PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
The Galileo spacecraft is reaching the end of its interplanetary cruise sequences and will soon begin the first of two Jupiter approach sequences. The spacecraft is nine weeks away from probe entry and Jupiter orbit insertion on December 7, 1995.
The last Earth-to-Jupiter cruise sequence, EJ-10, which ends October 2, has seen a variety of engineering tests and preparations for Jupiter arrival. Recently this included demonstrations of one-star attitude determination and other preparations for ensuring the most robust spacecraft performance during the critical probe relay and Jupiter orbit insertion. Readouts from the magnetometer, the extreme ultraviolet instrument, and the dust detector continued throughout this period at a frequency of twice per week.
On September 18, the spacecraft switched to the use of the suppressed-carrier downlink, which allows all of Galileo's radio signal to be used for the telemetry data, boosting the effective data-rate performance. Suppressed carrier is now Galileo's standard downlink configuration.
Telemetry data showed on September 18 that the power-on reset detector in one of the two command and data system power converters had detected a power drop, which was later determined to be transient. Analysis of the cause and implications is still under way. This event did not cause any interruption of the ongoing cruise sequence, EJ-10.
About two months ago, Galileo's dust detector observed the onset of the latest in a series of interplanetary dust storms that apparently began in mid-1994. This last storm was the most intense so far, reaching a peak of nearly 20,000 particle impacts per day, and may not have entirely abated. Recent counts are in the range of hundreds of particle impacts per day, still far above the previous interplanetary background of one every three days. A special series of dust measurements is planned for early October to intensely cover a 10-hour Jupiter-rotation period. These dust measurements are designed to search for any changes which may be related to Jupiter's rotation.
The spacecraft continues to operate normally, spinning at approximately 3 rpm and transmitting coded telemetry at 10 bits per second. It is now only 40.8 million kilometers (25.3 million miles) from Jupiter and 843 million kilometers (524 million miles) from Earth. Its speed around the Sun is 6.78 kilometers per second (about 15,000 miles per hour).