SeaWinds Mission Status

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011

NASA’s orbiting SeaWinds radar instrument, circling Earth’s
poles at an altitude of about 800 kilometers (500 miles), is in
excellent health and continues to collect high quality science
data despite a minor problem earlier this month with its inertial
reference gyros.

SeaWinds was restored to normal operations shortly after the
spacecraft had switched to a safe standby mode on January 1,
2000, when one of its three primary gyros degraded beyond an
assured level of operation. As designed, spacecraft fault
protection systems detected the gradually declining condition of
the gyro over several days and placed the satellite in a
protective orientation when the gyro degraded beyond a preset
threshold. SeaWinds’ solar panels were pointed toward the Sun and
the spacecraft was instructed to await commands from Earth. The
Ball Aerospace & Technologies Corp., Boulder, CO spacecraft
operations team returned the spacecraft to its normal Earth-
pointing position later that same day using the backup inertial
reference gyros. On January 2, the SeaWinds instrument was
returned to normal wind vector measurement operation, resulting
in a data gap of less than 36 hours. The spacecraft and
instrument performed as expected throughout the incident.

Spacecraft systems engineers realized prior to launch that
the gyros would degrade more rapidly than planned and might not
be able to support the entire first two years of the science
mission. However, they believed that the satellite’s star
trackers could be used to maintain the spacecraft’s pointing
accuracy without the gyros. After launch they determined that
minor software changes were necessary to enable this capability.
Ball Aerospace engineers have made these changes and are
currently testing them on the ground. The software package is
expected to be uploaded and operational in about a month. The
backup set of gyros will continue to keep the SeaWinds instrument
accurately pointed for many months if the software needs further
refinement.

Currently looping Earth every 101 minutes at a velocity of
about 7.4 kilometers per second (16,500 miles per hour), the
ocean-observing spacecraft continues to make measurements of
ocean wind speeds and directions over 90 percent of the globe
each day. The orbiting radar instrument is providing highly
accurate snapshots of storms, typhoons and cyclones, and giving
meteorologists a detailed glimpse of intricate wind patterns and
other large-scale phenomena, such as the movement and breakup of
polar ice. These observations are improving weather forecasting
and storm hazard prediction, as well as providing a long-term
data set for studying climate change.

SeaWinds is managed for NASA’s Office of Earth Science,
Washington, DC, by the Jet Propulsion Laboratory, which also
built the SeaWinds scatterometer instrument and is providing
ground science processing systems. NASA’s Goddard Space Flight
Center, Greenbelt, MD, managed development of the satellite,
which was designed and built by Ball Aerospace & Technologies
Corp., Boulder, CO. The National Oceanic and Atmospheric
Administration is a partner in the mission.

NASA’s Earth Sciences Enterprise is a long-term research and
technology program designed to examine Earth’s land, oceans,
atmosphere, ice and life as a total integrated system. The
agency’s Jet Propulison Laboratory is a division of the
California Institute of Technology, Pasadena, CA.