Jan. 27, 2000
Status 27 January 2000 The Terra solid-state recorder (SSR) has been reset by turning it off and back on again. This has restored the capability for recording engineering data, but software that was in place before the power was cycled needs to be reloaded before recording of science data can be resumed. This is expected to happen by this weekend. Upload of the MISR flight software and transition to science mode are currently scheduled for Saturday, but there is a good chance that the SSR activities could push this to Sunday. Preparations to insure that our Science Computing Facility at JPL is ready to receive and display MISR data (along with Superbowl XXXIV coverage) are progressing well. The performance of the spacecraft cooling system that supports the ASTER thermal-infrared (TIR) instrument has improved significantly. Spacecraft engineers have obtained a better understanding of the operational behavior of the control system, and some additional checkouts are planned for the next few days. Turn-on of the TIR instrument could occur as early as Monday. Checkout of the spacecraft propulsion system using two series of 1-second test burns was scheduled for today. During the first burn attempt this morning, a yaw rate measurement exceeded a threshold level, which caused the fault detection software to put the spacecraft in "safe" mode. The problem was quickly traced to an incorrect value for the threshold. As of this afternoon, the spacecraft has been brought out of safe mode and the test burns have been rescheduled for tomorrow. This may cause a 20-second engineering burn, now scheduled for Monday, to slip by a day or two. Following that, the overall ascent maneuver plan calls for six burns per day--three 30-second burns occurring within a span of about 10 minutes, followed several hours later by another cluster of three 30-second burns. The cumulative burn time to get to orbit is 1800 seconds, and should consume 39 kilograms of hydrazine fuel. Final orbit is expected to be achieved around February 12. The spacecraft safing event that occurred earlier today resulted in automatic safing of MISR (and the other instruments) as well. MISR responded properly, and the cameras and optical bench heaters turned off. Within two hours of the safing event, the optical bench cooled from 26 degrees to 20 degrees Centigrade, and the cooling trend is continuing. ("Replacement" heaters will keep the instrument from getting too cold.) This unplanned event has effectively given us a head start on the cool-down which would have occurred when the commands to load the flight software are sent, so we have opted simply to remain in safe mode for the next few days. Many of these hiccups the spacecraft has experienced are typical of early mission activations. In general, Terra and MISR are handling all that is happening very well. 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