Terra/MISR status 07 January 2000

Status, 7 January 2000

MISR continues to behave itself. No commanding activities are scheduled until January 19 but our tireless operations staff continues to babysit and monitor vital signs. Comparisons of currents, voltages, and temperatures with pre-flight tests and simulations all look very favorable.

Terra activation is proceeding on a busy schedule. CERES, MISR, MODIS, and MOPITT are now all powered on. Turn-on of the ASTER instruments began today, with all scheduled activities taking place successfully. More ASTER activities are scheduled for Sunday. Earlier this week the three MODIS latches were released, and the instrument is in outgas mode, with doors closed. The cooling systems for MOPITT and the ASTER shortwave-infrared instrument were activated this week. The cooling system for the ASTER thermal-infrared instrument will be activated in the next few days.

The high-data-rate link to be used for transmitting science data was successfully tested this week. A software patch and telemetry monitor ("TMON") to remove power from the High Gain Antenna drive during passage through the South Atlantic Anomaly has been designed, and is currently being written and tested. Whether this will needed over the long term is pending further analysis and laboratory testing of the radiation-sensitive part by the drive manufacturer.

The spacecraft star trackers are now being used for navigation. The GN&C (guidance, navigation, and control) subsystem detected a small oscillation, or "jitter", in the spacecraft orientation, induced by motion of the High Gain Antenna. The magnitude of the jitter is a little over one-hundredth of a degree. Although this is tiny, an oscillation of the spacecraft by this amount would be just detectable in MISR images, and would make straight roads look slightly wiggly. Because the oscillation follows a predictable pattern, however, the GN&C engineers have developed a method of anticipating and compensating for it using Terra's attitude control system. This has reduced the magnitude of the jitter by a factor of 10, to virtually undetectable levels from a MISR standpoint.

All of the propulsion system thrusters have now been successfully test fired. A slight reduction in power drawn by the propulsion subsystem was observed after the thruster test a few days ago. The cause has been identified and a procedure to deal with it during future burns has been established. Additional details on the propulsion system burns to raise the Terra orbit altitude to 705 kilometers are now available:

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