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Ulysses Mission Status Report


PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011


August 1, 1994

The Ulysses spacecraft -- currently exploring high latitude regions over the sun's southern pole -- has climbed to 75.5 degrees south of the sun's equator and is in the midst of its primary mission to examine the complex forces at work in these regions of space.

Ulysses was in a position to observe the impacts of comet Shoemaker-Levy 9 during mid-July. At the time Ulysses had a direct line of sight to the impact region at 74.5 degrees south of the sun's equator. The spacecraft was about 375 million kilometers (230 million miles) below the ecliptic plane in which the planets orbit and 795 million kilometers (490 million miles) from Jupiter. Ulysses' unified radio and plasma wave experiment was reconfigured to provide the highest level of sensitivity for detecting very low frequency radio waves of less than 1 megahertz that might have been generated by the comet impacts.

Data from the impact of fragment A on July 16 through the collision of fragment Q on July 20 have been processed and analyzed, but no clear evidence of changes in radio frequencies has been detected. Jupiter normally has considerable activity at these frequencies. Members of the Ulysses radio science team will continue to watch for the more subtle or long-term effects of the comet collisions, but they do not anticipate much new information in the aftermath of the event.

All spacecraft operations and science experiments continue to go well. Ground controllers are carrying out routine data-gathering activities and experiment readjustments as needed. The European Space Agency's tracking facility at Kourou, French Guiana, has been modified and brought on-line to help provide 24-hour coverage of Ulysses now that it is moving into the sun-Earth region where the spacecraft's axial boom is illuminated by the sun. This illumination causes uneven heating of the boom which, in turn, causes a slight wobble of the spacecraft. Shortly after launch, Ulysses went through a period of wobbling that was finally controlled by an onboard control system that is used to maneuver and keep the spacecraft pointing at Earth. Ground controllers must be in constant contact with the spacecraft to carry out this technique, allowing the onboard system to detect and reduce unwanted motion.

Today Ulysses is traveling at a velocity of about 74,000 kilometers per hour (46,000 miles per hour) with respect to the sun.

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