ACE Weekly Report (06/07/02  06/13/02)

All ACE spacecraft subsystems are performing nominally. No attitude 
maneuvers were executed this week.  The next attitude maneuver is scheduled 
for 06/20/02.

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OCRs Executed:

06/07/02 ==> OCR SWPX-034, SWEPAM recovery from DPU latchup on 05/17/02
      Loaded Flight Code Rev 1.14

06/07/02 ==> OCR SWX-028, SWICS recovery from DPU latchup on 05/17/02
      To restore BR and MR boundary parameters for SWICS which were reset 
by the DPU latchup on 05/17/02.

06/10/02 ==> OCR SWM-029, SWIMS Recovery from DPU latchup on 05/17/02
      To restore the E/q stepping sequence and TOF range for SWIMS which 
were reset by the DPU latchup on 05/17/02.

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34m UPL Demo

A 34m UPL Demo Pass with DSS-24 was executed on DOY 164, 06/13/02.

This was a demo pass to verify the new 34m UPL D2 command system.  As with 
the demo pass with DSS-54 on DOY 136, the DSS-24 pass had no problems and 
was nominal.  Command and command echo history files were reviewed and were 
nominal.

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Ongoing Activity:

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 through 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)

FDF predicts that the HGA will drift to around -6.5 degrees by the next 
maneuver on 6/20 (at 1800 GMT).  We will then be targeting to an HGA 
of      -3.77 degrees so that the HGA will again drift to -6.5 degrees on 
6/26 (at 1500 GMT) where ACE will be at the maximum range from Earth.

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ACE Lissajous Orbit Status from FDF:

The ACE Lissajous orbit 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.

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Anomalies:

06/11/02 DOY 162 - ACE Anomaly #G02-0067  Lost Monitor Blocks from D66 from 
16:59:05 to 18:07.
JPL notified D66 that they were not seeing their link to the LMC 
anymore.  D66 tried to reboot the LMC but it didn't work.  D66 then 
rebooted the SCP and the monitor blocks came back online.  IMPACT: 2 
minutes of data loss which was recovered after the playback was 
finished.  Loss of monitor block data for 1 hour and 8 minutes.  DR#M100768

06/13/02 DOY 164 - ACE Anomaly #G02-0069   No MFR data received in the DSN 
monitor blocks from D27.
D27 informed us that this is a known problem and they have their systems 
engineers looking into the cause. IMPACT:  No MFR data. DR#G101254