STEREO Weekly Meeting Minutes for 2015-06-30 (Week 27) ANNOUNCEMENTS ------------- * Weekly STEREO telecons are now resumed. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating in "safe mode" for superior solar conjunction. Normal operations should resume in July 2015. * There are currently no communications with the Behind spacecraft. See below for details. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 26 (Jun 22-28) and previous weeks * During the period when Ahead was passing behind the Sun, its carrier wave was detected several times by the Arecibo and Green Bank observatories. DSN passes for Ahead resumed last Friday, Jun 26. * On day 177 (Jun 26), during the DSS-14 support for Ahead, after the 31 HCLT initiated system reset with the observatory rotating at 5 degrees per minute on the 2nd HGA side lobe, telemetry was received for the first time post solar conjunction for 63 minutes during each 72 minute rotation. 723 good telemetry frames or 85% of the expected frames were received. * On day 177, June 26th, the first telemetry was received from STEREO Ahead post superior solar conjunction after the 31st HCLT initiated system reset at a 1.5 degree SPE angle. The DSN received a strong downlink signal early and telemetry was received at 1924z. The observatory is operating nominally continuing to rotate slowly 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 was on during the duration of solar conjunction recording at one packet per minute, is at 49.3 percent full. The HGA feed temperature was within the predicted range at 113 degrees C. System momentum was at the anticipated level of 8.0 Nms. As occurred during solar conjunction entry, after the 31st HCLT reset, the star tracker was again "lazy" to re-acquire a solution causing IMU2 to power on for two hours. One additional anomaly was noted, reaction wheel #3 was not responding to G&C torque commands. The reaction wheel current and temperature are both nominal. While the observatory continues to rotate nominally and is designed to do so with three reaction wheels, as the observatory is healthy, contingency response to this G&C anomaly will be delayed until no earlier than July 8th. 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. Once the uplink communication link is stable at the 2.0 degree SPE angle on day 189, July 8th, the observatory will be recovered, instruments will be powered on, and limited science data collection will resume using the 2nd HGA side lobe. Instruments are currently scheduled to begin powering up on day 191, July 10th. Once the HGA returns to the main lobe use in mid-November, nominal daily science collection and data return will resume. * On day 124, May 4th, through day 178, June 27th, Behind recovery operations were conducted as the observatory has cleared solar interference for LGA communications. Based on the Failure Review Board recommendations, the recovery operations consist of recovering the battery state of charge for the first two days. On the third day, the transmitter will be commanded on to receive the carrier. Recovery operations were significantly different than what was conducted in January. This included a faster frequency segmented acquisition sequence, sweeping a lower frequency range, battery state of charge recovery and powering on the transmitter using only short critical commands. The frequency segmented acquisition sequence is a significant departure for deep space communications which typically require a slow sweep of the entire best lock frequency range. The DSN staff cleverly developed a 10 second automated uplink sweep consisting of 18 one kHz frequency segments followed by repeatedly sending short commands. The JPL radio science receiver capability for the carrier recovery tracks was not used due to a funding issue. * On day 176 (Jun 25), during the DSS-14 70m support for Behind, 225 commands were sent for battery state of charge recovery. * On day 177 (Jun 26), the Behind DSS-14 70m support for battery state of charge recovery was moved to Ahead for the first opportunity for telemetry post solar conjunction. * On day 178 (Jun 27), during the DSS-63 70m station support for Behind, 320 commands were sent for powering on the transmitter. No downlink signal was detected. Due to the duration of the support and the increased commands for each step, only 16 of the 18 frequency segments were commanded. Three commands must be received sequentially to power on the transmitter. The Green Bank Radio Telescope also observed, with reduced sensitivity due to a cryogenics anomaly, for 3.25 hours beginning at 0945z, however, it did not detect the downlink. * Operations to recover Behind are now suspended, due to the spacecraft's retrograde motion back toward the Sun. * The Green Bank and Arecibo telescopes have not detected any signal from Behind, though Green Bank did detect Ahead's low gain antenna. * The acquisition sequence currently being used for Behind will be tested with Ahead, tentatively scheduled for the first week of September. * Uplink array tests will also be carried out with Ahead later in the year. The eventual plan is to combine the signal from three DSN stations, with one of the stations having significantly stronger uplink power than the other two. This capability is still under development. Week 27 (Jun 29-Jul 5) * On Monday, 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 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 49.9 percent full. The HGA feed temperature remains within the predicted range at 113 degrees C. System momentum is 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 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, as the observatory is healthy, contingency response to this G&C anomaly will be delayed until no earlier than July 8th. The G&C team is actively investigating the anomaly and determining corrective action. 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. * Another DSN track for Ahead was carried out this morning (Jun 30), this time on the -Z LGA. There was a solid carrier lock throughout the entire pass, but, as expected, the signal was not strong enough to achieve telemetry lock. * Three-hour tracks for Ahead are scheduled for every day up through next Wednesday (Jul 8), when the nominal track duration will be increased to 8 hours. * The 33rd HCLT reset will trigger early Thursday, Jul 2. The instrument teams can use the 2.5 hour track following this, starting at 15:50 UT, to test their ability to receive telemetry. * Friday, Jul 3, is an APL holiday for Independance Day. * Ahead will be at an SPE angle of 1.8 degrees on Saturday, Jul 4. * The 34th HCLT reset will trigger on Sunday, Jul 5. This will be followed by a 3.5 hour pass from Madrid. In between these passes with the HGA, there will also be passes using one or the other of the LGAs; however, it's doubtful that telemetry lock will be achieved. * There will be no passes for the Behind spacecraft during the week, due to retrograde motion carrying it back into solar conjunction. The SPE angle will be decreasing down as far as 2 degrees over the next few months. 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 will command itself to go back into 3-axis stabilized mode. It will then return to rotating once it switches to the -Z LGA. * 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. Instrument recovery will start on Friday, Jul 10, with SECCHI recovery starting on Saturday, Jul 11. * The uplink rates will be low, 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. * SWAVES asked whether it would be possible to submit time-tagged commands for uplink to the spacecraft. Because of the limited telemetry rate, the MOC will not be dumping the stored command buffer unless necessary. However, SWAVES can put their commands into the queue as usual, and they will go up when time is available. In this case, SWAVES doesn't anticipate needing to do real-time commanding. * SECCHI asked whether the weekly schedule generation had been resumed. It was confirmed that these are now appearing on the server. * There will be no passes for Behind during the week. Week 29 (Jul 13-19) * Ahead starts the week at an SPE angle of 2.2 degrees, on the second side lobe. * 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%. * 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. * All the 70 meter passes will be staffed by the MOC. These passes during general business hours, and are about 8 hours per day. * It is anticipated that the instruments will be recovered by Jul 17. * Instrument queues will be open during the 34 meter tracks. * A question was raised about tracking data. One-way tracking data is already available. Two-way tracking data will be available starting July 8. * Ephemeris data using post-recovery data will be available starting July 22. * There will be no passes for Behind during the week. Week 30 (Jul 20-26) * Ahead starts the week at an SPE angle of 2.5 degrees, on the second side lobe. * 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%. * Ahead reaches aphelion on Sun, Jul 26. * 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. * There will be a momentum dump for Ahead somewhere in late July or early August. * 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 55% 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, eight using 70 meter stations at 3 kbps, and nine 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. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 27: M Jun 29 (180) Ahead: 32nd hard command loss timer reset T Jun 30 (181) Leap second at end of UTC day W Jul 01 (182) T Jul 02 (183) Ahead: 33rd hard command loss timer reset F Jul 03 (184) Independence Day holiday S Jul 04 (185) S Jul 05 (186) Ahead: 34th hard command loss timer reset Notes: * Ahead in safe mode for superior solar conjunction. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2015: * Aug 17 Ahead: HGA on 1st side lobe * 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