Following commands from the Mars Exploration Rover flight team at NASA's Jet Propulsion Laboratory, Pasadena, Calif., the spacecraft first performed a calibration and check of its eight thrusters, then fired the thrusters to fine-tune its flight path toward Mars.

The main burn had two components. Thrusters that accelerate the rotating spacecraft along the direction of the rotation axis burned steadily for about 28 minutes. Then, thrusters that accelerate the spacecraft in a direction perpendicular to the rotation axis fired in pulses timed to the spacecraft's rotation rate -- with 264 pulses totaling about 22 minutes of burn time. The total maneuver increased Spirit's speed by 14.3 meters per second (32 miles per hour).

At the end of the trajectory correction, Spirit performed an attitude turn that adjusted its orientation in space to maintain the optimal combination of facing its solar array toward the Sun and pointing its low-gain antenna toward Earth. The spacecraft's next trajectory correction maneuver is scheduled for Aug. 1 and its next attitude turn for July 22.

All systems on the spacecraft are in good health. As of today at 6 a.m. Pacific Daylight Time, Spirit had traveled 27,390,000 kilometers (17,020,000 miles) since launch on June 10, and was at a distance of 2,660,000 kilometers (1,653,000 miles) from Earth. It was traveling at a speed of 32.22 kilometers per second (72,100 miles per hour) relative to the Sun. Spirit will arrive at Mars on Jan. 4, 2004, Universal Time (evening of Jan. 3, 2004, Eastern and Pacific times). The rover will examine its landing area in Mars' Gusev Crater for geological evidence about the history of water on Mars.

Spirit's twin, Opportunity, is being prepared at Cape Canaveral Air Force Station, Florida, for a first launch opportunity at 12:27:31 a.m. June 26, Eastern Daylight Time (9:27:31 p.m. June 25, PDT).

JPL, a division of the California Institute of Technology, manages the Mars Exploration Rover project for NASA's Office of Space Science, Washington, D.C. Additional information about the project is available from JPL at

http://mars.jpl.nasa.gov/mer

and from Cornell University, Ithaca, N.Y., at

http://athena.cornell.edu/ .

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