NASA's Discovery Program (as compared to New Frontiers or Flagship Programs) is a series of lower-cost, 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.
- 1 History
- 2 Missions
- 3 Selection process
- 4 Summary
- 5 References
- 6 External links
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. 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. On February 17, 1996, NEAR became the first mission to launch in the Discovery Program. 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 air bags that allowed the Sojourner rover to endure the landing. 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.
- NEAR Shoemaker (Mission #1), a mission to study asteroid 433 Eros. Launched on February 17, 1996, the spacecraft entered orbit around Eros in 2000 and successfully touched down on its surface one year later. It has succeeded its primary and extended mission and is now complete. The Project Scientist was Andrew Chang of The Johns Hopkins University Applied Physics Laboratory.
- Mars Pathfinder (Mission #2), a Mars lander to deploy Sojourner rover on the surface. Launched in 1996, it landed on Mars on July 4, 1997. It has completed its primary and extended mission. The Principal Investigator was Matthew Golombek of NASA’s Jet Propulsion Laboratory.
- Lunar Prospector (Mission #3), a Moon orbiter to characterize the lunar mineralogy. Launched in 1998, it spent 1½ years in lunar orbit. It has completed its primary and extended mission and deliberately impacted onto the Moon's surface. The Principal Investigator was Alan Binder of the Lunar Research Institute.
- Stardust (Mission #4), a mission to collect interstellar dust and dust particles from the nucleus of comet 81P/Wild for study on Earth. Launched in 1999, it successfully collected samples between 2000–2004, then the sample return capsule returned to Earth on January 15, 2006. The 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. The spacecraft was assigned a new task, called Stardust-NExT to revisit Tempel 1 and observe the crater left by Deep Impact. Having completed its primary and extend missions, Stardust did a final burn to deplete its remaining fuel on March 24, 2011. The Principal Investigator was Donald Brownlee of the University of Washington.
- Genesis (Mission #5), a mission to collect solar wind charged particles for analysis on Earth. Launched in 2001, it collected solar wind between 2002–2003. In Sept. 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. The Principal Investigator was Donald Burnett of the California Institute of Technology.
- Comet Nucleus Tour (CONTOUR) (Mission #6), was a failed mission to visit and study comets Encke and Schwassmann-Wachmann-3. It was launched on July 3, 2002. Six weeks after launch, 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 embedded solid-rocket motor burn. 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.
- MESSENGER (Mission #7) (Mercury Surface, Space Environment, Geochemistry and Ranging) conducted the first orbital study of Mercury. MESSENGER's 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 launched on August 3, 2004 and entered orbit around Mercury on March 18, 2011. The primary mission was completed on 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. The mission had two more extensions until the spacecraft ran out of propellant and was deorbited on April 30, 2015.
- Deep Impact (Mission #8), a mission in which a spacecraft released an impactor into the path of comet Tempel 1. Launched in January 2005, the impact occurred on July 4, 2005. After the successful completion of its mission, it was put in hibernation and then reactivated for a new mission designated EPOXI. The Principal Investigator was Michael A'Hearn of the University of Maryland.
- Dawn (Mission #9) was launched on September 27, 2007 to study the two most massive objects of the asteroid belt – the protoplanet Vesta and the dwarf planet Ceres. It reached Vesta in July 2011 and completed the study of Vesta by September 2012 and is currently orbiting Ceres, where it arrived in March 2015. It is using solar electric ion thrusters to orbit both asteroids in one mission, a feat that has not been attempted before. The Principal Investigator is Chris Russell of the University of California, Los Angeles.
- Kepler (Mission #10) is a space observatory 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. The spacecraft was launched on March 7, 2009, and announced its first exoplanet discoveries in January 2010. The Principal Investigator is William Borucki of NASA’s Ames Research Center.
- Gravity Recovery and Interior Laboratory, (GRAIL) (Mission #11) provided higher-quality gravity field mapping of the Moon to determine its interior structure; launched in September 2011. The Principal Investigator is Maria Zuber of the Massachusetts Institute of Technology. GRAIL spacecraft impacted the Moon on December 17, 2012. MoonKAM was an education related sub-program and instrument of this mission (Moon Knowledge Acquired by Middle school students.
- InSight (Mission #12), a lander that will study the structure and composition of the interior of Mars and advance understanding of the formation and evolution of terrestrial planets. Its launch has been delayed from 2016 to 2018. The Principal Investigator is W. Bruce Banerdt of the Jet Propulsion Laboratory.
- Lucy (Mission #13) will tour six Trojan asteroids in order to better understand the formation of the Solar System. The launch is planned for 2021. The Principal Investigator is Harold F. Levison of the Southwest Research Institute.
- Psyche (Mission #14), an orbiter that will travel to and study the asteroid 16 Psyche, the most massive metallic asteroid in the asteroid belt, thought to be exposed iron core of a protoplanet. The launch is planned for 2020. The Principal Investigator is Lindy Elkins-Tanton of Arizona State University.
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 specific extended mission for spacecraft that may different from its original purpose. Some examples include: M3, EPOXI, EPOCH, DIXI, and NEXT.
- Moon Mineralogy Mapper is a NASA-designed instrument placed on board the ISRO's Chandrayaan orbiter. 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 Dr. Carle Pieters of Brown University.
- Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) was selected in 2007. 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 Dr. L. Drake Deming of NASA's Goddard Space Flight Center.
- 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. Dr. Michael A'Hearn of the University of Maryland was the Principal Investigator.
- New Exploration of Tempel 1 (NExT) 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. Dr. Joseph Veverka of Cornell University is the Principal Investigator.
- 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.
- Strofio 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.
Examples of proposals
However often the funding comes in, there is a selection process with perhaps 2 dozen concepts. These sometimes get further matured and re-proposed in another selection or program. 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, 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.
- Hermes, a Mercury orbiter. (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. The concept was further matured and implemented as Juno in the New Frontiers program.
- Psyche — a mission to the metallic asteroid 16 Psyche.
- The Dust Telescope is a space observatory that would measure various properties of incoming cosmic dust. The dust telescope would combine a trajectory sensor and a mass spectrometer, to allow the elemental and even isotopic composition to be analyzed.
- OSIRIS (Origins Spectral Interpretation, Resource Identification and Security) was an asteroid observation and sample return mission concept selected in 2006 for further concept studies. It was further matured and launched September 8, 2016 as OSIRIS-REx in the New Frontiers Program.
- Hera is a mission concept for near-Earth asteroid sample return. Envisioned as the follow-on from the NEAR mission, the design was intended to collect three samples from three different asteroids. The initial proposal proposed 1999-AO10, 2000-AG6 and 1998-UQ asteroids, but this was later expanded to three of 40 different options.
- Small Body Grand Tour, an asteroid rendezvous mission. This 1993 concept reviews possible targets for what became NEAR— 4660 Nereus and 2019 Van Albada Other targets considered for an extended mission included Encke's comet (2/P), 433 Eros, 1036 Ganymed, 4 Vesta, and 4015 Wilson–Harrington(1979 VA). (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. (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.
- Mars focused
- Pascal, a Mars climate network mission.
- MAUDEEE (Mars Upper Atmosphere Dynamics, Energetics, and Evolution) (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.
- Merlin mission would place a lander on Mars' moon Deimos.
- Mars Moons Multiple Landings Mission (M4), would conduct multiple landings on Phobos and Deimos.
- Hall is a Phobos and Deimos sample return mission.
- Aladdin was a Discovery-class Phobos and Deimos sample return mission. It was a finalist in the 1999 Discovery selection, with a planned launch in 2001 and return of the samples by 2006. Sample collection was intended to work by sending projectiles into the moons, then collecting the ejecta.
- Mars Geyser Hopper is a lander that would investigate the springtime carbon dioxide Martian geysers found in regions around the south pole of Mars.
- 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.
- Red Dragon, a Mars lander and sample return.
- Lunar focused
- 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.
- EXOMOON, in situ investigation on Earth's Moon.
- PSOLHO, would use the Moon as an occulter to look for exoplanets.
- Lunette, a lunar lander.
- Twin Lunar Lander, a geophysics mission to the Moon.
- Venus focused
- 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.
- Vesper was a concept for a Venus orbiter focused on studying that planet's atmosphere. It was one of three concepts to receive funds for further study in the 2006 Discovery selection. Osiris and GRAIL were the other two, and eventually GRAIL was chosen and went on to be launched.
- V-STAR (Venus Sample Targeting, Attainment and Return) is a Venus atmosphere sample return mission. While returning samples from the surface of Venus has noted difficulties, a Discovery-class sample return from the upper atmosphere is being proposed. Something along the lines of Stardust mission but using a free-return trajectory (it would not go into Venusian orbit).
- VEVA (Venus Exploration of Volcanoes and Atmosphere) is an in atmosphere probe for Venus. The centerpiece is a 7-day balloon flight through the atmosphere accompanied by various tiny probes dropped deeper into the planet's thick gases.
- Venus Pathfinder, a long-duration Venus lander.
- RAVEN, a Venus orbiter radar mapping mission.
- VALOR, a Venus mission to study its atmosphere with a balloon. Twin balloons would circumnavigate the planet over 8 Earth-days.
- Venus Aircraft, a robotic atmospheric flight on Venus' atmosphere using a long-duration solar-powered aircraft system. It would carry 1.5 kg of scientific payload and it must contend with violent wind, heat and a corrosive atmosphere.
The first two Discovery missions were Mars Pathfinder and Near Earth Asteroid Rendezvous (NEAR) (later called Shoemaker NEAR) These initial missions did not follow the same selection process that started once the program was under-way. Mars Pathfinder was salvaged from the idea for a technology and EDL demonstrator from the Mars Environmental Survey program. Also, one of the goals of Pathfinder was to support the Mars Surveyor program. Later missions would be selected by a more sequential process involving Announcements of Opportunity. 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. A series of proposals limited to missions to a Near-Earth asteroid missions was reviewed in 1991. 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. NEAR was launched on February 15, 1996, and arrived to orbit asteroid Eros on February 14, 2000. 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.
Discovery 3 and 4
- ASTER- Asteroid Earth Return
- Comet Nucleus Penetrator
- Comet Nucleus Tour (CONTOUR)
- Cometary Coma Chemical Composition (C4)
- Diana (Lunar & Cometary Mission)
- FRESIP-A mission to Find the Frequency of Earth-sized Inner Planets
- Hermes Global Orbiter (Mercury Orbiter)
- Icy Moon Mission (Lunar Orbiter)
- Interlune-One (Lunar Rovers)
- Jovian Integrated Synoptic Telescope (IO Torus investigation)
- Lunar Discovery Orbiter 
- Lunar Prospector (Lunar Orbiter) Chosen in February 1995 for Discovery 3.
- Mainbelt Asteroid Exploration/Rendezvous
- Mars Aerial Platform (Atmospheric)
- Mars Polar Pathfinder (Polar Lander)
- Mars Upper Atmosphere Dynamics, Energetics and Evolution
- Mercury Polar Flyby
- Near Earth Asteroid Returned Sample
- Origin of Asteroids, Comets and Life on Earth
- PELE: A Lunar Mission to Study Planetary Volcanism
- Planetary Research Telescope
- Rendezvous with a Comet Nucleus (RECON)
- Suess-Urey (Solar Wind Sample Return) Discovery 4 finalist.
- Small Missions to Asteroids and Comets
- Stardust (Cometary/Interstellar Dust Return) Discovery 4 finalist.
- Venus Composition Probe (Atmospheric)
- Venus Environmental Satellite (Atmospheric)
- Venus Multi-Probe Mission(Atmospheric) Discovery 4 finalist.
In February 1995 Lunar Prospector, a lunar orbiter mission, was selected for launch, as NASA decided it was mature enough it could go directly to development without a final selection. Three other missions were left to undergo a further selection later in 1995 for the fourth Discovery mission, Stardust, Suess-Urey, and Venus Multiprobe. Stardust, a comet sample return mission, was selected in November 1995 over the two other finalists.
Discovery 5 and 6
The five finalists were:
- 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 8
In July 1999, NASA selected Messenger and Deep Impact as the next Discovery program missions. 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. Both missions targeted a launch in late 2004 and the cost was constrained at about $300 million USD each.
In 1998 five finalists had been selected to receive $375,000 USD to further mature their design concept. The five proposals were selected out of perhaps 30 with the goal of achieving the best science. Those missions were:
Aladdin and Messenger were also finalists in the 1997 selection.
Discovery 9 and 10
26 proposals were submitted to the Discovery solicitation, with budget initially targeted at 300 million USD. Three candidates were shortlisted in January 2001 for a phase-A design study: Dawn, Kepler, and INSIDE Jupiter. INSIDE Jupiter was similar to a later New Frontiers mission called Juno; Dawn is a mission to asteroids Vesta and Ceres, and Kepler is a space telescope mission aimed to discover extrasolar planets. The three finalists received $450,000 USD to further mature the mission proposal.
In December 2001, Kepler and Dawn were selected for flight by NASA. 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. Both Kepler and Dawn were initially projected for launch in 2006.
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.
The announcement of opportunity for this Discovery mission was released in April 2006. There were three finalists for this Discovery selection including GRAIL (the eventual winner), OSIRIS, and VESPER. OSIRIS was very similar to the later OSIRIS-REx mission, an asteroid sample return mission to 101955 Bennu, and Vesper, a Venus orbiter mission. A previous proposal of Vesper had also been a finalist in the 1998 round of selection. The three finalists were announced in October 2006 and awarded 1.2 million USD to further develop their propoals for the final round.
In November 2007 NASA selected the GRAIL mission as the next discovery mission, with a goal of mapping Lunar gravity and a 2011 launch. There were 23 other proposals that were also under consideration. The mission had budget of $375 million USD (then-year dollars) which included construction and also the launch.
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. Out of the 28, three finalists received US$3 million in May 2011 to develop a detailed concept study:
- 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.
Discovery 13 and 14
In February 2014, NASA released a Discovery Program 'Draft Announcement of Opportunity' for launch readiness date of December 31, 2021. The main mission was budgeted for up to 450 million USD, with various conditions but also bonuses available beyond this to support advancement of various technologies:
- An additional $30 million available if it attempts to demonstrate laser communication (as opposed to radio communication) in space, by sending data with lasers beyond one lunar distance (distance from Earth to the Moon).
- An additional $10 million available if it demonstrates a 3D woven heat shield
- An additional $5 million available if it incorporates the miniaturized Deep Space Atomic Clock
- The NEXT xenon ion thruster and a radioisotope heater unit are also available for the mission without additional incentives.
For the first time, the $450 million cost cap will not include post-launch operations expenses. The final requirements were released on November 5, 2014; amongst other things they clarified the laser communication package was not a requirement but, if included, could grant a budgetary bonus.
- Saturn system
- Enceladus Life Finder (ELF) — an astrobiology orbiter mission to assess Enceladus' habitability and search for biosignatures.
- Journey to Enceladus and Titan (JET) — an astrobiology orbiter mission to assess Enceladus' habitability and search for biosignatures in the plumes.
- Life Investigation For Enceladus (LIFE) — an astrobiology sample-return mission to assess Enceladus' habitability and search for biosignatures in a sample of a plume.
- Jupiter system
- Io Volcano Observer — a mission to explore Io's active volcanism and impact on the Jupiter system as a whole by measuring its global heat flow, its induced magnetic field, the temperature of its lava, and the composition of its atmosphere, volcanic plumes, and lavas.
- Advanced Jovian Asteroid eXplorer (AJAX) — a mission to a single Jupiter trojan
- Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI)− Atmospheric probe to Venus that would study the chemical composition of its atmosphere during a 63-minute descent. Selected as one of five finalists in September 2015.
- Radar at Venus (RAVEN) - High-resolution mapping of Venus
- Venus Atmosphere and Surface Explorer (VASE)— would measure the complete inventory of atmospheric noble gas and light stable isotopes and provide the first complete atmospheric structure profile from clouds to surface of temperature, pressure and wind.
- Venus Emissivity, Radio Science, InSAR Topography and Spectroscopy (VERITAS)— Orbiter that would produce global, high resolution topography and imaging of Venus' surface and global surface composition. Selected as one of five finalists in September 2015.
- Mars system
- Mars-Moons Exploration, Reconnaissance and Landed Investigation (MERLIN) misson to flyby Deimos and then orbit and land on Phobos.
- Phobos And Deimos Origin Assessment (PANDORA), to orbit Deimos and Phobos
- Phobos And Deimos & Mars Environment (PADME)
- Icebreaker Life would use the Phoenix/InSight platform but would carry a payload to search for past extraterrestrial life on Mars.
- Asteroid, comet, and lunar proposals
- Binary Asteroid in-situ Explorer (BASiX)— a mission to visit a binary asteroid and set off small explosions to see how they affect the movement of both objects.
- Comet Radar Explorer (CORE)
- Dark Asteroid Rendezvous (DARe)— a mission to visit up to nine asteroids using a spacecraft equipped with ion propulsion.
- Lucy — would perform the first reconnaissance of the Jupiter trojan asteroids. Some possible reported targets would be 3548 Eurybates, 21900 Orus, 11351 Leucus, the binary 617 Patroclus with its companion Menoetius, and main-belt asteroid 52246 Donaldjohanson. Selected as one of five finalists in September 2015.
- Moon Age and Regolith Explorer (MARE)
- NanoSWARM — CubeSat mission to study space weathering, lunar magnetism, lunar water and small-scale magnetospheres.
- Near-Earth Object Camera (NEOCam)— is a space infrared telescope designed to survey the Solar System for potentially hazardous asteroids. Selected as one of five finalists in September 2015.
- Proteus – mission to 238P/Read, a main-belt comet
- Psyche — orbiter to 16 Psyche, the most massive metallic asteroid in the asteroid belt, thought to be exposed iron core of a protoplanet. Selected as one of five finalists in September 2015.
- Kuiper Telescope — this would target multiple objects, including the giant planets, their satellites, and small bodies with a 1.2-meter diameter mirror space telescope placed at Earth L2 point.
On September 30, 2015, NASA selected five mission concepts—DAVINCI, VERITAS, Lucy, NEOcam and Psyche—as a first step in choosing one or possibly two of the missions for implementation. Each of the five finalists received $3 million for one-year of further refinement and study.
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
This section includes an image of most of the Discovery missions' patches or logos where available, as well as the launch year
This section includes an image of most of the Discovery missions' rockets, as well as the launch year
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