STEREO Weekly Meeting Minutes for 2015-07-21 (Week 30) ANNOUNCEMENTS ------------- * All the science instruments are now producing science data. The IMPACT SIT instrument is currently using an older table set because of commanding problems. See below for details. The IMPACT SWEA and STE instruments will remain off until the spacecraft is returned to the main lobe of the HGA in November. * G&C reaction wheel #3 was power-cycled on Thursday, Jul 16, and returned to normal operations. * The very small angle between the Sun and Earth directions caused problems with four of the HCLT resets starting on day 134 (May 14), causing the spacecraft to offpoint from the Sun temporarily after each reset, leading to some loss of power which resulted in the S/WAVES instrument being powered off for 12 days. See below for details. INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is back to normal operations on the second side lobe. * There are currently no communications with the Behind spacecraft. See below for details. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 29 (Jul 13-19) * On day 194 (Jul 13), during the DSS-63 support for Ahead, while the first 30 minutes RF communications were quite good, then the signal degraded significantly & continuously for the remainder of the support resulting in the disabling of the SSR playback to minimize data loss. A second downlink receiver was placed on-line, however, it showed the same behavior. Only 52% of expected telemetry frames were received. See DR# M108891 for more information. * On day 194 (Jul 13), during the DSS-14 support for Ahead, RF communications were quite good with only occasional dropouts due to solar interference with a command success rate of 98% and 52 missing telemetry frames resulting in over 99% of the expected telemetry frames received. * On day 195 (Jul 14), during the DSS-14 support for Ahead, RF communications were quite good with only occasional dropouts due to solar interference with a command success rate of 98% and 40 missing telemetry frames resulting in over 99% of the expected telemetry frames received. * On day 196 (Jul 15), during the DSS-14 support for Ahead, RF communications were quite good with only occasional dropouts due to solar interference with a command success rate of 100%. At 1726z, a DCD failover at the DSN contributed to the 6 missing telemetry frames resulting in over 99% of the expected telemetry frames received. See DR# G116425 for more information. * On day 196 (Jul 15), during the DSS-43 support for Ahead, RF communications were quite good with only occasional dropouts due to solar interference with a command success rate of 100% and 20 missing telemetry frames resulting in over 99% of the expected telemetry frames received. * On day 197 (Jul 16), during the DSS-14 support for Ahead, RF communications were quite good with only occasional dropouts due to solar interference with a command success rate of 100% and 3 missing telemetry frames resulting in over 99% of the expected telemetry frames received. * On day 198 (Jul 17), during the DSS-63 support for Ahead, RF communications were quite good with only occasional dropouts due to solar interference with 1 dropped command resulting in a command success rate of 97% and 16 missing telemetry frames resulting in over 99% of the expected telemetry frames received. * On day 199 (Jul 18), during the DSS-43 support for Ahead, turbo decoder lock was lost briefly at 0214z due to the effects of solar scintillation. This anomaly resulted in the loss of one frame of spacecraft SSR playback. * On day 199 (Jul 18), during the DSS-63 support for Ahead, turbo decoder lock was lost briefly at 1412z due to the effects of solar scintillation. This anomaly resulted in the loss of one frame of real-time data. * On day 199 (Jul 18), during the second DSS-43 support for Ahead, turbo decoder lock was lost briefly at 200-0046z due to the effects of solar scintillation. This anomaly resulted in the loss of 2 frames of spacecraft SSR playback and real-time data. * On day 200 (Jul 19), during the DSS-63 support, turbo decoder lock was lost intermittently between 1036z and 1739z due to the effects of solar scintillation. This anomaly resulted in the loss of 13 frames of spacecraft SSR playback and real-time data. * The Ahead observatory has successfully exited the 3 month long solar conjunction and all instruments are once again returning science for side lobe operations. The successful superior solar conjunction exit and return to science was highlighted in the NASA image of the day (http://www.nasa.gov /image-feature/stereo-a-spacecraft-returns-data-from-the-far-side-of-the-sun) displaying a recent SECCHI EUVI image. The Ahead observatory is operating nominally on the 2nd side lobe of the HGA to prevent overheating of the HGA feed assembly which is currently at 111 degrees C and decreasing with the HGA angle at 8.6 degrees and increasing, with respect to the spacecraft-Sun line. * On day 194, July 13th, during the track with DSS-14, the STEREO AHEAD observatory continued to operate nominally, 3-axis stabilized while communicating on the 2nd HGA side lobe. The HGA feed temperature remained within the predicted range at 112 degrees C. System momentum was at 7.9 Nms and increasing. Instruments Returned to Science: SWAVES - Continues to collect science. Was on and recording throughout solar conjunction, except for the 12 day period during the SLVS anomalies, May 14th through 26th (days 134-2239z through days 146-2305z). IMPACT MAG - Returned to science data collection on July 9th. IMPACT SEPT - Returned to science data collection on July 9th. SECCHI - Returned to science data collection on July 11th at 192-1955z. IMPACT HET - Returned to science data collection on July 13th. IMPACT Status (from Glenn Mason and Kristin Wortman): As of the end of the track today, HET is producing science. Due to solar interference, efforts to patch LET have been slowed. SWEA and STE will remain powered off until we return to the main lobe. The SIT-A high voltage ramp-up was completed today, and the analog HK values from the instrument are at nominal levels. The largest of the lookup SIT tables has not been successfully reloaded. A problem we had on Friday went away when Kristin switched back to the old GSE, so something in the new setup is causing the large “box” table to be rejected. The smaller SIT tables were loaded from the new GSE on Friday. Using the old GSE there were 2 attempts to load the box table today, and both failed before completing the task. The box table is used in the on-board classification scheme. Judging from the HK table checksum the tables are in some intermediate state, which puzzles us since we had believed that SIT gets the tables from the DPU only when they are complete. There are no particle intensities showing up on the beacon data web page, which could be due to the state of the tables, or might indicate some other problem. When we get today’s data tomorrow we can check this out; with the housekeeping we have only very limited information. PLASTIC Status (from David Heirtzler): Continued increasing high voltages on the PAC from 10 kV to 15 kV. The MCP voltages were stepped up from 1600 V, to 1800 V, and finally to 2400 V. SSR partitions percent full status: IMPACT space weather = 54.2 PLASTIC space weather = 51.0 SWAVES space weather = 52.6 S/C C&DH and G&C Housekeeping SSR Data Return: As analysis of the event and anomaly SSR data indicates that the SLVS anomalies began on day 134, the S/C housekeeping SSR read pointers were repositioned to day 133 to begin playing back anomaly data of interest. There are approximately 12 days of interest and all the G&C housekeeping data has been received. However, as the C&DH record rates are increased to 1 Hz for approximately 24 hours as part of the SLVS response, the C&DH downlink has been slowed. Data downlink today included: C&DH housekeeping = Days 135 through 135-0614z G&C housekeeping = Days 151 through 157-1923z * On Tuesday, July 14th, during the track with DSS-14, the STEREO AHEAD observatory continued to operate nominally, 3-axis stabilized while communicating on the 2nd HGA side lobe. The HGA feed temperature remained within the predicted range at 112 degrees C. System momentum is at 8.3 Nms and increasing. Instruments Returned to Science: SWAVES - Continues to collect science. Was on and recording throughout solar conjunction, except for the 12 day period during the SLVS anomalies, May 14th through 26th (days 134-2239z through days 146-2305z). IMPACT MAG - Returned to science data collection on July 9th. IMPACT SEPT - Returned to science data collection on July 9th. SECCHI - Returned to science data collection on July 11th at 192-1955z. IMPACT HET - Returned to science data collection on July 13th. IMPACT Status (from Glenn Mason and Kristin Wortman): As of the end of the track today, the Magnetometer, SEP, HET are producing science. SWEA and STE will remain powered off until the HGA returns to the main lobe. Due to solar interference, efforts to patch LET have been slowed. Regular science data from SIT-A from July 13 after the HV was ramped up showed that the instrument MCPs were triggering normally, and events were being analyzed. However, the on-board rate computation was returning 0 counts in all boxes, due to the dropouts in the table loads experienced on July 13. Kristin made another attempt to load the matrix box table and it also had dropouts and so was unsuccessful. We discussed the large number of problems experienced with commanding both SIT and LET, where many fairly sort commands do no make it successfully. Given this background we decided that loading the large SIT tables at this time would probably be fruitless. It was decided to reboot SIT-A, since this loads the original table set from SEP central. That table set is obsolete and is not optimally calibrated, but it does return approximately calibrated data which we consider an improvement over no data at all. After the reboot, SIT-A HV was ramped up again, with the last step taken just before the end of the pass (and therefore not observed at the MOC since the latency is about 45 min). Up until that point everything monitored was nominal, and as expected some intensity counts began appearing on the STEREO beacon page SIT-A plot. We will be able to examine the response to the last command step using science data on Wednesday. Our plan is to upload the up-to-date table set when the STEREO commanding link is more robust, perhaps on August 1st, when the SPE angle is at 3.0 degrees. PLASTIC Status (from David Heirtzler): 1.) MCPs brought up to 2590V which was our original operating voltage at the beginning of the mission. 2.) The PAC was brought to -18kV and then monitored for stability. 3.) After a while the PAC was brought to -20kV which is the full mission operating value. 4.) The instrument was put into mode 3 to collect monitor rates. SSR partitions percent full status: IMPACT space weather = 54.5 PLASTIC space weather = 51.3 SWAVES space weather = 52.8 S/C C&DH and G&C Housekeeping SSR Data Return: C&DH housekeeping = Days 135 through 135-0853z G&C housekeeping = Days 157 through 164-1249z Known Issues: 1. G&C reaction wheel #3, currently disabled by MOps, not responding to torque commands. Data analysis has determined that the wheel internal overspeed protection was tripped during a slew back to the Sun during the 2nd SLVS anomaly. A procedure to power cycle the wheel is being developed and tested. 2. Four soft low voltage shutdowns (SLVS) anomalies occurred during solar conjunction, centered about 0 degrees SPE. Analysis of the data received indicates that the observatory responded as designed. The root cause is resetting the observatory while the Earth and Sun vectors are closely aligned. Fault protection recovered the observatory each time. As the SLVS response will power down all instruments, SWAVES data will have a gap starting on day 134 for 12 days. * On Wednesday, July 15th, during the tracks with DSS-14 and 43, the STEREO AHEAD observatory continued to operate nominally, 3-axis stabilized while communicating on the 2nd HGA side lobe. The HGA feed temperature remained within the predicted range at 112 degrees C. System momentum is at 8.7 Nms and increasing. Instruments Returned to Science: SWAVES - Continues to collect science. SWAVES was on and recording throughout solar conjunction, except for the 12 day period during the SLVS anomalies, May 14th through 26th (days 134-2239z through days 146-2305z). IMPACT MAG - Returned to science data collection on July 9th. IMPACT SEPT - Returned to science data collection on July 9th. SECCHI - Returned to science data collection on July 11th at 192-1955z. IMPACT HET - Returned to science data collection on July 13th. IMPACT SIT - Returned to science data collection on July 14th. IMPACT LET - Returned to science data collection on July 15th. IMPACT Status (from Andrew Davis, Glenn Mason, and Kristin Wortman): As of the end of today’s tracks, the Magnetometer, SEPT, HET, SIT, and LET are producing science. SWEA and STE will remain powered off until the HGA returns to the main lobe. We successfully uploaded and verified the final patch for LET Ahead. LET Ahead is now fully operational and collecting science data. At this morning’s pass Kristin confirmed that SIT-A is at its operating HV level and you can see that some counts are appearing on the Beacon web page, although activity ls very low right now. The rate lookup table boxes from the pre-launch set have calibration problems: 1) He intensities are about a factor of 5 low 2) H, O, and Fe intensities are approximately correct (within a factor of 2) If we had PHA data these intensities could be correctly calculated on the ground; however, since all the PHA data is being suppressed that will not be possible. In any case the Beacon data would have the calibration problem, but I think that this is nevertheless much better than zero output from the intensities. Since the daily coverage is so sparse, I believe the actual science loss is very small at this point. We are not requesting any change in the suppression of PHA data. We do not want to attempt table loads until we have good assurance that they will succeed. This is because a failed attempt clears the existing tables and leaves us with nothing. To restore the original tables requires a reboot and then we need to bring up the HV, and that is not risk free. Kristin and I will be in touch with Dan Ossing the week of Aug 3 to assess the situation. Dan expects the link to be much improved then. We are hoping that maybe some other experiments will have been doing some significant commanding loads so that there is data to gauge the chances of the SIT loads going through. If it is dubious, we will wait some more. We never had table upload problems in the past, so this is just a matter of waiting for the communications to get back closer to normal. I am very pleased that SIT-A has survived the hibernation apparently without degradation, and feel sure that the table upload issue will be solved in the next month or so. I’d like to thank Kristin and the flight ops team for all the excellent support. PLASTIC Status (from David Heirtzler): Today we tweaked the high resolution rates so we could better make a determination of what changes are needed to our tables and what voltage we should put on our MCPs. SSR partitions percent full status: IMPACT space weather = 54.8 PLASTIC space weather = 51.5 SWAVES space weather = 53.0 S/C C&DH and G&C Housekeeping SSR Data Return: C&DH housekeeping = Days 135 through 135-1121z G&C housekeeping = Days 164 through 170-1828z Known Issues Status: 1. G&C reaction wheel #3, currently disabled by MOps, not responding to torque commands. Data analysis has determined that the wheel internal overspeed protection was tripped during a slew back to the Sun during the 2nd SLVS anomaly. A procedure to power cycle the wheel has been reviewed with the manufacturer and GSFC management and is scheduled for powering cycling on Thursday at 1645z. Note that fine pointing may be intermittent for a few minutes as momentum is re-distributed amongst the wheels. 2. The four soft low voltage shutdowns (SLVS) anomalies that occurred during solar conjunction were centered about 0 degrees SPE. Analysis of the data received indicates that the observatory responded as designed, however, it was not designed for being out of contact for 3 months. The root cause is resetting the observatory while the Earth and Sun vectors are closely aligned. Fault protection recovered the observatory each time. As the SLVS response will power down all instruments, SWAVES data will have a gap starting on day 134 for 12 days. * On Thursday, July 16th, during the track with DSS-14, the STEREO AHEAD observatory continued to operate nominally, 3-axis stabilized while communicating on the 2nd HGA side lobe. G&C was returned to normal operations today when wheel #3 was power cycled and resumed responding to G&C torque commands. The HGA feed temperature remained within the predicted range at 112 degrees C. System momentum is at 9.1 Nms and increasing. Instruments Returned to Science: SWAVES - Continues to collect science. SWAVES was on and recording throughout solar conjunction, except for the 12 day period during the SLVS anomalies, May 14th through 26th (days 134-2239z through 146-2305z). IMPACT MAG - Returned to science data collection on July 9th. IMPACT SEPT - Returned to science data collection on July 9th. SECCHI - Returned to science data collection on July 11th at 192-1955z. IMPACT HET - Returned to science data collection on July 13th. IMPACT SIT - Returned to science data collection on July 14th. IMPACT LET - Returned to science data collection on July 15th. IMPACT Status: SIT will load calibration tables when the observatory clears the region of solar interference, approximately 3.0 degrees for the 2nd side lobe communications, on or about August 3rd. SWEA and STE will remain powered off, due to very limited telemetry bandwidth during side lobe operations, until the HGA returns to the main lobe. PLASTIC Status (from David Heirtzler): Today we were able to determine that our MCP voltage needed to be raised, so we brought it up to 2950V. The operating value before solar conjunction was 3125V. The thinking we had was that with the new side of the MCP now being exposed we would not need so much bias to get the desired response. We also setup all of our S-channel switching, got all of our table loads in, and implemented limit checking and safing. The plan is to collect data in our science mode over the weekend and turn on our deflectors on Monday. That should have us in our nominal science mode. The reason we've been putting off the deflector and entrance system turn on until now is that we had an issue with a high current just before we went into conjunction and we want to make sure all of our safeties are in place before we do so. SSR partitions percent full status: IMPACT space weather = 55.0 PLASTIC space weather = 51.7 SWAVES space weather = 53.2 S/C C&DH and G&C Housekeeping SSR Data Return: C&DH housekeeping = Days 135 through 135-1403z G&C housekeeping = Days 170 through 177-1445z Known Issues: All closed. Summary of issues from solar conjunction are below. 1. G&C reaction wheel #3 not responding to torque commands. Data analysis determined that the wheel internal overspeed protection was tripped during a slew back to the Sun during the 2nd SLVS anomaly. Wheel #3 was power cycled today at 1645z and again began responding nominally to G&C torque commands. Fine pointing was lost intermittently for about 2 hours as momentum was re-distributed amongst the four wheels. 2. The four soft low voltage shutdowns (SLVS) anomalies that occurred during solar conjunction were centered about 0 degrees SPE. Analysis of the data received indicates that the observatory responded as designed, however, it was not designed for being out of contact for 3 months. The root cause is resetting the observatory while the Earth and Sun vectors are closely aligned. Fault protection recovered the observatory each time. As the SLVS response will power down all instruments, SWAVES data will have a gap starting on day 134 for 12 days. Week 30 (Jul 20-26) * Ahead starts the week at an SPE angle of 2.5 degrees, on the second side lobe. * The 78th momentum dump is scheduled for Thursday, Jul 23, with ignition at 21:00 UT. This momentum dump will be performed with the IMU on. * 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 for space weather is 72%. * 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 space weather 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, mostly between Monday to Wednesday, 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% space weather 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) * There is a return-to-service track for station 63 on Wednesday, Aug 12. There will be no commanding or SSR playback during this track. * 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 third 70 meter track (station 14) 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 space weather 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 space weather coverage of 31%. * Behind starts the week at an SPE angle of 2.4 degrees. There will be no passes for Behind during the week. Week 35 (Aug 24-30) * Ahead starts the week at an SPE angle of 3.9 degrees, on the first side lobe, with SWAVES being prime. * Ahead has 19 passes during the week, with seven passes at 10 kbps, and twelve passes at 633 bps, with overall space weather coverage of 39%. * Behind starts the week at an SPE angle of 2.2 degrees. There will be no passes for Behind during the week. Week 36 (Aug 31-Sep 6) * Ahead starts the week at an SPE angle of 4.1 degrees, on the first side lobe, with IMPACT being prime. * Ahead has 17 passes during the week, with eight passes at 18 kbps, and nine passes at 633 bps, with overall space weather coverage of 35%. * Behind starts the week at an SPE angle of 2.1 degrees. There will be no passes for Behind during the week. Other * A question was raised about the amount of 34 meter time expected during the fall. This will probably be less than currently, because of increasing contentions with other missions. * Ahead will be back on the main lobe starting in November. By the end of the year, the telemetry rate on the 70 meter stations will be back to 720 kbps. Also, once the spacecraft is back on the main lobe, the NOAA antenna partners will be able to bring down space weather telemetry again. * A question was raised about the PLASTIC current issue. The PLASTIC team reports that the high current that they were seeing just before solar conjunction is now lower, though still higher than it was earlier in the mission. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 30: M Jul 20 (201) T Jul 21 (202) W Jul 22 (203) T Jul 23 (204) Ahead: Momentum dump, 21:00 UT 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) Ahead: Return-to-service track with station 63 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. ------------------------------------------------------------------------------- Scheduled activities for Week 35: M Aug 24 (236) T Aug 25 (237) W Aug 26 (238) T Aug 27 (239) F Aug 28 (240) S Aug 29 (241) S Aug 30 (242) Notes: * Ahead operating on the first side lobe, in SWAVES-prime mode. * No tracks for Behind due to superior solar conjunction. ------------------------------------------------------------------------------- Scheduled activities for Week 36: M Aug 31 (243) T Sep 01 (244) W Sep 02 (245) T Sep 03 (246) F Sep 04 (247) S Sep 05 (248) S Sep 06 (249) 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