Spaceflight Now: Breaking News

Engine firing aborted by NASA's Terra spacecraft
Posted: Jan. 22, 2000

Artist's concept of NASA's Terra spacecraft orbiting Earth. Photo: NASA
After more than four weeks of the Terra spacecraft on-orbit, both the spacecraft and instruments continue to perform extremely well.

"All of the on-board instruments are continuing their outgas period," said Kevin Grady, Terra Project Manager at NASA's Goddard Space Flight Center, Greenbelt, Md. "The spacecraft is presently flying under the control of the spacecraft controls computer in its normal mission control mode, with the high gain antenna being used for both S and Ku band dumps."

X-band dumps are also being scheduled periodically, with analysis of the tape of the first X-band contact, recorded last week, indicating that it contained good recoverable data. Earlier in the week, testing of the high gain antenna motor drive electronics was completed, confirming that there are no parts stress issues associated with using the electronics in the South Atlantic Anomaly. Further, there are no operational constraints on the use of the high gain antenna through the South Atlantic Anomaly during Terra's science mission.

On Monday January 10, Terra completed its first maneuver to raise the orbit. This was a brief 11 second burn to establish the functionality of the thruster control modes. At the time, controllers believed they had validated the orbit adjust control capability of Terra. The following day, while attempting the first of four large maneuvers, the Terra flight computer aborted the maneuver 66 seconds into the burn. The flight software shutdown the maneuver when the computer detected a small rolling motion on the spacecraft. The spacecraft was safe at all times and no telemetry data was lost. The Team is in the process of analyzing the telemetry and developing a new burn sequence to get Terra to its final orbit at the earliest possible date. Controls engineers have identified a number of factors which are potential causes for the roll motion, and are in the process of developing a plan for the corrective action and new orbit ascent sequence.

The Lockheed Martin Atlas 2AS rocket blasts off from the rebuilt Space Launch Complex-3 East at Vandenberg. Photo: Bechtel Corp.
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 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, Greenbelt, Md., 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.

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