ACE Weekly 08/27/04 - 09/02/04 All ACE spacecraft subsystems are performing nominally. An attitude maneuver was successfully executed on 08/27/04. The next attitude maneuver is scheduled for 09/03/04. ============================================================================ Orbit Events: From Craig Roberts (FDF) regarding SK-33: The ACE L1 Lissajous orbit stationkeeping maneuver SK-33 was executed successfully on Friday, August 20, 2004 following a scheduled attitude reorientation maneuver during the same pass on DSS-16. Key data concerning the burn follows. -- Burn Start: 16:34:32 UTC -- Burn Stop: 16:35:36 UTC -- Delta-V = 0.3642 m/sec (anti-Sunward) -- Burn Duration = 63.7559 sec (continuous firing) -- Fuel Usage = 0.2434 lbm (0.1104 kg) -- Final Fuel Mass per tank = 44.1972 lbm (times 4 tanks) -- Fuel remaining = 176.7888 lbm (80.1896 kg) -- Thrusters: Top-deck Axials 1A and 2A -- Spin axis right ascension = 154.02 deg -- Spin axis declination = 15.91 deg -- Initial spin rate = 5.0103 rpm -- Final spin rate = 4.9888 rpm -- Spin rate change = -0.0215 rpm Real-time Doppler measurement of the line-of-sight delta-V component, which was expected to be -0.3623 m/sec, showed the burn to be just 0.22 percent hot. This represents a performance deviation of 0.8 millimeter/sec. A very short-arc (approx. 5 days) post-burn orbit determination solution has since confirmed that SK-33 went well. ACE's Lissajous orbit has now transitioned to an opening pattern, so the ACE motion will now be counterclockwise about L1 (and for that matter, the Sun) for quite a long time to come. +++++++++++++++++++++++++++++++++++++++++ The ACE transit of the Solar Exclusion Zone (SEZ) continue through 09/11/04. The minimum Sun angular radius was 0.32 degrees (as seen from Earth's center) on 08/30/04. Features of this transit are given in the following table. 8/18 4.96 deg inbound 8/25 2.13 deg inbound 8/29 0.61 deg inbound 8/30 0.32 deg minimum SEZ angle this transit 8/31 0.41 deg outbound 9/05 2.30 deg outbound 9/11 4.78 deg outbound More data regarding the transit will be included in coming weeklies. ===================================================================== OCRs Executed: None ===================================================================== Ongoing Activities: TAPS: - Installation of TAPS release 4.3 occurred on 07/20/04. FOT testing of this release is ongoing. -- Of the 6 DRs fixed in release 4.3, all have been verified. -- Two (2) new DRs have been opened to date. ---------------------------------------------------------------------------- Automation (ROBOTT): - On 08/25/04, ROBOTT v0.8.1 was installed on String 1 (OCR GND-143). -- Operations is being conducted in the "auto" mode with the FOT closely monitoring and noting any discrepancies. - Testing of v0.8.1 by the FOT will continue on String 2. -- To date all DRs fixed in this release have been tested. One (1) DR has failed and five (5) new DRs have been written. ============================================================================ Extra Spacecraft Activities: None ===================================================================== Anomalies: DOY 04239 (08/26/04) ACE Anomaly G04-0100 - GDS 26m (DSS-16) Receiver B Out-of-Lock DSS-16 ended their sweep for the uplink at 14:35:55, however the second receiver on the spacecraft (RCVR B) lost its lock on the uplink. FOT requested DSS-16 resweep and receiver B locked up on signal. IMPACT: Since Automation did not see a good active foward link C&C would have not continued. DSN would have not know of the problem because it is not a part of the two-way loop. None of the activities would have started that day. C&C had to be rebooted after receiver B locked. DR# N102329 (Left off previous weekly) DOY 04243 (08/30/04) ACE Anomaly G04-0088 (Appended) - ADS Failure Received error when attempting to start ADS. Killed processes on workstation and rebooted the software. IMPACT: Delayed pass activities. DOY 04245 (09/01/04) ACE Anomaly G04-0101 - GDS 34m (DSS-27) Reliable Network Server (RNS) Problem AT 14:15 the FOT received extensive VC2 Errors (BOT 14:05). Notified JPL Comm. Telemetry good at 15:05:40. IMPACT: Delayed SSR activities during SEZ transit. Data had to be retrieved via CDR file. DR# N102342 DOY 04245 (09/01/04) ACE Anomaly S04-0007 - SSR-B Full/Failover SSR B Full due to inability to dump recorder during SEZ transit. Autonomy Bin 42 failover occurred as expected. IMPACT: None. DOY 04246 (09/02/04) ACE Anomaly G04-0102 - GDS 34m (DSS-27) Reliable Network Server (RNS) Problem AT 14:03 FOT received telemetry dropouts (BOT 14:05). Queried station for TLM dropouts, and station indicated that errors were due to their RNS. Station performed TLP re-initialization at ~14:06. Team experienced momentary TLM dropouts until telemetry returned reliably at 14:27:58. IMPACT: Delayed pass activities. Data had to be retrieved via CDR file. DR# G104777 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Glen A. Miller ACE Flight Operations Observatory Engineer Honeywell Technology Solutions Inc. Goddard Space Flight Center Building 14, Room W10A Mail Stop 428.2 Greenbelt, MD 20771 Office: 301-286-7071 Pager: 800-425-3174 Fax: 301-286-1729 gamiller@pop500.gsfc.nasa.gov ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~