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Deep Space 1 Mission Status

December 17, 1999

Deep Space 1, which successfully completed its primary
mission of testing advanced technologies late last September,
remains in a safe standby mode. The mission team conducted
crucial tests on the spacecraft on Wednesday, December 14, in
response to a problem with the spacecraft’s star tracker that
caused Deep Space 1 to enter this mode last month.

In the tests, the team successfully maneuvered the
spacecraft’s orientation to point its high-gain antenna toward
Earth as part of a rotation movement. This capability not only
begins the important process of developing the ability to point
the spacecraft without the star tracker, but also opens up the
possibility of uploading software that can compensate for the
apparent loss of the sensor so that the spacecraft’s
instrumentation can return further technology validation and
scientific information during its current extended mission.

The tests included a series of maneuvers, including stopping
the slow rotation that is typical of Deep Space 1’s safe standby
mode; turning the spacecraft so that it was no longer pointing
its antenna at the Sun, which is also typical of this mode;
turning and stopping the spacecraft in 10-degree increments;
rotating the spacecraft in a cone-like, circular movement, during
which the low-gain antenna was intermittently aimed toward Earth;
switching to the high-gain antenna while continuing with this
rotation; stopping the rotation; returning to the low-gain
antenna; rotating further; and stopping again. At the end of the
tests, the team returned the spacecraft to its standby state.

These maneuvers helped the team gain experience in turning
and pointing the spacecraft without the star tracker. There will
be future tests as the team continues to work on the techniques
necessary to operate the spacecraft independent of this sensor.

The star tracker, a new, sophisticated device that helps
determine the spacecraft’s orientation, is neither part of
the navigation system nor one of the 12 advanced technologies
whose testing was the focus of Deep Space 1’s primary mission.
Since shortly after launch, it has displayed many unexplained,
intermittent problems in reporting its orientation properly to
the spacecraft computer. In all previous cases, the device
resumed normal operation within less than one hour. This time,
however, it has not resumed functioning correctly, and the team
has determined that it probably cannot be used for the duration
of the mission.

Deep Space 1 is now more than 246 million kilometers, or 153
million miles from Earth. At this distance, radio signals,
traveling at the speed of light, take more than 27 minutes to
make the round trip between Earth and the spacecraft.