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Galileo Probe Release Status


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July 1, 1995

The Galileo flight team is making final preparations for the launching of the atmospheric probe on its solo flight to Jupiter's atmosphere, due to arrive Dec. 7, 1995. The probe release sequence was transmitted to the spacecraft on June 28. This sequence, which was activated on July 5 and continued through July 13, will command a series of activities culminating in the probe release, scheduled for 0530 Universal Time on July 13. Confirmation of release events will be received on Earth 37 minutes later, at 11:07 Pacific Daylight Time on July 12.

The probe's internal timer will be set to activate six hours before atmospheric entry, then be switched to internal battery power and place the probe in its dormant cruise mode. The cable linking the probe and orbiter will be cut and then the orbiter will turn to put the probe in the proper orientation to enter the atmosphere. The spacecraft will spin up to 10.5 rpm to stabilize the probe's orientation. Finally the release nuts will be opened and springs will launch the probe on its 83-million-kilometer (52-million-mile) flight to Jupiter.

The previous sequence on June 23 had allowed for a trajectory correction -- the 24th since launch -- but the navigation team found the aim so good from the 23rd maneuver last April that the last maneuver was not needed.

Galileo is scheduled to use its main engine in a large maneuver for the first time to aim the orbiter away from the probe trajectory and toward its own Jupiter approach path. On Dec. 7 this trajectory will deliver Galileo to travel to within 1,000 kilometers of the volcanic surface of Jupiter's moon Io, and into position to receive and record the probe's scientific data. Next the spacecraft will reach the point where another large maneuver will put it in the first orbit around the giant planet.

The spacecraft continues to operate normally, spinning at about 3 rpm and transmitting telemetry at 8, 10 and 16 bits per second. It has been undergoing a variety of engineering tests as Jupiter arrival draws near, as well as frequent readouts of scientific data on the surrounding space environment. The gravity wave experiment started in May was concluded on June 28.

Galileo is now nearly 789 million kilometers (490 million miles) from the Sun, almost as far away as it is to Jupiter. The spacecraft has traveled 3.7 billion kilometers (2.3 billion miles) since launch in October 1989. Today its speed in orbit, gradually slowing as it recedes from the Sun, is 16,076 miles per hour.

Galileo Probe Release Status Updates

Summary of Today's News, 7/6/95

Today at about 1:24 p.m. PDT the Galileo flight team sent the first of three go-ahead commands to the Galileo spacecraft. This command will switch the probe to internal power tomorrow morning, in preparation for probe release next week. The probe and orbiter continue to operate normally; telemetry indicates all subsystems are in good health, and all teams are reporting green lights for probe separation.

Probe Release Status,7/6/95 12 noon PDT

The Project Go#1 status review was held this morning. The Probe Engineering Team had reviewed all Probe data and found no Probe system anomalies and recommended we continue with Release as scheduled. Other teams (Orbiter Engineering Team, Navigation, and Ground Systems) all had no anomalies or faults and the Project directed that the GO command be sent. The GO command will be sent in about an hour. The sequence will continue tonight, when at about 3 am, the Probe relays will be closed to put the Probe on internal battery power, and the Probe (except for the coast timer) will be turned off. The relay closures will be verified in Orbiter telemetry, and six minutes of data will be collected prior to shutting down the Probe to observe continued successful operation of the coast timer. The Probe data will be downlinked and analyzed over the weekend, while the sequence is on its second hold (Cable-Cut hold) The Project GO#2 status review is scheduled for Monday morning.

Probe Release Status, 7/5/95, 7 pm PDT

All 6 minutes of Probe data has been read out from the CDS memory. The Data Management Team (DMT) processed the tape and delivered it to the Probe Engineering Team (PET) at 5:33 pm PDT (well before the deadline). It was processed in the Probe Flight Operations Equipment (PFOE) by 6:00 pm. The coast timer was loaded correctly and decrementing properly. All Probe data was as expected and indicated nominal operation. A full team review of the data is scheduled for 7 am tomorrow morning.

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