ACE Weekly 08/07/2013 - 08/13/2013 All ACE spacecraft subsystems are performing as expected. ======================================================================== Orbit/Attitude: Type Attitude Date 08/13/2013 DOY 225 2013 Thrusters 2R 4R+ 4R- Duration 20:17 min Start 16:40:16z Stop 17:00:33z HGAStart -8.77 deg HGAStop +8.82 deg SunStart 10.74 deg SunStop 10.89 deg SpinStart 4.9476 rpm SpinStop 4.9527 rpm Nutation 0.21 deg Firing 100 pulses FuelUsed 0.2994 lbm FuelRemain 112.5532 lbm FinalSCMass 1346.813 lbm The next attitude maneuver is scheduled for Tuesday 08/20/2013. This week's attitude maneuver (0.30 lbm) is larger than usual (0.09-0.18 lbm). ACE crossed the ecliptic plane on Friday (8/9/2013; DOY 221) and this maneuver turned the spacecraft from pointing 7 degrees above the ecliptic plane to 9 degrees below the ecliptic plane. This is to keep the spacecraft at larger sun angles. These large maneuvers will happen every 3 months (last occurrence 5/7/2013). Fuel usage with "weekly attitude maneuvers" has been at the same rate as fuel usage with "maximum time attitude between maneuvers" (~6.5 lbm/year); even with large maneuvers every 3 months. There are other factors: shorter burns are less efficient, longer burns are more "circular" due to sun-pulse based firing, etc. But the end result is that attitude maneuver fuel usage has not changed with the increased frequency of maneuvers. ======================================================================== OCRs: None ======================================================================== Activities: Data Capture: 100% DOY 216-223 2013 A fourth Santiago range test is scheduled for Wednesday 7/14/2013. Over the course of these tests, several issues have been resolved and Santiago may be close to the point where FDF can use their range/tracking data. The buffer overflow problem has not been resolved (a 10,000,000,000 nanosecond round-trip-light-time cannot be stored by a 4 byte integer 4,294,967,296), but FDF seems to be able to account for this by adding 8,589,934,592 to the range data (2 "overflows"). If DSN antenna time becomes problematic with the reduction from 13 to 12 antennas (12/23/2013), it may be worthwhile to investigate using Santiago to supplement ACE's southern-hemisphere ranging needs. (These tests were originally planned so that DSCOVR could use Santiago.) ======================================================================== Anomalies: None