STEREO Weekly Meeting Minutes for 2016-05-31 (Week 22) ANNOUNCEMENTS ------------- * None INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally on the main lobe of the high gain antenna. * There are currently no communications with the Behind spacecraft. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 21 (May 23-29) * On day 144 (May 23), during the DSS-55 support for Ahead, turbo decoder lock was lost briefly at 1734z. This anomaly resulted in the loss of 1 frame of SSR data. * On day 147 (May 26), before the DSS-25 support for Ahead began, at 1230z, it was noticed that the SLE telemetry binds were lost on all command workstations. While this should have been due to the scheduled JPL to GSFC RIONet circuit switching maintenance, this maintenance had been postponed. After several failed re-attempts, the binds were successfully acquired before the track started. Also, the Ahead voice box was not functioning properly prior to the DSS-25 track, i.e., JPL could hear us, but we could not hear them (the Behind voice box was working nominally). The fault was isolated to a misconfiguration at NASCOM to rectified and two-way voice communications with JPL. Later in the support, turbo decoder lock was lost intermittently between 1655z and 148-0045z. These anomalies resulted in the loss of 11 frames of SSR data. * On day 148 (May 27), during the DSS-55 support for Ahead, turbo decoder lock was lost briefly at 1142z. This anomaly resulted in the loss of 5 frames of SSR data. * On day 150 (May 29), during the DSS-55 support for Ahead, telemetry lock was lost intermittently between 1556z and 1729z due to heavy rain at the Madrid complex. This anomaly resulted in the loss of 12,406 frames of real-time telemetry and SSR data. See DR #M109390 for more information. There was some speculation during the meeting that El Nino might be responsible for the large number of storms that the Madrid station seems to be experiencing lately. * The Ahead observatory operated nominally during this week on the center of the HGA main lobe. The HGA feed assembly was at 94 degrees C and decreasing with the HGA angle at 11.4 degrees and increasing, with respect to the spacecraft-Sun line. * On day 145 (May 24), the G&C wheel speed avoidance (CTL_WHLBADOFFSET) parameter for increasing the band about zero speed to 30.79 rads/second was adjusted in RAM on Ahead at 1602z. This update is attempting to minimize the increase in fine pointing losses from wheel 2 stiction when it passes through zero speed. * On day 147 (May 26), during the DSS-25 support for Ahead, PLASTIC real-time commanding was conducted to switch geometric factors from the main channel to the small channel to improve science data return, based on whether the particle flux is large or small. * The average daily science data return for Ahead was 5.7 Gbits during this week. * On day 148 (May 27), during the DSS-26 34m support for Behind, using the 80 kW transmitter to minimize 70m contentions, 270 commands were sent for battery state of charge recovery. * On day 149 (May 28), during the DSS-26 34m support for Behind, using the 80 kW transmitter to minimize 70m contentions, 351 commands were sent for battery state of charge recovery. * On day 150 (May 29), during the DSS-14 70m support for Behind, 500 commands were sent for transmitter carrier recovery. The Allen Telescope Array observed concurrently; however, no downlink signal was detected by them or the DSN. Due to the duration of the support and the increased commands for each step, only 25 of the 36 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. * As time goes by, the ephemeris error increases degrading DSN antenna pointing. However, with time the spacecraft range also decreases improving RF communications and the ability for other assets to acquire data on Behind. Analysis indicates that the total RF gain change is significant and the probability of command success increases with time. * The next phased uplink array attempt to contact Behind will be Jun 11, 12. Starting in July, attempts to contact Behind will be reduced to once monthly, alternating months between phased uplink array passes, and single-dish passes which have a wider beam. This will continue through June 2017, after which recovery attempts will be suspended until January 2020, when the nominal uplink rate returns to 125 bps. Week 22 (May 30-Jun 5) * Turbo decoder lock was lost briefly this morning (May 31) during the station 55 pass for Ahead. This resulted in the loss of 5 frames of data. * The 88th momentum dump on Ahead will be carried out this afternoon (May 31), with ignition at 20:00 UT. This will be the seventh momentum dump without using the gyros. * Jun 2, the MOC will be loading new C&DH fault protection rules (version 2.3.19) and macros (version 1.1.29) to EEPROM. These changes are designed to provide better protection in case of the loss of one of the reaction wheels, or low solar array voltage. These are the same procedures that were used during the recovery last July. * Ahead has 12 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, three at 360 kbps, five at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 15.0 degrees. There are no passes for Behind during the week. Week 23 (Jun 6-12) * Ahead has 10 passes during the week, and overall coverage is nominal. There are 4 passes at 720 kbps, one pass at 360 kbps, four passes at 240 kbps, and one pass at 160 kbps. * Behind starts the week at an SPE angle of 15.1 degrees. * Uplink array attempts to recover Behind are scheduled for June 11, 12. Each pass will start out with Ahead for 1.9 hours for phase calibration. There will be no instrument calibration or SSR playback during these calibration passes. Following calibration, the stations will attempt to command Behind for 3.3 hours on June 11 for battery recovery, and for 5.3 hours on June 12 for carrier recovery along with station 14. The last 35 minutes will be below the 27.5 degree elevation limit, so a waiver has been requested. Otherwise, the broadcast power would be reduced from 80 to 60 kW. The Allen Telescope Array will also listen for a signal from Behind. Week 24 (Jun 13-19) * Ahead has 12 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, four at 360 kbps, five at 240 kbps, and one at 160 kbps. * Behind starts the week at an SPE angle of 15.1 degrees. There are no tracks for Behind during the week. Week 25 (Jun 20-26) * Ahead has 10 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, two at 360 kbps, four at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 15.2 degrees. Recovery efforts for Behind are Monday-Wednesday, Jun 20-22. The battery recovery tracks will be undertaken with the 80 kW transmitter on station 26. The Allen Telescope Array will listen for a signal Behind spacecraft, along with Arecibo for 1.3 hours. Week 26 (Jun 27-Jul 3) * The 5th battery discharge operation on Ahead is scheduled for Monday, Jun 27, for about 2 hours starting at 17:00. * Ahead has 12 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, two at 360 kbps, four at 240 kbps, and three at 160 kbps. * Behind starts the week at an SPE angle of 15.2 degrees. There are no tracks for Behind. Week 27 (Jul 4-10) * Monday, July 4 is a holiday for APL. * Monday, July 4 is aphelion for Ahead. * The 89th momentum dump on Ahead is on Wednesday Jul 6 at 16:00 UT. This will be the eighth momentum dump without using the gyros. * Ahead has 15 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, two at 360 kbps, five at 240 kbps, and four at 160 kbps. * Behind starts the week at an SPE angle of 15.1 degrees. Recovery efforts for Behind are currently scheduled for Friday-Sunday, Jul 8-10. The battery recovery tracks will be undertaken with the 80 kW transmitter on station 26. Station 14 will be used for carrier recovery on July 10, along with the Allen Telescope Array. Week 28 (Jul 11-17) * Ahead has 10 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, one at 360 kbps, four at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 15.1 degrees. * Uplink array attempts for Behind are scheduled for July 16, 17. The first 1.9 hours each day will use the Ahead spacecraft to calibrate the phasing between the stations. There will be no SSR playback or instrument commanding during these passes. Following the calibration, there will be a 3.3 hour pass for Behind on Jul 16 for battery recovery, and a 5.3 hour pass on Jul 17 for carrier recovery. The elevation will drop below 27.5 degrees for the last 48 minutes, so a waiver has been requested; otherwise, the station 26 power would need to be reduced from 80 to 60 kW. Station 14 will listen for the Behind carrier, along with the Allen Telescope Array. * A decision will be made in the near future as to whether the July attempt to recovery Behind will be the single-dish option or the phased array option. Other * A question was raised about the use of the DSN science receiver for Behind recovery. The MOC has requested the use of this receiver, but has not heard back yet. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 22: M May 30 (151) Memorial Day T May 31 (152) Ahead: Momentum dump, 20:00 UT W Jun 01 (153) T Jun 02 (154) F Jun 03 (155) S Jun 04 (156) S Jun 05 (157) ------------------------------------------------------------------------------- Scheduled activities for Week 23: M Jun 06 (158) T Jun 07 (159) W Jun 08 (160) T Jun 09 (161) F Jun 10 (162) S Jun 11 (163) Behind: Phased array recovery attempt S Jun 12 (164) Behind: Phased array recovery attempt ------------------------------------------------------------------------------- Scheduled activities for Week 24: M Jun 13 (165) T Jun 14 (166) W Jun 15 (167) Ahead: STEREO Subsystem Assessment Review T Jun 16 (168) F Jun 17 (169) S Jun 18 (170) S Jun 19 (171) ------------------------------------------------------------------------------- Scheduled activities for Week 25: M Jun 20 (172) T Jun 21 (173) W Jun 22 (174) T Jun 23 (175) F Jun 24 (176) S Jun 25 (177) S Jun 26 (178) ------------------------------------------------------------------------------- Scheduled activities for Week 26: M Jun 27 (179) Ahead: Battery maintenance, 17:00 UT T Jun 28 (180) W Jun 29 (181) T Jun 30 (182) F Jul 01 (183) S Jul 02 (184) S Jul 03 (185) ------------------------------------------------------------------------------- Scheduled activities for Week 27: M Jul 04 (186) Independence Day Ahead: Perihelion T Jul 05 (187) Juno arrival at Jupiter W Jul 06 (188) Ahead: Momentum dump, 16:00 UT T Jul 07 (189) F Jul 08 (190) S Jul 09 (191) S Jul 10 (192) ------------------------------------------------------------------------------- Scheduled activities for Week 28: M Jul 11 (193) T Jul 12 (194) W Jul 13 (195) T Jul 14 (196) F Jul 15 (197) S Jul 16 (198) Behind: Phased array recovery attempt S Jul 17 (199) Behind: Phased array recovery attempt ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2016: * Dec Behind: Resume LGA downlink capability on 70 m DSN 2017: 2018: * Mar 5 Ahead: Mercury transit 2019: * Mar Ahead: Switch downlink rate to 240 kbps for 34 meter * Apr Behind: Switch downlink rate to 240 kbps for 34 meter 2020: * May Behind: Switch downlink rate to 360 kbps for 34 meter * Jun Ahead: Switch downlink rate to 360 kbps for 34 meter * Jun Behind: Switch downlink rate to 480 kbps for 34 meter * Sep Ahead: Switch downlink rate to 480 kbps for 34 meter 2021: * Jul Behind: Switch downlink rate to 720 kbps for 34 meter * Aug Ahead: Switch downlink rate to 720 kbps for 34 meter