Probe Release Status Updates

Summary of Today's News

The probe has been successfully released.

A NASA 7/11/95 Press Release on probe release is available. So is a 7/12/95 Press Release.

Galileo Probe Status July 13, 1995

Jupiter is in the evening sky these days, second in brightness only to the nearly-full moon. Just below and to the left of Jupiter is a tiny speck of the collective soul of humankind...

At 11:06:56pm PDT, Wednesday, July 12 1995 (06:06:56 UTC DOY 194), points on a monitor repeating Navigation Doppler data in the Galileo Mission Support Area took a sudden dip indicating a change in the Orbiter's velocity along the Earth-line of some tens of millimeters per second. Approximately 9 minutes later, telemetry updates indicated that the Pyro capacitor banks had charged and fired, and that the microswitches on the Probe pushoff springs had opened.

There are now two distant specks out there by Jupiter.

The Probe has been released.

GALILEO MISSION STATUS July 13, 1995

Last night the Galileo atmospheric probe was launched on its five-month solo flight to Jupiter from the Galileo orbiter spacecraft. The Galileo project team observed the event at 11:07 p.m. PDT July 12; signals took 37 minutes to reach Earth from the spacecraft.

The probe and orbiter were pushed gently apart by springs after small explosive charges opened the retaining nuts which have held probe and orbiter together since before Galileo's launch in October 1989.

Prior to the release, a sequence of commands transmitted to the spacecraft computers had prepared the probe for its solo flight and atmospheric mission. A clock to begin probe scientific operations six hours before atmospheric entry was set and started, and the probe was switched to internal battery power. Then the cable that electrically linked probe and orbiter was cut. The Galileo spacecraft was turned to orient the probe correctly for entering Jupiter's atmosphere, and spun up to 10.5 rpm to stabilize the probe in that orientation through its 83-million-kilometer (52-million-mile) flight to Jupiter.

The probe weighs 339 kilograms (746 pounds) and carries six instruments to collect scientific data inside the atmosphere of Jupiter. It will enter the atmosphere Dec. 7, 1995, and will descend by parachute through the clouds, transmitting its data to the orbiter spacecraft overhead for about 75 minutes. The orbiter will then use its main rocket engine to go into orbit around Jupiter for a two-year survey of the planet, its satellites and its magnetosphere.

Galileo continues to operate normally. It is about 664 million kilometers (413 million miles) from Earth, and almost 790 million kilometers (491 million miles) from the Sun. Its speed in orbit around the Sun is more than 7 kilometers per second, or about 16,000 miles per hour.

Probe Release status 7/12/95 8 am

The successful results of the spacecraft reorientation to the Probe Release attitude and the spin up to 10.5 rpm were presented at the last Project Go#3 status review this morning. All spacecraft teams signed the Go request and the Project approved transmission of the Go command. The commands to separate the Probe will execute at 10:30 pm PDT, and will be verified at Earth at 11:07 pm. There are two contact switches between the Orbiter and the Probe, and their telemetered states will be used to confirm Probe release. Also, the navigation team will have a real-time display of the downlink communications signal frequency from the Orbiter. When the Probe separates, the change in the Orbiter's velocity will change the frequency in its received signal at Earth. This will also be used to confirm Probe release.

Probe Release Status, 7/11/95

This morning, July 12, from 1:37am to 2:10am PDT (08:37-09:10 UTC) Galileo spun up from 3 RPM to 10.5 RPM. This is to provide gyroscopic stabilization of the Probe during its 5-month fall to Jupiter.

The Project will meet at 6:30am PDT to review the final GO for Probe release.

Following the receipt of the GO command, and in the absence of any anomalies or intervention from the ground, the spacecraft will execute the commands to release the Probe at 10:30pm PDT tonight (05:30 UTC DOY 194), with the first indication reaching the ground 36min 52sec later at both DSS-14 at Goldstone, California and DSS-43 at Canberra, Australia.

Probe Release Status, 7/10/95 11 pm PDT

At 10:27 pm tonight the data was received to confirm successful cable cut. The RRH-1 receiver was powered off at 10:10, the RRH-1 oscillator at 10:12. At 10:27, all Probe temperature data went from their nominal values to the maximum reading, indicating the circuit had opened and confirming cable cut. With the cable cut, we can no longer command the Probe. From this point on, through the end of mission, the Probe will be running on its pre-programmed command sequence using its internal batteries for power. The release sequence will continue with the Orbiter turning to release attitude tomorrow morning and spinning up to 10.5 rpm Wednesday morning. The sequence will enter its last hold after spin up and before Probe release for all teams to review spacecraft status. Release is scheduled for 11:07 pm PDT ERT Wednesday night.

Probe Release Status, 7/11/95

At 10:32pm PDT on Monday, July 10 1995, the three Probe temperature measurements that pass through the umbilical cable to the Orbiter suddenly changed to 255dn, or full-scale, indicating that the Probe Umbilical Cable had indeed been severed by the pyro-driven guillotine blade.

The Probe is now electrically isolated from the Galileo Orbiter.

Probe Release Status, 7/10/95 8 am

The Probe is configured and ready for cable cut and release. The command sequence is currently in the Cable-Cut hold. At the Project status meeting this morning, all teams (Probe Engineering, Orbiter Engineering, Navigation, and Mission Control Teams) reported they were ready for cable cut. The Flight Director approved the transmission of the Go command to end the hold. Tonight, at 10:36 pm PDT Earth Receive Time (the one-way light time is about 37 minutes) the cable providing a command, data and power link between the Orbiter and the Probe will be cut. Verification will be provided when then the Probe temperature measurements either short or open.

Probe Release Status, 7/10/95 10:55 am PDT

GO #2 to cut the Galileo Probe umbilical cable is now aboard the spacecraft. Without further intervention from the ground, the stored sequence will execute the commands necessary to fire pyros to drive the guillotine blade through the umbilical cable at 9:50pm PDT tonight. The telemetry associated with that event (three Probe temperature indications passing through the umbilical cable should begin misbehaving at that moment) will arrive on the ground approximately 37 minutes later, and take 4-6 minutes to be processed by the Mission Ground Data System. Thus we should know by 10:33pm tonight that the cable has indeed been severed.

Probe Release Status, 7/10/95 7:30 am PDT

The Project approved the radiation of GO #2 to cut the Probe umbilical cable. The window opens at 8:31am PDT over DSS-43 in Canberra, Australia, with opportunities over all three Deep Space Network stations today.

The GO command will be accompanied by a Delayed Action Command which will execute several minutes before the sequence commands the spacecraft to high-spin (10.5 RPM) early Wednesday morning. This command will reposition the RTG (Radioisotope Thermoelectric Generators - the spacecraft's massive power sources) Booms to adjust the center-of-mass for minimum wobble at high-spin.

Probe Release Status, 7/6/95 11 am PDT

The Probe Release sequence is currently in the Cable-Cut Hold. Last night at about 3 am PDT the Probe K relays were closed, connecting the Probe to its internal battery power. Four relays were closed to place the coast timer bus on battery power and six minutes of Probe data were collected to observe continued operation of the coast timer. Then, the final two relays were closed to place the G-switch bus on battery power as well. The final two non-coast Probe loads, the exciter and the Data and Command Processor (DCP), were removed and Orbiter power to the Probe was turned off. All relay and power configuration commands have been verified in Orbiter telemetry. The six minutes of Probe data have been downlinked and the Data Management Team delivered a data tape to the Probe Engineering Team at about 8:15 am this morning which was processed through the Probe Operations Flight Equipment before 9 am. Although the PET is continuing to examine the data, the Probe shows continuing nominal operation, with the coast timer continuing to count down as expected.

Probe Release Status, 7/6/95

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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