STEREO Weekly Meeting Minutes for 2015-01-13 (Week 03) 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 02 (Jan 5-11) * On day 011 (Jan 11), during the DSS-25 support for Ahead, turbo decoder lock was lost intermittently between 1740z through 2029z due to heavy rain at the Goldstone complex. This anomaly resulted in the loss of 18 frames of real-time data. See DR# G115835 for more information. It also appears that command bind was dropped, resulting in the dropping of a SECCHI command needed for the telemetry rate test on Monday, Jan 12. * The Ahead observatory is operating on the second side lobe of the HGA to prevent overheating of the HGA feed assembly which is currently at 106 degrees C with the HGA angle at 9.8 degrees, with respect to the spacecraft-Sun line. * On day 006 (Jan 6), the 75th momentum dump on Ahead was executed successfully at 1300z, which imparted a delta V of 0.102 m/sec. * On day 008 (Jan 8), PLASTIC powered off the entrance system on Ahead at 2200z for fault isolation of an increasing power supply current indication. It had been powered off before the holidays, but was autonomously powered on again after the momentum dump on day 006. * The average daily science data return for Ahead, while operating on the first side lobe on the HGA, was 21 Mbits during this week. * Detailed status of the activities that occurred on the Behind loss of communication anomaly, which occurred on day 2014-274 (Oct 1), 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 009 through 011 (Jan 9-11), during the DSN 70 meter supports, recovery commanding 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 03 (Jan 12-18) * On Monday, Jan 12, SECCHI was scheduled to perform a test of downlinking through the entire pass, including the period when the spacecraft housekeeping on the SSR is being played back. However, the command to properly set the telemetry rate for the pass was dropped, so the SECCHI telemetry rate was too low for a proper test. This test has been rescheduled for Saturday, Jan 17, during the first station 43 pass of the day, from 5:00-7:05 UT. * The playback of spacecraft housekeeping telemetry from the SSR continues to fall behind on the second side lobe. MOps would like to use the 5 hour support on Sunday, Jan 18, to catch up. After some discussion, it was decided that SECCHI should schedule observations for this pass in the normal manner, but may see telemetry dropouts. * Ahead has 10 passes during the week, all at 3 kbps on the second side lobe. * Behind has 3 passes during the week to attempt recovery, between Monday-Wednesday. Week 04 (Jan 19-25) * If the Behind spacecraft has been recovered by this time, preparations for superior solar conjunction would begin on Jan 19, starting with the instruments powering down (except SWAVES). The SSR would be played back on Jan 20, and on Jan 22, the spacecraft would be reset to rotate at 5 degrees per minute. * 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 12 passes during the week, seven at 3 kbps, and five 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) * 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, all at 3 kbps. 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) * Ahead has 7 passes during the week, all at 3 kbps. Overall coverage is short 5.25 hours between Monday-Thursday. * No passes are scheduled for Behind due to superior solar conjunction. Other * Green Bank observatory is planning to use the radio signal from the STEREO Ahead spacecraft during the period of superior solar conjunction to study Faraday rotation in the solar corona. During this period, the spacecraft will be switching between the antennas, spending 24 hours each on the second side lobe of the HGA antenna, then on the -Z LGA, and then on the +Z LGA. (Previously tested was 48 hours on the HGA, followed by 12 hours each on the two LGAs.) MOps is looking into how best to communicate the expected transition times. Between about Apr 5 to Jun 28, the only expected detections of the spacecraft carrier signal would be from Green Bank. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 02: M Jan 05 (005) Ahead: Start of second side operations. T Jan 06 (006) Ahead: Momentum dump, 13:00 UT W Jan 07 (007) T Jan 08 (008) F Jan 09 (009) S Jan 10 (010) S Jan 11 (011) Notes: * Ahead operating on second side lobe. ------------------------------------------------------------------------------- Scheduled activities for Week 03: M Jan 12 (012) Ahead: Test of SECCHI telem. during SSR playback, 15:50-17:50 T Jan 13 (013) W Jan 14 (014) T Jan 15 (015) F Jan 16 (016) S Jan 17 (017) Ahead: Test of SECCHI telem. during SSR playback, 05:00-07:05 S Jan 18 (018) Notes: * Ahead operating on second side lobe. * Instrument telemetry dropouts may occur during the 5 hour station 43 support for Ahead on Jan 18 due to extended playback of the SSR. ------------------------------------------------------------------------------- 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