PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
The Galileo orbiter and probe are now flying independently to their separate encounters with Jupiter on December 7, 1995. After the orbiter had been precisely targeted for the probe's atmospheric entry point, the probe was separated for its free flight at 11:07 p.m. PDT (Earth received time) July 12. The orbiter was then re-targeted for its Jupiter approach, including Io flyby, reception of probe data, and Jupiter orbital entry. This maneuver involved a 5-minute burn of Galileo's main rocket engine, used for the first time during this sequence.
The probe is now scheduled to enter Jupiter's atmosphere at 2204 Universal Time, communicating with the orbiter spacecraft a few minutes later. The orbiter is targeted for a flyby 1,000 kilometers (about 600 miles) above the surface of the volcanic satellite Io more than four hours earlier at 1746 Universal (Earth received time 10:38 a.m. PST); after receiving and recording the probe's data for about 75 minutes the orbiter will fire its main engine for about 47 minutes and go into orbit around Jupiter. This engine, which develops 400 newtons (equivalent to about 80 pounds) of thrust, is part of the Galileo propulsion system developed and built by Messerschmitt-Bolkow-Blohm and provided by the German Space Agency as a partner in the Galileo project.
Both the probe separation and the orbiter deflection maneuver were controlled by computer sequences that issued commands for the various preparations as well as the main operations. In each case the spinning Galileo spacecraft had to be oriented precisely in space and then spun up to 10.5 rpm to stabilize the craft in that orientation. After the deflection maneuver the orbiter was returned to its normal attitude and 3-rpm spin rate for the interplanetary cruise. Probe separation was monitored by the JPL Galileo flight team and by the probe team of NASA's Ames Research Center and Hughes Aircraft Company.
The Galileo orbiter is healthy and operating normally; it is transmitting telemetry at 10 bits per second. The Galileo probe was checked out before separation and found to be healthy; it will transmit telemetry again on Dec. 7. The two craft are almost 700 million kilometers (435 million miles from Earth; they are about 72 million kilometers from Jupiter, approaching it at about 5.8 kilometers per second (almost 13,000 mph).
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