NASA's Discovery Program (as compared to New Frontiers, Explorer, 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.
- 1 History
- 2 Missions in progress, in space
- 3 In development
- 4 Future mission
- 5 Summary
- 6 See also
- 7 References
- 8 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 endure the landing.
- 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 in 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 has been assigned a new task, called Stardust-NExT. 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 30 April 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 27 September 2007 to study the two most massive objects of the asteroid belt – the protoplanet Vesta and the dwarf planet Ceres. It completed the study of Vesta on 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.
- 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.
- 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.
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.
- 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 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.
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 other mission class. This list is a mix of previous and current proposals.
Additional examples of Discovery-class mission proposals include:
- Titan Mare Explorer (TiME) spacecraft for landing in, and floating on, a large methane-ethane sea on Saturn's moon Titan.
- Comet Hopper (CHopper) study cometary evolution by landing on a comet multiple times and observing its changes as it interacts with the Sun.
- Io Volcano Observer
- Pascal, a Mars climate network mission.
- EXOMOON, in situ investigation on Earth's Moon.
- PSOLHO, would use the Moon as an occulter to look for exoplanets.
- Suess-Urey, similar to the later Genesis mission.
- 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.
- MAUDEEE (Mars Upper Atmosphere Dynamics, Energetics, and Evolution) (compare to MAVEN of the Mars Scout program)
- Hermes, a Mercury orbiter. (compare to MESSENGER Mercury orbiter)
- Lunette, a lunar lander.
- 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.
- 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.
- 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 will be launched in September 2016 as OSIRIS-REx in the New Frontiers Program.
- 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.
- Psyche — a mission to the metalic 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Red Dragon, a Mars lander and sample return.
- Small Body Grand Tour, an asteroid rendezvous mission.
- 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))
- Twin Lunar Lander, a geophysics mission to the Moon.
- 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.
- 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).
- 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.
Missions in progress, in space
- Dawn, a mission to study the dwarf planet Ceres and large asteroid Vesta; launched in September 2007. It reached Vesta in July 2011. Dawn uses ion propulsion, allowing both Ceres and Vesta to be orbited in one mission. The Principal Investigator is Chris Russell of the University of California, Los Angeles. It is currently in orbit around Ceres.
- Kepler, a space telescope mission that continuously observed 100,000 stars in a fixed field of view in order to detect transits by exoplanets orbiting those stars. It was launched in March 2009 and announced its first exoplanet discoveries in January 2010. Kepler is the first spacecraft capable of finding Earth-size planets around other stars. The Principal Investigator is William Borucki of NASA’s Ames Research Center. It is currently experiencing technical difficulties, but may have a follow on mission.
Missions of opportunity
- 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.
InSight Mars lander
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. 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. An Announcement of Opportunity for a Discovery mission was released by NASA on June 7, 2010. Out of 28 proposals from 2010, three finalists received US$3 million in May 2011 to develop a detailed concept studies. In August 2012, InSight was selected for development and launch. According to the BBC, of the 28 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.
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.
- 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.
Discovery Mission 13
On 30 September 2015, NASA selected five mission concepts for refinement during the next year, as a first step in choosing one. Each mission will receive $3 million for a one-year study. The winner will be chosen around September 2016, and must be ready to launch by the end of 2021.
NASA has stated it may choose not just one, but possibly two of the missions for development in 2016.
The five semifinalists are: 
- 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 — it would explore the origin of planetary cores by studying the metallic asteroid 16 Psyche. (It has not been visited before)
- 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 (1981 EQ5).
The budget is planned to be 450 million USD, but there is some special technology and bonuses available beyond this.
- An additional 30 million USD becomes available if it attempts to demonstrate a laser (as opposed to radio) communication system at extra-Lunar distances
- An additional 10 million USD becomes available if it demonstrates 3D woven heat shield
- An additional 5 million USD becomes available to the mission if it incorporates the Deep Space atomic clock
- Ion engines are also available for mission
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.
In February 2014, NASA released a Discovery Program 'Draft Announcement of Opportunity' for launch readiness date of December 31, 2021. As with previous Discovery missions such as Dawn, solar electric propulsion may allow increased mission options if applicable. Technologies may include the NEXT ion thruster, laser communication, and/or re-entry technology. The main mission is budgeted for up to 450 million USD, with various conditions but also bonuses. For the first time, the $450 million cost cap will not include post-launch operations expenses.
The final requirements were changed later in 2014. 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. 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). The deadline for proposals was February 16, 2015 and may have included some of the following missions candidates:
- Saturn system
- Enceladus Life Finder (ELF) — an astrobiology orbiter mission to asses Enceladus' habitability and search for biosignatures.
- Journey to Enceladus and Titan (JET) — an astrobiology orbiter mission to asses Enceladus' habitability and search for biosignatures in the plumes.
- Life Investigation For Enceladus (LIFE) — an astrobiology sample-return mission to asses 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
- 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)
- 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.
- 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 tour Trojan asteroids
- Mission to 16 Psyche — the most massive metallic asteroid in the asteroid belt, thought to be exposed iron core of a protoplanet.
- Moon Age and Regolith Explorer
- 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
- 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.
|Deep Impact||Stardust||Genesis||GRAIL||Kepler Observatory||Dawn||MESSENGER|
|Lunar Prospector||Mars Pathfinder||NEAR||InSight|
This section includes an image of most of the Discovery missions' rockets, as well as the launch year
- Explorer program
- Mars Exploration Program
- Mars Scout Program
- New Frontiers Program
- New Millennium Program
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- "CONTOUR Mishap Investigation Board Report" (PDF). NASA. 2003-05-21. Archived (PDF) from the original on 2006-01-03.
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- "DAWN – A Journey to the Beginning of the Solar System". Dawn Mission Timeline. Jet Propulsion Laboratory. Archived from the original on 2013-10-19.
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- "Deep Impact Heads to New Comet". Space.com. 2006-10-31. Archived from the original on 2006-11-02.
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- "Discovery Missions Under Consideration". Goddard Space Flight Centre, NASA. Archived from the original on 2014-03-01.
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- "Robotics Institute: EXOMOON - A Discovery and Scout Mission Capabilities Expansion Concept". Robotics Institute, Carnegie Mellon University. 2011-06-15. Archived from the original on 2014-02-28.
- Clarke, T. L. "Planetary System Occultation from Lunar Halo Orbit (PSOLHO): A Discovery Mission". Astrophysics Data System. Harvard-Smithsonian Centre for Astrophysics. Retrieved 2014-02-28.
- "MUADEE: A Discovery-class mission for exploration of the upper atmosphere of Mars". Netherlands: Delft University of Technology. Retrieved 2014-02-28.
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- "NASA announces Discovery mission finalists". Space Today. 2001-01-04. Archived from the original on 2003-09-16.
- "Space Missions Roster". Lunar and Planetary Laboratory. The University of Arizona. Archived from the original on 2014-03-13.
- "Deep Impact: Five Discovery Mission Proposals Selected for Feasibility Studies". Deep Impact. University of Maryland. 1998-11-12. Archived from the original on 2002-06-20.
- "NASA - Vesper Could Explore Earth's Fiery Twin". NASA. Archived from the original on 2007-08-23.
- "The VESPER Mission to Venus". Astrophysics Data System. Harvard-Smithsonian Centre for Astrophysics.
- "NASA Announces Discovery Program Selections". News Release. NASA. 2006-10-30. Archived from the original on 2009-06-29.
- "OSIRIS-REx Factsheet" (PDF). University of Arizona. Archived (PDF) from the original on 2013-07-22.
- Pieters, C.; Murchie, S.; Cheng, A.; Zolensky, M.; Schultz, P.; Clark, B.; Thomas, P.; Calvin, W.; McSween, H.; Yeomans, D.; McKay, D.; Clemett, S.; Gold, R. "ALADDIN - Phobos-Deimos sample return". Astrophysics Data System. Harvard-Smithsonian Centre for Astrophysics.
- Pieters, C.; Calvin, W.; Cheng, A.; Clark, B.; Clemett, S.; Gold, R.; McKay, D.; Murchie, S.; Mustard, J.; Papike, J.; Schultz, P.; Thomas, P.; Tuzzolino, A.; Yeomans, D.; Yoder, C.; Zolensky, M.; Barnouin-Jha, O.; Domingue, D. "ALADDIN: Exploration and Sample Return of Phobos and Deimos" (PDF). Lunar and Planetary Science. Lunar and Planetary Institute. Archived (PDF) from the original on 2004-09-05.
- Elkins-Tanton, L.T.; Asphaug, E.; Bell, J.; Bercovici, D.; Bills, B.G.; Binzel, R.P.; Bottke, W.F.; Jun, I.; Marchi, S.; Oh, D.; Polanskey, C.A.; Weiss, B.P.; Wenkert, D.; Zuber, M.T. "Journey to a Metal World: Concept for a Discovery Mission to Psyche" (PDF). 45th Lunar and Planetary Science Conference (2014). Universities Space Research Association. Archived (PDF) from the original on 2014-02-27.
- "Cosmic Dust - Messenger from Distant Worlds" (PDF). University Stuttgart. Archived (PDF) from the original on 2014-02-24.
- Colaprete, A.; Bellerose, J.; Andrews, D. "PCROSS - Phobos Close Rendezvous Observation Sensing Satellite". Astrophysics Data System. Harvard-Smithsonian Centre for Astrophysics. Retrieved 2014-02-28.
- Rivkin, A. S.; Chabot, N. L.; Murchie, S. L.; Eng, D.; Guo, Y.; Arvidson, R. E.; Trebi-Ollennu, A.; Seelos, F. P. "Merlin : Mars-Moon Exploration, Reconnaissance and Landed Investigation" (PDF). SETI. Archived (PDF) from the original on 2014-02-28.
- Lee, Pascal; Hoftun, Christopher; Lorbe, Kira. "Phobos and Deimos: Robotic Exploration in Advance of Humans to mars Orbit" (PDF). Concepts and Approaches for Mars Exploration (2012). Lunar and Planetary Institute. Archived (PDF) from the original on 2014-03-01.
- Lee, Pascal; Veverka, Joseph; Bellerose, Julie; Boucher, Marc; Boynton, John; Braham, Stephen; Gellert, Ralf; Hildebrand, Alan; Manzella, David; Mungas, Greg; Oleson, Steven; Richards, Robert; Thomas, Peter C.; West, Michael D. "HALL: A Phobos and Deimos Sample and Return Mission" (PDF). 41st Lunar and Planetary Science Conference (2010). Lunar and Planetary Institute. Archived (PDF) from the original on 2014-02-27.
- Bassett, S.; Sears, D. W. G. "The Hera Mission: Meeting Discovery Class Mission Precedents for Education and Public Outreach" (PDF). Arkansas Centre for Space and Planetary Sciences. Archived (PDF) from the original on 2005-12-28.
- Sears, Derek; Allen, Carl; Britt, Dan; Brownlee, Don; Franzen, Melissa; Gefert, Leon; Gorovan, Stephen; Pieters, Carle; Preble, Jeffrey; Scheeres, Dan; Scott, Ed (2003-05-19). "The Hera Mission : Multiple Near-Earth Asteroid Sample Return" (PDF). Planetary Geosciences Group, Brown University. Archived (PDF) from the original on 2010-06-24.
- Klaasen, Kenneth; Greeley, Ronald (2003-03-31). "VEVA Discovery mission to Venus: exploration of volcanoes and atmosphere". Science Direct.
- Lorenz, Ralph D.; Mehoke, Doug; Hill, Stuart. "Venus Pathfinder: A Stand-Alone Long-Lived Venus Lander Mission Concept" (PDF). 8th International Planetary Probe Workshop (IPPW-8). National Institute of Aerospace. Archived (PDF) from the original on 2014-02-27.
- Sharpton, V. L.; Herrick, R. R.; Rogers, F.; Waterman, S. "RAVEN - High-resolution Mapping of Venus within a Discovery Mission Budget". Astrophysics Data System. Harvard-Smithsonian Centre for Astrophysics. Retrieved 2014-02-28.
- Baines, Kevin H.; Hall, Jeffery L.; Balint, Tibor; Kerzhanovich, Viktor; Hunter, Gary; Atreya, Sushil K.; Limaye, Sanjay S.; Zahnle, Kevin. "Exploring Venus with Balloons: Science Objectives and Mission Architectures for small and Medium-Class Missions" (PDF). Georgia Tech Library. Archived (PDF) from the original on 2014-02-27.
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- "Red Dragon", Feasibility of a Dragon-derived Mars lander for scientific and human-precursor investigations (PDF), SpaceX, 2011-10-31, archived (PDF) from the original on 2012-06-16
- Farquhar, Robert; Jen, Shao-Chiang; McAdams, Jim V. (2000-09-12). "Extended-mission opportunities for a Discovery-class asteroid rendezvous mission". Astrophysics Data System. Harvard-Smithsonian Centre for Astrophysics.
- Sandford, Scott A.; A'Hearn, Michael; Allamandola, Louis J.; Britt, Daniel; Clark, Benton; Dworkin, Jason P.; Flynn, George; Glavin, Danny; Hanel, Robert; Hanner, Martha; Hörz, Fred; Keller, Lindsay; Messenger, Scott; Smith, Nicholas; Stadermann, Frank; Wade, Darren; Zinner, Ernst; Zolensky, Michael E. "The Comet Coma Rendezvous Sample Return" (PDF). Lunar and Planetary Institute. Archived (PDF) from the original on 2010-06-28.
- Neal, C. R.; Banerdt, W. B.; Alkalai, L. "Lunette: A Two-Lander Discovery-Class Geophysics Mission to the Moon" (PDF). 42nd Lunar and Planetary Science Conference (2011). Lunar and Planetary Institute. Archived (PDF) from the original on 2014-03-01.
- Riedel, Joseph E.; Marrese-Reading, Colleen; Lee, Young H. (2013-06-19). "A Low-Cost NEO Micro Hunter-Seeker Mission Concept" (PDF). Low-Cost Planetary Missions Conference, LCPM-10. California Institute of Technology. Archived (PDF) from the original on 2014-03-01.
- "Venus Sample Targeting, Attainment, and Return (V-STAR)" (PDF). 2007 NASA Academy at the Goddard Space Flight Center. The Henry Foundation. Archived (PDF) from the original on 2012-03-15.
- Sweetser, Ted; Peterson, Craig; Nilsen, Erik; Gershman, Bob. "Venus Sample Return Missions - A Range of Science, A Range of Costs" (PDF). California Institute of Technology. Archived (PDF) from the original on 2010-05-26.
- Duke, M. B.; Clark, B. C.; Gamber, T.; Lucey, P. G.; Ryder, G.; Taylor, G. J. "Sample Return Mission to the South Pole Aitken Basin" (PDF). Workshop on New Views of the Moon II. Lunar and Planetary Institute. Archived (PDF) from the original on 2004-11-09.
- "NASA Selects Investigations For Future Key Planetary Mission". NASA. Archived from the original on 2011-05-07.
- "New NASA Mission to Take First Look Deep Inside Mars". NASA. 2012-08-20. Archived from the original on 2012-08-22.
- Agle, DC; Webster, Guy; Brown, Dwayne (2012-08-20). "New NASA Mission To take First Look Deep Inside Mars". Mars Exploration Program. JPL, NASA. Archived from the original on 2012-10-05.
- Vastag, Brian (2012-08-20). "NASA will send robot drill to Mars in 2016". The Washington Post.
- Hand, Eric (2011-09-02). "Venus scientists fear neglect". Nature. Archived from the original on 2012-05-26.
- "Discovery Program - Strofolio". NASA. Archived from the original on 2011-03-01.
- Kane, Van (2014-02-20). "Boundaries for the Next Discovery Mission Selection". Future Planets. Archived from the original on 2014-03-07.
- "Small Bodies Dominate NASA's Latest Discovery Competition". SpaceNews.com. July 7, 2015. Retrieved 2015-08-09.
- Clark, Stephen (24 February 2014). "NASA receives proposals for new planetary science mission". Space Flight Now. Retrieved 2015-02-25.
- Kane, Van (December 2, 2014). "Selecting the Next Creative Idea for Exploring the Solar System". Planetary Society. Retrieved 2015-02-10.
- Spaceflight Now - NASA might pick two Discovery missions, but at a price Posted on October 5, 2015 by Stephen Clark
- Brown, Dwayne C.; Cantillo, Laurie (30 September 2015). "NASA Selects Investigations for Future Key Planetary Mission". NASA News (Washington, D.C.). Retrieved 2015-10-01.
- Dreier, Casey; Lakdawalla, Emily (30 September 2015). "NASA announces five Discovery proposals selected for further study". The Planetary Society. Retrieved 2015-10-01.
- The DAVINCI spacecraft October 6, 2015 by Matt Williams, Universe Today
- "NASA Discovery Program Draft Announcement of Opportunity". NASA Science Mission Directorate (SpaceRef). 2014-02-19.
- "Evaluation of Solar Electric Propulsion Technologies for Discovery-Class Missions". American Institute of Aeronautics and Astronautics. Retrieved 2014-02-28.
- Clark, Stephen (3 March 2015). "NASA eyes ion engines for Mars orbiter launching in 2022". Space Flight Now. Retrieved 2015-03-04.
- "NASA Discovery Program Draft Announcement of Opportunity". SpaceRef. 2014-02-19.
- Clark, Stephen (April 6, 2015). "Diverse destinations considered for new interplanetary probe". Space Flight Now. Retrieved 2015-04-07.
- NASA Drops Laser Comm Requirement From Discovery Solicitation. Space News, Dan Leone. November 5, 2014
- NASA Sorting Through Latest Discovery Proposals
- Enceladus life finder: the search for life in a habitable moon. Geophysical Research Abstracts. Vol. 17, EGU2015-14923, 2015 EGU General Assembly 2015.
- Kane, Van (3 April 2014). "Discovery Missions for an Icy Moon with Active Plumes". The Planetary Society. Retrieved 2015-04-09.
- LIFE: Life Investigation For Enceladus: A Sample Return Mission Concept in Search for Evidence of Life. Astrobiology Volume 12, Number 8, 2012 DOI: 10.1089/ast.2011.0813
- Io Volcano Observer (IVO). Geophysical Research Abstracts, Vol. 11, EGU2009-6448-1, 2009. EGU General Assembly 2009.
- John F. Mustard, Scott L. Murchie, Andrew S. Rivkin, Douglas A. Eng, Elena Y. Adams, Patrick N. Peplowski, David J. Lawrence, Goestar Klingelhoefer (June 9–11, 2015). The Advanced Jovian Asteroid Explorer (PDF). 11th Low Cost Planetary Missions Conference.
- RAVEN - High-resolution Mapping of Venus within a Discovery Mission Budget
- Venus Atmosphere and Surface Explorer. American Astronomical Society, DPS meeting #46, #214.15 (2014)
- MERLIN: The Creative Choices Behind a Proposal to Explore the Martian Moons (Merlin and PADME info also)
- Phobos And Deimos & Mars Environment (PADME). 45th Lunar and Planetary Science Conference (2014).
- McKay, Christopher P.; Stoker, Carol R.; Glass, Brian J.; Davé, Arwen I.; Davila, Alfonso F.; Heldmann, Jennifer L.; Marinova, Margarita M.; Fairen, Alberto G.; Quinn, Richard C.; Zacny, Kris A.; Paulsen, Gale; Smith, Peter H.; Parro, Victor; Andersen, Dale T.; Hecht, Michael H.; Lacelle, Denis; Pollard, Wayne H. (2013-04-05). "The Icebreaker Life Mission to Mars: A Search for Biomolecular Evidence for Life". Astrobiology 13 (4): 334–353. Bibcode:2013AsBio..13..334M. doi:10.1089/ast.2012.0878. PMID 23560417.
- Choi, Charles Q. (2013-05-16). "Icebreaker Life Mission". Astrobiology Magazine. Archived from the original on 2013-08-15.
- McKay, C. P.; Stoker, Carol R.; Glass, Brian J.; Davé, Arwen I.; Davila, Alfonso F.; Heldmann, Jennifer L.; Marinova, Margarita M.; Fairen, Alberto G.; Quinn, Richard C.; Zacny, Kris A.; Paulsen, Gale; Smith, Peter H.; Parro, Victor; Andersen, Dale T.; Hecht, Michael H.; Lacelle, Denis; Pollard, Wayne H. (2012), "The Icebreaker Life Mission to Mars: A Search for Biochemical Evidence for Life", Concepts and Approaches for Mars Exploration (PDF), Lunar and Planetary Institute, archived (PDF) from the original on 2013-12-03
- Binary Asteroid in-situ Explorer Mission (BASiX): A Mission Concept to Explore a Binary Near Earth Asteroid System. 45th Lunar and Planetary Science Conference (2014)
- Dark Asteroid Rendezvous (DARe). 46th Lunar and Planetary Science Conference (2015)
- Five Solar System sights NASA should visit
- JOURNEY TO A METAL WORLD: CONCEPT FOR A DISCOVERY MISSION TO PSYCHE. (PDF) 45th Lunar and Planetary Science Conference (2014)
- Kuiper - A Discovery-Class observatory
- Official NASA website for Discovery Program
- Official NASA website for Discovery & New Frontiers Programs Office