ACE Weekly 10/8/2015 - 10/14/2015

All ACE spacecraft subsystems are performing as expected.

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Attitude/Orbit:


Type               Attitude                        SK-77
Date             10/14/2015                   10/14/2015
DOY                287 2015                     287 2015
Thrusters        2R 4R+ 4R-                        1A 2A
Duration      15:20 minutes                   50 seconds
Start             19:24:51z                    20:47:06z
Stop              19:40:11z                    20:47:56z
ra,decStart    199.80,-21.78                214.59,-18.27
ra,decStop     214.59,-18.27                214.39,-17.65
ra,decExpect   215.26,-18.30                214.59,-18.27
Deviation          0.60 deg (-4.0%)
HGAStart          -9.56 deg                     9.33 deg
HGAStop            9.33 deg                     8.83 deg
SunStart          13.67 deg                    13.67 deg
SunStop           18.06 deg                    17.53 deg
SpinStart        5.0373 rpm                   5.0419 rpm
SpinStop         5.0419 rpm                   5.0274 rpm
Nutation           0.09 deg                     0.81 deg
Firing            78 pulses                   Continuous
FuelUsed         0.2317 lbm                   0.1694 lbm
FuelRemain      95.1388 lbm                  95.9694 lbm
FinalSCMass    1329.399 lbm                 1329.230 lbm

Note:

Most station keeping maneuvers have a smaller nutation. Historically,
station keeping maneuvers performed using thrusters 1A and 2A have
had a higher nutation than those using 3A and 4A, but also occur less
often - the last time was for SK-66 on 2013 DOY 190. The nutation will
dissipate over time (i.e, within 9.5 hrs per the 1/e time constant of
the ACE nutation dampers). It is also worth noting that during SK-77
thruster operations, the 1A catalytic bed heated up noticeably less
than 2A (resulting in lower thruster efficiency/performance), which
potentially explains the observed (higher) nutation.

Next attitude maneuver: Tuesday, 10/20/2015

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OCRs:

Reminder/Update on ACE-355: Relaxing the ACE antenna constraint from 9
to 11 degrees for the 2015 Summer Campaign.

The 2015 Summer Campaign, which started on 5/19/2015, will conclude
with the 10/20/2015 attitude maneuver.  The return to the 9 degree
upper limit antenna constraint will allow ACE to resume operations
with WS1.


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Activities:

Data Capture: 99.985%  DOY 277-284 2015

Notes:

As a consequence of the DOY 274 DSS-34 lost pass (as described in last
week's report; S-ACE-37/DR #C111407), autonomous SSR fail-overs were
performed on DOY 277 (at 277-05:12:02.06 UTC) and DOY 282 (at
282-14:42:16.216 UTC). The SSR failover transitions were responsible
for 62 seconds of data loss.

An additional (net) 36-seconds in data gaps were identified for (VC4)
playback data during the 278-19:10:38 (UT) - 283-04:22:11 (UT) time
window (distributed in multiple short windows).

Inspection of the DOY 278-283 event logs and the DSN DR system does not
yield any ground system problems which correlates with the 36 sec data
gaps. However, it is worth noting that the playback data for the affected
time frame covers data that was carried over from multiple days due to
the lasting impact of the DSS-34 lost pass on DOY 274 (i.e, and data loss
during a re-dump cannot be further playback, leading to a permanent data
gap).

Per standard procedure, the FOT will retrieve the corresponding IDR
data and confirm if there are any differences from the MOC-acquired
SLE data.


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Anomalies:

None