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:
| Burn | Date and time | Duration | Hydrazine fuel used |
| Engineering test | 10 Jan. 9:55 AM PST | 11.0 seconds | 0.3 kilograms |
| Ascent #1 | 11 Jan. 3:18 PM PST | 523.3 seconds | 11.8 kilograms |
| Ascent #2 | 18 Jan. 1:55 PM PST | 702.8 seconds | 14.9 kilograms |
| Ascent #3 | 21 Jan. 2:39 PM PST | 241.4 seconds | 4.9 kilograms |
| Ascent #4 | 23 Jan. 1:59 PM PST | 408.9 seconds | 8.1 kilograms |
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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