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.

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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.

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OCRs:

None

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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.

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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.