PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
FOR IMMEDIATE RELEASE                                                May 17, 1991


       The Magellan spacecraft, now in its second Venus mapping cycle, went through an orbit trim maneuver Friday morning so it would not duplicate the first cycle's altimeter data.

       The altimeter measures the height of features on the surface.

       While planning for the second 243-day (one Venus rotation) mapping cycle, project controllers found the altimeter track would fall exactly in line with the altimeter track of cycle 1, which ended Thursday.

       In order to improve the quality of data, it was decided to slightly rotate the spacecraft's orbit around the node -- an imaginary line drawn through the poles of Venus.

       The maneuver, which required a 33-minute burn of the spacecraft's thrusters, did not change the period of the orbit, nor its altitude or latitude of periapsis, its closest approach to the planet.

       The burn started at 11:13 a.m. PDT. The one-way communication time between Earth and Venus is eight minutes, so the start and end of the burn occurred at 11:21 a.m. and 11:55 a.m., Earth receive time, respectively.


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5/17/91 JJD
#1376