Jan. 5, 2000
Status 5 January 2000, 6:15 PM PST Terra mission activation is having its ups and downs. The manufacturer of the High Gain Antenna (HGA) has expressed concern about flying through the South Atlantic Anomaly (SAA) with the gimbal drive power turned on. They are worried that the associated high radiation doses on a particular transistor, while it is powered, could eventually lead to burn out of the device. To provide time to assess this situation, the HGA was turned off this afternoon (possibly for 1-3 days) and contact with the spacecraft is temporarily relying only on the omnidirectional antenna. The omni is being used at its nominal 1 kilobit-per-second (kbps) data rate, with occasional bursts at 16 kbps. At the lower transmission rate, only instrument health and safety telemetry data are available. More detailed instrument and camera telemetry data are being provided during the 16 kbps contacts. Resolution of the power subsystem anomaly which occurred at the end of yesterday's propulsion burn has not been finalized. In light of this and the more limited data capability currently available, the 11-second engineering burn of the spacecraft thrusters, originally scheduled for tomorrow, has been postponed for at least a day. MISR instrument and camera telemetry data are looking good. The optical bench has reached a temperature of about 20 degrees Centigrade, and the camera focal planes have stabilized at around 25 degrees Centigrade. 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