ACE Weekly 10/15/2014 - 11/12/2014 All ACE spacecraft subsystems are performing as expected. This report covers 4 weeks since the team has been working the Wind CAP Anomaly. ======================================================================== Orbit/Attitude: Type Attitude Attitude Attitude Attitude Date 10/21/2014 10/28/2014 11/05/2014 11/12/2014 DOY 294 2014 301 2014 309 2014 316 2014 Thrusters 2R 4R+ 4R- 2R 4R+ 4R- 2R 4R+ 4R- 2R 4R+ 4R- Duration 9:51 min 11:39 min 11:15 min 10:09 min Start 16:05:37z 16:31:24z 16:53:10z 16:42:09z Stop 16:15:28z 16:43:03z 17:04:25z 16:52:18z ra,decStart 205.73,-23.40 215.93,-22.90 227.06,-19.84 232.12,-11.88 ra,decStop 215.71,-23.01 226.95,-20.03 232.20,-12.01 239.91,-10.10 ra,decExpect 216.12,-23.08 227.68,-19.94 232.77,-10.59 241.98,-10.00 Deviation 0.38 deg -4% 0.69 deg -6% 1.53 deg -14% 2.04 deg -20% HGAStart -9.47 deg -7.33 deg -3.54 deg -8.28 deg HGAStop +8.76 deg +6.98 deg +6.09 deg +8.23 deg SunStart 12.71 deg 10.28 deg 7.58 deg 7.39 deg SunStop 15.44 deg 15.37 deg 11.99 deg 14.28 deg SpinStart 4.9973 rpm 4.9994 rpm 5.0003 rpm 5.0025 rpm SpinStop 4.9995 rpm 5.0006 rpm 5.0027 rpm 5.0025 rpm Nutation 0.27 deg 0.09 deg 0.11 deg 0.27 deg Firing 50 pulses 59 pulses 57 pulses 51 pulses FuelUsed 0.1572 lbm 0.1825 lbm 0.1768 lbm 0.1598 lbm FuelRemain 103.2712 lbm 103.0888 lbm 102.9120 lbm 102.7520 lbm FinalSCMass 1337.531 lbm 1337.349 lbm 1337.172 lbm 1337.012 lbm The next attitude maneuver is scheduled for Tuesday 11/18/2014. The past 2 maneuvers have not reached their targets (11/5 -14% and 11/12 -20%), more so than the previous maneuvers (10/21 -4% and 10/28/2014 -6%). The thruster catbed's decreased heating rate correlates with the maneuvers not reaching the target. Also, 4R- and 4R+ thrusters (+X fuel line) are synchronous in their decreased heating rates, but asynchronous with the 2R thruster (-X fuel line). The best theory continues to be that nitrogen bubbles from the pressurant temporarily decrease the pressure down the fuel line when the bubbles pass through the internal/external line juncture. There is not yet a good theory as to why and when the bubbles enter the fuel line. It may just take more time to discern a pattern. ======================================================================== OCRs: None ======================================================================== Activities: Data Capture: 99.999% DOY 285-313 2014 DOY 307 01:21:12-01:21:13 2 seconds WS1 (Near Earth Network) performed 2 ranging proficiency tests while ACE was in the low downlink rate. 10/08/2014 DOY 281 1815-1930z 10/22/2014 DOY 295 2010-2040z Santiago (Near Earth Network) performed 2 ranging tests for DSCOVR while ACE was in the low downlink rate. 10/29/2014 DOY 302 1730-1835z 10/30/2014 DOY 303 1600-1705z There have been 2 passes with WS1 (11/4 DOY 308 and 11/7 DOY 311) and 2 passes are scheduled in the coming week (11/14 DOY 318 and 11/16 DOY 320). The WS1 passes help to ensure sufficient antenna time for data capture, but require that the spacecraft antenna angle be kept within 9 degrees of Earth. The spacecraft antenna angle has been kept within 9 degrees since 10/21/2014 which ended the summer campaign of larger sun angles for SWEPAM. ======================================================================== Anomalies: Update for S13-0001 - B1 Fuel Tank Temperature Anomaly Starting 10/14/2014, the fuel tank heaters have returned to turning off regularly (off 15-30 minutes every ~2 hours) as the spacecraft warms and approaches perihelion. Throughout the mission, the tank heaters had remained on. The theory is that the B1 Fuel Tank thermostat detached (Sep-Dec 2013), causing the thermostat to read a higher than normal temperature and therefore turn off the tank heaters. During the last perihelion, the tank heaters had been turning off regularly from 12/22/2013 to 05/22/2014 but only occasionally during the summer. During the 11/5 and 11/12 maneuvers, the B2 fuel tank temperature increased from ~18.5C to ~21.5C and the -X external fuel line decreased from ~18.5C to ~15.5C. After the maneuver completed, the temperatures returned to their normal values. The change in temperatures do not correspond to any heaters turning on or off. The B2 fuel tank is next to the -X side of the spacecraft. This may be due a structural shift, for instance a warm component disconnecting from the -X spacecraft wall and connecting to tank B2. With only 2 temperatures changing, it is difficult to discern what might have shifted. There are occasional minor issues. If the issues are minimal, they are not reported in GSFC's SOARS (Space Orbital Anomaly Reporting System). An example of this occurred in the past week. DOY 313 11/09/2014 Postgres database vacuum Two MMOC software components use Postgres databases: ITOS for tlm/cmd and MUS for connecting to DSN. On Sunday 11/9 inbetween passes, the databases stopped accepting commands. The MMOC system administrator came in to "vacuum" the database to reclaim space.