Galileo spacecraft

Originally known simply as the Jupiter Orbiter/Probe, Galileo, like many interplanetary orbiters, was spin-stabilized. When part of a spacecraft rotates, it acts like a gyroscope and helps to keep the craft in its desired attitude without the need for constant and wasteful corrections by the thrusters. In Galileo's case, the upper section, including antennae, field and particle experiments, and computers, rotated at three revolutions per minute. The lower section, containing cameras, other remote-sensing instruments, and the guidance sensors, kept a fixed orientation.

READY TO GO

Galileo stands in Kennedy Space Center's Vertical Processing Facility (VPF), ready for mating with its Inertial Upper Stage booster before its 1989 launch.

DEVELOPMENT TESTS

Before any spaceprobe is built, numerous mock-ups are produced to test how it might operate in outer space. Here, a model of Galileo is shown in its launch configuration at the JPL facility.

number of instruments 10 on orbiter spacecraft total mass 2,223kg (4,900lb)

power source 2 X 7.8kg (17.21b) plutonium RTGs manufacturer jet Propulsion Laboratory launch date 18 October 1989

termination of mission 21 September 2003

baffle to shield spacecraft electronics from RIG radiation height 5.3m (17ft 5in)

scan platform

BROKEN ANTENNA

Galileo's main high-gain "umbrella" antenna dish undergoes testing. When Galileo tried to unfold its high-gain antenna on the way to Jupiter, one of the spokes became trapped, leaving the craft's communications system crippled.

-gain antenna high-gain antenna (shown fully open)

thruster retropulsion module low bus Sunshade for protection in inner Solar System one of two Radioisotope Thermoelectric Generators (RTGs) produces 250 watts of power for spacecraft

RTG boom, 5m (16ft Sin) long

magnetometer sensor

10.9m (35ft 9in) fibre-gloss boom isolates sensitive instruments from probe's own electromagnetic fields plosma wove subsystem measures electric fields

INSTALLATION

Golileo and its Inertial Upper Stage (IUS) were stowed in Atlanta's payload bay (left) prior to launch (below). The IUS attaches to a turntable that swivels upright in orbit, spins and then releases the probe.

JUPITER AT LAST

After years of delays to its proposed launch date and then a six-year journey through the Solar System, Galileo finally arrived at Jupiter on 7 December 1995 - where it would carry out eight years of work.

GIANT TO JUPITER

The Galileo probe was designed to operate for an extended period in one of the Solar System's most hostile environments - the radiation belts around Jupiter. Its computers were vulnerable to damage from radiation and strong electric fields, and they were designed and programmed with a high level of fault protection to reduce the risk of errors.

10.9m (35ft 9in) fibre-gloss boom isolates sensitive instruments from probe's own electromagnetic fields

MONITORING GALILEO

Mission Control was at the Jet Propulsion Laboratory in Pasadena, California. During the long cruise to Jupiter, the controllers found a way to compensate for the crippled antenna on Galileo.

magnetometer sensor plosma wove subsystem measures electric fields mortar cover main parachute pack descent module

Galileo Spacecraft Instruments

number of instruments 6

total mass 339kg (746lb)

power source Onboard battery manufacturer German Space Agency ring deployment date 13 July 1995

jupiter atmosphere entry 7 December 1995

diameter 1.3m (4ft 3in)

communications antenna lightning detector spin vane payload heat shield ___

mortar cover number of instruments 6

total mass 339kg (746lb)

power source Onboard battery payload manufacturer German Space Agency ring deployment date 13 July 1995

jupiter atmosphere entry 7 December 1995

diameter 1.3m (4ft 3in)

main parachute pack descent module heat shield ___

THE JUPITER ATMOSPHERIC PROBE

Galileo's probe was designed to plunge into the giant planet's upper doudtops, sending data back to the orbiter as it fell. Like the main spacecraft, it used spin to stabilize its motion through space - the spacecraft itself was deliberately spun up to a higher rate prior to the probe's release. After a journey of almost five months, the probe entered the Jovian atmosphere. A heat shield protected it for the first three minutes of entry, then fell away as the drogue and then the main parachute deployed. The probe transmitted data back to the orbiter for some 59 minutes before contact was lost.

communications antenna lightning detector spin vane

PARACHUTE TESTING

The braking characteristics of the probe's parachute were tested in the wind tunnels at NASA's Langley Center. However, it eventually deployed a minute later than planned. Afterwards, technicians diagnosed a wiring fault - it was fortunate that the parachute opened at all.

DESCENT MODULE

Tested in a specially designed "Giant Planet Facility", the probe wos built to withstand the forces of Jovian gravity, heat, and atmospheric pressure.

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