Feb. 16, 2000
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