Scheduled Maintainence Keeps Spacecraft in Top Shape
July 7, 1998
The Cassini spacecraft's routine flight operations schedule was dominated by light "housekeeping" and maintenance activities over the past month, with the spacecraft remaining in excellent health.
For telecommunications with Earth, Cassini switched from low-gain antenna 1 to low-gain antenna 2 as planned; the antenna selected depends on the relative geometry of the Sun, Earth and the spacecraft.
The quarterly periodic spacecraft engineering maintenance was performed, which includes activities to lubricate the reaction wheel assembly mechanisms, which are one of two systems on Cassini used to provide pointing control for the spacecraft. The assemblies are electrically powered wheels that are mounted in three orthogonal axes onboard Cassini. To rotate the spacecraft in any one direction, the appropriate wheel is spun in the opposite direction. More complicated maneuvers may involve two or even three reaction wheels. There are four wheels; one serves as a backup. The quarterly maintenance also included lubrication of the actuators for the two duplicate main rocket engines, and a software clean-up of any bit errors that may have occurred in the spacecraft's attitude and articulation control subsystem during the quarter.
Cassini is traveling at more than 107,000 kilometers per hour (66,000 miles per hour) and has traveled more than 769 million kilometers (478 million miles) since it left Earth last October.
Additional information about Cassini-Huygens is online at http://saturn.jpl.nasa.gov.
Cassini will begin orbiting Saturn on July 1, 2004, and release its piggybacked Huygens probe about six months later for descent through the thick atmosphere of the moon Titan. Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Office of Space Science, Washington, D.C.