With so many spacecraft actively exploring the Solar System, it is hard to keep track of what is currently going on. The following is a complete international guide to the missions at each planet as well as the asteroids and comets.

Mercury: MESSENGER was launched on August 3, 2004 and is a U.S. mission well on its way to entering orbit around Mercury on March 18, 2011. It will make two more passes of Mercury on October 6, 2008 and September 29, 2009 after its successful flyby earlier this year on January 14. The European Space Agency (ESA) is planning a dual orbiter mission called BepiColombo. It has been plagued with delays and cost overruns, but is currently scheduled to launch during August 2013 with arrival at Mercury during August 2019.

Venus: The European Space Agency’s Venus Express is currently in orbit exploring the clouds and atmosphere of Venus. Although the release of data has been slow and sporadic, the mission is doing well. The Japan Aerospace Exploration Agency (JAXA) is planning to launch the Venus Climate Orbiter during June 2010 with arrival during December 2010. The goal is to map the clouds and circulation of Venus by using a sounding device with the hopes of detecting volcanic eruptions and thunder. It will also be able to map the characteristics of the surface and the heat flow.

Moon: JAXA launched Kaguya on September 12, 2007 and is in orbit around the Moon to make detailed maps of the surface, probe its interior and study the lunar gravitational field. The U.S. is planning to launch the Lunar Reconnaissance Orbiter by the end of this year and will be the most sophisticated spacecraft ever sent to the Moon. It will orbit only 30 miles above the surface and make detailed maps that will help determine where future manned missions will land. Chandrayaan-1 is an Indian Space Research Organization (ISRO) mission that will launch in a few months to orbit the Moon with the objective of mapping the mineral composition of the surface. It also carries a 20-pound probe designed to be released from the spacecraft and penetrate the lunar surface. Chang'e 1, the first of a series of Chinese missions to the Moon, was launched on October 24, 2007 and is studying the lunar environment and surface regolith from orbit. It will map the lunar surface and study the overall composition and radioactive components of the Moon. It will map the thickness of the lunar regolith, and collect data on the solar wind and near-lunar region.

Mars: This is the planet with the most intense exploration currently underway. Mars Odyssey is the oldest spacecraft at Mars and was launched on April 7, 2001 with arrival on October 24, 2001. It is an orbiter mission that is doing very well considering the radiation damage it acquired from solar flares early in its mission. It is measuring the chemistry and ice on the surface of Mars and acts as a link to relay data from the Rovers: Spirit and Opportunity. These rovers continue to explore the surface and have outlasted their warranty nearly 15 times over. Spirit was launched on June 10, 2003 and landed on January 3, 2004 within Gusev Crater. It continues to rove and explore Columbia Hills. Opportunity was launched on July 7, 2003 and landed on January 24, 2004 on the plains of Meridiani. It continues to explore the area in and around Victoria Crater. Both have survived winters as cold as -150ºF and a global dust storm. Mars Express is an ESA mission that was launched on June 2, 2003 and arrived on December 25, 2003. It is an orbiter mission that is returning beautiful 3-D images of the surface from above and in natural color giving the effect of flying above the surface in an airplane. The Mars Reconnaissance Orbiter is a big U.S. mission that was launched on August 12, 2005 and arrived on March 10, 2006. It is mapping the surface in such fine detail that it has imaged spacecraft on the surface including the Viking Landers, Pathfinder, and the rovers. Phoenix was launched on August 4, 2007 and successfully landed on May 25, 2008 in the arctic region.

The U.S. has the Mars Science Laboratory well under development. It is a large rover with a launch period that is scheduled to extend from September 15 through October 4, 2009. The corresponding arrival period would begin on July 10, 2010 and would last until September 14, 2010. It will do everything that the current rovers do and more and is expected to far outdistance and outlast them. ExoMars is ESA’s version of a large rover mission that will be combined with an orbiter. The goal is to further characterize the biological environment on Mars in preparation for robotic missions and then human exploration. Data from the mission will also provide information in the study of exobiology, which is the search for life on other planets. It is scheduled for launch during 2013 with arrival at Mars in 2014. Russia is planning to launch Phobos-Grunt (soil) during October 2009 with the goal to collect soil samples from Phobos, a satellite of Mars, and to bring the samples back to Earth for study by August 2012.

Asteroids: Dawn is finally on its way after blasting off on September 27, 2007 following numerous delays and will arrive at Vesta during September 2011. It will go into orbit around Vesta until April 2012 and then take off for Ceres with arrival during February 2015. It will orbit Ceres until at least July 2015 and could be sent off to explore Pallas, although this is not yet certain.

Jupiter: There are no spacecraft currently at Jupiter after Galileo ended its mission on September 22, 2003. Juno is the next spacecraft to fly and is a polar orbiter mission with launch during August 2011 and arrival on October 19, 2016.

Saturn: Cassini is currently in orbit around Saturn and remains healthy and active as it continues to explore Saturn and its moons, especially Titan and Enceladus. Cassini was launched on October 15, 1997 and arrived at Saturn on June 30, 2004. No other missions have been approved, but plans to explore Titan and Enceladus more intensely are under way.

Uranus: There are currently no active missions and none planned.

Neptune: There are currently no active missions and none approved, but an orbiter mission is under study along with a flyby mission called Argo that would use the same design as the Pluto New Horizons spacecraft.

Pluto: New Horizons was launched on January 19, 2006 and is scheduled to fly past Pluto on July 14, 2015. It is healthy and in hibernation mode for most of its remaining journey to Pluto as it is now passing Saturn’s orbit. After the Pluto flyby it is expected to fly past one or several of the icy Kuiper Belt objects, of which Pluto is now considered one of, from 2016-2022.

Comets: The biggest mission ever to a comet is ESA’s Rosetta. It was launched on March 2, 2004 with arrival at Comet Churyumov-Gerasimenko during May 2014. It will go into orbit around the comet and drop a lander called Philae onto the surface, which will give the first in-depth analysis of a comet’s surface. Deep Impact was launched on January 12, 2005 and slammed a 750-pound copper projectile into Comet Temple 1 on July 4, 2005. Now it is on an extended mission in which it will fly past Comet Hartley 2 on October 11, 2010. It does not have another impactor, but will still provide plenty of pictures and give a general idea on the composition of the surface. Stardust was launched on February 7, 1999 and is also on an extended mission; it will fly past Comet Temple 1 on February 14, 2011 to inspect the crater created by the impactor from Deep Impact.

Anything can happen to these spacecraft with those that are currently active having failures and those being planned or built facing cancellation from the ever-increasing budget tightening. Whatever happens, these travelers are part of an exciting era of exploration that will give us greater understanding into Earth’s place within the Solar System.