last update
11:36 UTC
SFI: 72 | Ap index:  6  | Kp index:  1  ( 1 @12:15,  1 @15:15) | X-ray flux:  A4.6 
SW: Density= 1.0 p/cm3 | Speed= 456.8 km/s | Temp=40(x1000)K
IMF: Bx=-1.3nT | By=1.5nT | Bz= 1.7 nT | Bt= 2.7 nT | Lat= 40.7 ° | Lon=132.2°
Sunspots: 12 | Area: 10 10-6/Hemi | New regions: 0
[i]X-ray flares: C=0 M=0 X=0 | Optical flares: M1=0 M2=0 M3=0 | Sub-flares=0
There have been six attempts to contact the STEREO Behind spacecraft using 70 meter stations between September 27 and October 9 without success. The last telemetry received from Behind was on September 18, and the last time the carrier wave was detected was on September 23. Recovery attempts for STEREO Behind have moved back to a monthly schedule until the spacecraft has returned to a point in its orbit where the attitude is in a favorable configuration for power and communications.

The following summarizes the activies that have taken place since the last update on September 19. On September 20, commands were sent for increasing the battery charge rate to C/4 and closing latch valves. The carrier signal was very low, intermittent, and carrier lock could not be maintained. After switching to the +Z LGA, no downlink signal was received. Commands were sent to the place the TWTA in standby and power on the propulsion tank primary heaters. No telemetry frames were received. On Friday, September 23, during the 70m track with DSS-43, the radio science team detected an extremely weak (~10 dB-Hz SNR) at 2200z for 15 seconds.

The following Tuesday, September 27, during the 2 hour support with DSS-14, no downlink carrier was detected by the DSN after individually commanding and loading the test macro to power on the TWTA. The FDF received 17 tracking points labeled as 2-way. Residuals roamed between -200 and 1054 m/s, with a few points at similar levels. Mission Operations then directed DSN to begin configuring for automated battery recovery operations (i.e. repeated multiple sweeps in a 3 kHz range). At 1455z, automated battery recovery operations commenced, with MOC repeatedly commanding the following configuration through EOT - IEM switched power and 1553 off; TWTA to standby, primary and secondary propulsion tank and -Y panel (R4) heaters on.

BEHIND observatory status: Low main bus voltage, 2 (#6 & 9) out of 11 battery cells are currently not functioning, high battery temperature, attitude uncontrolled, rotating at a ~45 second period about its principal axis of inertia. Current orientation support may support some solar array input; RF communications on the +Z LGA only supports uplink of short commands to an LGA. While propellant is suspected to be frozen, from the last telemetry received on Sep 18th, both propulsion tank latch valves are open, and pressure transducer #2 is not functioning. Power switching boards are on; nearly all switched loads off including the IEM (avionics) and PDU 1553 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. As the uncontrolled communications link is degrading, necessary macro sequences to allow the peak power tracker in C&DH standby mode to protect the battery will be loaded when the communications link supports.

On Saturday, September 17, during an uplink array, which consisted of three 34m stations (DSS-24, 25, & 26) which provided an estimated 10.4 dB gain at the spacecraft over a standalone 34m uplink at 20 kW, 360 commands were sent for configuring the spacecraft for a low power mode by powering off excess loads, powering on all power switching boards, and ensuring the reaction wheels are powered off in a known configuration. On Sunday, September 18, during a 2nd uplink array with 70m station DSS-43 monitoring the downlink, during 2 brief TWTA sampling periods, the carrier signal was received on time with a continuously fluctuating signal of -170 dBm to -178 dBm with a period of ~45 seconds. Subcarrier lock was intermittent. While the uplink can support short critical commands, the downlink cannot support telemetry. The radio science receiver team reported a modulated downlink. As the SNR was not stable long enough for post-pass telemetry extraction, the LGA was swapped to the -Z LGA to improve SNR. This improved the carrier level by ~3 dB, with levels of -167 dBm to -174 dBm. Two telemetry frames were received. While the battery pressure was good, the temperature needs to be reduced. Daily two hour 70 m supports have been requested to prevent further battery functional degradation.

Mission operations has announced that they are suspending STEREO Behind recovery attempts until the telemetry situation improves, sometime next year. The spacecraft is now spinning at a rate of approximately once every 52 seconds, which allows only short commands to be uplinked, and does not support telemetry downlink. Communication with the spacecraft degraded over the weekend. Once a month communication attempts will resume, starting with the phased array attempt this weekend, Sep 16-17. Each month will switch between single station and phased array attempts until recovery operations resume.

The carrier from STEREO Behind was detected once again by the DSN during the morning of September 10. During 3 brief TWTA sampling periods, the carrier signal had a lower peak signal of -166 dBm and a period of ~60 seconds continuously. Subcarrier lock did not occur. While the uplink can support short critical commands, the downlink cannot support telemetry. The spacecraft was configured for a low power mode by powering off all power switching boards and loads. EA mode was enforced as to prevent the use of the HGA in C&DH standby mode.

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