En route
Rosetta, launched after several delays and mission changes, is currently on an intercept course with 67P/Churyumov-Gerasimenko. It will deploy a lander for further investigation after reaching the comet.
New Horizons was the fastest artificially-accelerated object and will be the fifth probe to leave the solar system. It will be the first spacecraft to study Pluto, ultimately destined for the Kuiper Belt.
Juno is on route to Jupiter and upon arrival will enter a polar orbit around the gas giant.
Mission in progress
The Cassini orbiter began studying Saturn and its moons after passing Venus and Jupiter and deploying the Huygens landing probe to Titan. It is primarily investigating Saturn's rings, its magnetosphere, and the geologic composition of its satellites; the mission may potentially continue until 2017.
2001 Mars Odyssey, a tribute to the classic novel and film, is one of three active human-made Mars satellites. It will continue its mission to map the surface of Mars until at least September 2010.
Mars Express: Mars orbiter designed to study the planet's atmosphere and geology, search for sub-surface water, and deploy the Beagle lander. Mission extended until at least December 2012.
MESSENGER is studying Mercury. It is only the second probe to do so and is the first to orbit the planet. Technologically, it is far superior to its 1975 predecessor, Mariner 10. Having previously passed Earth once, Venus twice and Mercury three times, it entered orbit in March 2011.
Opportunity Rover landed on Meridiani Planum. Expected to last 90 Martian days (sols), it continues to function effectively after sol 2470. Its twin, Spirit Rover, explored an area on the other side of the planet, but became stuck in soft soil May 1, 2009, and communication was lost March 22, 2010 (sol 2210).
Mars Reconnaissance Orbiter is the second NASA satellite orbiting Mars. It is specifically designed to analyze the landforms, stratigraphy, minerals, and ice of the red planet, which will aid in selecting a landing site for future lander Mars Science Laboratory.
Venus Express, modeled after the Mars Express, is collecting data on the Venusian atmosphere and cloud conditions. Mission extended until at least December 2012.
Dawn successfully entered asteroid Vesta's orbit on July 16 2011. It will study Vesta until July 2012, when it will depart for dwarf planet Ceres and arrive sometime in 2015.
Lunar Reconnaissance Orbiter is engaged in lunar mapping.
Chang'e 2 is studying the geography of the Moon.
Mission complete: New mission in progress
Voyager 2 has not yet left the solar system, but will become one of the first five probes to do so eventually. Its mission to study all four gas giants was one of NASA's most successful, yielding a wealth of new information. As of January 2010 it is some 91 AU from the sun,[2] and it is hoped that it will continue to operate until at least 2020. As with Voyager 1, scientists are now using Voyager 2to learn what the solar system is like beyond the heliosphere.
Voyager 1 is currently the farthest man-made object from Earth. As of January 2010 it lies about 112 AU from the sun[2] (10 billion miles, or 0.0018 light years), and it will not be overtaken by any other craft. It was originally tasked with investigating Jupiter and Saturn, and the moons of these planets. Its continuing data feed offers the first direct measurements of the heliosheath and may eventually provide data on the heliopause. It is hoped that Voyager 1 will continue operating until at least 2020.
Deep Impact was designed to study Comet Tempel 1 by impacting it with a high-speed projectile and photographing the results. This accomplished, a mission extension to Comet Hartley 2 was authorised (target changed from Comet Boethin).
New mission under consideration
ISEE-3's original mission was to study the solar wind; later, redesignated ICE, it flew by Comet Giacobini-Zinner. It is currently[when?] in a 355-day heliocentric orbit. Deactivated on 1997-05-05 leaving only a carrier signal, it was reactivated on 2008-09-18. NASA began considering using the spacecraft to observe additional comets in 2017 or 2018. No decision has been reached on the future use of the spacecraft. If no future uses are made, the spacecraft could be captured and given to the Smithsonian Institution in 2014. Reuse of the spacecraft would delay the possible capture to 2040s.
Akatsuki would have been the first Japanese Venusian probe. Also known as Planet-C and Venus Climate Orbiter, Akatsuki failed to enter Venusian orbit in December 2010. It is still functioning, and has a possible second chance to orbit Venus in 2017.
No future missions projected
Pioneer 6, launched in 1965, is the oldest functioning probe (if still operating). Contact was last attempted 8 December 2000 to celebrate its thirty-fifth anniversary, and the attempt was successful.[3] Like the three craft which superseded it, it took measurements of the solar wind, solar magnetic field and cosmic rays.
Pioneer 7 was last contacted 31 March 1995; no attempt has been made since, and this probe may or may not be operational.
Pioneer 8 was last contacted in 22 August 1996; no attempt has been made since, and this probe may or may not be operational.
Giotto approached within 600 kilometers of Halley's Comet on its flyby mission, and survived some particulate impact on the inbound flight to capture scientific data and stunning images of the comet's nucleus. Its multicolor camera was subsequently destroyed, but the probe remained otherwise functional. Its mission completed, deactivation commands were transmitted on 15 March 1986. Awakened four years later on 2 July, it studied the comet Grigg-Skjellerup as it approached within 200 kilometers eight days later, and was again deactivated on the 23rd.
Genesis returned a capsule with a solar wind sample to Earth in 2004. The rest of the probe was put into a parking orbit near Earth's L2 point.
Raisins ahoy!
For no particular raisin, except that I don't want that butt-ugly picture at the top of my blog for long, here's a list of probes active in our solar system. There are currently five probes heading out of our system. The oldest active probe, if it is active, is Pioneer 6, launched in 1965.