Voyager II

> Voyager 2

The Voyager 2 spacecraft was launched in 1977. It is identical to its sister Voyager program craft, Voyager 1, but Voyager 2 followed a somewhat different trajectory during its Saturn encounter, bypassing a close encounter with Titan to take advantage of a gravitational slingshot to travel on to Uranus and Neptune. It thus became the first and so far only probe to visit those two planets and the first spacecraft to make the Grand Tour of Jupiter, Saturn, Uranus and Neptune. This was possible only due to a rare geometric arrangement of those four planets that only occurs once every 175 years.

The Voyager II launch

Contents:

1. Mission, Planning and launch

2. Jupiter

3. Saturn

4. Uranus

5. Neptune

6. Escaping the Solar System

Mission, planning and launch

Voyager 2 was originally planned to be Mariner 12, part of the Mariner program.

Voyager 2 was launched on August 20, 1977, from Cape Canaveral, Florida aboard a Titan III-E Centaur rocket.

Ground crews became engrossed in a launch problem with Voyager 1 and forgot to send an important activation code to Voyager 2. This caused the probe to shut down its main high-gain antenna. Fortunately, ground crews were able to establish contact through the craft's low-gain antenna and reactivate it.

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Jupiter

The closest approach to Jupiter occurred on July 9, 1979.

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Saturn

The closest approach to Saturn occurred on August 25, 1981.

Saturn taken by Voyager 2

While behind Saturn (as viewed from Earth), Voyager 2 probed Saturn's upper atmosphere with its radar, to measure temperature and density profiles. Voyager 2 found that at the highest levels (70 millibars or 7.0 kilopascals) Saturn's temperature was 70 kelvins, while at the deepest levels measured (1200 millibars or 120 kilopascals) the temperature increased to 143 kelvins. The North pole was found to be 10 kelvins cooler, although this may be seasonal.

After the Saturn fly-by, the camera platform on Voyager 2 locked up briefly, putting plans to officially extend the mission to Uranus and Neptune in jeopardy. Fortunately, the mission team were able to fix the problem, and the probe was given the go-ahead to examine Uranus.

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Uranus

The closest approach to Uranus occurred on January 24, 1986.

Uranus' photo taken by Voyager II

Uranus viewed from 18 million kilometers.

Voyager 2 discovered 10 previously unknown moons; studied the planet's unique atmosphere, caused by its axial tilt of 97.77°; and examined its ring system.

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Neptune

The closest approach to Neptune occurred on August 25, 1989. Since this was the last major planet Voyager 2 could visit, it was decided to make a close flyby of the moon Triton, regardless of the consequences to the trajectory, as with Voyager 1's encounter with Saturn and its moon Titan. This was a wise decision, as Triton turned out to have a fascinating surface.

Voyager 2 image of Neptune

The probe also discovered the Great Dark Spot, which has since disappeared, according to Hubble Space Telescope observations.

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Escaping the Solar System

Since its planetary mission is over, Voyager 2 is now described as working on an Interspace Mission, which NASA is using to find out what the solar system is like beyond the heliosphere.

As of January 11, 2005, Voyager 2 is at a distance of 75.4 AU and is escaping the solar system at a speed of about 3.3 AU per year (ca. 15.6 km/s). Although it has not yet escaped the solar system, it is believed to be on the verge of doing so.

Voyager 2 is expected to keep on transmitting into the 2030's.

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