STEREO Weekly Meeting Minutes for 2015-07-07 (Week 28) ANNOUNCEMENTS ------------- * The 78th momentum dump for Ahead is expected to be scheduled for sometime near the end of July, though it may be earlier. * When the Ahead solid state recorder is reconfigured after side-lobe operations, 108.7 Mbits previously reserved for EA mode will be released to the instrument teams. A plan for using this allocation was previously passed around. Since there were no responses from the instrument teams, it is assumed that this plan meets with their approval. The plan increases the IMPACT, PLASTIC, and SWAVES recorder allocations by the following amounts: IMPACT: 453 + 41.5 = 494.5 PLASTIC: 453 + 41.5 = 494.5 SWAVES: 281 + 25.7 = 306.7 INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating in "safe mode" for superior solar conjunction. Transition to normal operations starts tomorrow (Jul 8). * There are currently no communications with the Behind spacecraft. See below for details. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 27 (Jun 29-Jul 5) * On day 180 (Jun 29), during the DSS-14 support for Ahead, after the 32 HCLT initiated system reset with the observatory rotating at 5 degrees per minute on the 2nd HGA side lobe, telemetry was received for 65 minutes during each 72 minute rotation. 488 good telemetry frames or 65% of the expected frames were received. * On day 181 (Jun 30), during the DSS-63 support for Ahead, with the observatory rotating at 5 degrees per minute on the –Z LGA, telemetry lock was never received due to the low signal strength as the LGA is on the edge of the hemispherical pattern. Carrier lock was solid throughout the support with the carrier power between -169 and –172 dBm. * On day 182 (Jul 1), during the DSS-43 support for Ahead, with the observatory rotating at 5 degrees per minute on the +Z LGA, telemetry lock was never received due to the low signal strength as the LGA is on the edge of the hemispherical pattern. Carrier lock was good, with occasional drop outs, with the carrier power between -169 and –174 dBm. * On day 183 (Jul 2), during the DSS-14 support for Ahead, after the 33rd HCLT initiated system reset with the observatory rotating at 5 degrees per minute on the 2nd HGA side lobe, telemetry reception was very poor, most likely due to solar interference from a CME, with only 81 good telemetry frames or 13% of the expected frames were received. * On day 184 (Jul 3), during the DSS-43 support for Ahead, with the observatory rotating at 5 degrees per minute on the -Z LGA, telemetry lock was never received due to the low signal strength as the LGA is on the edge of the hemispherical pattern. Carrier lock was good, with intermittent drop outs for several minutes, with the carrier power between -168 and –170 dBm. * On day 185 (Jul 4), during the DSS-14 support for Ahead, with the observatory rotating at 5 degrees per minute on the +Z LGA, telemetry lock was never received due to the low signal strength as the LGA is on the edge of the hemispherical pattern. Carrier lock was good, with occasional drop outs, with the carrier power between -168 and –174 dBm. * On day 186 (Jul 5), during the DSS-43 support for Ahead, after the 34th HCLT initiated system reset with the observatory rotating at 5 degrees per minute on the 2nd HGA side lobe, telemetry was received for 66 minutes during each 72 minute rotation. 847 good telemetry frames or 94% of the expected frames were received. * The behavior of the telemetry reception during the week shows that it's very sensitive to solar activity. Current space weather predictions show a 45% chance of an M-class flare. The MOC is scheduling extra time to account for space weather effects. Daily status emails will be distributed to keep every up-to-date. * On day 180, June 29th, after the 32nd HCLT initiated system reset at a 1.6 degree SPE angle, the DSN received a strong downlink signal again from STEREO AHEAD post superior solar conjunction at 2303z. The observatory was operating nominally, rotating as planned at 5 deg/min while communicating on the 2nd HGA side lobe. The IMPACT and PLASTIC space weather SSR partitions are unchanged, 53 and 51 percent full respectively, and SWAVES, which continues to be on recording at one packet per minute, was at 49.9 percent full. The HGA feed temperature remains within the predicted range at 113 degrees C. System momentum was constant at the anticipated level of 8.0 Nms. As occurred during solar conjunction entry, after the 32nd HCLT reset, the star tracker was again “lazy” in re-acquiring a solution causing IMU2 to power on for two hours. G&C reaction wheel #3 continued to not respond to G&C torque commands. * On day 183, July 2nd, after the 33rd HCLT initiated system reset at a 1.7 degree SPE angle, the DSN received a strong downlink signal again from STEREO AHEAD post superior solar conjunction at 1515z. The observatory was operating nominally, rotating as planned at 5 deg/min while communicating on the 2nd HGA side lobe. The IMPACT and PLASTIC space weather SSR partitions are unchanged, 53 and 51 percent full respectively, and SWAVES, which continues to be on recording at one packet per minute, was at 50.5 percent full. The HGA feed temperature remains within the predicted range at 113 degrees C. System momentum was constant at the anticipated level of 8.0 Nms. As occurred during solar conjunction entry, after the 33rd HCLT reset, the star tracker was again “lazy” in re-acquiring a solution causing IMU2 to power on for two hours. G&C reaction wheel #3 continued to not respond to G&C torque commands. * On day 186, July 5th, after the 34th HCLT initiated system reset at a 1.8 degree SPE angle, the DSN received a strong downlink signal again from STEREO AHEAD post superior solar conjunction at 1408z. The observatory continues to operate nominally, rotating as planned at 5 deg/min while communicating on the 2nd HGA side lobe. The IMPACT and PLASTIC space weather SSR partitions are unchanged, 53 and 51 percent full respectively, and SWAVES, which continues to be on recording at one packet per minute, is at 51.0 percent full. The HGA feed temperature remains within the predicted range at 113 degrees C. System momentum is at 7.8 Nms. As occurred during solar conjunction entry, after the 34th HCLT reset, the star tracker was again “lazy” in re-acquiring a solution causing IMU2 to power on for two hours. G&C reaction wheel #3 continues not responding to G&C torque commands. While the observatory continues to rotate nominally and is designed to do so with three reaction wheels, after reviewing hardware simulator and G&C standalone simulation results for transitioning to 3-axis control, wheel #3 G&C control will be disabled on July 8th. Further contingency response to this G&C anomaly will be conducted after G&C SSR data is downlinked and analyzed. Detailed G&C anomaly data, which was captured on the SSR, may take 6 weeks to receive, due to the low downlink rate on the 2nd HGA side lobe and depending upon when the anomaly occurred. * Simulations show that the spacecraft should be safe when it transitions from rotating at 5 degrees per minute to 3-axis stabilized, even before wheel #3 is disabled. Examination of the behavior while the spacecraft is rotating shows that it has an average speed of 5 degrees per minute, but the instantaneous speed varies, with the speed being lower for part of the rotation, and then being faster for another part to catch up. Attitude information is being stored once every 30 seconds, which SWAVES can use in the analysis of their stored data. Attitude data will not be available for periods when the star tracker is off, which is believed to be for about 4-5 minutes after the system resets. * Recovery operations for Behind have been suspended until the SPE angle gets beyond 3.5 degrees, which will happen in late November. Coverage for Behind starts in December. Tracks will be longer than what were used previously, with ~4 hour tracks for the first two days, and then a 6.5 hour track on the third day to try to turn on the transmitter. The Failure Review Board’s recommended faster frequency segmented acquisition sequence will be tested with the Ahead observatory in September. The DSN uplink arraying capability will be tested again with the Ahead observatory in October and November, and when it is ready, it will be used to increase the spacecraft received signal power to assist with Behind recovery commanding. With time the spacecraft range improves RF communications and the ability for other assets to acquire data on Behind. LGA uplink margin returns to 6 dB for the 7.8 bps rate in March 2016 and 125 bps in December 2019 and the LGA downlink margin returns to 3 dB for the 12 bps rate in December 2016 and 35 bps in March 2018. Week 28 (Jul 6-12) * The Ahead spacecraft starts the week at 1.9 degrees SPE, increasing to 2 degrees on Tuesday, Jul 7. * At 00:00 UT on Tuesday, Jul 7, the spacecraft commanded itself to go back into 3-axis stabilized mode. As far as the MOC can determine, this happened as planned. There was no change in the downlink signal level. About three hours later, it then returned to rotating once it switched to the -Z LGA. Solid carrier lock was achieved during the following station 63 pass. * The 35th HCLT reset will occur on Wednesday, Jul 8, following which the spacecraft will go back into 3-axis stabilized mode. Spacecraft recovery will begin during the track following this reset, starting at 13:50 UTC. The telemetry rate will be commanded to 3 kbps. One of the first commands will be to disable wheel #3. A recent leap second will be applied. Instrument recovery will start on Friday, Jul 10, with SECCHI recovery starting on Saturday, Jul 11. The MOC will send daily status emails. If the Sun is quiet, it may be possible to start instrument recovery sooner; on the other hand, it might be later than planned. Current plans are to power on the IMPACT IDPU at 17:00 on Friday, followed by the SEP, and then PLASTIC. SECCHI power-up will occur on Saturday, Jul 11, due to the team being currently on travel. * The uplink rates will be low, 125 bps, and the communication status will depend both on the weather at the station, and on space weather. Because of solar scintillation, there will be more margin on the downlink than on the uplink. Coordination of who will be commanding at any time will done via the voicebox. The round-trip light-time is 33 minutes. There is an 8 hour support every day. Week 29 (Jul 13-19) * There is a 70 meter pass for Ahead every day, starting at around 14:00 UT. These passes will be staffed by the MOC. * Ahead starts the week at an SPE angle of 2.2 degrees, on the second side lobe. * New Horizons will make its closest approach to Pluto on Tuesday, Jul 14. However, New Horizons and STEREO do not share views, so this will not have an effect on STEREO coverage. * There are 15 tracks for Ahead during the week. Eleven of these tracks are with 70 meter stations at 3 kbps; the rest are with 34 meter stations at 633 bps. Overall coverage for space weather is 45%. Week 30 (Jul 20-26) * Ahead starts the week at an SPE angle of 2.5 degrees, on the second side lobe. * Ahead reaches aphelion on Sun, Jul 26. * Ahead has 21 tracks during the week, with eight 70 meter tracks at 3 kbps, and thirteen 34 meter tracks at 633 bps. There are 70 meter tracks every day, with about 8 hours per track. Total coverage is 73%. * Behind starts the week at an SPE angle of 3.1 degrees. There will be no passes for Behind during the week. Week 31 (Jul 27-Aug 2) * Ahead starts the week at an SPE angle of 2.8 degrees, on the second side lobe. * Ahead has 18 tracks during the week, with eight 70 meter tracks at 3 kbps, and ten 34 meter tracks at 633 bps. Total coverage is 59%. * Behind starts the week at an SPE angle of 2.9 degrees. There will be no passes for Behind during the week. Behind reaches perihelion on Aug 2. Week 32 (Aug 3-9) * Ahead starts the week at an SPE angle of 3.1 degrees, on the second side lobe. * Ahead has 19 tracks during the week. It is short 8.1 hours of 70 meter time, due to critical events for the Juno mission, but there are 70 meter tracks every day. Ten tracks are with 34 meter stations, resulting in 65% coverage during the week. * Behind starts the week at an SPE angle of 2.7 degrees. There will be no passes for Behind during the week. Week 33 (Aug 10-16) * Ahead starts the week at an SPE angle of 3.3 degrees, on the second side lobe. This will be the last week on the second side lobe. * Ahead will shift to the 1st side lobe near the end of the second 70 meter track on Sunday, Aug 16. There will be a 34 meter support following this shift, though still at 633 bps. * Ahead has 17 tracks during the week, nine using 70 meter stations at 3 kbps, and eight using 34 meter stations at 633 bps, giving an overall coverage of 55%. * Behind starts the week at an SPE angle of 2.5 degrees. There will be no passes for Behind during the week. Week 34 (Aug 17-23) * Ahead starts the week at an SPE angle of 3.6 degrees, on the first side lobe. Alternating weeks of IMPACT-prime and SWAVES-prime will resume, starting with IMPACT being prime. * Ahead has 14 passes during the week, with seven passes at 10 kbps, and 7 passes at 633 bps, with overall coverage of 31%. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 28: M Jul 06 (187) T Jul 07 (188) Ahead: 3-axis stabilized for several hours starting 0:00 UT W Jul 08 (189) Ahead: 35th HCLT reset, followed by spacecraft recovery T Jul 09 (190) F Jul 10 (191) Ahead: Start of instrument recovery S Jul 11 (192) Ahead: Start of SECCHI recovery S Jul 12 (193) Notes: * Ahead operating on second side lobe starting Jul 8. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 29: M Jul 13 (194) T Jul 14 (195) W Jul 15 (196) T Jul 16 (197) F Jul 17 (198) S Jul 18 (199) S Jul 19 (200) Notes: * Ahead operating on second side lobe. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 30: M Jul 20 (201) T Jul 21 (202) W Jul 22 (203) T Jul 23 (204) F Jul 24 (205) S Jul 25 (206) S Jul 26 (207) Ahead: Aphelion Notes: * Ahead operating on second side lobe. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 31: M Jul 27 (208) T Jul 28 (209) W Jul 29 (210) T Jul 30 (211) F Jul 31 (212) S Aug 01 (213) S Aug 02 (214) Notes: * Ahead operating on second side lobe. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 32: M Aug 03 (215) T Aug 04 (216) W Aug 05 (217) T Aug 06 (218) F Aug 07 (219) S Aug 08 (220) S Aug 09 (221) Notes: * Ahead operating on second side lobe. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 33: M Aug 10 (222) T Aug 11 (223) W Aug 12 (224) T Aug 13 (225) F Aug 14 (226) S Aug 15 (227) S Aug 16 (228) Ahead: Switch to first side lobe. Notes: * Ahead operating on second side lobe. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 34: M Aug 17 (229) T Aug 18 (230) W Aug 19 (231) T Aug 20 (232) F Aug 21 (233) S Aug 22 (234) S Aug 23 (235) Notes: * Ahead operating on the first side lobe, in IMPACT-prime mode. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2015: * Nov 10 Ahead: HGA on main lobe, offpoint 1 degree, 240 kbps Ahead: SSR playback and reconfiguration, S/C checkout Ahead: Resume space weather broadcast to NOAA stations * Nov 12 Ahead: Instrument recommissioning * Nov 16 Ahead: HGA on main lobe, offpoint 1 degree, 360 kbps Behind: Resume Behind recovery efforts * Nov 20 Behind: HGA on 1st side lobe * Nov 30 Ahead: HGA on main lobe, offpoint 1 degree, 480 kbps * Dec 30 Ahead: HGA on main lobe 2016: * Jan 2 Behind: HGA on main lobe, offpoint 1 degree Behind: SSR playback and reconfiguration, S/C checkout * Jan 5 Behind: Instrument recommissioning * Jan 12 Behind: HGA on main lobe * 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