NATIONAL OC
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D ATMOSPHER
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Serendipitous Characterization of the Microwave Sounding Unit
during an Accidental Spacecraft Tumble
TRATION
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Thomas J. Kleespies
NOAA/NESDIS/STAR Camp Springs, MD 20736 USA
Thomas.J.Kleespies@noaa.gov
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Conclusions
Pitch Manuever
This was a carefully planned event in which the normal
forward pitching of the spacecraft was stopped for one orbit.
0 Deg into POM at 80 Deg north Lat ascending over Russia
90 Deg into POM at 10 Deg north Lat descending from Wallops
Tumble
• The nominal earth scene viewing space records
different brightness temperatures than the space
calibration view.
• There is a marked asymmetry in the nominal earth
scene, and the characteristics of the asymmetry
differ for the two different polarizations (1&3V,2&4H)
• Position 1 difference from space reads higher values
than position 2. This suggests that that side of the
scan may be seeing part of the spacecraft or another
instrument.
• Channel 2 difference from space look is sensing
about 1-1/2 counts colder during the tumble than
during the pitch. The other channels either have
no change, or the difference from space look is
positive (warmer).
• The absolute average of all scene positions is
warmer during the tumble than during the pitch.
This was an unplanned event in which a thruster
released hydrazine, causing the spacecraft to tumble
Pitch FOV difference from Cold Load
5
4
3
270 Deg into POM at 10 Deg south Lat ascending away from McMurdo
Count Difference
2
180 Deg into POM at 80 Deg south Lat descending towards McMurdo
1
Ch1
Ch2
0
1
2
3
4
5
6
7
8
9
10
11
-1
Ch3
Ch4
-2
-3
NOAA-14 at three discrete times during early phase of tumble.
-4
-5
Scan Position
Average space looks minus average scene
counts during the pitch maneuver.
Tumble FOV difference from Cold Load
5
4
Count Difference
3
2
Ch1
1
Ch2
0
1
2
3
4
5
6
7
8
9
10
11
Ch3
Ch4
-1
-2
-3
-4
Scan Position
Average space looks minus average scene
counts during the spacecraft tumble.
Change in FOV difference from Cold Load
from Pitch to Tumble
1.5
1
MSU brightness temperatures plotted on the earth during the pitch maneuver.
The instruments lift off the earth on the descending node (left) and re-acquire
the earth on the ascending node (right).
Count Difference
0.5
0
1
2
3
4
5
6
7
8
9
10
11
-0.5
Ch1
Ch2
Ch3
Ch4
-1
-1.5
MSU brightness temperatures plotted on the earth during the tumble event.
The instrument is on the earth during the first descending node (inside, left).
The tumble event began over South America. The instrument periodically
viewed the earth (colored bands within the white fields).
-2
-2.5
Scan Position
Change in average difference between scene
and cold looks between pitch and tumble.
Change in mean counts Pitch to Tumble
12
Mean Count Change
10
8
Ch1
Ch2
6
Ch3
Ch4
4
2
0
1
2
3
4
5
6
7
8
9
10
11
12
Scan Position
Change in average scene and space look counts
between pitch and tumble.
MSU temperature telemetry for the orbit before, during and after
the pitch maneuver. The vertical lines denote the orbit of the
maneuver. The instrument temperatures during the maneuver
were not greatly different than before and after the maneuver.
Acknowledgements
The STK spacecraft depictions were
provided by the NOAA Office of
Satellite Operations POES Engineering
Branch.
MSU temperature telemetry for the orbit before the tumble event,
and during the tumble until the instrument was turned off. The vertical
line indicated when the tumble began. The instrument temperatures
during the tumble were not greatly different than before the tumble.