The craft are further grouped by mission status – "en-route", "mission in progress" or "mission complete" – based on their primary mission. For example, though Voyager 1 is still contactable en-route to the Oort Cloud and has exited the Solar System, it is listed as "mission complete" because its primary task of studying Jupiter and Saturn has been accomplished. Once a probe has reached its first primary target, it is no longer listed as "en route" whether or not further travel is involved.
Mission: studying the effect of the solar wind on the Moon. Originally launched as Earth satellites, they were later repurposed and moved to lunar orbit.
Mission: Orbiter engaged in lunar mapping intended to identify safe landing sites, locate potential resources on the Moon, characterize the radiation environment, and demonstrate new technology.
Mission: Lander engaging in low-frequency radio spectrometry experiment, neutron and dosimetry experiment, and biological experiment. Rover seeking to characterize lunar far-side environment (including possible lunar mantle material) using visible/near-infrared spectrometer, ground penetrating radar, cameras, and neutral particle analyzer.[2]
Mission: Spacecraft consists of the Mercury Transfer Module (MTM), Mercury Planetary Orbiter (MPO), and the Mercury Magnetospheric Orbiter (MMO or Mio). MTM and MPO are built by ESA while the MMO is mostly built by JAXA. Once the MTM delivers the MPO and MMO to Mercury orbit, the two orbiters will have the following objectives: to study Mercury's form, interior structure, geology, composition, and craters; to study the origin, structure, and dynamics of its magnetic field; to characterize the composition and dynamics of Mercury's vestigial atmosphere; to test Einstein's theory of general relativity; to search for asteroids sunward of Earth; and to generally study the origin and evolution of a planet close to a parent star.[4]
Mission: Mars Odyssey was designed to map the surface of Mars and also acts as a relay for the Curiosity rover.[5] Its name is a tribute to the novel and 1968 film 2001: A Space Odyssey.
Mission: Mars orbiter designed to study the planet's atmosphere and geology and search for sub-surface water.[6] In 2017 the mission was extended until at least the end of 2020.[7]
Mission: the second NASA satellite orbiting Mars. It is specifically designed to analyze the landforms, stratigraphy, minerals, and ice of the red planet.
Mission: searching for evidence of organic material on Mars, monitoring methane levels in the atmosphere, and engaging in exploration of the landing site at Gale Crater.
Mission: find evidence for current and past life and produce Martian surface maps. Orbital studies of Martian surface morphology, soil, and atmosphere.
Montage of planets and some moons that the two Voyager spacecraft have visited and studied, still active in the 2020s they are heading out into interstellar space returning data from newly explored distances
Mission: mission to study Jupiter's three icy moons Callisto, Europa and Ganymede, eventually orbiting Ganymede as the first spacecraft to orbit a satellite of another planet.
Mission: the first spacecraft to study Pluto up close, and ultimately the Kuiper Belt. It was the fastest spacecraft when leaving Earth and will be the fifth probe to leave the Solar System.
Mission: investigating Jupiter and Saturn, and the moons of these planets. Its continuing data feed offered the first direct measurements of the heliosheath and the heliopause. It is currently the furthest man-made object from Earth, as well as the first object to leave the heliosphere and cross into interstellar space. As of November 2017 it has a distance from the Sun of about 140 astronomical units (AU)[10] (21 billion kilometers, or 0.002 light years), and it will not be overtaken by any other current craft. In August 2012, Voyager 1 became the first human-built spacecraft to enter interstellar space. Though declining, the onboard power source should keep some of the probe's instruments running until 2025.[11]
Mission: studying all four giant planets. This mission was one of NASA's most successful, yielding a wealth of new information. As of November 2017 it is some 116 AU from the Sun (17.34 billion kilometers).[10] It has left the heliosphere and crossed into interstellar space in December 2018. As with Voyager 1, scientists are now using Voyager 2 to learn what the Solar System is like beyond the heliosphere.
