Aerospace Supports Landsat Anomaly Investigation Team
EL SEGUNDO, Calif. (3/15/06) -- When your home’s solar panels fail to capture energy, the worst thing that can happen is there’s no hot water. But when the solar-gathering power for a multi-million dollar satellite is compromised, the satellite draws upon the limited supply of its batteries to carry out its functions. The end result is a spacecraft emergency where technical experts unite to try and determine how to restore the satellite’s ability to collect solar energy.
That’s what technical experts from a cross section of organizations at The Aerospace Corporation did as part of an anomaly investigation team formed to address a solar power emergency on a U.S. Geological Survey (USGS) Landsat 5 satellite. Landsat 5 provides images of the Earth’s surface from space.
Landsat 5’s solar array drive mechanism began exhibiting problems in late November 2005 when its rotation rate became sporadic. With the solar array not held to an optimal pointing angle to the sun, it was unable to produce sufficient energy to maintain power balance, resulting in a deep depth of discharge of the batteries and a declared spacecraft emergency. After stabilizing the mission, payload operations were suspended and the team was assembled to identify the source of the problem and develop strategies for recovery.
The USGS contacted Steve Covington of The Aerospace Corporation's Civil and Commercial Operations, who serves as the USGS Landsat 7 flight systems manager and international coordinator for the corporation. Members of the Mechanical Systems Department provided support to the team that included representatives from NASA, USGS, Lockheed Martin, the Science Applications International Corp., and SGT, Inc., a systems engineering and technical assistance organization that supports multiple efforts at NASA Goddard Space Flight Center.
Aerospace provided insight from similar solar array drive designs and the aspects of the tribology (mechanism lubrication) in these designs. This early support helped direct the team’s investigation toward the leading theory of the solar array drive’s erratic behavior: the exhaustion of lubrication within the mechanism’s bearing surfaces leading to increased system resistance.
Landsat 5 was launched into a sun synchronous orbit in 1984 with a three-year design life. The solar array drive that was intended to provide 16,000 rotations in orbit now has endured about 116,000. Through the team’s investigation, Landsat 5 has been returned to operational status using a modified operational profile for the solar array drive management that Aerospace helped develop.
The Aerospace Corporation, with headquarters in El Segundo, Calif., is an independent, nonprofit company that provides objective technical analyses and assessments for national security space programs and selected civil and commercial space programs in the national interest.
Media Information: contact Dave Jonta, 310-336-5041, david.l.jonta@aero.org
