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 176 years [2].

For details on the Voyager instrument packages, see the separate article on the Voyager program.

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 activate it.

Jupiter

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

Saturn

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

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 (see also Saturn Oppositions).

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.

Uranus

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

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.

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.

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

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. Unlike Voyager 1, which is believed to have crossed the termination shock into the heliosheath in December 2004, Voyager 2 is currently not believed to have left the heliosphere yet.

As of December 30, 2005, Voyager 2 is at a distance of 78.4 AU from Sun 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 2030s.

Current Position

Voyager 2, as of January 2006, was at -52.41° declination and 19.688hrs Right Ascension, placing it in the constellation Telescopium.

Current Voyager 2 data processing and operations

There were 41.1 hours of DSN scheduled support for Voyager 2 of which 22.5 hours were large aperture coverage. There were no real-time or scheduled support changes or significant outages during the period.

Science instrument performance was nominal for all activities during this period. One frame of GS-4 data was recorded this week. The EDR backlog is 2 days.

Voyager 2 command operations consisted of the uplink of seven bracketed command loss timer resets sent on five-minute centers using 1.0 Hz steps on 03/16 [DOY 075/0342z]. The spacecraft received two of the seven commands sent.

This information is available from: http://voyager.jpl.nasa.gov/mission/weekly-reports/index.html

Voyager 2 in fiction and popular culture

• The motion picture Starman portrayed Voyager 2 as having been located by an alien intelligence who subsequently sent one of their own race to investigate intelligent life on Earth.
• In the episode " Parasites Lost" of the animated show Futurama, Leela scrubs the remains of Voyager 2 off the windscreen of her spaceship while refuelling at an interplanetary service station.
• Stephen Baxter's novel Titan ( 1997) describes what will happen to the Voyager probes billions of years in the future as the metal from which they are constructed gradually disintegrates.