ACE Weekly 03/26/2008 - 04/01/2008 All ACE spacecraft subsystems are performing nominally. ============================================================================ Orbit/Attitude: Type Attitude Date 03/26/2008 DOY 086 2008 Thrusters 2R 4R+ 4R- Duration 14:40 min Start 15:08:00z Stop 15:22:40z HGAStart -6.30deg HGAStop +7.00deg SunStart 6.75deg SunStop 11.32deg Nutation 0.39deg Firing 75 pulses FuelUsed 0.2401lbs FuelRemain 150.8236lbs FinalSCMass 1385.083lbs The next attitude maneuver is scheduled for Wednesday 04/16/2008. =========================================================================== OCRs: None ============================================================================ Activities: None ============================================================================ Anomalies: DOY 086 03/26/2008 S-ACE-0294 G08-0034 DSS-66/Network Error/SLE Abort After a brief network error at 17:11:59, the ACE MOC SLE software issued a "Protocol Abort" and the ACE MOC automatically attempted to rebind. The Bind attempts were not successful. When the ACE MOC issues a Protocol Abort, the station must set the TCP Production Status to "halt" and then back to "operate". The ACE MOC was finally able to bind at 17:29:58. DR#M104724 This problem last occurred on 01/11/2008 (AR#G08-0005). IMPACT: Commanding delayed 18 minutes DOY 090 03/30/2008 S-ACE-0295 G08-0035 Excessive Network Loss Network data loss was 1.1% for most of the pass with DSS-27 (2111-2302z). DR#N104779 IMPACT: All data available on CDR. CDR verified before the beginning of the next pass. Background Information During a pass, it is not possible to determine whether data gaps will be available at DSN's CDR Facility. Therefore, after a playback is done, all data gaps are redumped as time permits. If the pass has excessive data loss and is staffed, the CDR files are checked to determine if they contain the missing data. If the pass is not staffed, redumps are continued on the next support until certain constraints are met. DSN has discussed of changing the network connection from UDP to TCP (guaranteed delivery). This would simplify ACE operations. There is a concern that TCP would add a delay to data delivery. For ACE operations, it is better to have guaranteed delivery even if the data delay is 5-10 seconds. Note, other missions may have different priorities. Furthermore, downloading the CDR ultimately results in a doubling of the ACE network usage (once for the pass and once for verifying the data is on the CDR). Guaranteed delivery would reduce the need to download CDR files.