STEREO Weekly Meeting Minutes for 2015-01-20 (Week 04) ANNOUNCEMENTS ------------- * None. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating on the second side lobe of the HGA to prevent overheating of the feed assembly. * There are currently no communications with the Behind spacecraft. See below for details. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 03 (Jan 12-18) * The Ahead observatory is operating on the second side lobe of the HGA to prevent overheat ing of the HGA feed assembly which is currently at 107 degrees C with the HGA angle at 9.7 degrees, with respect to the spacecraft-Sun line. * On day 016 (Jan 16), PLASTIC on Ahead loaded commands for testing the entrance system on day 020 to determine the cause of an increasing power supply current indication. * On day 017 (Jan 17), during the first DSS-43 support for Ahead that day, a test of downlinking real-time SECCHI images during SSR playback at the low downlink rate of 3 kbps was successfully conducted. * On day 018 (Jan 18), during the second DSS-43 support for Ahead that day, the SSR playback of spacecraft data was extended for the 5.25 hour duration of the support to assist in emptying the spacecraft partitions. Only 16% of the data was down linked due to the 3 kbps downlink rate. * The average daily science data return for Ahead, while operating on the second side lobe on the HGA, was 21 Mbits during this week. * On day 015 (Jan 15), the Behind spacecraft emergency declaration was terminated as the observatory will enter superior solar conjunction on day 022 (Jan 22). Recovery efforts will resume post solar conjunction on day 075 with increasing the ground transmit power through arraying uplink stations and implementing the Failure Review Board recommendations. * Detailed status of the activities that occurred on the Behind loss of communication anomaly, which occurred on day 2014-274, are listed below. To ensure communications on the LGA during long term recovery efforts, the Behind track coverage have been reduced to 3 hour 70 meter supports for 3 days in a row each week. * On days 012 through 014 (Jan 12-14), during the DSN 70 meter supports, recovery commanding for Behind was conducted to ensure that the transmitter is in its operational configuration. No signal was received by the DSN radio science receivers. Significant findings to date: 1. Analysis of the three DSN extracted telemetry frames from the carrier signal just before the planned observatory reset/anomaly occurred on day 2014-274, October 1st, showed nominal performance of the spacecraft, i.e., no anomalies, IMU off, and the star tracker providing an attitude solution. 2. Post reset, from the very limited telemetry, three packets, extracted from the carrier signal by the DSN, the X-axis gyro on IMU-A had failed. Unfortunately, this telemetry contained only G&C anomaly data and no spacecraft summary data, i.e., the state of the RF, G&C, fault protection and other subsystems is not known at the time of the anomaly. With a failed IMU and the star tracker being off-line for an undetermined duration, the sun sensors will keep the observatory pointed at the Sun, though the G&C will not have any roll knowledge, and cannot roll the observatory as part of the safing configuration to re-establish communications on the LGAs. From analysis of this telemetry and initial G&C simulations, it is highly suspected that the observatory is rotating about the principal axis of inertia due to an autonomous momentum dump initiated by bad gyro data flagged good, but this has not yet been confirmed. 3. At least two anomalies occurred post reset, the star tracker not promoting to AAD mode and the X-axis gyro failure. Unfortunately, due to the number of possible combinations, the STEREO fault protection system is not designed for simultaneous failures. The cause and effect analysis of the loss of communications from the LGAs is continuing. G&C simulations using the bad gyro data flagged good are continuing to better understand the potential impact to the observatory state. Recovery from a negative power state is also being investigated. While the recovery and analysis efforts continue on Behind, as the Ahead observatory will enter superior solar conjunction in March, the primary focus of the engineering team is on developing operational configuration changes to add robustness to the G&C rate sensor usage to ensure the Ahead observatory’s continued safety. * Once communications are restored and the anomaly resolved, the operational plan for exiting the solar conjunction testing will continue to return the Behind observatory back to nominal science data collection as soon as safely possible. Week 04 (Jan 19-25) * Tomorrow, Jan 21, a patch will be loaded to GNC RAM on Ahead to prevent bad data from going into the GNC. * Regardless of the state of the spacecraft, DSN coverage for Behind ends on Jan 26. * Ahead has 14 passes during the week, nine at 3 kbps, and five at 633 bps. * Behind has 3 passes during the week to attempt recovery, on Thursday, Friday, and Sunday. Week 05 (Jan 26-Feb 01) * A dry run for the Solar Conjunction Readiness Review will be held on Jan 29. The review itself is scheduled for Feb 12. * Ahead has 16 passes during the week, seven at 3 kbps, and nine at 633 bps. Overall 70 meter coverage is short about 6.2 hours. * No passes are scheduled for Behind due to superior solar conjunction. Week 06 (Feb 2-8) * DSCOVR first launch opportunity now Feb. 8. * On Wednesday, Feb 4, the restricted IONet at APL will be down for maintenance for four hours starting at 15:00 UT. This should not effect operations, as there are no passes during this time. * Ahead has 8 passes during the week, seven at 3 kbps, and one at 633 bps. Overall 70 meter coverage is about 6.5 hours short, mainly between Monday to Thursday, along with 2 hours on Saturday. An ESA Malargue pass was added on Monday, Feb 2, to help fill in the gap. * No passes are scheduled for Behind due to superior solar conjunction. Week 07 (Feb 9-15) * The 76th momentum dump on Ahead is scheduled for Tuesday, Feb 10, starting at 15:30 UT. * The solar conjunction readiness review is scheduled for Thursday, Feb 12, starting at 8:30 A.M at APL. * Ahead has 10 passes during the week, seven at 3 kbps, and three at 633 bps. Overall 70 meter coverage is short about 7 hours spread throughout the week. * No passes are scheduled for Behind due to superior solar conjunction. Week 08 (Feb 16-22) * Ahead has 7 passes during the week, six at 3 kbps one at 633 bps. Overall coverage is short 4.5 hours between Tuesday to Sunday. * No passes are scheduled for Behind due to superior solar conjunction. Week 09 (Feb 23-Mar 1) * Daylight saving time begins in continental US at 07:00 UT on March 1. * Ahead has 7 passes during the week, all at 3 kbps. Overall coverage is short 4.25 hours between Monday-Thursday. * No passes are scheduled for Behind due to superior solar conjunction. Week 10 (Mar 2- 8) * Ahead has 8 passes during the week, seven at 3 kbps, one at 633 kbps. Coverage is even * No passes are scheduled for Behind due to superior solar conjunction. Other: * There has been difficulty during the 2nd side-lobe operations in downloading the spacecraft housekeeping data from times outside of ground contact. As a result, the MOC would like to extend the playback time for this data, as was done last Sunday (Jan 18, see above). During that time there was a loss of SECCHI data packets and maybe some from the other instruments. They would like some feedback on the extent of such data losses and the extent to which is is acceptable. There will be an email on this topic coming out later. * The dates will be changing for the return to first side-lobe and main-lobe operations - we will be able to change to these earlier than previously scheduled. The schedule will be updated in the next week or so. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 04: M Jan 19 (019) T Jan 20 (020) W Jan 21 (021) T Jan 22 (022) F Jan 23 (023) S Jan 24 (024) S Jan 25 (025) Notes: * Ahead operating on second side lobe. ------------------------------------------------------------------------------- Scheduled activities for Week 05: M Jan 26 (026) T Jan 27 (027) W Jan 28 (028) T Jan 29 (029) Solar Conjunction Readiness Review dry run. F Jan 30 (030) S Jan 31 (031) S Feb 01 (032) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 06: M Feb 02 (033) T Feb 03 (034) W Feb 04 (035) T Feb 05 (036) F Feb 06 (037) S Feb 07 (038) S Feb 08 (039) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 07: M Feb 09 (040) T Feb 10 (041) Ahead: Momentum dump, 15:30 UT W Feb 11 (042) T Feb 12 (043) Solar Conjunction Readiness Review F Feb 13 (044) S Feb 14 (045) S Feb 15 (046) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 08: M Feb 16 (047) T Feb 17 (048) W Feb 18 (049) T Feb 19 (050) F Feb 20 (051) S Feb 21 (052) S Feb 22 (053) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 09: M Feb 23 (054) T Feb 24 (055) W Feb 25 (056) T Feb 26 (057) F Feb 27 (058) S Feb 28 (059) S Mar 01 (060) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2015: * Jan 19 Behind: Instrument power down (except SWAVES) * Jan 20 Behind: Replay SSR * Jan 22 Behind: Reset into 5 degrees/minute rotation mode. * Jan 22 - Mar 23 Behind: Spacecraft behind Sun * Feb 12 Solar Conjunction Readiness Review * Mar DAWN - Ceres arrival * Mar 22 Ahead: Instrument power down (except SWAVES) * Mar 23 - Apr 06 Behind: S/C SSR Playback at 3 kbps * Mar 24 - Jul 07 Ahead: Spacecraft behind Sun * Mar 30 Behind: Instrument power on * Apr 25 Behind: HGA on 1st side lobe * Jul DAWN - End of nominal mission * Jul 8 Behind: HGA on 2nd side lobe * Jul 7-28 Ahead: S/C SSR Playback at 3 kbps * Jul 14 Ahead: Instrument power on * Sep 24 Ahead: HGA on 1st side lobe * Nov 20 Behind: HGA on 1st side lobe * Dec 29 Ahead: HGA on main lobe, offpoint 1 degree Ahead: SSR playback and reconfiguration, S/C checkout * Dec 31 Ahead: Instrument recommissioning 2016: * Jan 2 Behind: HGA on main lobe Behind: SSR playback and reconfiguration, S/C checkout * Jan 5 Behind: Instrument recommissioning * Jan 27 Both: HGA calibration * Feb 19 Ahead: HGA on main lobe * Mar 16 Both: Post Solar Conjunction Assessment Review * Jul 5 Juno arrival at Jupiter 2017: * Jul 11 Ahead: Switch downlink rate to 160 kbps * Jul 22 Behind: Switch downlink rate to 160 kbps 2018: * Mar 5 Ahead: Mercury transit