Artist's concept of NASA's QuikScat spacecraft with SeaWinds instrument orbiting Earth. Photo: NASA

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.