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. ============================================================================ 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. ============================================================================ 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) ============================================================================ 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. ============================================================================ 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.