Dave Steitz

NASA Headquarters

(Phone: 202/358-1730)

Allen Kenitzer

Goddard Space Flight Center

Greenbelt, Md. 20771

(Phone: 301/286-2806)


Thursday, Jan. 20, 2000

10:00 a.m. EST

After more than four weeks of the Terra spacecraft in 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

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, Jan. 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 were 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 corrective action and a 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” in the Earth Observing
System (EOS) series of satellites. EOS is a precedent-setting program
designed to provide daily information on the health of our home planet.

The primary objective of the Terra Mission is to simultaneously
study clouds, water vapor, small particles in the atmosphere (called
“aerosol”), 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 is also available via the Internet at