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. ============================================================================ 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. ============================================================================ 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. ============================================================================ 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. ============================================================================ 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. ============================================================================ 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