STEREO Weekly Meeting Minutes for 2017-09-12 (Week 37) 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. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 36 (Sep 4-10) * On day 247 (Sep 4) Monday, during the DSS-14 support, SLE command and telemetry binds were lost at 1843z. At 1856z, command and telemetry binds were reestablished. This anomaly resulted in the loss of 13 minutes of commanding and real-time telemetry data. * On day 247 (Sep 4), the STEREO Ahead star tracker reset yesterday. Autonomy recovered the star tracker after 35 seconds. This resulted in fine pointing being lost for 85 seconds, with the spacecraft rolling by 0.4 degrees before recovering attitude control. The star tracker would have to be unavailable for 30 minutes before autonomy turns on the IMU. This was the 6th reset since launch, and the first since the cooler was set to a lower temperature set point back in December 2014. The last star tracker reset occured in September 2014, coincidently also on Labor Day, and was caused by a large flux of high energy particles. In that previous case, both STEREO spacecraft were affected, and it took several hours for the star trackers to promote back to operational mode. In the present case, there was an M-class flare directed towards Earth, but the space environment at the STEREO Ahead spacecraft was quiet. * On day 250 (Sep 7) Thursday, during the DSS-34 support,a DSN project interface test was conducted to validate SLE telemetry server operations and data delivery with SLE software V1.4. As this was a test track, there was no SSR playback or instrument commanding. The MOC configured the primary command workstation to connect to the test SLE server at the DSN with the backup command workstation using the operational SLE server. Each workstation received the same number of telemetry frames for each virtual channel. Four commands were successfully received by the Ahead observatory. * On day 253 (Sep 10) Sunday, during the DSS-63 support,turbo decoder lock was lost briefly at 1747z. This anomaly resulted in the loss of 2 frames of SSR data. * On day 247 (Sep 4) Monday, the star tracker on STEREO Ahead reset at 11:32:38z. The star tracker was immediately promoted back to AAD mode by fault protection at 247-11:32:57z. Diagnostic data indicated the reset cause was due to a CPU Error, same as previous resets. With no rate data available for that 19 seconds, a 0.4 degree X-axis roll error occurred which resulted in the loss of fine pointing for a total of 85 seconds, from 11:32:44z through 11:34:09z. This was the 6th star tracker reset on the Ahead observatory since launch. * On day 249 (Sep 6) Wednesday, the 102nd momentum dump was executed successfully at 1730z, which imparted an estimated delta V of 0.108 m/sec. This was the 21st momentum dump that did not use the IMU. After thruster operations complete, there was a 0.42 degree of roll angle error which was dampened out over the next 4.2 minutes. Fine pointing stabilized 2.25 minutes after completion of the momentum dump. During the momentum dump, there was an autonomy rule fire that disabled the COR-1 telescope. This is still being investigated (question as to whether it was the temperature limit or autonomy rule limit that was in error). * Ahead operating nominally with average daily return was 5.8 Gbits during this week. * Ahead has 10 tracks during the week, and overall coverage is nominal. There are seven tracks at 720 kbps, two at 240 kbps, and one at 160 kbps. * Recovery tracks for Behind are scheduled each day, of 2.5-4 hour durations. Last week, recovery attempts occurred once per day, station 14 was used for the whole week. Unfortunately, no carrier was detected. The transmitter had problems on 4 of 7 tracks, which happens. Requesting maximum power output for transmission of 20 kWatts. * On day 247 (Sep 4) Monday, during a 3.5 hour support for Behind with DSS-14, 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 248 (Sep 5) Tuesday, during a 3 hour support for Behind with DSS-14, the uplink was delayed due to low transmit power. The transmitter was recalibrated for 20 kW at 1233z and 207 commands were transmitted for battery state of charge recovery. This anomaly resulted in the loss of commanding during the first two frequency segments. See DR #G118420 for more information. * On day 249 (Sep 6) Wednesday, during a 4 hours support for Behind with DSS-14, 440 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 22 of the 36 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. * On day 250 (Sep 7) Thursday, during a 3 hour support for Behind with DSS-14,the uplink was delayed 24 minutes due to transmitter calibration issue. The transmitter was recalibrated for 17 kW at 1242z and 280 commands were transmitted during the support. See DR #G118427 for more information. 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 251 (Sep 8) Friday, during a 4 hour support for Behind with DSS-14,the maximum transmit power was limited to 16 kW, due to a transmitter calibration issue, and 420 commands were transmitted during the support. See DR #G118430 for more information. 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 252 (Sep 9) Saturday, during a 4 hour support for Behind with DSS-14, 420 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 253 (Sep 10) Sunday, during a 4 hour support for Behind with DSS-14,the transmitter tripped off-line for 11 minutes at 1319z. See DR #G118439 for more information. 399 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 255 (Sep 12) Tuesday begins the window for expecting to hear from Behind based on sufficient solar array input to power up the batteries & geometry of one of the LGAs to be visible from the Earth. Week 37 (Sep 11-17) * On day 254 (Sep 11) Monday, Ahead experienced low transmit power on Station 14, the transmit power was dropped to 4.4 kWatts, which is sufficient. * On day 256 (Sep 13) Wednesday, Behind will test the DSN conical search patterns using 0.4 degree conical search pattern (that forms a honeycombed shape) to search for the downlink on Behind. DSN has tested this before and will test it again tomorrow. * Ahead has 11 tracks during the week, and overall coverage is nominal. There are seven tracks at 720 kbps, three at 240 kbps, and one at 160 kbps. * Recovery tracks for Behind are scheduled every day, of 2.5-4 hour durations, also recorded by radio science folks for increased fidelity on the downlink signal detection. For two of the tracks, we will use 1 kHz sweep pattern with Thursday for battery recovery and Friday for carrier recovery. This is the original sweep frequency used last year for detecting downlink. Week 38 (Sep 18-24) * Behind reaches perihelion on Sep 18. * A demonstration test (SLE track & telemetry commanding (V1.4)) with Ahead using station 25 is scheduled for Thursday, Sep 21. There will be no SSR playback or instrument commanding during this track. The downlink rate will be 160 kbps. This will be the transition track for Ahead with the new DSN software. * Ahead has 8 tracks during the week, all at 720 kbps, and overall coverage is nominal. * Recovery tracks for Behind are scheduled every day with 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. Week 39 (Sep 25-Oct 1) * The current extended mission #3 officially ends on Sep 30. The Senior Review is ongoing. * Ahead has 10 tracks during the week, and overall coverage is nominal. There are seven tracks at 720 kbps, one at 240 kbps, and two at 160 kbps. * Recovery tracks for Behind are scheduled every day using the 70-m antenna, of 3-3.8 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Monday for battery recovery and Tuesday for carrier recovery. 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 3-3.8 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Monday for battery recovery and Tuesday for carrier recovery. 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 3-3.8 hour durations with the 1 kHz frequency segmented acquisition sequence being used on Monday for battery recovery and Tuesday for carrier recovery. 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. 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. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 37: M Sep 11 (254) T Sep 12 (255) W Sep 13 (256) T Sep 14 (257) F Sep 15 (258) S Sep 16 (259) S Sep 17 (260) 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. ------------------------------------------------------------------------------- Scheduled activities for Week 38: M Sep 18 (261) Behind: Perihelion T Sep 19 (262) W Sep 20 (263) T Sep 21 (264) Ahead: Demonstration test with station 25 F Sep 22 (265) S Sep 23 (266) S Sep 24 (267) 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. ------------------------------------------------------------------------------- Scheduled activities for Week 39: M Sep 25 (268) T Sep 26 (269) W Sep 27 (270) T Sep 28 (271) F Sep 29 (272) S Sep 30 (273) S Oct 01 (274) 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. ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- Scheduled activities for Week 43: M Oct 16 (296) T Oct 17 (297) W Oct 18 (298) T Oct 19 (299) F Oct 20 (300) S Oct 21 (301) S Oct 22 (302) 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. ------------------------------------------------------------------------------- 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=