Status, 5 January 2000, 8:45 AM PST
A major step forward in the MISR activation sequence took place this
morning, and all went perfectly!
A scheduled acquisition of signal from Terra through the TDRSS
geostationary satellite system occurred at 6:38 AM PST this morning.
Uploading of commands to turn MISR's cameras on, one by one, began almost
immediately thereafter. Our team at the EOS Operations Center at Goddard
gave the "go" signals at the appropriate intervals and monitored MISR's
engineering telemetry during the process. By 6:42 AM all nine cameras were
on. Currents and voltages are all reading as expected.
Between 6:43 AM and 6:46 AM, commands were sent to turn on the heaters in
each of the camera focal planes. The focal planes are the surfaces where
the cameras form their images. In film cameras, this is where the film is
located, whereas in digital cameras, like those in MISR, this is where the
solid-state electronic detectors are located. During science operations,
MISR's focal planes will be cooled using "thermo-electric" coolers, and the
focal plane heaters will be used to automatically maintain the detectors at
a temperature of -5 degrees Centigrade. Right now, however, during the
outgassing period the thermo-electric coolers are off and the "set point"
for the focal plane heaters has been established as 24 degrees Centigrade.
(A set point serves the same purpose as when you set the thermostat in your
home.) At 6:53 AM, our operations team verified that they were beginning to
see the focal plane temperatures begin to rise.
At 6:54 AM, a command to turn on the optical bench heaters with a set point
of 34 degrees Centigrade was sent. Although we don't expect the bench to
reach this high a temperature, this set point serves the purpose of
insuring that the bench heaters remain on throughout the outgas period.
Since the cameras are mounted on the optical bench, warming the bench will
also cause the cameras to warm up. All of this warming is beneficial
because it drives contaminants (such as hydrocarbons and water) out of the
instrument into the vacuum of space, and since these contaminants can
re-condense on cold surfaces we also keep the cameras warm to prevent this
from happening. Telemetry is showing that the optical bench has begun to
warm up.
At 6:55 AM, our operations team scanned the engineering telemetry once
again and declared the entire set of procedures a success. This is
wonderful news!
Although the cameras are now on, we cannot read out the image data until
after upload of the flight software program to the MISR computer. This is
scheduled to happen in two weeks when the outgassing period completes.
Then, the thermal set points will also be established at the values
appropriate for science operations.
You can see earlier status reports by checking the "News" link of the MISR
web site at http://www-misr.jpl.nasa.gov.
David Diner
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