Mark Hess
Goddard Space Flight Center
Greenbelt, Md. 20771
(Phone: 301/286-8955)

Terra Status Report #3
Thursday, Dec. 23

Activation of the Terra spacecraft is continuing.

"Overall the mission is going extremely well, with the performance of both the team and the spacecraft superb," said Kevin Grady, Terra project manager at NASA's Goddard Space Flight Center, Greenbelt, Md. "All of the activities planned to be completed by mission day 5 have now been accomplished, with the exception of the turn-on of one of the instrument outgas heaters. A number of spacecraft components have been powered-on over the past three days, and the performance of these have been excellent."

The solid state star trackers, the science formatting electronics, the capillary pumped loop for Canada's Measurements of Pollution in the Troposphere (MOPITT) instrument and the solid state recorder have all been powered-on or configured for nominal operations. The star trackers are being used to update the on-board attitude solution and preliminary indications are that the trackers are producing excellent results.

The MOPITT capillary loop was turned-on early to help stabilize thermal cycling which the instrument could have been exposed too. The Terra solar array is producing over 8100 watts of power and the batteries are working properly.

The high gain antenna, which communicates with the Tracking and Data Relay Satellite (TDRS) system, was placed back in the normal program track mode on Monday midday. On the previous evening, during a pass through the South Atlantic Anomaly (SAA), the high gain antenna gimbal stopped and the real-time pass was terminated shortly thereafter. While the root cause is not known for certain at this time, this shutdown is now believed to be caused by a proton radiation transient event, or single event upset.

Early Tuesday morning, the spacecraft controls computer halted, and the independent safe-hold processor took control of the spacecraft. As a result of analyses overnight, the flight operations team now knows that an exception generated by the navigation software was the cause of the control computer shutdown. The flight software engineers are examining the navigation code now to determine the cause and corrective action. The spacecraft will fly under the control of the independent safe-hold processor while the software corrective action is developed. The spacecraft remains in a safe power and thermal attitude.

Initial instrument activation activities also are proceeding. The Multi-angle Imaging SpectroRadiometer (MISR) instrument was powered on and three launch latches in the instrument were released. Both of the Clouds and Earth's Radiant Energy System (CERES) instruments were powered-on and the instruments were placed in a safe mode while out-gassing continues.

"Overall, we are off to an extraordinary start," Grady said. "Spacecraft activation and operations are full of these minor problems, and this team has been up to the task on every one of them, whether they were flight or ground problems. Most of the flight operations team will be working through the two holiday weekends. In January, we will be fully engaged in instrument activation, 100 mbs second data flows on X- and Ku-band systems, and a long series of attitude and orbit maneuvers. Based on results of the past six days, there is no question that this team is up to the task. "

Terra was launched from Vandenberg Air Force Base, Calif., on Dec. 18, 1999, at 1:57 p.m. EST, and is the "flagship" to the Earth Observing System series of satellites, part of a precedent setting program designed to provide daily information on the health of the Planet.

The Terra satellite was built by Lockheed Martin assembled and tested the Terra spacecraft at its production facility in Valley Forge, Pa., under management from NASA's Goddard Space Flight Center, Greenbelt, Md.

The primary objective of the Terra Mission is to simultaneously will study clouds, water vapor, small particles in the atmosphere (called "aerosol" particles), trace gases, land surface and oceanic properties, as well as the interaction between them and their effect on the Earth's energy budget and climate.

Terra is managed by NASA's Goddard Space Flight Center for NASA's Office of Earth Science, Washington, DC. A goal of the Earth Science Enterprise is to expand knowledge of the Earth System, from the unique vantage point of space. Earth Science Enterprise data, which will be distributed to researchers worldwide at the cost of reproduction, is essential to people making informed decisions about their environment.

See Terra Status Reports Index.

For more information:

About Terra
Terra Animations
Terra Web Site

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