his is an artists concept of Cassini during the Saturn Orbit Insertion (SOI) maneuver, just after the main engine has begun firing.
his is an artists concept of Cassini during the Saturn Orbit Insertion (SOI) maneuver, just after the main engine has begun firing.

NASA's Cassini spacecraft successfully completed a course adjustment April 3 during its journey toward Saturn.

The maneuver was designed using new procedures the mission will employ for course adjustments while orbiting Saturn. The spacecraft fired its main engine for 9.8 seconds to accomplish the maneuver.

Cassini is in good health. As of April 28, it will have traveled 3 billion kilometers (about 1.9 billion miles) since its launch in October 1997. It will reach Saturn on July 1, 2004.

This week's engine burn, just the 13th since launch and the first since February 2001, was planned both for tweaking Cassini's trajectory and for routine maintenance of the propulsion system. To keep fuel-lines flowing freely, engineers do not allow Cassini to go much more than one year between engine firings, said Earl Maize, Cassini spacecraft operations team manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

During its orbital tour at Saturn, Cassini will need to fire its main engine for trajectory correction maneuvers as frequently as once every five days. Until now, the tasks in preparing and executing each maneuver were spread out over as much as three weeks.

"We streamlined the process this time," said JPL systems engineer Joel Signorelli, leader of the maneuver-design team.

The team used new software that automates some of the preparatory steps. Then, within a nine-hour span of two-way communications between Cassini and NASA's Deep Space Network, safety checks were performed, commands were sent to the spacecraft, the engine ran for the prescribed time, and engineering data confirming the successful burn were sent down. Scientific instruments monitoring the space environment around the spacecraft continued to gather data during the procedure, which will be a valuable capability during the orbital tour but had not been attempted during previous flight path correction maneuvers.

The engine applies 445 newtons (100 pounds) of force to the 5-ton spacecraft. "It's about like me pushing on a school bus," Maize said. The next burn planned for Cassini will be a flight path correction maneuver in May 2003.

Nearly six months after it begins orbiting Saturn, Cassini will release its piggybacked Huygens probe for descent through the thick atmosphere of the moon Titan on Jan. 14, 2005. 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. Additional information about Cassini-Huygens is available online at http://saturn.jpl.nasa.gov .


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