Press Release

Terra Status Report 1 Feb 2000

By SpaceRef Editor
February 1, 2000
Filed under

Dave Steitz

NASA Headquarters

(Phone: 202/358-1730)

Allen Kenitzer

EST Goddard Space Flight Center

Greenbelt, Md. 20771

(Phone: 301/286-8955)


GSFC Press Release 00-13

The Terra Mission operations are going well as instrument activation and outgassing continue after more than
six weeks on-orbit.

During the week of January 24th, while most of the Washington area was shut down for two days because of
the snow storm, operations in the Terra Control Center continued. “It is fortunate that even this recent blizzard
did not impede this Team,” said Kevin Grady, Terra project manager at NASA’s Goddard Space Flight Center,
Greenbelt, Md. “The commitment of individuals on this Team remains phenomenal.”

Last week began with the MODIS instrument opening their space view door and configuring into science mode.
Both of these activities were completed as planned. The first recorder dump of MODIS science data executed as
planned and the data was routed to the DAAC and the MODIS Science Team for analysis. The nadir (Earth
viewing) aperture door on MODIS is still closed, and it will remain in that state until the first engineering image is
taken sometime in late February.

In the middle of the snow storm, the ASTER instrument also took the opportunity to perform two pointing
checks. Both of these movements were successful.

The anomaly which has been given attention in recent weeks is the issue of the orbit ascent maneuvers. During
the attempt of the first long ascent maneuver, Terra’s flight computer detected a roll attitude anomaly, and
properly aborted the maneuver approximately one minute into the burn. The data has now been analyzed and a
strategy mapped-out for completing an ascent sequence. Three items have been identified as potential
contributing factors to the anomalous behavior. Four firings will take place over the next week to prepare for
the ascent sequence, and eliminate (or establish) anomalous thruster performance as one of the contributing
factors. The first two firings are planned for this week.

Controllers have a plan of performing a series of burns, which will place Terra in the operational orbit, in
formation with Landsat 7. “It is a challenging plan, but safety is always first and foremost when the
maneuvering of Terra is planned,” Grady added.

Just as the blizzard started last Tuesday morning, controllers were confronted with a data recorder anomaly
on Terra. During a routine housekeeping recorder playback, the solid state recorder playback hung-up. This
housekeeping playback operation followed a successful MODIS science playback and replay on the previous
orbit. A number of diagnostics were run on the recorder in the hung state, and finally the recorder was reset to
clear the anomaly. Housekeeping and science data recording and playback are now working nominally. Analysis
and simulation are in process to determine the cause for this hang-up.

High gain antenna radiation hits have been occurring periodically. Controllers are now seeing them on the
descending passes through the South Atlantic Anomaly. The telemetry monitor continues to successfully restart
the antenna after each of these events.

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 during the week of Feb. 7, 2000.

More information on Terra also is available via the Internet at

SpaceRef staff editor.