STEREO Weekly Meeting Minutes for 2017-10-03 (Week 40) ANNOUNCEMENTS ------------- * None INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally on the main lobe of the high gain antenna. * Attempts to recover Behind have transitioned from a weekly schedule to a daily schedule. Two days each week use the older 1 kHz frequency acquisition sequence, in case the nominal frequency has shifted, with one day devoted to battery recovery, and one day devoted to carrier recovery. This typically is scheduled for Monday and Tuesday. The remainder of the week uses the faster 4 kHz frequency acquisition sequence. Two of those days use a search pattern consisting of two diamonds, based on the estimated uncertainty in the ephemeris. The double diamond pattern is executed twice, once to send commands, and then again 40 minutes later to listen for the carrier. This search pattern will be run twice a week, once for battery recovery, and once for carrier recovery. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 39 (Sep 25-Oct 1) * On day 270 (Sep 27), during the DSS-35 support for Ahead, real-time monitor data was lost in the MOC for 3 minutes beginning at 0712z. See DR #N110742 for more information. * On day 272 (Sep 29), during the DSS-14 support for Ahead, telemetry lock was lost for one minute starting at 1654z. This anomaly resulted in the loss of 2299 frames of real-time telemetry and SSR data. See DR #G118516 for more information. * The average daily science data return for Ahead was 6.0 Gbits during this week. * On day 268 (Sep 25), during a 3.8 hour support for Behind with DSS-14, 297 commands were transmitted for battery state of charge recovery. Due to the duration of the support, only 30 of the 36 frequency segments were commanded. * On day 269 (Sep 26), during a 3.5 hours support for Behind with DSS-14, 380 commands were sent for transmitter carrier recovery. No carrier was detected by either the DSN station or the radio science receiver team. Due to the duration of the support and the increased commands for each step, only 19 of the 36 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. * On day 270 (Sep 27), during a 3.1 hour support for Behind with DSS-14, the uplink was delayed 56 minutes due to a transmitter calibration issue. The issue was resolved at 1336z and 210 commands were transmitted during the support for battery state of charge recovery. The 1st use of a newly developed diamond shaped repeating search pattern with 0.037 degree steps and 10.8 minute dwells. Commanding started at the 6th of 16 positions in search pattern. See DR #G118507 for more information. * On day 271 (Sep 28), during a 3.6 hour support for Behind with DSS-43 for Behind, 380 commands were transmitted during the support. No carrier was detected by either the DSN station or the radio science receiver team after attempting to power on the TWTA for 30 minutes. Transitioned to battery recovery operations for the remainder of the support which consists of repeatedly sweeping a 4 kHz uplink range and sending commands for IEM switched power and PDU 1553 interface bus off. * On day 272 (Sep 29), during a 3 hour support for Behind with DSS-14, the station initially used an incorrect sweep range, resulting in 25 missed commands from 1st and 2nd positions in the search pattern. The issue was resolved at 1302z and 295 commands were transmitted during the support for carrier recovery. This was the 2nd test of the diamond shaped repeating search pattern with 0.037 degree steps and 10.8 minute dwells. The initial starting point was set to 0.02 degrees for 100% uplink optimization. * On day 273 (Sep 30), during a 3 hour support for Behind with DSS-14, 320 commands were transmitted during the support. No carrier was detected by either the DSN station or the radio science receiver team after attempting to power on the TWTA for 30 minutes. Transitioned to battery recovery operations for the remainder of the support which consists of repeatedly sweeping a 4 kHz uplink range and sending commands for IEM switched power and PDU 1553 interface bus off. * On day 274 (Oct 1), during a 3 hour support for Behind with DSS-63, 320 commands were transmitted during the support. No carrier was detected by either the DSN station or the radio science receiver team after attempting to power on the TWTA for 30 minutes. Transitioned to battery recovery operations for the remainder of the support which consists of repeatedly sweeping a 4 kHz uplink range and sending commands for IEM switched power and PDU 1553 interface bus off. * Based on G&C geometric analysis and GSFC modeling, daily recovery efforts began on August 21st, and will continue through November 5th. With significant support of the DSN, three different acquisition sequences are being utilized weekly to re-establish communications with STEREO Behind using a 70m track: 1. 4 kHz Sweep - consists of repeatedly sweeping a 4 kHz uplink frequency range for which the BLF was found during the first recovery attempt. Commands are sent to power on the transmitter for 30 minutes. If no carrier signal is detected, the transmitter is powered off and battery recovery commands are sent consisting power off the IEM switched power and PDU 1553 interface bus. This acquisition sequence is used 3 times each week. 2. Frequency Segmented 1 kHz - To ensure command reception, the original faster frequency segmented acquisition sequence is used 2 days each week. This consists of an 18 kHz frequency range divided into 18, 1 kHz segments, each swept at a 1 kHz rate, stepping down in frequency and them back up again. During each segment, the MOC sends for battery recovery on the first day and on the second day, carrier recovery commands. This was the acquisition sequence that originally detected the Behind downlink in August 2016. 3. 4 kHz Sweep with Search Pattern - The DSN created a diamond shaped search pattern with 7 steps of 0.037 deg, dwelling 10 min & 49 sec/step. There are two diamond patterns of 4 steps to cover the area of the estimated ephemeris error. The starting point is offset 0.02 deg for uplink optimization. Repeating each diamond pattern accounts for the 30 minute RTLT. This search pattern acquisition sequence is used twice weekly during 3 hour supports, sending battery recovery commands at each step during the first day and on the second day, sending carrier recovery commands at each step. Week 40 (Oct 2-8) * Ahead has 13 tracks during the week, and overall coverage is nominal. There are seven tracks at 720 kbps, three at 240 kbps, and three at 160 kbps. * Recovery tracks for Behind are scheduled every day using the 70-m antenna, of 3-4 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Monday for battery recovery and Tuesday for carrier recovery. Diamond shaped search patterns will be used on Wednesday (battery) and Thursday (carrier). Week 41 (Oct 9-15) * The 103rd momentum dump on Ahead is scheduled for Monday, Oct 9, starting at 12:00 UT. This will be the 22nd momentum dump without using the gyros. The dump is being scheduled early due to track coverage. * Due to entering a DSN high contention period, STEREO will start using the ESA 35 meter stations again. The ESA Malarque station will be used for 3 hours on Tuesday, Oct 10, with a telemetry rate of 160 kbps. Station 43 is going down for 5-6 months, and will be followed by station 63 for a similar period. * Ahead has 12 tracks during the week, and overall coverage is nominal. There are five tracks at 720 kbps, two at 240 kbps, and five at 160 kbps. * Recovery tracks for Behind are scheduled every day using the 70-m antenna, of 2.5-4 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Monday for battery recovery and Tuesday for carrier recovery. Double diamond shaped search patterns will be used on Thursday (battery) and Friday (carrier). Week 42 (Oct 16-22) * Four ESA stations will be used three times during the week, including both New Norcia and Malargue stations. * Ahead has 16 tracks during the week, and overall coverage is nominal. There are three tracks at 720 kbps, two at 240 kbps, and eleven at 160 kbps. * Recovery tracks for Behind are scheduled every day using the 70-m antenna, of 2.5-3.7 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Thursday for battery recovery and Friday for carrier recovery. Double diamond shaped search patterns will be used on Monday (battery) and Wednesday (carrier). Week 43 (Oct 23-29) * 11th launch anniversary of the STEREO mission on Oct. 25th. * Ahead has 19 tracks during the week, and overall coverage is nominal. There are three tracks at 720 kbps, four at 240 kbps, and twelve at 160 kbps (two tracks are using ESA stations). * Recovery tracks for Behind are scheduled every day using the 70-m antenna, of 2.5-4 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Tuesday for battery recovery and Wednesday for carrier recovery. Double diamond shaped search patterns will be used on Monday (battery) and Thursday (carrier). Week 44 (Oct 30-Nov 5) * Daily standard time in the US ends on Sunday, Nov 5. * Ahead has 16 tracks during the week, and overall coverage is nominal. There are two tracks at 720 kbps, three at 240 kbps, and eleven at 160 kbps. * This is the last week of daily attempts to contact Behind. Recovery tracks are scheduled every day using 70 m stations, of 2-3.2 hour durations. DSN time starting this week is very contentious due to the line-up of multiple missions in the same region of the sky, and the fact that only two 70 meter DSN dishes are operating. The 1 kHz frequence segmented acquisition sequence will be used on Tuesday for battery recovery, and Wednesday for carrier recovery. Double iamond shaped search patterns will be used on Monday (battery) and Friday (carrier). Week 45 (Nov 6-12) * Ahead has 18 tracks during the week, and overall coverage is nominal. There are two tracks at 720 kbps, three at 240 kbps, and thirteen at 160 kbps. Four of these tracks use ESA stations. * Tracks to recover Behind switch to a weekly schedule, with tracks scheduled to keep within the 3 day onboard timer. Behind recovery tracks are scheduled for Tuesday, Friday, and Saturday. The Tuesday and Friday passes will use the double diamond search pattern, with the first for battery recovery, and the second for carrier recovery. Week 46 (Nov 13-19) * The 104th momentum dump on Ahead is scheduled for Wednesday, Nov 15, with ignition at 16:00 UT. This will be the 23rd dump without using the gyros. * A 2.2 hour demonstration track with station 25 is scheduled for Monday, Nov 13. There will be no instrument commanding or SSR playback during this track. * Ahead has 16 tracks during the week, and overall coverage is nominal. There is one track at 720 kbps, three at 240 kbps, and twelve at 160 kbps. Two of those tracks use ESA stations. * Double diamond search patterns for Behind recovery are scheduled for Thursday, Nov 16 (battery) and Saturday, Nov 19. Another recovery track is scheduled for Monday, Nov 13. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 40: M Oct 02 (275) T Oct 03 (276) W Oct 04 (277) T Oct 05 (278) F Oct 06 (279) S Oct 07 (280) S Oct 08 (281) Notes: * Behind recovery attempts each day. The Monday and Tuesday Behind recovery passes use the original frequency acquisition sequence with the broader 18 kHz range. The first pass is for battery recovery, and the second is for carrier recovery. Double diamond shaped search patterns on Wednesday (battery) and Thursday (carrier). ------------------------------------------------------------------------------- Scheduled activities for Week 41: M Oct 09 (282) Ahead: Momentum dump, 12:00 UT T Oct 10 (283) W Oct 11 (284) T Oct 12 (285) F Oct 13 (286) S Oct 14 (287) S Oct 15 (288) Notes: * Behind recovery attempts each day. The Monday and Tuesday Behind recovery passes use the original frequency acquisition sequence with the broader 18 kHz range. The first pass is for battery recovery, and the second is for carrier recovery. Double diamond shaped search patterns on Thursday (battery) and Friday (carrier). ------------------------------------------------------------------------------- Scheduled activities for Week 42: M Oct 16 (289) T Oct 17 (290) W Oct 18 (291) T Oct 19 (292) F Oct 20 (293) S Oct 21 (294) S Oct 22 (295) Notes: * Behind recovery attempts each day. The Thursday and Friday Behind recovery passes use the original frequency acquisition sequence with the broader 18 kHz range. The first pass is for battery recovery, and the second is for carrier recovery. Double diamond shaped search patterns on Monday (battery) and Wednesday (carrier). ------------------------------------------------------------------------------- Scheduled activities for Week 43: M Oct 23 (296) T Oct 24 (297) W Oct 25 (298) 11th anniversary of STEREO launch T Oct 26 (299) F Oct 27 (300) S Oct 28 (301) S Oct 29 (302) Notes: * Behind recovery attempts each day. The Tuesday and Wednesday Behind recovery passes use the original frequency acquisition sequence with the broader 18 kHz range. The first pass is for battery recovery, and the second is for carrier recovery. Double diamond shaped search patterns on Monday (battery) and Thursday (carrier). ------------------------------------------------------------------------------- Scheduled activities for Week 44: M Oct 30 (303) T Oct 31 (304) W Nov 01 (305) T Nov 02 (306) F Nov 03 (307) S Nov 04 (308) S Nov 05 (309) Daylight savings time ends in US Notes: * Behind recovery attempts each day. The Tuesday and Wednesday Behind recovery passes use the original frequency acquisition sequence with the broader 18 kHz range. The first pass is for battery recovery, and the second is for carrier recovery. Double diamond shaped search patterns on Monday (battery) and Friday (carrier). ------------------------------------------------------------------------------- Scheduled activities for Week 45: M Nov 06 (310) T Nov 07 (311) Behind: Recovery track, DSN 14 (search pattern, battery) W Nov 08 (312) T Nov 09 (313) F Nov 10 (314) Behind: Recovery track, DSN 14 (search pattern, carrier) S Nov 11 (315) Behind: Recovery track, DSN 14 S Nov 12 (316) Notes: * Behind recovery attempts switch back to weekly, roughly every 2-3 days. ------------------------------------------------------------------------------- Scheduled activities for Week 46: M Nov 13 (317) Ahead: Demonstration track with station 25 Behind: Recovery track, DSN 63 T Nov 14 (318) W Nov 15 (319) Ahead: Momentum dump, 16:00 UT T Nov 16 (320) Behind: Recovery track, DSN 63 (search pattern, battery) F Nov 17 (321) S Nov 18 (322) Behind: Recovery track, DSN 63 (search pattern, carrier) S Nov 19 (323) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 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 2022: 2023: * May 5 Behind: Mercury transit * Jul 17 Behind: Closest approach to Earth * Aug 13 Ahead: Closest approach to Earth 2024: 2025: * Apr 7 Ahead: Mercury transit 2026: 2027: * Feb 1 Behind: Mercury transit 2028: 2029: * Jun 30 Ahead: Mercury transit