STEREO Weekly Meeting Minutes for 2016-10-04 (Week 40) ANNOUNCEMENTS ------------- * None INSTRUMENT and SPACECRAFT STATUS -------------------------------- * Ahead is operating nominally on the main lobe of the high gain antenna. * Attempts to recover Behind are transitioning back to a monthly schedule. See below for details. DISCUSSION AND OPERATIONS CONSTRAINTS ------------------------------------- Week 39 (Sep 26-Oct 2) * On day 270 (Sep 26), during the DSS-14 support for Ahead, the command uplink was lost at 1606z due to a transmitter issue. The station was directed to stay one-way for the remainder of the track to avoid further data loss. This anomaly resulted in the loss of 1358 frames of real-time telemetry only. See DR# G117506 for more information. * On day 271 (Sep 27), during the DSS-25 support for Ahead, turbo decoder lock was lost briefly at 1843z. This anomaly resulted in the loss of one frame of SSR data. * On day 273 (Sep 29), during the DSS-54 support for Ahead, turbo decoder lock was lost briefly at 1244z. This anomaly resulted in the loss of five frames of SSR data. * On day 275 (Oct 1), during the DSS-55 support for Ahead, the transmitter was red for the entire support. Also, turbo decoder lock was lost briefly at 1104z. These anomalies resulted in the loss of 4.5 hours of commanding and two tracking data and one frame of SSR data. See DR# M109576 for more information. * On day 276 (Oct 2), during the DSS-55 support for Ahead, the transmitter was red for the entire support. This anomaly resulted in the loss of 4.3 hours of commanding and two tracking data. See DR# M109578 for more information. * On day 271 (Sep 27), the 36th SECCHI stepped calibration on Ahead was executed successfully at 1155z. This was the 5th SECCHI stepped calibration roll to be conducted without gyro use. The SECCHI/COR1 team reported that one of the nine positions had to be thrown out, but the other eight positions were analyzed successfully. * The average daily science data return for Ahead was 5.1 Gbits during this week. * Behind Observatory Status: From the last telemetry received on September 18th, low main bus voltage, 2 (#6 & 9) out of 11 battery cells are currently not functioning, attitude uncontrolled, rotating at a ~45 second period about its principal axis of inertia. Current orientation may support some solar array input. While propellant is suspected to be frozen, both propulsion tank latch valves are open and pressure transducer #2 is not functioning. Power switching boards are on; nearly all switched loads are off including the IEM (avionics) and PDU 1553 interface bus with the TWTA in standby and propulsion primary and secondary tank heaters on and -Y panel (R4) heaters on. EA mode is enabled. The battery charge rate is C/10. Necessary macro sequences have been tested to allow the peak power tracker in C&DH standby mode to protect the battery. These macro sequences will be loaded to EEPROM when the communications supports longer commands. Active recovery operations began with the carrier detection on August 21, 2016. Detailed status of the recovery activities to restore operations from the Behind loss of communication anomaly, which occurred on October 1, 2014, are listed below. * On day 271 (Sep 27), during the two hour support for Behind with DSS-14, no carrier was detected by the DSN after repeatedly attempting to power on the TWTA. Transitioned to battery recovery operations which consisted of repeatedly sweeping a 3 kHz uplink range and sending commands for IEM switched power and 1553 off, TWTA to standby, primary and secondary tank and -y panel (R4) heaters on. * On day 274 (Sep 30), during the 2 hour support for Behind with the 34m station DSS-26 using the 80 KW transmitter to minimize 70m contentions, 200 commands were sent for battery state of charge recovery. This consisted of repeatedly sweeping a 3 kHz uplink range and sending commands for IEM switched power and 1553 off, TWTA to standby, primary and secondary tank and -y panel (R4) heaters on. * On day 276 (Oct 2), during the two hour support for Behind with DSS-63, no carrier was detected by the DSN after repeatedly attempting to power on the TWTA first using the -Z LGA then switching to the +Z LGA. Week 40 (Oct 3-9) * Ahead has 12 passes during the week, and overall coverage is nominal. There are five passes at 720 kbps, three at 240 kbps, and four at 160 kbps. * Behind has six tracks scheduled during the week. Tracks yesterday (Oct 3) and today (Oct 4) were for battery recovery; no signal was detected when the transmitter was commanded on. Carrier recovery will be attempted on Thursday, Oct 6, with station 14. The previously scheduled single station recovery attempts for Behind are Friday-Sunday, Oct 7-9. The battery recovery passes will be carried out with the 80 kW transmitter on station 26. Week 41 (Oct 10-16) * The 92nd momentum dump on Ahead is scheduled for Monday, Oct 10, with ignition at 23:45 UT. This is the 11th dump without using the gyros. * Ahead has 11 passes during the week, and overall coverage is nominal. There are seven passes at 720 kbps, and four at 160 kbps. * Behind starts the week at an SPE angle of 13.5 degrees. There are no passes scheduled for Behind during the week, as recovery attempts for Behind are back to a monthly schedule. Week 42 (Oct 17-23) * Ahead has 12 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, six at 240 kbps, and three at 160 kbps. * Behind starts the week at an SPE angle of 13.5 degrees. There are no passes scheduled for Behind during the week, as recovery attempts for Behind are back to a monthly schedule. Week 43 (Oct 24-30) * Oct 25 (Tuesday) the 10th STEREO Launch Date Anniversary. * Ahead has 13 passes during the week, and overall coverage is nominal. There are four passes at 720 kbps, four at 240 kbps, and five at 160 kbps. * Behind starts the week at an SPE angle of 13.6 degrees. There are no passes scheduled for Behind during the week, as recovery attempts for Behind are back to a monthly schedule. Week 44 (Oct 31-Nov 6) * Daily savings time in the United States ends on Sunday, Nov 6. * Ahead has 12 passes during the week, and overall coverage is nominal. There is one track at 720 kbps, six at 240 kbps, and five at 160 kbps. * Behind starts the week at an SPE angle of 13.6 degrees. There are no passes scheduled for Behind during the week, as recovery attempts for Behind are back to a monthly schedule. Week 45 (Nov 7-13) * The 12th and 13th uplink arrays for Behind are scheduled for Friday, Nov 11, and Sunday, Nov 13. The first 1.9 hours of each pass will use the Ahead spacecraft for calibration. The downlink rate will be 160 kbps. There will be no SSR playback or instrument commanding during these calibration passes. Station 26 will be below the 27.5 degree limit for the entire duration of the Ahead tracks; a waiver has been requested to transmit at 80 kW. * Following the Ahead tracks, there will be a 2.4 hour track for battery recovery on Behind on Friday, Nov 11, and a 3.2 hour track for carrier recovery on Sunday, Nov 13, with station 14 for 2.2 hours using the radio science receiver. Waivers have been requested for dropping below the 27.5 degree limit for 80 kW for 0.8 hours on Friday, and 1.5 hours on Sunday. * Ahead has 9 tracks during the week, and overall coverage is nominal. There are four tracks at 720 kbps, three at 240 kbps, and two at 160 kbps. * Behind starts the week at an SPE angle of 13.8 degrees. There are no passes for Behind beyond the uplink array passes discussed above. Week 46 (Nov 14-20) * The 93rd momentum dump for Ahead is scheduled for Wednesday, Nov 16, with ignition at 14:30 UT. This will be the 12 dump without the gyros. * Ahead has 11 passes during the week, and overall coverage is nominal. There are three passes at 720 kbps, one at 240 kbps, and seven at 160 kbps. * Behind starts the week at an SPE angle of 13.9 degrees. There are no passes scheduled for Behind during the week, as recovery attempts for Behind are back to a monthly schedule. COORDINATED OBSERVATIONS ------------------------------------------------------------------------------- Scheduled activities for Week 40: M Oct 03 (277) T Oct 04 (278) W Oct 05 (279) T Oct 06 (280) F Oct 07 (281) Behind: Battery recovery pass with station 26 S Oct 08 (282) Behind: Battery recovery pass with station 26 S Oct 09 (283) Behind: Carrier recovery pass with station 14 ------------------------------------------------------------------------------- Scheduled activities for Week 41: M Oct 10 (284) Ahead: Momentum dump, 23:45 UT T Oct 11 (285) W Oct 12 (286) T Oct 13 (287) F Oct 14 (288) S Oct 15 (289) S Oct 16 (290) ------------------------------------------------------------------------------- Scheduled activities for Week 42: M Oct 17 (291) T Oct 18 (292) W Oct 19 (293) T Oct 20 (294) F Oct 21 (295) S Oct 22 (296) S Oct 23 (297) ------------------------------------------------------------------------------- Scheduled activities for Week 43: M Oct 24 (298) T Oct 25 (299) W Oct 26 (300) T Oct 27 (301) F Oct 28 (302) S Oct 29 (303) S Oct 30 (304) ------------------------------------------------------------------------------- Scheduled activities for Week 44: M Oct 31 (305) T Nov 01 (306) W Nov 02 (307) T Nov 03 (308) F Nov 04 (309) S Nov 05 (310) S Nov 06 (311) Daily savings time ends in U.S. ------------------------------------------------------------------------------- Scheduled activities for Week 45: M Nov 07 (312) T Nov 08 (313) W Nov 09 (314) T Nov 10 (315) F Nov 11 (316) Behind: Uplink array pass for battery recovery S Nov 12 (317) S Nov 13 (318) Behind: Uplink array pass for carrier recovery ------------------------------------------------------------------------------- Scheduled activities for Week 46: M Nov 14 (319) T Nov 15 (320) W Nov 16 (321) Ahead: Momentum dump, 14:30 UT T Nov 17 (322) F Nov 18 (323) S Nov 19 (324) S Nov 20 (325) ------------------------------------------------------------------------------- Upcoming events: Behind events are contingent on recovering the spacecraft. 2016: * 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