.

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Anomalies:

06/03/02 DOY 154 - ACE Anomaly #G02-0065   One CLTU Not Received By The 
Spacecraft **** Station notified but no actions were required by the 
site.  Performed a "resync" of the ground system command counters and 
retransmitted command.  Command was accepted and pass activities were 
resumed.  No impact to pass activities or telemetry.

06/04/2002 DOY 155 - ACE Anomaly #S02-0014  +15V Supply Current Limit 
Violation **** At 15:22:29, the +15V power supply, which is one of two 
supplies that feeds the 30kV supply, flagged a yellow high limit with a 
value of 288.38mA. The supply returned within limits at 15:24:29 with a 
value of 280.87.  Notified Mark Popecki.

06/06/2002 DOY 157 - ACE Anomaly #S02-0015  +15V Supply Current Limit 
Violation **** At 15:13:12, the +15V power supply, which is one of two 
supplies that feeds the 30kV supply, flagged a yellow high limit with a 
value of 288.38mA. The supply returned within limits at 15:15:12 with a 
value of 283.87.  Notified Mark Popecki.