Galileo Status Report - June 25, 1996

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

GALILEO MISSION STATUS

June 25, 1996

NASA's Galileo spacecraft proceeded toward its first close flyby of Jupiter's big moon, Ganymede, scheduled to occur at 6:29 a.m. Universal Time on June 27, 1996 (11:29 p.m. on June 26 Pacific Daylight Time). One-way light time from the spacecraft to Earth at that time will be 35 minutes, so the spacecraft’s signal showing that the closest approach has occurred will be received on Earth at 12:04 a.m. PDT June 27.

Initial observations of the Io plasma tours by the ultraviolet experiment are complete and the first remote observations of Io by the camera were done today. Tomorrow, Galileo's instruments will be looking at both Ganymede and Jupiter's Great Red Spot.

Yesterday afternoon, Galileo's energetic particle detector (EPD) was autonomously turned off by the spacecraft and placed in a "safe" mode. This is a standard safety feature built into the particle detector's operating software and is triggered if the instrument's own computer detects that any one of a number of readings are above or below pre-determined limits. The automatic turn-off allows EPD engineers to search for the cause of the anomaly and determine whether the instrument can safely be turned on.

To avoid interfering with the Ganymede encounter sequence now being executed by the spacecraft, Galileo engineers have decided to leave the EPD instrument off until at least a day or two after the Ganymede flyby is completed. Meanwhile, engineering data being received from the spacecraft may point toward the problem that initiated the instrument's automatic shut-off. No other scientific instruments are affected and all of Galileo's other observations are proceeding as planned.

The EPD is one of several instruments on Galileo that measure Jupiter's magnetic fields and particles. Systematic measurements of the Jovian magnetic environment and particle population began on Sunday. The instruments will continuously send data back to Earth during Galileo's close passes of Jupiter, the moons and from other specially chosen locations within the planet's magnetic environment.

Today Galileo is 1.3 million kilometers (862,000 million miles) from Ganymede and 627 million kilometers (389 million miles) from Earth. One-way communication time is about 35 minutes. Galileo's is approaching Ganymede at a speed of 16 kilometers per second (30,900 miles per hour).

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