ACE Weekly Report (06/14/02  06/20/02)

All ACE spacecraft subsystems are performing nominally.
An attitude maneuvers was executed on 06/20/02. The next
attitude maneuver is tentatively scheduled for 06/26/02.

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OCRs Executed:

06/14/02 ==> OCR S3D-002, 003, 004 Reload patches to recover from partial
DPU reset that occurred on 05/17/02.

06/19/02 ==> OCR SWX-029 Reset SWICS Priority Mask
The value of the SWICS priority mask cannot currently be verified in the 
telemetry.
Therefore, it is being reset to guarantee the value.

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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
06/26/02 ~-6.5

On 06/20/02 an HGA of -3.77 degrees was targeted so that the HGA will again 
drift to -6.5 degrees on 6/26 when ACE will be at the maximum range from Earth.

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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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DSN 34m UPL Status:

ACE has successfully completed its 34m UPL testing. The new UPL system will
be utilized as the prime equipment effective DOY 175/0000z.

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Anomalies:

06/14/02 DOY 165 - ACE Anomaly #G02-0070 DTF 21 Monitor Blocks online.
 From 16:59:53 to 17:37:13 monitor blocks from DTF 21 were online 
intermittently between our monitor blocks from D66. Notified JPL Comm and 
the Ops Chief. DTF 21 disabled their monitor blocks. IMPACT: Intermittent 
Monitor Blocks from DTF 21. DR# N100468

06/14/02 DOY 165 - ACE Anomaly #G02-0071 DSN - Exciter Problem/Incorrect 
Mod Index
While executing the S3D OCR's, we noticed that every time we sent a 
command, we would also get a VC2 hit. Notified D66 of the problem. Sent 
NO-OP commands to help them diagnose the problem. D66 informed us that 
their Modulation Index was set too high. Later D66 told us that they were 
also having exciter problems which is why they needed to reconfigure their 
equipment. We sent another no_op after they readjusted their equipment, and 
no further problems were seen during commanding. IMPACT: VC2 hits during 
each command that was sent until D66 fixed the problem. Most of the data 
was recovered. DR# M100792

06/14/02 DOY 165 - ACE Anomaly #G02-0072 DSN - Transmitter Problem
At 18:31 (4 minutes before EOT) we lost our receiver lock. D66 said they 
had an alarm on their transmitter at 18:31:02. We were still receiving 
telemetry. IMPACT: Lost receiver lock for the last 4 minutes of the pass.

06/15/02 DOY 166 - ACE Anomaly #G02-0073 DSN - LMC Problem
At 17:09:22 DSN monitor blocks went offline. D27 informed us that they lost 
their interface to the LMC. D27 had to reboot the SCP to restore the 
monitor block data which was back online at 17:24:27. IMPACT: No DSN 
monitor blocks for about 15 minutes. One VC2 hit while the SCP was 
rebooted; that data was recovered in a playback. DR# G101263

06/15/02 DOY 166 - ACE Anomaly #S02-0016 SSSP15I Yellow High Limit Violation
At 18:29:40, SSSP15I violated the yellow high limit value of 287mA, with a 
value of 288.38mA. The mnemonic returned within limits at 18:31:40 with a 
value of 277.86mA. On DOY 167 at 15:28:00, the SSSP15I violated again at 
288.38mA. The mnemonic returned within limits at 15:30:00 with a value of 
273.36mA. Notified Mark Popecki.
On DOY 167 (Sunday) Mark called us back and said that the increase in the 
+15I is due to the slight increase in the 30KI. The 30KI draws some of its 
current from the +15I. Mark is going to work out some new limits for the 
+15I and for now he just wants us to watch both of these currents.