STEREO Weekly Meeting Minutes for 2016-01-19 (Week 03) ANNOUNCEMENTS ------------- * None INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally, back on the main lobe of the high gain antenna. * There are currently no communications with the Behind spacecraft. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 02 (Jan 11-17) * On day 013 (Jan 13), MOps was alerted that the DSS-14 transmitter had been declared red due with an ETRO of DOY 019-2300z. To allow for repair work on the transmitter, the DSS-14 track for Ahead was shortened by one hour to a duration of 1.3 hours. Two additional supports, on day 017 with DSS-54 and day 018 with DSS-74, ESA New Norcia, were added to preserve daily commanding on Ahead. Thankfully, STEREO has access to the ESA stations. This anomaly resulted in the loss of 1.1 hours of commanding and two-way tracking data. See DR# G116883 for more information. * On day 014 (Jan 14), during the DSS-55 support for Ahead, the SSR pointers were repositioned to prevent data loss due to ending the previous DSS-14 support an hour early. * On day 014 (Jan 14), the 5th uplink array test for STEREO using DSS-24, 25, and 26 was successfully conducted by the DSN. The new configuration consisted of three 34m stations using the 80 kW and two 20 kW transmitters with the HGA main lobe and with the MOC sending no-op commands. An approximate 12 dBm increase in received uplink power, as compared to a single 34m, was demonstrated with all 10 no-op commands being received correctly using the 7.8125 bps uplink rate. This is roughly equivalent to four times the received power of a 70 meter station. * The Ahead observatory operated nominally during this week on the center of the HGA main lobe. The HGA feed assembly was at 117 degrees C and decreasing with the HGA angle at 7.4 degrees and increasing, with respect to the spacecraft-Sun line. * On day 014 (Jan 14), the Ahead observatory reached perihelion in the orbit. * On day 015 (Jan 15), the SECCHI SSR science partition (#19) filled and blocked at 2106z for 0.25 hours. This was due to the shortening of the DSS-14 track on day 013 by one hour to support transmitter repair work. However, the SSC reported that no data gap was evident for SECCHI on that day, so the filling of the buffer appears to have had minimal impact. * The average daily science data return for Ahead was 4.5 Gbits during this week. * On day 015 (Jan 15), MOps was alerted that DSS-26 80 kW transmitter had been declared red with an ETRO of DOY 020-2300z. The 20 kW transmitter was used to send 180 commands for battery state of charge recovery on Behind. During the support, the transmitter tripped off-line at 1846z. After recalibrating, the transmitter resumed uplinking at 1849z. This anomaly resulted in the loss of commanding one frequency segment. See DR# G116889 and G116893 for more information. * On day 016 (Jan 16), during the DSS-26 34m support for Behind, using the 20 kW transmitter as the 80 kW transmitter was red, 207 commands were sent for battery state of charge recovery. * On day 017 (Jan 17), during the DSS-14 70m support for Behind, 380 commands were sent for transmitter carrier recovery. The Green Bank Radio Telescope and Allen Telescope Array observed concurrently, however, no downlink signal was detected by them or the DSN. Due to the duration of the support and the increased commands for each step, only 19 of the 36 frequency segments were commanded. The pass duration was sufficient to send all the frequency segments at least once, but not twice as desired. Three commands must be received sequentially to power on the transmitter. Week 03 (Jan 18-24) * A 2.6 hour ranging test with station 15 with Ahead was carried out yesterday (Jan 18). * The 84th momentum dump for Ahead is scheduled for Thursday, Jan 21, with ignition at 23:00 UT. The telemetry rate will be 160 kbps. This will be the third momentum dump without using the IMU. * Ahead has 11 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, two passes at 240 kbps, and five passes at 160 kbps. An additional ESA pass was added on Monday, Jan 18, due to the station 14 transmitter being red. * Behind starts the week at an SPE angle of 7.2 deg. Recovery efforts for Behind are Monday, Tuesday, and Wednesday, Jan 18-20. The Tuesday pass is being undertaken with station 26 using the 20 kW transmitter, because the 80 kW transmitter is currently red. The Allen Telescope Array will be supporting the carrier recovery pass tomorrow (Jan 20). * SECCHI would like to upload a software patch to address the scheduling problems they've been having, and ask if there are any constraints they should be aware of. The MOC responded that there were no constraints other than those which appear in the weekly schedule. SECCHI will let the MOC know when they plan to upload the patch. * SECCHI has two avenues with which they are addressing their scheduling problems. One is a workaround which they've adopted, and which they're currently evaluating to see if it is robust enough to support next month's calibration roll. The other is the software patch. Once they've verified that at least one of these approaches work, they'll notify the MOC that they're ready for the roll. * A large snowstorm is predicted to hit the Washington area at the end of the week. The MOC is expected to operate correctly even if unattended, and backup power is available if the commercial power is lost. * The SECCHI patch is a two-step process, and will be tested first before being committed. Week 04 (Jan 25-31) * The 3.75 hour station 55 pass on Sunday, Jan 31, has been converted into a DSN tracking test pass. There is plenty of coverage from other passes during this period. There will be no instrument commanding or SSR playback during the station 55 pass. * Ahead has 10 passes during the week, and overall coverage is nominal. There are two passes at 720 kbps, three passes at 240 kbps, and five passes at 160 kbps. * Behind starts the week at an SPE angle of 7.7 degrees. Recovery efforts for Behind are Wednesday, Thursday, and early Saturday, Jan 27-30. The first two tracks will be undertaken with station 26 using the 80 kW transmitter. Week 05 (Feb 1-7) * Ahead has 10 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, three passes at 240 kbps, and four passes at 160 kbps. * Behind starts the week at an SPE angle of 8.3 degrees. Recovery efforts for Behind are Monday, Tuesday, and Thursday, Feb 1-4. The battery conditioning tracks will be undertaken with the 80 kW transmitter on station 26. Week 06 (Feb 8-14) * The third EEPROM refresh on both IMUs on STEREO Ahead will be carried out on Wednesday, Feb 10. This refresh is recommended by the manufacturer, and is carried out every three years. The IMUs will be powered up, but disabled. The operation takes a few minutes, and IMUs will be powered down again at the end. * Behind will be at aphelion on Friday, Feb 12. * Ahead has 12 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, two passes at 240 kbps, and six passes at 160 kbps. * Behind starts the week at an SPE angle of 8.8 degrees. Recovery efforts for Behind are on Friday, Saturday, and Sunday, Feb 12-14. The battery conditioning tracks will be undertaken with the 80 kW transmitter on station 26. Week 07 (Feb 15-21) * The sixth and final uplink array test with Ahead will be carried out on Feb 19. This will combine the previously tested phased array of stations 24, 25 at 20 kW, and station 26 at 80 kW, with the frequency segmented acquisition mode for recovering Behind. The total pass duration is 4 hours. Combining array phasing with the frequency segmented acquisition mode is very challenging. If this test works, then it will be ready for use with the Behind recovery efforts, starting in March, and once a month thereafter. The uplink rate will be 7.8 bps, and the downlink will be non-coherent. There will be no instrument commanding or SSR playback during the test. * Ahead has 9 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, two at 240 kbps, and three at 160 kbps. * Behind starts the week at an SPE angle of 9.4 degrees. Recovery efforts for Behind are on Friday, Saturday, and Sunday, Feb 19-21. The battery conditioning track on Saturday will be carried out with the 80 kW transmitter on station 26. Week 08 (Feb 22-28) * The 85th momentum dump on Ahead is scheduled for Monday, Feb 22, with ignition at 22:00 UT. This will be the fourth no-gyro momentum dump. * Ahead has 13 passes during the week, and overall coverage is nominal. There are four passes at 720 kpbs, three at 240 kbps, and six at 160 kbps. * Behind starts the week at an SPE angle of 9.9 degrees. Recovery efforts for Behind are on Friday, Saturday, and Sunday, Feb 26-28. The battery conditioning tracks will be carried out with the 80 kW transmitter on station 26. Other * Starting around the middle of March, the frequency of attempts to contact Behind will be decreased from once a week to once every other week, to reduce the load on the DSN. Attempts using the uplink array configuration will be scheduled once a month. * A question was raised about the telemetry rate for the instruments. If some of the telemetry time originally projected for Behind was diverted to Ahead, then more data could be brought down from Ahead. The MOC pointed out that STEREO is using less overall DSN time than originally projected, but that more of it was 70 meter time. They will consider asking for more DSN time for Ahead. The SSC expressed the opinion that additional telemetry would be used to undo some of the changes made for the extended mission, as described in the STEREO Science Operations Plan (SOP). For reference, this document is available at http://stereo-ssc.nascom.nasa.gov/publications/stereo_sop.pdf * The SSC pointed out that, based on the average daily downlink volumes in recent weeks, the in situ instruments might already be able to increase their telemetry rates. Because the 70 meter stations are currently being used more heavily than they were before conjunction, the current downlink volumes are closer to those predicted for the 240 kbps rate than for the 160 kbps, as expressed in Table 1.10 of the SOP. However, station 14 will be going down for maintenance for several months starting in the next few days, and it might be worth waiting to see how this will affect the data return. Some instrument teams expressed that they would prefer data continuity to a higher telemetry rate. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 03: M Jan 18 (018) Ahead: Ranging test with station 15 T Jan 19 (019) W Jan 20 (020) T Jan 21 (021) Ahead: Momentum dump, 23:00 UT F Jan 22 (022) S Jan 23 (023) S Jan 24 (024) ------------------------------------------------------------------------------- Scheduled activities for Week 04: M Jan 25 (025) T Jan 26 (026) W Jan 27 (027) T Jan 28 (028) F Jan 29 (029) S Jan 30 (030) S Jan 31 (031) Ahead: DSN tracking test with station 55 ------------------------------------------------------------------------------- Scheduled activities for Week 05: M Feb 01 (032) T Feb 02 (033) W Feb 03 (034) T Feb 04 (035) F Feb 05 (036) S Feb 06 (037) S Feb 07 (038) ------------------------------------------------------------------------------- Scheduled activities for Week 06: M Feb 08 (039) T Feb 09 (040) W Feb 10 (041) Ahead: IMU EEPROM refresh T Feb 11 (042) F Feb 12 (043) Behind: Aphelion S Feb 13 (044) S Feb 14 (045) ------------------------------------------------------------------------------- Scheduled activities for Week 07: M Feb 15 (046) T Feb 16 (047) W Feb 17 (048) T Feb 18 (049) F Feb 19 (050) Ahead: Uplink array test with stations 24,25,26 S Feb 20 (051) S Feb 21 (052) ------------------------------------------------------------------------------- Scheduled activities for Week 08: M Feb 22 (053) Ahead: Momentum dump, 22:00 UT T Feb 23 (054) W Feb 24 (055) T Feb 25 (056) F Feb 26 (057) S Feb 27 (058) S Feb 28 (059) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2016: * Mar 3 Behind: Resume LGA uplink capability on 70 m DSN * Apr 6 Ahead: Resume LGA uplink capability on 70 m DSN * May 16 Both: Post Solar Conjunction Assessment Review * Jul 5 Juno arrival at Jupiter * Dec Behind: Resume LGA downlink capability on 70 m DSN 2017: 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