Wednesday, Dec. 22, 1999
10:00 a.m. EST
Activation of the Terra spacecraft, which was launched on Saturday, December 18th, is continuing, with the
mission going extremely well. A number of spacecraft components have been powered-on over the past two
days, and the performance has been nominal.
The high gain antenna, which communicates with the Tracking and Data Relay Satellite (TDRS) system, has
been placed back in the normal program track mode. In this mode, the antenna tracks one of four of the
on-orbit TDRS spacecraft which are used by Terra. Stored commands from the spacecraft’s flight computer
direct the high gain antenna to point to the proper TDRS satellite. The anomaly which occurred on Sunday
evening, where the high gain antenna program track mode stopped, is now believed to have been a transient
event. The motion of the antenna today eliminated the potential for any mechanical interference type issue.
During the period in which high gain antenna pointing was not occurring, the flight operations team took the
opportunity to flow 16 kbps data from the spacecraft’s omni to the TDRS system. This mode, which was
not an operational requirement, will be a significant asset for the flight operations team during future
non-nominal Terra operations.
Initial instrument activation activities also are proceeding. The MISR instrument will be powered-up shortly
to unlatch 3 launch latches contained in the instrument. Immediately after that, both of the CERES
instruments will be powered-up and placed in a standby mode while outgassing continues.
“The spacecraft has been operating quite well,” said Kevin Grady, Terra project manager at NASA’s
Goddard Space Flight Center, Greenbelt, Md. “All data indicate we have a very healthy spacecraft.”
Terra began a new generation of Earth science – one that studies the Earth’s land, oceans, air, ice and life as
a total global system, when it launched from Vandenberg Air Force Base, Calif., on Dec. 18, 1999, at 1:57
p.m. EST. The Terra mission 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, 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.
The next Terra status report will be issued on or about Dec. 23, 1999.
