STEREO Weekly Meeting Minutes for 2015-02-03 (Week 06) 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 05 (Jan 26-Feb 01) * On day 026 (Jan 26), during the DSS-74 support for Ahead, no telemetry was received for the duration of the support. This was a short, low elevation track with ESA New Norcia, for which the second side lobe operations had not been tested. This anomaly resulted in the loss of 1.3 hours of commanding, tracking, and real-time data. * On day 027 (Jan 27), during the DSS-84 support for Ahead, turbo decoder lock was lost intermittently between 1215z through 1615z. This anomaly resulted in the loss of several minutes of real-time data. * On day 030 (Jan 30), during the DSS-45 support for Ahead, turbo decoder lock was lost intermittently between 0618z through 0626z due to heavy rain at the Canberra complex. This anomaly resulted in the loss of 38 frames of real-time data. See DR# C110921 for more information. * 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 108 degrees C with the HGA angle at 9.4 degrees, with respect to the spacecraft-Sun line. * On day 027 (Jan 27), Fault Protection release 2.3.17 and MOps macro release 1.1.27 were loaded to C&DH EEPROM and verified. These releases will apply a patch to the G&C application to prevent bad IMU data flagged by the IMU as good from being used by the G&C application after each system reset. Also they will configure to use the HGA and the LGA antennas each for 24 hours after a system reset in preparation for solar conjunction. * On day 027 (Jan 27), PLASTIC tested the entrance system at 2040z and again on 030-2215z to determine the cause of an increasing power supply current indication. The information from these tests is being evaluated by the engineers. * The average daily science data return for Ahead, while operating on the second side lobe on the HGA, was 20 Mbits during this week. * Detailed status of the activities that occurred on the Behind loss of communication anomaly, which occurred on day 2014-274, are listed below. * On day 022 (Jan 22), the Behind observatory entered superior solar conjunction at the 2 degree SPE angle. Recovery efforts will resume post solar conjunction on day 082 with increasing the ground transmit power through arraying uplink stations and implementing the Failure Review Board recommendations. * 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 06 (Feb 2-8) * The playback of spacecraft housekeeping from the SSR is being extended throughout the pass, starting with the pass this morning (Feb 3). * Tomorrow (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. * The first launch opportunity for the DSCOVR mission is Sunday, Feb. 8 at 23:10 UT. Daily launch opportunities continue through day 42 (Feb 11), and then pick up again on days 51, 52 (Feb 20-21). This launch will have minimal impact on STEREO, since STEREO is now mostly dependent on the 70 meter stations. * 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 7 passes during the week, all at 3 kbps. The previously scheduled 34 meter passes have been given up to the DSCOVR mission. 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 and 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) * 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) * Daylight saving time begins on the US east coast at 07:00 UT on March 8. * On Wednesday, Mar 4, at 14:00 UT, the restricted IONet at APL will be taken down while the prime router is replaced. * Ahead has 8 passes during the week, seven at 3 kbps, one at 633 kbps. Overall coverage is nominal. * No passes are scheduled for Behind due to superior solar conjunction. Week 11 (Mar 9-15) * On Thursday, Mar 12, during overlapping tracks for 34 meter stations 24 and 25, there will be an uplink array test with Ahead. There will be telemetry downlink, but no commanding during this time. This test is in preparation for Behind recovery efforts. * Ahead has 12 passes during the week, six at 3 kbps and six at 633 kbps. Overall coverage is short 4 hours between Monday-Wednesday. * No passes are scheduled for Behind due to superior solar conjunction. Week 12 (Mar 16-22) * Preparations for solar conjunction on Ahead will start during the week. The Sun-Earth-spacecraft angle will be 2.2 degrees at the beginning of the week, approaching 2 degrees toward the end of the week. * The 77th momentum dump on Ahead is scheduled for Tuesday, Mar 17, with ignition at 23:00 UT. The system momentum target will be 13 N-m-s, selected to minimize the chance of an autonomous momentum dump during the solar conjunction period. * The instrument teams (except SWAVES) are requested to start configuring their instruments between Mar 16-19 for power down. IMPACT, PLASTIC, and SECCHI will be powered off via time-tagged command on Friday, Mar 20, at 16:00 UT. * Scheduled track coverage for Behind has been reallocated to Ahead. * Ahead has 13 passes during the week, and overall coverage is nominal. * On Tuesday, Mar 24, the spacecraft will be reset into solar conjunction mode, and the signal will be monitored for the remainder of the week. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- Scheduled activities for Week 10: M Mar 02 (061) T Mar 03 (062) W Mar 04 (063) T Mar 05 (064) F Mar 06 (065) S Mar 07 (066) S Mar 08 (067) Start of daylight savings time in U.S. Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 11: M Mar 09 (068) T Mar 10 (069) W Mar 11 (070) T Mar 12 (071) Ahead: Uplink array test with stations 24 and 25. F Mar 13 (072) S Mar 14 (073) S Mar 15 (074) Notes: * Ahead operating on second side lobe. * No passes for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 12: M Mar 16 (075) T Mar 17 (076) Ahead: Momentum dump, 23:00 UT W Mar 18 (077) T Mar 19 (078) F Mar 20 (079) Ahead: Instrument power down (except SWAVES) 16:00 UT S Mar 21 (080) S Mar 22 (081) 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 22 - Mar 23 Behind: Spacecraft behind Sun * Feb 12 Solar Conjunction Readiness Review * Mar DAWN - Ceres arrival * 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 * Aug 17 Ahead: HGA on 1st side lobe * Nov 10 Ahead: HGA on main lobe, offpoint 1 degree Ahead: SSR playback and reconfiguration, S/C checkout * Nov 12 Ahead: Instrument recommissioning * Nov 20 Behind: HGA on 1st side lobe * Dec 30 Ahead: HGA on main lobe 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 * 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 2019: * Mar Ahead: Switch downlink rate to 240 kbps * Apr Behind: Switch downlink rate to 240 kbps 2020: * May Behind: Switch downlink rate to 360 kbps * Jun Ahead: Switch downlink rate to 360 kbps * Jun Behind: Switch downlink rate to 480 kbps * Sep Ahead: Switch downlink rate to 480 kbps 2021: * Jul Behind: Switch downlink rate to 720 kbps * Aug Ahead: Switch downlink rate to 720 kbps