ACE Weekly 04/09/2014 - 04/15/2014 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude Date 04/15/2014 DOY 105 2014 Thrusters 2R 4R+ 4R- Duration 9:28 min Start 15:41:44z Stop 15:51:12z HGAStart -8.13 deg HGAStop +9.73 deg SunStart 11.00 deg SunStop 14.18 deg SpinStart 4.9906 rpm SpinStop 4.9927 rpm Nutation 0.18 deg Firing 48 pulses FuelUsed 0.1527 lbm FuelRemain 107.6056 lbm FinalSCMass 1341.866 lbm This maneuver targeted a spacecraft antenna angle (HGA) of 10 degrees (9.73 degrees achieved). The ~2.5 dB drop in the downlink signal due to the increased antenna angle is in-line with expectations. Next week's maneuver will target a spacecraft angle of 11 degrees. Refer to OCR ACE-337 below. antenna angle Signal to Noise Ratio 8.13 deg 15 dB 9.73 deg 12.5 dB The next attitude maneuver is scheduled for Tuesday 04/22/2014. Station Keeping maneuver #69 is scheduled for 05/13/2014. Note that there are 4 months, instead of the usual 3 months, since the last station keeping maneuver. This is because the observed delta-V from SK-68 on 1/15/2014 had exactly matched the planned delta-V. The variation in thruster performance is usually between -2 to +2%, but it is pleasant to note when the maneuver is right-on. ======================================================================== OCRs: ACE-337 Increase antenna constraint from 9 to 11 degrees for summer With DSN's decommission of DSS-27 (12/23/2013), ACE has been using the better 34m antennas. And during the summer, DSN northern hemisphere views are longer (9 out of 12 DSN antennas are in the northern hemisphere), which reduces the need for ACE using WS1 (21m). Turning the spacecraft an additional 2 degrees will improve the SWEPAM-I density measurement by ~10%. We expect that the instrument deck temperature will increase slightly (~0.2C), but that is more than offset by the 2-4C drop that occurs due to aphelion (7/3/2014). Attitude maneuvers will target an 11 degree spacecraft antenna angle and drift back to 11 degrees on the day after the next scheduled maneuver, which allows the attitude maneuver to slip a day if needed. Although WS1 will not be able to acquire the high-rate telemetry with the spacecraft at 11 degrees, the range-only passes with WS1 and Santiago can still continue. ======================================================================== Activities: Data Capture: 100% DOY 096-103 2014 The Near Earth Network performed one more Santiago range test. 04/09/2014 099 1300-1400 AGO FDF's certification status for the complete week of WS1 and Santiago range passes (3/26/2014 - 4/1/2014) has not yet been delivered. ======================================================================== Anomalies: Update on Anomaly #G14-0005 (S-ACE-0677) DSS-15 Earth Receive Time (ERT) The DSN Earth Receive Time continues to have occasional problems, but DSN's halting and re-acquiring the TLP has corrected it when it occurs. There have been no problems with the clock reports sent to ASC and NOAA. Fri 4/11/2014 DSS-15 no problem found Sat 4/12/2014 DSS-15 17:56:36 ERT -0.182 sec. Corrected 17:56:51 Sun 4/13/2014 DSS-15 21:29:31 ERT -0.363 sec. Corrected 21:29:47 Mon 4/14/2014 DSS-15 no problem found Background Info: The ERT is behind by an integer multiple of telemetry frames (high-rate = 0.091 seconds per frame). This occurs after the spacecraft's data-rate change (from low-rate RTSW to high-rate). This is an intermittent problem (DR# G114836/AR 118839) with the Receiver, Ranging, and Telemetry (RRT) software v11.3.6 that is currently undergoing soak testing at DSN's Goldstone site.