Galileo became the first spacecraft to orbit Jupiter in 1995
On this day · 7 December 1995
On December 7, 1995, Galileo braked into orbit around Jupiter — years late, with a jammed main antenna, and on the busiest day of its mission.
NASA’s Galileo became the first spacecraft to orbit Jupiter on December 7, 1995, firing its main engine to brake into a first loop lasting 198 days. Every earlier visitor had merely flown past; Galileo stayed for nearly eight years.
It got there late and half-deaf:
- 1977: approved for a shuttle launch in 1981, which later slips to 1986.
- 1986: the Challenger accident that January grounds it again, and NASA then cancels the powerful Centaur upper stage it was meant to ride.
- October 1989: Galileo leaves on the weaker IUS from Space Shuttle Atlantis, swinging past Venus once and Earth twice to make up the speed, stretching a two-year trip to six years.
- April 1991: its 4.8-metre high-gain antenna fails to unfurl, probably because three of its 18 ribs stuck by friction.
Engineers spent years writing new compression software and upgrading ground stations so the mission could run through its slow low-gain antennas instead.
Arrival day
Galileo flew past Europa and Io, at about 33,000 km and 900 km respectively. Four hours later came closest approach to Jupiter, with a dose of radiation 25 times what would kill a person. The atmospheric probe, released in July, hit the cloud tops at 170,000 km/h and radioed data for 58 minutes before the heat silenced it. An hour after its last signal, Galileo fired its engine and was captured.
The crippled orbiter still delivered: evidence of a saltwater ocean under Europa’s ice, Io’s intense volcanism and a magnetic field around Ganymede. In 2003 controllers steered it into Jupiter so it could never contaminate Europa.
Sources & references
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