Discovery Program

The Discovery Program's latest mission, Mars InSight lander, has its parachute tested

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.

History

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.^[1] 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.^[1] On February 17, 1996, NEAR became the first mission to launch in the Discovery Program.^[1] 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.^[1]

Missions

Standalone missions

Asteroid 253 Mathilde

Mars Pathfinder's view

Animation of the rotation of 433 Eros.

• Mars Pathfinder (Mission #1), 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.
• NEAR Shoemaker (Mission #2), a mission to study asteroid 433 Eros. Launched on 17 February 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.
• 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 Jan. 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 24 March 2011.^[2] 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.^[1][3] 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 imaging Mercury's surface hollows at Sholem Aleichem.^[4]

• 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 30 April 2015.^[5]
• 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 27 September 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.^[6][7] 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.^[8] The spacecraft was launched on March 7, 2009,^[9] 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.^[10] 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.^[11]

Insight lander in assembly (April 2015, NASA)

• InSight (Mission #12)– An Announcement of Opportunity for the 2016 Discovery mission was released by NASA on June 7, 2010. Twenty-eight proposals were submitted, and on May 5, 2011, three were chosen for further study.^[12] Following these one-year preliminary design studies, the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission was selected in August 2012. InSight (initially named Geophysical Monitoring Station or GEMS) will study the structure and composition of the interior of Mars and advance understanding of the formation and evolution of terrestrial planets.^[13] An Announcement of Opportunity for a Discovery mission was released by NASA on June 7, 2010. Out of 28 proposals from 2010,^[14] three finalists received US$3 million in May 2011 to develop a detailed concept studies.^[12] In August 2012, InSight was selected for development and launch^[15]; however, persistent problems with the vacuum seal on the seismometer meant that the payload was not ready in time for the mission to make the 2016 launch window ^[16].

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.^[17] 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.

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 Nov. 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 Feb. 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^[18] 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

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 2 dozen concepts. These sometimes get further matured and re-proposed in another selection or program.^[19] 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,^[19] 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.^[19]
• Hermes, a Mercury orbiter.^[20] (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.^[21] The concept was further matured and implemented as Juno in the New Frontiers program.^[22]
• Psyche — a mission to the metallic asteroid 16 Psyche.^[23]
• The Dust Telescope is a space observatory that would measure various properties of incoming cosmic dust.^[24] The dust telescope would combine a trajectory sensor and a mass spectrometer, to allow the elemental and even isotopic composition to be analyzed.^[24]
• OSIRIS (Origins Spectral Interpretation, Resource Identification and Security) was an asteroid observation and sample return mission concept selected in 2006 for further concept studies.^[25] It was further matured and will be launched in September 2016 as OSIRIS-REx in the New Frontiers Program.^[26]
• Hera is a mission concept for near-Earth asteroid sample return.^[27] Envisioned as the follow-on from the NEAR mission, the design was intended to collect three samples from three different asteroids.^[28] The initial proposal proposed 1999-AO10, 2000-AG6 and 1998-UQ asteroids, but this was later expanded to three of 40 different options.^[28]
• Small Body Grand Tour, an asteroid rendezvous mission.^[29] This 1993 concept reviews possible targets for what became NEAR— 4660 Nereus and 2019 Van Albada^[29] 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).^[29] (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.^[30] (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.^[31]

Mars focused

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.^[32]
• MAUDEEE (Mars Upper Atmosphere Dynamics, Energetics, and Evolution)^[33] (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.^[34]
• Merlin mission would place a lander on Mars' moon Deimos.^[35]
• Mars Moons Multiple Landings Mission (M4), would conduct multiple landings on Phobos and Deimos.^[36]
• Hall is a Phobos and Deimos sample return mission.^[37]
• Aladdin was a Discovery-class Phobos and Deimos sample return mission.^[38] It was a finalist in the 1999 Discovery selection, with a planned launch in 2001 and return of the samples by 2006.^[39] Sample collection was intended to work by sending projectiles into the moons, then collecting the ejecta.^[39]
• Mars Geyser Hopper is a lander that would investigate the springtime carbon dioxide Martian geysers found in regions around the south pole of Mars.^[40][41]
• 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.^[42]
• Red Dragon, a Mars lander and sample return.^[43]

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.^[44]
• EXOMOON, in situ investigation on Earth's Moon.^[45]
• PSOLHO, would use the Moon as an occulter to look for exoplanets.^[46]
• Lunette, a lunar lander.^[47]
• Twin Lunar Lander, a geophysics mission to the Moon.^[48]

The Venus Multiprobe Mission involved sending 16 atmospheric probes into Venus in 1999.^[49]

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.^[19]
• Vesper was a concept for a Venus orbiter focused on studying that planet's atmosphere.^[50][51][52] It was one of three concepts to receive funds for further study in the 2006 Discovery selection.^[51] Osiris and GRAIL were the other two, and eventually GRAIL was chosen and went on to be launched.^[25]
• V-STAR (Venus Sample Targeting, Attainment and Return) is a Venus atmosphere sample return mission.^[53][54] While returning samples from the surface of Venus has noted difficulties, a Discovery-class sample return from the upper atmosphere is being proposed.^[53] Something along the lines of Stardust mission but using a free-return trajectory (it would not go into Venusian orbit).^[53]
• VEVA (Venus Exploration of Volcanoes and Atmosphere) is an in atmosphere probe for Venus.^[55] The centerpiece is a 7-day balloon flight through the atmosphere accompanied by various tiny probes dropped deeper into the planet's thick gases.^[55]
• Venus Pathfinder, a long-duration Venus lander.^[56]
• RAVEN, a Venus orbiter radar mapping mission.^[57]
• VALOR, a Venus mission to study its atmosphere with a balloon.^[58] Twin balloons would circumnavigate the planet over 8 Earth-days.^[58]
• Venus Aircraft, a robotic atmospheric flight on Venus' atmosphere using a long-duration solar-powered aircraft system.^[59] It would carry 1.5 kg of scientific payload and it must contend with violent wind, heat and a corrosive atmosphere.^[59]

Selection process

The first two Discovery missions were Mars Pathfinder and Near Earth Asteroid Rendezvous (Shoemaker)

Discovery 3 selection

In February 1995 Lunar Prospector, a lunar orbiter mission, was selected for launch.^[60] NASA decided it was mature enough it could go directly to development without a final selection, which left three other missions to undergo a further selection later in 1995.^[60] Those three missions were Stardust, Suess-Urey, and Venus Multiprobe.^[60] There were 28 proposals submitted to NASA in October 1994.^[60] The announcement of opportunity was in August 1994.^[60]

A full list of proposals was released by NASA for this selection:^[60]

1. ASTER- Asteroid Earth Return
2. Comet Nucleus Penetrator
3. Comet Nucleus Tour (CONTOUR)
4. Cometary Coma Chemical Composition (C4)
5. Diana (Lunar & 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)^[61]
10. Jovian Integrated Synoptic Telescope (IO Torus investigation)
11. Lunar Discovery Orbiter ^[62]
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 semi-finalist)
24. Small Missions to Asteroids and Comets
25. Stardust (Cometary/Interstellar Dust Return) (Discovery 4 semi-finalist, chosen in the fall of 1995 for selection)
26. Venus Composition Probe (Atmospheric)
27. Venus Environmental Satellite (Atmospheric)
28. Venus Multi-Probe Mission (Atmospheric)^[63] (Discovery 4 semi-finalist)

Lunar prospector was selected in early 1995 and Stardust later that year, becoming the third and fourth Discovery missions respectively.

Discovery 4 selection

Stardust succeeded. Comet Wild 2 shown here

Stardust, a comet sample return mission was selected in November 1995 over two other finalists, Venus Multiprobe and Suess-Urey.^[64] These three mission were selected of 28 proposals submitted in October 1994.^[64] Stardust planned to use an aerogel to capture particles of Comet Wild 2 and return them to Earth.^[64]

Discovery 5 and 6 selection

In October 1997, NASA selected Genesis and Contour as the next discovery missions, out of 34 proposals that were submitted in December 1996.^[65] The four previously selected missions at this time were NEAR, Pathfinder, Lunar prospector, and Stardust.

The five finalists were:^[66]

• 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 selection

Deep Impact nails a comet nucleus

In July 1999, NASA selected Messenger and Deep Impact as the next Discovery program missions.^[67] Messenger would be the first Mercury orbiter and mission to that planet since Mariner 10, and the Deep Impact would send a projectile into the Comet P/Tempel 1.^[67] Both mission would target a launch in late 2004 and cost constraint of about 300 million USD.^[67]

In 1998 five semi-finalists were selected to receive $375,000 USD to further develop their design.^[68] The five proposals were selected out of perhaps 30 with the goal of achieving the best science.^[68] Those missions were:^[68]

• Aladdin
• Deep Impact
• Messenger
• Inside Jupiter
• Vesper

Aladdin and Messenger were also semi-finalists in the 1997 selection.^[68]

Discovery 9 and 10 selection

Scale comparison of Vesta, Ceres, and Earth's moon

Kepler spacecraft art

In December 2001 NASA selected the Kepler mission for launch.^[69] At this time only 80 exoplanets had been detected, and that was part of the mission of Kepler, to look for more exoplanets especially an Earth-sized one.^[69] Kepler became the tenth Discovery mission selected for flight.^[70] Also in December 2001, the Dawn mission to asteroids Vesta and Ceres was selected.^[71] Both missions were initially selected for a launch in 2006.^[71]

The past Discovery missions are NEAR Shoemaker, Mars Pathfinder and Lunar Prospector, all of which successfully completed their missions. Stardust and Genesis are in space; both have begun collecting science data, although Stardust has not yet arrived at its target comet. CONTOUR is scheduled to launch next summer, Deep Impact in January 2004 and MESSENGER in March 2004. ASPERA-3 and NetLander are Discovery Missions-of-Opportunity that are under development.

— Status of the Discovery Program at the end of 2001.^[69]

NASA selected Dawn and Kepler out of 26 proposals, and their budged initially targeted about 300 million USD.^[71] The semi-finalists were selected in January 2001 and included three missions: Dawn, Kepler, and INSIDE Jupiter.^[72] INSIDE Jupiter was similar to a later New Frontier's mission called Juno. The Discovery fell on hard-times after this, several mission experienced cost-over runs and one mission blew up trying to leave Earth 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 onto receive a four-year mission extension, and Dawn likewise successfully orbited both Vesta and Ceres in the 2010s. 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 polished the image of 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 three semi-finalists received 450,000 thousand USD to further study the mission proposal.^[73]

Discovery 11 selection

In November 2007 NASA selected the GRAIL mission as the next discovery mission, with a goal of mapping Lunar gravity and 2011 launch.^[74] There was 23 other proposals that were also under consideration.^[74] The mission had budget of $375 million USD (then-year dollars) which included construction and also the launch.^[74]

The announcement of opportunity for this Discovery mission was released in April 2006.^[75] There were three semi-finalists for this Discovery selection including GRAIL (which won), OSIRIS, and VESPER.^[76] OSIRIS was very similar to the later OSIRIS-REx mission, an asteroid sample return mission to 101955 Bennu, and Vesper, a Venus orbiter mission.^[76] A previous proposal of Vesper had also been a semi-finalist in the 1998 round of selection.^[76] The three finalists were announced in October 2006 and awarded 1.2 million USD to further develop there propoals for the final round.^[77] Three missions of opportunity which were selected for study were EPOXI, EPOCH, and DIXI.^[77] Some concurrent events to this period was that the ESA Venus Express successfully entered Venus orbit in the Spring of 2006 and also Hayabusa achieved rendezvous with a small asteroid.

Discovery 12 selection

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. The Advanced Stirling radioisotope generator was later cancelled.

Out of 28 proposals from 2010,^[78] Insight was one of the three Discovery Program finalists receiving US$3 million in May 2011 to develop a detailed concept study.^[79] In August 2012, InSight was selected for development and launch.^[15]

Huygens in situ image from Titan's surface

Same image with contrast enhanced.

The three semi-finalists:

• InSight, this Mars lander was selected from among the finalists
• 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, and even the existing Cassini-Huygens orbiter has found itself so stretched for funding its planning a "grand finale" (a kamikazee-like impact into Saturn to end its mission)
• Comet Hopper (CHopper) study cometary evolution by landing on a comet multiple times and observing its changes as it interacts with the Sun.

According to the BBC, of the 28 first round mission proposals, 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.^[80]

Future mission

Discovery Mission 13

NASA made the NEXT ion thruster technology available for this Discovery Program mission.^[81]

On 30 September 2015, NASA selected five mission concepts for refinement during the next year, as a first step in choosing one or possibly two of the missions for development in 2016.^[82]

Each mission received $3 million for a one-year study. The winner will be chosen around September 2016,^[83] and must be ready to launch by the end of 2021.^[84][85]

The five semifinalists are:^[86]

• Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) − it would study the chemical composition of Venus' atmosphere during a 63-minute descent.
• Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERITAS) — it would produce global, high resolution topography and imaging of Venus' surface and global surface composition.
• Psyche Orbiter — it would explore the origin of planetary cores by studying the metallic asteroid 16 Psyche.

Concept art of Veritas orbiter at Venus

• Near Earth Object Camera (NEOCam) — is a space infrared telescope designed to survey the Solar System for potentially hazardous asteroids.
• Lucy — it would perform the first reconnaissance of the Jupiter trojan asteroids. Some possible reported targets would be 3548 Eurybates, (21900) 1999 VQ10, (11351) 1997 TS25, the binary (617) Patroclus I Menoetius, and main-belt asteroid (52246) 1981 EQ5.^[87]

The budget is planned to be 450 million USD, but there is some special technology and bonuses available beyond this.^[88]

• An additional 30 million USD becomes available if it attempts to demonstrate a laser (as opposed to radio) communication system at extra-Lunar distances^[88]
• An additional 10 million USD becomes available if it demonstrates 3D woven heat shield^[88]
• An additional 5 million USD becomes available to the mission if it incorporates the miniaturized Deep Space Atomic Clock^[88]
• A xenon ion engine and a radioisotope heater unit are also available for the mission without additional incentives^[88]

For example, a mission that includes the Laser communication and atomic clock could boost its budget to 485 (450+30+5) million, but it does not have to include these technologies.

Selection process

In February 2014, NASA released a Discovery Program 'Draft Announcement of Opportunity' for launch readiness date of December 31, 2021.^[89] As with previous Discovery missions such as Dawn, solar electric propulsion may allow increased mission options if applicable.^[90] Technologies may include the NEXT ion thruster,^[91] laser communication,^[84] and/or re-entry technology.^[81] The main mission is budgeted for up to 450 million USD, with various conditions but also bonuses.^[81][92] For the first time, the $450 million cost cap will not include post-launch operations expenses.^[93]

The final requirements were changed later in 2014.^[94] In regard to the laser communication package: it is not required, but if included, could grant an additional 30 million USD bonus on top of the existing budget.^[94] That feature is the "Deep Space Optical Communications payload", and involves sending data with lasers beyond one lunar distance (distance from Earth to the Moon).^[95] The deadline for proposals was February 16, 2015 and may have included some of the following mission candidates:^[93][96]

Saturn system

• Enceladus Life Finder (ELF) — an astrobiology orbiter mission to assess Enceladus' habitability and search for biosignatures.^[97]
• Journey to Enceladus and Titan (JET) — an astrobiology orbiter mission to assess Enceladus' habitability and search for biosignatures in the plumes.^[98]
• Life Investigation For Enceladus (LIFE) — an astrobiology sample-return mission to assess Enceladus' habitability and search for biosignatures in a sample of a plume.^[99]

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.^[100]
• Advanced Jovian Asteroid eXplorer (AJAX) — a mission to a single Jupiter trojan^[101]

Venus

• Radar at Venus (RAVEN) - High-resolution mapping of Venus^[102]
• 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.^[103]
• Venus Emissivity, Radio Science, InSAR Topography and Spectroscopy (VERITAS)

Mars system

• Phobos Surveyor would deploy an orbiter and mini-rovers on Phobos.
• Mars-Moons Exploration, Reconnaissance and Landed Investigation (MERLIN) misson to flyby Deimos and then orbit and land on Phobos.^[104]
• Phobos And Deimos Origin Assessment (PANDORA), to orbit Deimos and Phobos^[104]
• Phobos And Deimos & Mars Environment (PADME)^[104][105]
• Icebreaker Life would use the Phoenix/InSight platform but would carry a payload to search for past extraterrestrial life on Mars.^{[106][107][108]}

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.^[109]
• Comet Radar Explorer (CORE)
• Dark Asteroid Rendezvous (DARe)— a mission to visit up to nine asteroids using a spacecraft equipped with ion propulsion.^[110]
• Lucy — would tour Trojan asteroids^[111]
• Psyche Orbiter to 16 Psyche asteroid — the most massive metallic asteroid in the asteroid belt, thought to be exposed iron core of a protoplanet.^[112]
• Moon Age and Regolith Explorer (MARE)^[113]
• NanoSWARM — CubeSat mission to study space weathering, lunar magnetism, lunar water and small-scale magnetospheres.
• Near-Earth Object Camera (NEOCam)
• Proteus – mission to 238P/Read, a main-belt comet^[114]

Other

• 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.^[115]

Summary

Discovery Program
NEAR 1996	Mars Pathfinder 1996	Lunar Prospector 1998	Stardust 1999	Genesis 2001	MESSENGER 2004
Deep Impact 2005	Dawn 2007	Kepler Observatory 2009	GRAIL 2011	InSight 2018

Mission insignias

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

Discovery Program
NEAR 1996	Mars Pathfinder 1996	Lunar Prospector 1998	Stardust 1999	Genesis 2001	MESSENGER 2004
Deep Impact 2005	Dawn 2007	Kepler Observatory 2009	GRAIL 2011	InSight 2018

Launches

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

Discovery Program
NEAR 1996	Mars Pathfinder 1996	Lunar Prospector 1998	Stardust 1999	Genesis 2001	MESSENGER 2004
Deep Impact 2005	Dawn 2007	Kepler Observatory 2009	GRAIL 2011	InSight 2018

See also

• Explorer program
• Mars Exploration Program
• Mars Scout Program
• New Frontiers Program
• New Millennium Program

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External links

• Official NASA website for Discovery Program
• Official NASA website for Discovery & New Frontiers Programs Office