STEREO Weekly Meeting Minutes for 2016-06-28 (Week 26) 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 25 (Jun 20-26) * On day 172 (Jun 20), during the DSS-63 support for Ahead, turbo decoder lock was lost briefly at 0846z. This anomaly resulted in the loss of 19 frames of SSR data. See DR #M109430 for more information. * On day 173 (Jun 21), during the DSS-55 support for Ahead, initial telemetry acquisition occurred 35 minutes late at 0845z as the antenna was red. SSR pointers were repositioned to minimize data loss. Later in the support, turbo decoder lock was lost briefly at 1212z. These anomalies resulted in the loss of 8 frames of SSR data. See DR #M109435 for more information. * On day 176 (Jun 24), during the DSS-25 support for Ahead, turbo decoder lock was lost briefly at 1654z and again at 1818z. This anomaly resulted in the loss of 2 frames of SSR data. * On day 176 (Jun 24), a Subsystem Assessment Review for the spacecraft bus was held at APL to review performance post solar conjunction for AHEAD. All subsystems reported continuing nominal performance post conjunction on the Ahead observatory, with the exception of the known increase in fine pointing loss for G&C. While the impact to imaging science has been reduced by tuning G&C parameters, the G&C team is continuing to analyze performance and determine the cause of the changed behavior. * The Ahead observatory operated nominally during this week on the center of the HGA main lobe. The HGA feed assembly was at 86 degrees C and decreasing with the HGA angle at 12.5 degrees and increasing, with respect to the spacecraft-Sun line. * The average daily science data return for Ahead was 5.6 Gbits during this week. * On day 172 (Jun 20), during the DSS-26 34m support for Behind, using the 80 kW transmitter to minimize 70m contentions, the transmitter tripped off-line at 1714z. This was originally thought to be due to a coolant flow anomaly, but has now been traced to a faulty connector. The transmitter was re-calibrated and placed back on line at 1810z. This anomaly resulted in the failure to radiate approximately 72 battery recovery commands covering 8 frequency segments. 279 commands were sent for battery state of charge recovery. See DR# G117268 for more information. * On day 173 (Jun 21), 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 174, during the DSS-14 70m support for Behind, 560 commands were sent for transmitter carrier recovery. The Arecibo Observatory (2.3 hours) and the Allen Telescope Array observed concurrently, however, no downlink signal was detected by them or the DSN, which included the Radio Science Receiver. Due to the duration of the support and the increased commands for each step, only 28 of the 36 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. * 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. The next uplink array attempt will be Jul 16-17. * A question was raised about the effect of the recent high temperatures in California on DSN operations. Each transmitter has its own coolant system, and the same procedures are used regardless of the temperature. Week 26 (Jun 27-Jul 3) * The 5th battery discharge operation on Ahead was successfully carried out yesterday (Jun 27). No problems were noted. * Turbo decoder lock was lost briefly yesterday, resulting in the loss of 102 telemetry frames. * An uplink frequency ramping test was carried out this morning (Jun 28) between ESA/ESOC and STEREO Ahead. This test is in support of the Cassini mission. Science data collection was unaffected, but 2-3 minute gaps in the space weather data are expected. * 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 Juno mission will arrive at Jupiter late on July 4 (UT: early July 5), which is resulting in a tight DSN schedule. * 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. There are no tracks for Behind during the week, since recovery attempts are now only once a month. Week 28 (Jul 11-17) * A MOC interface test with the new station 36 at Canberra is scheduled for Wednesday, Jul 13, for 1 hour starting at 14:00 UT. This will not involve the spacecraft. * Station 35 will conduct an engineering test of pointing to the Ahead spacecraft on Thursday, Jul 14, in support of the upcoming OSIRIS-REx mission. There will be no effect on operations. * 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, using the Radio Science Receiver, along with the Allen Telescope Array. Week 29 (Jul 18-24) * The 35th SECCHI stepped calibration roll for Ahead is scheduled for Monday, Jul 18, starting at 13:00 UT. System momentum will be about 6 N-m-s. This is the aphelion roll, and the fourth without using the gyros. * A 3 hour project interface test with the new station 36 at Canberra is scheduled for Wednesday, Jul 20. The new station is expected to be operational sometime later this year. The downlink rate will be 160 kbps, and there will be no SSR playback or instrument commanding during the pass. * Ahead has 12 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, three at 360 kbps, five at 240 kbps, and one at 160 kbps. * Behind starts the week at an SPE angle of 15.0 degrees. There are no tracks for Behind during the week. Week 30 (Jul 25-31) * Ahead has 11 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, two at 360 kbps, and seven at 240 kbps. One of the 70 meter passes was converted to a 34 meter pass to help out the Rosetta mission, which is nearing the end of their mission. * Behind starts the week at an SPE angle of 14.9 degrees. There are no tracks for Behind during the week. Week 31 (Aug 1-7) * Ahead has 12 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, two at 360 kbps, seven at 240 kbps, and one at 160 kbps. * Behind starts the week at an SPE angle of 14.7 degrees. There are no tracks for Behind during the week. Week 32 (Aug 8-14) * The 90th momentum dump on Ahead is scheduled for 19:30 UT on Tuesday, Aug 9. This will be the nineth momentum dump without using the gyros. * Ahead has 14 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, four at 360 kpbs, six at 240 kbps, and one at 160 kbps. * Behind starts the week at an SPE angle of 14.6 degrees. There are no tracks for Behind during the week. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 26: M Jun 27 (179) Ahead: Battery maintenance, 17:00 UT T Jun 28 (180) Ahead: Uplink frequency ramping test with ESA/ESOC 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: Aphelion 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) MOC interface test with station 36, 14:00 UT T Jul 14 (196) Ahead: Station 35 pointing test for OSIRIS-REx F Jul 15 (197) S Jul 16 (198) Behind: Phased array recovery attempt S Jul 17 (199) Behind: Phased array recovery attempt ------------------------------------------------------------------------------- Scheduled activities for Week 29: M Jul 18 (200) Ahead: SECCHI stepped calibration roll, 13:00 UT T Jul 19 (201) W Jul 20 (202) Ahead: Project interface test with station 36 T Jul 21 (203) F Jul 22 (204) S Jul 23 (205) S Jul 24 (206) ------------------------------------------------------------------------------- Scheduled activities for Week 30: M Jul 25 (207) T Jul 26 (208) W Jul 27 (209) T Jul 28 (210) F Jul 29 (211) S Jul 30 (212) S Jul 31 (213) ------------------------------------------------------------------------------- Scheduled activities for Week 31: M Aug 01 (214) T Aug 02 (215) W Aug 03 (216) T Aug 04 (217) F Aug 05 (218) S Aug 06 (219) S Aug 07 (220) ------------------------------------------------------------------------------- Scheduled activities for Week 32: M Aug 08 (221) T Aug 09 (222) Ahead: Momentum dump, 19:30 UT W Aug 10 (223) T Aug 11 (224) F Aug 12 (225) S Aug 13 (226) S Aug 14 (227) ------------------------------------------------------------------------------- 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