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Header of the Discovery Program website (January 2016)[1]
Depictions of Lucy and Psyche missions
Asteroid Eros regolith, as viewed by Discovery's NEAR Shoemaker mission

NASA's Discovery Program is a series of lower-cost (as compared to New Frontiers or Flagship Programs), highly focused American scientific space missions that are exploring the Solar System. It was founded in 1992 to implement then-NASA Administrator Daniel S. Goldin's vision of "faster, better, cheaper" planetary missions. Discovery missions differ from traditional NASA missions where targets and objectives are pre-specified. Instead, these cost-capped missions are proposed and led by a scientist called the Principal Investigator (PI). Proposing teams may include people from industry, small businesses, government laboratories, and universities. Proposals are selected through a competitive peer review process. All of the completed Discovery missions are accomplishing ground-breaking science and adding significantly to the body of knowledge about the Solar System.

NASA also accepts proposals for competitively selected Discovery Program Missions of Opportunity. This provides opportunities to participate in non-NASA missions by providing funding for a science instrument or hardware components of a science instrument or to re-purpose an existing NASA spacecraft. These opportunities are currently offered through NASA's Stand Alone Mission of Opportunity program.

On January 4, 2017 NASA announced that the next Discovery mission selection included the double-selection of ''Lucy'', to visit several asteroids and Trojans, and ''Psyche'', to visit the metal asteroid Psyche, as the thirteenth and fourteenth Discovery missions, respectively.[2]



In 1989, the Solar System Exploration Division (SSED) at NASA Headquarters initiated a series of workshops to define a new strategy for exploration through the year 2000. The panels included a Small Mission Program Group (SMPG) that was chartered to devise a rationale for missions that would be low cost and allow focused scientific questions to be addressed in a relatively short time.[3] A fast-paced study for a potential mission was requested and funding arrangements were made in 1990. The new program was called 'Discovery' and the panel assessed a number of concepts that could be implemented as low-cost programs, with 'Near Earth Asteroid Rendezvous' (NEAR) as the first mission to be implemented.[3]

On February 17, 1996, NEAR became the first mission to launch in the Discovery Program.[3] The Mars Pathfinder launched on December 4, 1996, demonstrated a number of innovative, economical, and highly effective approaches to spacecraft and planetary mission design such as the inflated airbags that allowed the Sojourner rover to endure the landing.[3] Note that the two Mars Exploration Rovers, Opportunity and Spirit, were not a part of the Discovery Program, although they did re-use the overall landing system of Mars Pathfinder. Also, Phoenix and MAVEN were in the Mars Scout Program and not the Discovery Program.

Mission timelineEdit

Jupiter Icy Moons ExplorerEuropa ClipperDouble Asteroid Redirection TestOSIRIS-RExJuno (spacecraft)New HorizonsPsyche (spacecraft)Lucy (spacecraft)BepiColombo#Mercury Planetary OrbiterInSightLunar Reconnaissance OrbiterGRAILKepler (spacecraft)Moon Mineralogy MapperDawn (spacecraft)EPOXIDeep Impact (spacecraft)MESSENGERMars Express#Scientific instrumentsCONTOURGenesis (spacecraft)Stardust (spacecraft)#New Exploration of Tempel 1 (NExT)Stardust (spacecraft)Lunar ProspectorMars PathfinderNEAR Shoemaker 


Standalone missionsEdit

Standalone Discovery Program missions
Name Targets Launch date Rocket Launch mass First science Status Principal investigator Cost
million USD
1 NEAR Shoemaker 433 Eros (lander), 253 Mathilde February 17, 1996 Delta II
800 kg
(1,800 lb)
June 1997 Completed in 2001 Andrew Cheng
Near Earth Asteroid Rendezvous – Shoemaker (named after Eugene Shoemaker) performed a flyby of 253 Mathilde on 27 June 1997, and an Earth flyby in 1998. It flew by 433 Eros once in 1998, before a second approach allowed it to enter orbit around Eros of February 14, 2000. After a year of orbital observations, the spacecraft was landed on the asteroid on February 2001, and surprisingly continued to function successfully touched down softly at under 2 m/s, becoming the first probe to soft-land on an asteroid. The probe continued to emit signals until February 28, 2001, and the final attempt to communicate with the spacecraft was on December 10, 2002.
2 Mars Pathfinder Mars (rover) December 4, 1996 Delta II
264 kg
(582 lb)
July 4, 1997 Completed in 1998 Joseph Boyce
It was launched a month after the Mars Global Surveyor. After entering the Martian atmosphere, the hypersonic capsule deployed complex landing system including a parachute and an airbag to hit the surface at 14 m/s. The lander deployed Sojourner rover (10.5 kg) on the surface on July 4, 1997 on Mars's Ares Vallis thus becoming the first rover to operate outside the Earth-Moon system. It carried a series of scientific instruments to analyze the Martian atmosphere, climate, geology and the composition of its rocks and soil. It completed its primary and extended mission and after over 80 days, the last signal was sent on September 27, 1997. Mission was terminated on March 10, 1998.
3 Lunar Prospector Moon January 7, 1998 Athena II
296 kg
(653 lb)
January 16, 1998 Completed in 1999 Alan Binder
A Moon orbiter to characterize the lunar mineralogy, including polar ice deposits, measurements of magnetic and gravity fields, and study of lunar outgassing events. After preliminary mappings, it achieved the targeted primary Lunar orbit on January 16. Primary mission in this orbit lasted one year until January 28, 1999, followed up by a half-year extended mission in a lower orbit for higher resolution. On July 31, 1999 it deliberately impacted into the Shoemaker crater near the Lunar South pole in hope to produce water vapor plumes that would be observable from Earth.[9][10][7]
4 Stardust 81P/Wild (sample collect), 5535 Annefrank, Tempel 1 February 7, 1999 Delta II
391 kg
(862 lb)
November 2, 2002 Completed in 2011 Donald Brownlee
Mission to collect interstellar dust and dust particles from the nucleus of comet 81P/Wild for study on Earth. After a flyby of Earth and then of asteroid 5535 Annefrank in November 2002. After a flyby of comet Wild 2 in January 2004, during which the Sample Collection plate collected dust grain samples from the coma. Later, it separated from its sample-return capsule, which returned to Earth on January 15, 2006. This capsule is on display at the National Air and Space Museum in Washington D.C. Scientists worldwide are studying the comet dust samples while citizen scientists are finding interstellar dust bits through the Stardust@home project, and in 2014, scientists announced the identification of possible interstellar dust particles. Meanwhile, the spacecraft averted reentry, and was diverted for a flyby of Tempel 1 comet, as part of Stardust-NExT extension, to observe the crater left by Deep Impact. 'Stardust did a final burn to deplete its remaining fuel on March 24, 2011.[12]
5 Genesis Solar wind (collect at Sun–Earth L1) August 8, 2001 Delta II
494 kg
(1,089 lb)(dry)
December 3, 2001 Completed in 2004 Donald Burnett
Mission to collect solar wind charged particles for analysis on Earth. After reaching L1 orbit on November 16, 2001, it collected solar wind for 850 days between 2001–2004. It left Lissajous orbit and began its return to Earth on April 22, 2004, but on September 8, 2004, the sample-return capsule's parachute failed to deploy, and the capsule crashed into the Utah desert. However, solar wind samples were salvaged and are available for study. Despite the hard landing, Genesis has met or anticipates meeting all its baseline science objectives.
6 CONTOUR Encke, Schwassmann-Wachmann-3 July 3, 2002 Delta II 7425
398 kg
(877 lb)
after launch
Joseph Veverka
Comet Nucleus Tour was a failed mission to visit and study comets. On August 15, 2002, after a planned maneuver that was intended to propel it out of Earth orbit and into its comet-chasing solar orbit, the spacecraft was lost. The investigation board concluded the probable cause was structural failure of the spacecraft due to plume heating during the Star-30 solid-rocket motor burn.[3][16] Subsequent investigation revealed that it broke into at least three pieces, the cause likely being structural failure during the rocket motor burn that was to push it from Earth orbit into a solar orbit.
7 MESSENGER Mercury, Venus August 3, 2004 Delta II
1,108 kg
(2,443 lb)
August 2005 Completed in 2015 Sean Solomon
Mercury Surface, Space Environment, Geochemistry and Ranging conducted the first orbital study of Mercury. Its science goals were to provide the first images of the entire planet and collect detailed information on the composition and structure of Mercury's crust, its geologic history, the nature of its thin atmosphere and active magnetosphere, and the makeup of its core and polar materials. It was only the second spacecraft to flyby Mercury, after Mariner 10 in 1975. After one Earth flyby, two of Venus and three of Mercury, it finally entered orbit around Mercury on March 18, 2011. The primary science mission began on April 4, 2011 and lasted until March 17, 2012. It achieved 100% mapping of Mercury on March 6, 2013, and completed its first year-long extended mission on March 17, 2013. After two extension missions, the spacecraft ran out of propellant and was deorbited on April 30, 2015.[19][17]
8 Deep Impact Tempel 1 (impactor), 103P/Hartley January 12, 2005 Delta II
650 kg
(1,430 lb)
April 25, 2005 Completed in 2013 Michael A'Hearn
The spacecraft released a 350 kg impactor into the path of comet Tempel 1 on July 3, 2005. The impact occurred on July 4, 2005 releasing an energy equivalent of 4.7 tons of TNT. Plume of the impact were observed with several space-based observatories. The 2007 Stardust spacecraft NExT mission determined the resulting crater's diameter to be 150 meters (490 ft). After the successful completion of its mission, it was put in hibernation and then reactivated for a new mission designated EPOXI. On November 4, 2010 it performed a flyby of comet Hartley 2.[20] In 2012 it performed long-distance observations of comet Garradd C/2009 P1, and in 2013 of Comet ISON. Contact was lost in August 2013, later attributed to a Y2K-like error.
9 Dawn 4 Vesta, Ceres September 27, 2007 Delta II
1,218 kg
(2,685 lb)
May 3, 2011 Completed in 2018 Christopher T. Russell (UCLA)[22] 472
Dawn is the first spacecraft to orbit two extraterrestrial bodies, the two most massive objects of the asteroid belt: the protoplanet Vesta and the dwarf planet Ceres. This was made possible by employing highly efficient solar electric ion thrusters, with just 425 kg of xenon for the entire mission after escaping Earth. After a 2009 Mars flyby, it entered orbit around Vesta on July 16, 2011. It entered its lowest Vesta orbit on December 8, 2011, and after a year-long Vesta mission, it left its orbit on September 5, 2012. It entered Ceres' orbit on March 6, 2015 thus becoming the first spacecraft to visit a dwarf planet. It began its lowest orbit on December 16, 2015, and in June 2016 it was approved for an extended mission.[24][25] On October 19, 2017, NASA announced that the mission would be extended until its hydrazine fuel runs out, possibly in the second half of 2018.
10 Kepler transiting exoplanet survey March 7, 2009 Delta II
1,052 kg
(2,319 lb)
May 12, 2009 Completed in 2018 William Borucki
(NASA Ames)
A space observatory named after Johannes Kepler in an heliocentric, Earth-trailing orbit tasked to explore the structure and diversity of exoplanet systems, with a special emphasis on the detection of Earth-size planets in orbit around stars outside our Solar System.[27] It announced its first exoplanet discoveries in January 2010. Initially planned for 3.5 years, it is still functional after 9 years, including a K2 "Second Light" extension mission. By 2015, the spacecraft had detected over 2,300 confirmed planets,[28][29] including hot Jupiters, super-Earths, circumbinary planets, and planets located in the circumstellar habitable zones of their host stars. In addition, Kepler has detected over 3,600 unconfirmed planet candidates[30][31] and over 2,000 eclipsing binary stars.[31] The telescope retired on October 30, 2018 after finally running out of fuel.[32]
11 GRAIL Moon September 10, 2011 Delta II
307 kg
(677 lb)
Mar 7, 2012 Completed in 2012 Maria Zuber
Gravity Recovery and Interior Laboratory provided higher-quality gravitational field mapping of the Moon to determine its interior structure.[34] The two small spacecrafts GRAIL A (Ebb) and GRAIL B (Flow) separated soon after the launch and entered Lunar orbits on December 31, 2011 and January 1, 2012, respectively. The primary scientific phase was achieved in May 2012. After the extended mission phase, the two spacecrafts impacted the Moon on December 17, 2012. MoonKAM (Moon Knowledge Acquired by Middle school students) was an education related sub-program and instrument of this mission.[35]
12 InSight Mars (lander) May 5, 2018 Atlas V
721 kg
(1,590 lb)
November 2018 Operational W. Bruce Banerdt
Interior Exploration using Seismic Investigations, Geodesy and Heat Transport is a 358 kg lander reusing technology from the Mars Phoenix lander. It is intended to study the interior structure and composition of Mars and advance understanding of the formation and evolution of terrestrial planets.[37] Its launch was delayed from 2016 to May 2018.[38] The lander touched down successfully on November 26, 2018, at a site about 600 km (370 mi) from the Curiosity rover.[39]
13 Lucy Jupiter trojans October 2021 TBA 2025
In development
Harold F. Levison
450 + launch[40]
Named after the hominin Lucy, it will tour six Trojan asteroids in order to better understand the formation and evolution of the Solar System.[41] The launch is planned for 2021.[42] It will arrive at Jupiter's L4 Trojan cloud in 2027 to visit 3548 Eurybates, 15094 Polymele, 11351 Leucus, and 21900 Orus. After an Earth flyby, Lucy will arrive at the L5 Trojan cloud (trails behind Jupiter) to visit the 617 Patroclus−Menoetius binary in 2033. It will also fly by the inner main-belt asteroid 52246 Donaldjohanson in 2025.
14 Psyche 16 Psyche 2022 TBA 2026
In development
Lindy Elkins-Tanton
450 + launch[40]
Psyche orbiter will travel to and study the asteroid 16 Psyche, the most massive metallic asteroid in the asteroid belt, thought to be the exposed iron core of a protoplanet.[43] The launch is planned for 2022.[44] It will carry an imager, a magnetometer, and a gamma-ray spectrometer.

Missions of opportunityEdit

This provides opportunities to participate in non-NASA missions by providing funding for a science instrument or hardware components of a science instrument, or specific extended mission for spacecraft that may different from its original purpose. Some examples include: ASPERA-3, M3, EPOXI, NExT, and Strofio.

  • ASPERA-3, an instrument designed to study the interaction between the solar wind and the atmosphere of Mars, is flying on board the European Space Agency's Mars Express orbiter. Launched in June 2003, it has been orbiting Mars since Dec. 2003. The Principal Investigator is David Winningham of Southwest Research Institute.
  • Moon Mineralogy Mapper (M3) is a NASA-designed instrument placed on board the ISRO's Chandrayaan orbiter selected in February, 2005.[45] Launched in 2008, it was designed to explore the Moon's mineral composition at high resolution. M3's detection of water on the Moon was announced in Sept. 2009, one month after the mission ended. The Principal Investigator was Carle Pieters of Brown University.
  • Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) was selected in July, 2007.[46][47] It was a series of two new missions for the existing Deep Impact probe following its success at Tempel 1:
    • The Extrasolar Planet Observations and Characterization (EPOCh) mission used the Deep Impact high-resolution camera in 2008 to better characterize known giant extrasolar planets orbiting other stars and to search for additional planets in the same system. The Principal Investigator was L. Drake Deming of NASA's Goddard Space Flight Center.
      Nucleus of Comet Hartley 2
    • The Deep Impact eXtended Investigation of Comets (DIXI) mission used the Deep Impact mission's spacecraft for a flyby mission to a second comet, Hartley 2. The goal was to take pictures of its nucleus to increase our understanding of the diversity of comets. The flyby of Hartley 2 was successful with closest approach occurring on November 4, 2010. Michael A'Hearn of the University of Maryland was the Principal Investigator.
  • New Exploration of Tempel 1 (NExT) was selected in July, 2007 together with the EPOXI extension.[47] It was a new mission for the Stardust spacecraft to fly by comet Tempel 1 in 2011 and observe changes since the Deep Impact mission visited it in July 2005. Later in 2005, Tempel 1 made its closest approach to the Sun, possibly changing the surface of the comet. The flyby was completed successfully on February 15, 2011. Joseph Veverka of Cornell University is the Principal Investigator.
  • Strofio[48] is a unique mass spectrometer that is part of the SERENA instrument package that will fly on board the European Space Agency's BepiColombo/Mercury Planetary Orbiter spacecraft. Strofio will study the atoms and molecules that compose Mercury's atmosphere to reveal the composition of the planet's surface. Stefano Livi of Southwest Research Institute is the Principal Investigator.
  • In addition, the Lunar Reconnaissance Orbiter has been managed under the Discovery Program since the Lunar Precursor Robotic Program was terminated.


Possible configuration of a lunar sample return spacecraft
Mercury by Discovery's MESSENGER

However often the funding comes in, there is a selection process with perhaps two dozen concepts. These sometimes get further matured and re-proposed in another selection or program.[49] An example of this is Suess-Urey Mission, which was passed over in favor of the successful Stardust mission, but was eventually flown as Genesis,[49] while a more extensive mission similar to INSIDE was flown as Juno in the New Frontiers program. Some of these concepts went on to become actual missions, or similar concepts were eventually realized in another mission class. This list is a mix of previous and current proposals.

Additional examples of Discovery-class mission proposals include:

  • Whipple, space-observatory to detect Oort cloud by transit method
  • Io Volcano Observer
  • Comet Hopper (CHopper)
  • Titan Mare Explorer (TiME)
  • Suess-Urey, similar to the later Genesis mission.[49]
  • Hermes, a Mercury orbiter.[50] (compare to MESSENGER Mercury orbiter)
  • INSIDE Jupiter, an orbiter that would map Jupiter's magnetic and gravity fields in an effort to study the giant planet's interior structure.[51] The concept was further matured and implemented as Juno in the New Frontiers program.[52]
  • The Dust Telescope is a space observatory that would measure various properties of incoming cosmic dust.[53] The dust telescope would combine a trajectory sensor and a mass spectrometer, to allow the elemental and even isotopic composition to be analyzed.[53]
  • OSIRIS (Origins Spectral Interpretation, Resource Identification and Security) was an asteroid observation and sample return mission concept selected in 2006 for further concept studies.[54] It was further matured and launched September 8, 2016 as OSIRIS-REx in the New Frontiers Program.[55]
  • Hera is a mission concept for near-Earth asteroid sample return.[56] Envisioned as the follow-on from the NEAR mission, the design was intended to collect three samples from three different asteroids.[57] The initial proposal proposed 1999-AO10, 2000-AG6 and 1998-UQ asteroids, but this was later expanded to three of 40 different options.[57]
  • Small Body Grand Tour, an asteroid rendezvous mission.[58] This 1993 concept reviews possible targets for what became NEAR— 4660 Nereus and 2019 Van Albada.[58] Other targets considered for an extended mission included Encke's comet (2P), 433 Eros, 1036 Ganymed, 4 Vesta, and 4015 Wilson–Harrington (1979 VA).[58] (NEAR did visit 433 Eros and Dawn visited 4 Vesta)
  • Comet Coma Rendezvous Sample Return, a spacecraft designed to rendezvous with a comet, make extended observations within the cometary coma (but not land on the comet), gently collect multiple coma samples, and return them to Earth for study.[59] (See also Stardust (spacecraft))
  • Micro Exo Explorer would use a new form of micro-electric propulsion, called 'Micro Electro-fluidic-spray Propulsion' to travel to a near Earth object and gather important data.[60]

Mars focusedEdit

Mars Geyser Hopper would investigate 'spider' features on Mars, as imaged by an orbiter. Image size: 1 km (0.62 mi) across.
  • Pascal, a Mars climate network mission.[61]
  • MUADEE (Mars Upper Atmosphere Dynamics, Energetics, and Evolution)[62] (compare to MAVEN of the Mars Scout program)
  • Phobos Surveyor is an orbiter mission concept to the Mars moon Phobos, which would also deploy special rovers for the moon's low gravity environment.
  • PCROSS, based on LCROSS but to Mars' moon Phobos.[63]
  • Merlin mission would place a lander on Mars' moon Deimos.[64]
  • Mars Moons Multiple Landings Mission (M4), would conduct multiple landings on Phobos and Deimos.[65]
  • Hall is a Phobos and Deimos sample return mission.[66]
  • Aladdin was a Discovery-class Phobos and Deimos sample return mission.[67] It was a finalist in the 1999 Discovery selection, with a planned launch in 2001 and return of the samples by 2006.[68] Sample collection was intended to work by sending projectiles into the moons, then collecting the ejecta by means of a collector spacecraft flyby.[68]
  • Mars Geyser Hopper is a lander that would investigate the springtime carbon dioxide Martian geysers found in regions around the south pole of Mars.[69][70]
  • MAGIC (Mars Geoscience Imaging at Centimeter-scale) is an orbiter that would provide images of the Martian surface at 5–10 cm/pixel, permitting resolution of features as small as 20–40 cm.[71]
  • Red Dragon, a Mars lander and sample return.[72]

Lunar focusedEdit

  • Lunar sample return from the South Pole–Aitken basin. No geologic model adequately accounts for all of the characteristics of the area and disagreements are fundamental.[73]
  • EXOMOON, in situ investigation on Earth's Moon.[74]
  • PSOLHO, would use the Moon as an occulter to look for exoplanets.[75]
  • Lunette, a lunar lander.[76]
  • Twin Lunar Lander, a geophysics mission to the Moon.[77]
The Venus Multiprobe Mission involved sending 16 atmospheric probes into Venus in 1999.[78]

Venus focusedEdit

  • Venus Multiprobe, proposed for a 1999 launch, would have dropped 16 atmospheric probes into Venus, and fall slowly to the surface, making pressure and temperature measurements.[49]
  • Vesper was a concept for a Venus orbiter focused on studying that planet's atmosphere.[79][80][81] It was one of three concepts to receive funds for further study in the 2006 Discovery selection.[80] Osiris and GRAIL were the other two, and eventually GRAIL was chosen and went on to be launched.[54]
  • V-STAR (Venus Sample Targeting, Attainment and Return) is a Venus atmosphere sample return mission.[82][83] While returning samples from the surface of Venus has noted difficulties, a Discovery-class sample return from the upper atmosphere is being proposed.[82] Something along the lines of Stardust mission but using a free-return trajectory (it would not go into Venusian orbit).[82]
  • VEVA (Venus Exploration of Volcanoes and Atmosphere) is an in atmosphere probe for Venus.[84] The centerpiece is a 7-day balloon flight through the atmosphere accompanied by various tiny probes dropped deeper into the planet's thick gases.[84]
  • Venus Pathfinder, a long-duration Venus lander.[85]
  • RAVEN, a Venus orbiter radar mapping mission.[86]
  • VALOR, a Venus mission to study its atmosphere with a balloon.[87] Twin balloons would circumnavigate the planet over 8 Earth-days.[87]
  • Venus Aircraft, a robotic atmospheric flight on Venus' atmosphere using a long-duration solar-powered aircraft system.[88] It would carry 1.5 kg of scientific payload and it must contend with violent wind, heat and a corrosive atmosphere.[88]

Selection processEdit

Discovery 1 and 2Edit

Mars Pathfinder's Sojourner mini-rover taking its Alpha Particle X-ray Spectrometer measurement of the Yogi Rock (1997)

The first two Discovery missions were Near Earth Asteroid Rendezvous (NEAR) (later called Shoemaker NEAR) and Mars Pathfinder. These initial missions did not follow the same selection process that started once the program was under-way.[89] Mars Pathfinder was salvaged from the idea for a technology and EDL demonstrator from the Mars Environmental Survey program.[89] Also, one of the goals of Pathfinder was to support the Mars Surveyor program.[89] Later missions would be selected by a more sequential process involving Announcements of Opportunity.[89]

NEAR again has a slightly different background: when Discovery was established in 1990, soon after a working group for the program recommended that the first mission should be to a near-Earth asteroid.[90] A series of proposals limited to missions to a Near-Earth asteroid missions was reviewed in 1991.[90] What would be the NEAR spacecraft mission was formally selected in December 1993, after which a 2-year development period would follow prior to launch.[90] NEAR was launched on February 15, 1996, and arrived to orbit asteroid Eros on February 14, 2000.[90] Mars Pathfinder launched on December 4, 1996, and would land on the planet Mars on July 4, 1997, bringing along with it the first NASA Mars rover.[91]

Discovery 3 and 4Edit

Thorium concentrations on the Moon, as mapped by Lunar Prospector

In August 1994, NASA made an announcement of opportunity for the next proposed Discovery missions.[92] There were 28 proposals submitted to NASA in October 1994:[92]

  1. ASTER- Asteroid Earth Return
  2. Comet Nucleus Penetrator
  3. Comet Nucleus Tour (CONTOUR)
  4. Cometary Coma Chemical Composition (C4)
  5. Diana (Lunar and Cometary Mission)
  6. FRESIP-A mission to Find the Frequency of Earth-sized Inner Planets
  7. Hermes Global Orbiter (Mercury Orbiter)
  8. Icy Moon Mission (Lunar Orbiter)
  9. Interlune-One (Lunar Rovers)[93]
  10. Jovian Integrated Synoptic Telescope (IO Torus investigation)
  11. Lunar Discovery Orbiter[94]
  12. Lunar Prospector (Lunar Orbiter) – chosen in February 1995 for Discovery 3.
  13. Mainbelt Asteroid Exploration/Rendezvous
  14. Mars Aerial Platform (Atmospheric)
  15. Mars Polar Pathfinder (Polar Lander)
  16. Mars Upper Atmosphere Dynamics, Energetics and Evolution
  17. Mercury Polar Flyby
  18. Near Earth Asteroid Returned Sample
  19. Origin of Asteroids, Comets and Life on Earth
  20. PELE: A Lunar Mission to Study Planetary Volcanism
  21. Planetary Research Telescope
  22. Rendezvous with a Comet Nucleus (RECON)
  23. Suess-Urey (Solar Wind Sample Return) – Discovery 4 finalist.
  24. Small Missions to Asteroids and Comets
  25. Stardust (Cometary/Interstellar Dust Return) – Discovery 4 finalist.
  26. Venus Composition Probe (Atmospheric)
  27. Venus Environmental Satellite (Atmospheric)
  28. Venus Multi-Probe Mission(Atmospheric)[95] – Discovery 4 finalist.

In February 1995, Lunar Prospector, a lunar orbiter mission, was selected for launch. Three other missions were left to undergo a further selection later in 1995 for the fourth Discovery mission, Stardust, Suess-Urey, and Venus Multiprobe.[92] Stardust, a comet sample return mission, was selected in November 1995 over the two other finalists.[96]

Discovery 5 and 6Edit

In October 1997, NASA selected Genesis and CONTOUR as the next Discovery missions, out of 34 proposals that were submitted in December 1996.[97]

The five finalists were:[98]

  • Aladdin (Mars' moon sample return)
  • Comet Nucleus Tour (CONTOUR)
  • Genesis (Solar wind sample return)
  • Mercury Surface, Space Environment, Geochemistry and Ranging mission (MESSENGER)
  • Venus Environmental Satellite (VESAT)

Discovery 7 and 8Edit

Deep Impact collided with a comet nucleus

In July 1999, NASA selected MESSENGER and Deep Impact as the next Discovery Program missions.[99] MESSENGER was the first Mercury orbiter and mission to that planet since Mariner 10, and the Deep Impact sent a projectile into the comet Tempel 1.[99] Both missions targeted a launch in late 2004 and the cost was constrained at about $300 million USD each.[99]

In 1998 five finalists had been selected to receive $375,000 USD to further mature their design concept.[100] The five proposals were selected out of perhaps 30 with the goal of achieving the best science.[100] Those missions were:[100]

Aladdin and MESSENGER were also finalists in the 1997 selection.[100]

Discovery 9 and 10Edit

Scale comparison of Vesta, Ceres, and the Moon
Kepler spacecraft art

26 proposals were submitted to the 2000 Discovery solicitation, with budget initially targeted at 300 million USD.[101] Three candidates were shortlisted in January 2001 for a phase-A design study: Dawn, Kepler, and INSIDE Jupiter.[102] INSIDE Jupiter was similar to a later New Frontiers mission called Juno; Dawn was a mission to asteroids Vesta and Ceres, and Kepler was a space telescope mission aimed to discover extrasolar planets. The three finalists received $450,000 USD to further mature the mission proposal.[103]

In December 2001, Kepler and Dawn were selected for flight by NASA.[104] At this time only 80 exoplanets had been detected, and that was part of the mission of Kepler, to look for more exoplanets, especially Earth-sized.[104][105] Both Kepler and Dawn were initially projected for launch in 2006.[101]

The Discovery Program fell on hard-times after this, with several mission experiencing cost overruns, and the CONTOUR mission experiencing an engine failure in orbit. Although both Dawn and Kepler would become widely praised success stories, they missed their somewhat ambitious 2006 launch target, launching in 2007 and 2009 respectively. Kepler would go on to receive a mission extensions, and Dawn likewise successfully orbited both Vesta and Ceres. Nevertheless, the next selection would take longer than previous as the program selection of new missions slowed down. As the successes of the new missions enhanced the image of the Discovery Program, the difficulties began to fade from the limelight. Also, the number of active missions in development or active began to increase as the program ramped up.

Discovery 11Edit

The announcement of opportunity for this Discovery mission was released in April 2006.[106] There were three finalists for this Discovery selection including GRAIL (the eventual winner), OSIRIS, and VESPER.[107] OSIRIS was very similar to the later OSIRIS-REx mission, an asteroid sample return mission to 101955 Bennu, and Vesper, a Venus orbiter mission.[107] A previous proposal of Vesper had also been a finalist in the 1998 round of selection.[107] The three finalists were announced in October 2006 and awarded 1.2 million USD to further develop their propoals for the final round.[108]

In November 2007 NASA selected the GRAIL mission as the next Discovery mission, with a goal of mapping Lunar gravity and a 2011 launch.[109] There were 23 other proposals that were also under consideration.[109] The mission had budget of $375 million USD (then-year dollars) which included construction and also the launch.[109]

Discovery 12Edit

Artist's impression of proposed TiME lake lander for Saturn's moon Titan

This was an especially tough selection: coming on the heels of a successful Mars rover landing and the termination of the Mars Scout program (parent program of Phoenix and MAVEN), it meant that the proposals to the very popular red-planet competed with more obscure destinations. On the other hand, Titan had just been landed on by Huygens and Comets were getting the full-treatment by the flagship-class ESA Rosetta mission.

28 proposals were received in 2010; according to the BBC, 3 were for the Moon, 4 for Mars, 7 for Venus, 1 Jupiter, 1 to a Jupiter Trojan, 2 to Saturn, 7 to asteroids, and 3 to Comets.[110][111] Out of the 28, three finalists received US$3 million in May 2011 to develop a detailed concept study:[112]

  • InSight, a Mars lander.
  • Titan Mare Explorer (TiME) spacecraft for landing in, and floating on, a large methane-ethane sea on Saturn's moon Titan. A Titan moon "lake" lander was previously considered Titan Saturn System Mission and other concepts, but have lost out to other missions which have themselves been cancelled.
  • Comet Hopper (CHopper) study cometary evolution by landing on a comet multiple times and observing its changes as it interacts with the Sun.

In August 2012, InSight was selected for development and launch.[113]. The mission launched in May 2018 and successfully landed on Mars on November 26, 2018.

Discovery 13 and 14Edit

NASA made ion thruster technology available for proposals for the thirteenth Discovery Program mission.[114]

In February 2014, NASA released a Discovery Program 'Draft Announcement of Opportunity' for launch readiness date of December 31, 2021.[115] On 30 September 2015, NASA selected five mission concepts as finalists,[116][117] each received $3 million for one-year of further study and concept refinement.[118][119]

On January 4, 2017, Lucy and Psyche were selected for the 13th and 14th Discovery missions, respectively.[2][120] Lucy will flyby five Jupiter trojans, asteroids which share Jupiter's orbit around the Sun, orbiting either ahead of or behind the planet.[121][120] Psyche will explore the origin of planetary cores by orbiting and studying the metallic asteroid 16 Psyche.[121]


Discovery has visited asteroids, comets, Mars, Mercury, and the Moon. There were two sample return missions, one for comet dust, another for solar wind, and that also detected interstellar dust, and one observatory focused on finding exoplanets.

Artists' impressionsEdit

Discovery Program
NEAR Shoemaker
Mars Pathfinder
Lunar Prospector
Deep Impact

Mission insigniasEdit

This section includes an image of the Discovery missions' patches or logos, as well as the launch year.

Discovery Program
NEAR Shoemaker
Mars Pathfinder
Lunar Prospector
Deep Impact


This section includes an image of the Discovery missions' rockets, as well as the launch year.

Discovery Program
NEAR Shoemaker
Mars Pathfinder
Lunar Prospector
Deep Impact


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External linksEdit