Status 16 February 2000
Since transition to science mode on January 30, MISR has been operating
primarily in the "global" science configuration. The "dark" data from
the cameras are proving extremely useful for verying instrument
performance and
for checking out our science data processing software. We have also
developed a special data extraction procedure to highlight the
sensitivity to proton radiation in the South Atlantic Anomaly, and
are currently in the process of constructing a global map of these
data. Who would have predicted that MISR's first "science" product
would be generated while the cover is still closed!
All 36 of MISR's imaging channels (four color bands in nine cameras)
instrinsically provide data in which the "footprint" of the individual
picture elements ("pixels") making up the images measures 275 meters on the
ground (about the size of the Rose Bowl). In the "global" science mode, the
data in all four colors of the camera which looks straight down and the red
band of the other eight cameras are normally transmitted at this "high
resolution", while the data in the other channels are digitally averaged
within the instrument to coarser, 1.1-kilometer pixels. This is done to
reduce the overall data volume. Last Sunday we successfully tested the
"local" science mode, in which selected areas of the Earth will be imaged
at high resolution in all 36 channels. More "local mode" checkouts are
planned for tomorrow. Two sequences that activate MISR's calibration
photodiodes have also been performed. So far only one set of these
data has been received at JPL, but a preliminary look indicates the
expected diode readings for a "dark" scene.
The Terra orbit adjustment maneuvers are proceeding extremely well.
Thruster firings lasting up to five minutes have been successfully
accomplished and five more burns are planned to reach the desired
orbit altitude. The daylight equator crossing time is 10:45 am and is
expected to increase to 10:47 am in about a year, after which it will
drift earlier, reaching 10:30 am in about three-and-a-half years. An
additional four-minute orbit inclination adjustment burn to prevent
the crossing time from increasing past 10:45 am, and to reach 10:30
am in less than three years, is being considered. This is of little
benefit to MISR, but other teams, particularly MODIS, prefer the
closer proximity to Landsat 7 and the reduced ocean sunglint that
would be achieved. If the Terra Project decides to schedule this
activity immediately following the ascent burns, opening of MISR's
cover, currently planned for February 25, will be delayed by 3 or 4
days. MISR has notified the Terra Project of our concern regarding
the impact on several planned field experiments which are expecting
to coordinate with Terra overflights in that time period.
The random occurrences of "bit flips" or occasional data errors that have
been seen in MISR data have also been documented in other instruments,
notably ASTER and MODIS. This means that the problem is not
originating within MISR itself. The Terra Project is formulating a
plan to isolate the source of these errors.
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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