Terra Status Report #6

Dave Steitz

NASA Headquarters

(Phone: 202/358-1730)

Allen Kenitzer

Goddard Space Flight Center

Greenbelt, Md. 20771

(Phone: 301/286-8955)

Terra STATUS REPORT #6

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.

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.

For additional information on the Terra mission, call the Goddard Newsroom at (301) 286-8955. The next
Terra status report will be issued on approximately Jan. 28, 2000.

More information on Terra also is available via the Internet at: http://terra.nasa.gov