ACE Weekly 05/21/04 - 05/27/04 All ACE spacecraft subsystems are performing nominally. Attitude and stationkeeping maneuvers were successfully executed on 05/27/04. The next attitude maneuver is scheduled for 06/11/04. ============================================================================ Orbit Events: The ACE transit of the old Solar Exclusion Zone (SEZ) will continue through 06/14/04. For the first time ever, ACE will transit the solar disk on 06/01/04. On that date, the Sun's angular radius is 0.2629 degree (as seen from Earth's center). The solar transit will last nearly 21 hours (again, as seen from Earth's center). The main features of this transit are given in the following table (times are UTC). 5/19 01:42 4.75 deg inbound 5/27 07:45 2.0 deg inbound 5/30 23:39 0.63 deg inbound 6/01 01:18 0.2629 deg (kissing solar disk inbound) 6/01 10:46 0.197 deg (radius of closest approach to solar center) 6/01 22:14 0.2629 deg (kissing solar disk outbound) 6/02 23:28 0.63 deg outbound 6/06 11:15 2.0 deg outbound 6/14 07:18 4.75 deg outbound The 0.63 deg epochs are included because that radius represents the closest approach during our last transit in February/March. ACE will spend almost exactly 3 days within this zone. ******************************** From Craig Roberts (FDF): ACE stationkeeping maneuver SK-32 was successfully performed on 05/27/04 following a successful attitude reorientation maneuver earlier in the same pass. Continuous-mode firing of the aft-end axial jets 3A and 4A commenced at 16:45:45 UTC and ended at 16:47:24. The key burn parameters were: -- delta-V = 0.5358 m/sec (Sunward) -- burn duration = 98.7061 sec -- fuel used = 0.37132 lbm (0.1684 kg) As was expected, the spin rate decreased during the SK burn. It dropped from 4.9372 rpm to 4.9142 rpm, a decrease of 0.023 rpm and very close to the prediction. As 4.9142 rpm is sufficiently within constraints, no spin-up burn was performed today (a spin-up burn is very likely come the next stationkeeping maneuver, however). ===================================================================== OCRs Executed: NONE ===================================================================== Ongoing Activities: TAPS: - Transition from GTAS to TAPS occurred on 03/18/04. All trending activities are being accomplished using TAPS. - Installation of TAPS release 4.3 is tentatively scheduled for the first week of July 2004. All open DRs will be fixed in this release. - An additional DR has been opened. The FOT found that TAPS drops 3 frames per every 152 frames processed for product generation. ---------------------------------------------------------------------------- Automation (ROBOTT): - Release 0.6 installed on String 1 on 05/13/04. Operations has moved to String 2. -- 22 DRs have been verified out of 25 reported fixed in this release. -- 1 new DR opened this week. -- 17 DRs have been opened as a result of FOT testing of Release 0.6. - 20 DRs are OPEN to date. - It has been determined that Release 0.6 will not be used operationally, however testing will continue until Release 0.7 is delivered. - SUG development is ongoing. A DRAFT version has been delivered and is still being reviewed by the FOT. Comments will be provided to the developer. - FOT training on ROBOTT began 05/05/04 and additional sessions are being developed. ============================================================================ Extra Spacecraft Activities: NONE ===================================================================== Anomalies: DOY 04142 (05/21/04) ACE Anomaly G04-0042 - GDS 26m (DSS-16) Telemetry Outage At 16:03:20, the FOT lost telemetry from DSS-16. Telemetry resumed at 16:04:30. Station reported the problem was with the X-axis in auto track mode. Station switched to Program Mode of tracking and achieved solid telemetry lock. IMPACT: None. Telemetry was subsequently retrieved via recorder dump. DR# G104427 DOY 04144 (05/23/04) ACE Anomaly G04-0043 - MAD 26m (DSS-66) Incorrect Command Modulation Index During G_INITIAL_CONTACT, the FOT noticed RCVR_A/B_AGC limit violations. After successfully running the procedure the FOT checked the DSNMON 0158 data for the value of the carrier suppression (command modulation index). The value was going from 0 dB to 7.16 dB, which is incorrect. The FOT informed DSS-66 of the possible problem and requested they confirm their command modulation index value. DSS-66 stated they had a modulation index value of 0.60 radians (nominal value is 0.86). The FOT requested the operator change the value to 0.86 radians. The value was changed and the FOT sent a /no_op to confirm a good command link. IMPACT: Delayed pass activities. DR# G104439 DOY 04146 (05/25/04) ACE Anomaly G04-0044 - GDS 26m (DSS-16) MFR Swap Telemetry dropped out from 14:48:50 - 14:50:30. Contacted DSS-16 and they were looking into the problem. The MFR2 dropped lock for unknown reasons causing TCP1 TS1 & TS2 to also drop Telemetry lock. They had to switch to MFR3 to solve the problem. IMPACT: Delayed pass activities. Telemetry was subsequently retrieved via recorder dump. DR# G104436 DOY 04147 (05/26/04) ACE Anomaly G04-0045 - GDS 26m (DSS-16) Commands Not Getting to Spacecraft Attempt to send initial NO-OP command at beginning of pass was unsuccessful. DSS-16 notified of problem. Station found composite at .87 vice 1.29. Operator manually entered mil directive and commands were successfully received by the spacecraft. IMPACT: Delayed pass activities. DR# G104439 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~