STEREO Weekly Meeting Minutes for 2014-12-23 (Week 52) ANNOUNCEMENTS ------------- * There will be no STEREO operations telecon on Dec 30. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating on the first 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 51 (Dec 15-21) * On day 349 (Dec 15), during the DSS-43 support for Ahead, turbo decoder lock was lost briefly at 0328z. This anomaly resulted in the loss of five frames of real-time data. * The Ahead observatory is operating on the first side lobe of the HGA to prevent overheating of the HGA feed assembly which is currently at 118 degrees C with the HGA angle at 7.2 degrees, with respect to the spacecraft-Sun line. * On day 351 (Dec 17), PLASTIC powered off the entrance system at 1900z for fault isolation of an increasing power supply current indication. For safety, PLASTIC will be left in this state over the holidays. Turning off the entrance system reduced the current as expected. The cause of the increasing current has not yet been determined. * The average daily science data return for Ahead, while operating on the first side lobe on the HGA, was 81 Mbits during this week. * On day 352, during the DSS-43 support, the command uplink was stopped at 2250z and was unavailable for the remainder of the support due to azimuth antenna brakes being set as a result of an equipment anomaly at the station. This anomaly resulted in the loss of 85 minutes of commanding. See DR #C110800 for more information. * 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 day 351 (Dec 17), during the DSS-43 support for Behind, the DSN begin aberration corrections to optimize the uplink margin during the uplink sweep and blind commanding for the first hour of each support. * On days 351 through 353 (Dec 17-19), during the DSN 70 meter supports for Behind, 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 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 52 (Dec 22-28) * Thursday, Dec 25, is Christmas. APL will be closed Dec 25-26 for the holiday. * The station 14 pass on Saturday, Dec 27, has been changed to a Project Interface Test pass to test out a new version of the downlink software. There will be no instrument commanding or SSR playback during this pass. However, realtime telemetry will be available. A longer 4.2 hour support using station 43 is scheduled for later in the day. * The uplink sweep range for Behind was increased yesterday (Dec 22) from 4 kHz to the maximum of 14 kHz. This in preparation for the test next week of phasing together two stations to increase uplink power. * Command uplink was 10 minutes late yesterday (Dec 22) during the station 43 pass for Behind. * Ahead has 9 passes during the week, all at 10 kbps on the first side lobe in IMPACT-prime mode. * Behind has 3 passes during the week to attempt recovery, between Monday-Wednesday. Week 01 (Dec 29-Jan 4) * APL will be closed Jan 1-2 for the New Year holiday. * The HGA angle bias for the Ahead spacecraft will be updated on Jan 4 in preparation for second-side lobe operations in the following week. Instruments should configure their instruments for the 3 kbps downlink rate in advance of the switch on Jan 5. The change in angle bias will result in the last few minutes of the track being lost. POC queues will be disabled 20 minutes before the end of the track. * A test will be conducted on Jan 4 of phasing together stations 70 and 25 to boost the uplink power to the spacecraft. This should increase the signal strength by 3 dB. * Ahead has 8 passes during the week, all at 10 kbps on the first side lobe in SWAVES-prime mode. * Behind has 3 passes during the week to attempt recovery, between Tuesday-Thursday, along with the two-station test on Sunday, Jan 4. Week 02 (Jan 5-11) * Second side lobe operations at 3 kbps on Ahead start Monday, Jan 5. The uplink rate will also drop to 125 bps. The instrument teams are requested to reconfigure their telemetry rates before the 19:55 UT start of the pass. * If Behind is recovered by this time, it too is scheduled to start using the 2nd side lobe during the week. * The 75th momentum dump on Ahead is scheduled for Tuesday, Jan 6, with ignition at 13:00 UT. This is earlier than normal because of the lower target used for the previous momentum dump. * On Wednesday, Jan 7 the restricted IONet at APL will be down for maintenance for three hours starting at 15:30 UT. This should not effect operations, as there are no passes during this time. * Ahead has 10 passes during the week, six at 3 kbps on the second side lobe, and four at 633 bps. * Behind has 3 passes during the week to attempt recovery, between Friday-Sunday. Week 03 (Jan 12-18) * On Monday, Jan 12, SECCHI will perform a test of downlinking through the entire pass, including the period when the spacecraft housekeeping on the SSR is being played back. * 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. 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 10 passes during the week, nine at 3 kbps, and one 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 10 passes during the week, seven at 3 kbps, and three at 633 bps. Overall coverage is short about 6.2 hours, mainly on Monday or Thursday. An ESA New Norcia pass on Monday, and an ESA Malargue pass on Thursday, have been scheduled to help fill in the gaps. Week 06 (Feb 2-8) * Ahead has 8 passes during the week, seven at 3 kbps, and one at 633 bps. Overall 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. Week 07 (Feb 9-15) * The solar conjunction readiness review is scheduled for Thursday, Feb 12, starting at 8:30 A.M at APL. * Ahead has 7 passes during the week, all at 3 kbps. Overall coverage is short about 7 hours spread throughout the week. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 52: M Dec 22 (356) T Dec 23 (357) W Dec 24 (358) T Dec 25 (359) Christmas F Dec 26 (360) S Dec 27 (361) Ahead: PIT test with station station 14. S Dec 28 (362) Notes: * Ahead operating on first side lobe, in IMPACT-prime mode. ------------------------------------------------------------------------------- Scheduled activities for Week 01: M Dec 29 (363) T Dec 30 (364) W Dec 31 (365) T Jan 01 (001) New Year F Jan 02 (002) S Jan 03 (003) S Jan 04 (004) Ahead: Update HGA angle bias for second side lobe operations. Behind: Test of phasing together stations 14 and 25 Notes: * Ahead operating on first side lobe, in SWAVES-prime mode. ------------------------------------------------------------------------------- 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) S Jan 18 (018) Notes: * Ahead operating on second side lobe. ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- Scheduled activities for Week 07: M Feb 09 (040) T Feb 10 (041) 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. ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2015: * Jan 6 Behind: HGA on 2nd side lobe * Jan 12 Behind: Test with 34 meter at 633 bps * Jan 19 Behind: Instrument power down * 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 * 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