Status 10 February 2000
The sequence to raise and circularize Terra's orbit began this
afternoon and the 60-second firing of the spacecraft thrusters
completed successfully. MISR remained in science mode throughout the
event. The next planned maneuver is a 150-second burn on Saturday
afternoon, February 12. Burns of five-minute duration are planned
every other day from February 14 - 22. The sequence is scheduled to
complete with a 50-second burn on February 24.
MISR activation continues February 11 with a command to turn on its
calibration photodiodes for two minutes. These photodiodes will
eventually be used to "radiometrically calibrate" the MISR cameras.
Calibration is the process of translating the digital data being
generated by the cameras into quantitative measures of light
intensity. After the cover opens, this will involve occasional
deployment of panels that will illuminate the cameras with diffusely
reflected sunlight. The photodiodes are very stable detectors that
will accurately monitor this illumination. Since the cover is still
closed, we cannot deploy the panels so tomorrow's test will verify
electrical operability of the photodiodes and enable some checkout of
the software which decodes their data. We will test sensitivity of
the photodiodes to charged particle radiation by repeating the same
test on Saturday during a passage through the South Atlantic Anomaly.
MISR continues to provide a wealth of data that is being used to
exercise our science data processing software in preparation for
"first light" on orbit.
More than a trillion binary digits, or bits, of data have been
received so far. Infrequent errors are observed (changes in the value
of a bit from 0 to 1 or vice versa), which when decoded result in an
incorrect time stamp, data sequencing counter, or similar indicator.
Our processing software has been designed to expect these anomalies
and work around them. Checkout is still underway, but in several
cases we have confirmed that the errors are being handled correctly.
Since data from other instruments are also exhibiting "bit flips", it
is quite possible that the ones we are seeing do not originate in
MISR but instead arise somewhere downstream in the data flow.
In addition to the South Atlantic Anomaly-related "stars" and
horizontal "stripes", the dark data from MISR's cameras
intermittently exhibit some regularly-spaced tapered vertical stripes
resembling "jail bars" or a "backgammon board". An explanation for
these extremely faint features has remained elusive, but we expect
them to be swamped by the much larger Earth signal once the cover
opens. Otherwise the patterns in the dark data are generally random.
Some of our software engineers claim to have detected the outline of
a cockroach, suggesting that our team is taking the mandate to shake
the bugs out of the system very seriously. I am unaware of any Elvis
sightings, but this month auspiciously marks the 38th anniversary of
his release "Good Luck Charm". This bodes well for opening of MISR's
cover on February 25.
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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