Editing Discovery Program (section)

==Proposals and concepts==
[[File:Lunar Sample.jpg|thumb|Possible configuration of a lunar sample return spacecraft]]
[[File:Mercury in color - Prockter07 (cropped).jpg|thumb|Mercury by Discovery's ''MESSENGER'']]
However often the funding comes in, there is a selection process with perhaps two dozen concepts. These sometimes get further matured and re-proposed in another selection or program.<ref name="nasa">{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/discovery3.html |title=3 Proposed Discovery Missions |publisher=National Space Science Data Center, NASA |archive-url=https://web.archive.org/web/20140301113019/http://nssdc.gsfc.nasa.gov/planetary/discovery3.html |archive-date=March 1, 2014 |url-status=live}}</ref> An example of this is ''Suess-Urey Mission'', which was passed over in favor of the successful ''[[Stardust (spacecraft)|Stardust]]'' mission, but was eventually flown as [[Genesis (spacecraft)|Genesis]],<ref name="nasa" /> while a more extensive mission similar to INSIDE was flown as ''[[Juno (spacecraft)|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 (spacecraft)|Whipple]], a space-observatory to detect objects in the [[Oort cloud]] by transit method.<ref name="whipple">{{cite web|last1=Alcock|first1=Charles|last2=Brown|first2=Michael|last3=Tom|first3=Gauron|last4=Cate|first4=Heneghan|title=The Whipple Mission Exploring the Oort cloud and the Kuiper Belt|url=http://whipple.cfa.harvard.edu/inc/documents/Alcock_AGUPoster_2014dec.pdf|url-status=live|archive-url=https://web.archive.org/web/20151117031224/http://whipple.cfa.harvard.edu/inc/documents/Alcock_AGUPoster_2014dec.pdf|archive-date=November 17, 2015|access-date=21 February 2021}}</ref>
* [[Io Volcano Observer]], was proposed for missions 15 or 16, a Jupiter orbiter designed to make 10 flybys of the volcanically active moon [[Io (moon)|Io]].<ref name="McEwen2021LPSC">{{cite conference|last=McEwen|first=A. S.|date=2021|title=The Io Volcano Observer (IVO)|url=https://www.hou.usra.edu/meetings/lpsc2021/pdf/1352.pdf|conference=[[Lunar and Planetary Science Conference]]|id=Abstract #1352|access-date=9 February 2021}}</ref>
* [[Comet Hopper]] (CHopper), a mission to comet [[46P/Wirtanen]] that would've utilised multiple short flights to repeatedly land on the comet's nucleus in order to map various geological processes such as [[outgassing]].<ref name="AdamsBrief">{{cite web|title=Planetary Science Division Update|url=http://solarsystem.nasa.gov/docs/Adams%20PPS%2005102011.pdf|url-status=dead|archive-url=https://web.archive.org/web/20111114141842/http://solarsystem.nasa.gov/docs/Adams%20PPS%2005102011.pdf|archive-date=14 November 2011|access-date=May 23, 2011|publisher=[[NASA]]}}</ref>
* [[Titan Mare Explorer]] (TiME), a lander mission to explore one of the [[Lakes of Titan|methane lakes]] found in the north polar region of [[Titan (moon)|Titan]], a moon of [[Saturn]].<ref>{{Cite news|last=Taylor Redd|first=Nola|date=14 April 2017|title=Lander Designed for Titan's Methane Seas Tests Tech on Chilean Lake|work=[[Space.com]]|url=https://www.space.com/36476-titan-lander-design-test-chilean-lake.html|access-date=21 February 2021}}</ref>
* '''Suess-Urey''', similar to the later [[Genesis (spacecraft)|Genesis]] mission.<ref name="nasa" />
* '''Hermes''', a Mercury orbiter.<ref>{{cite journal |title=1994LPI 25..985N Page 985 |journal=Astrophysics Data System |pages = 985|publisher=Harvard-Smithsonian Centre for Astrophysics |bibcode = 1994LPI....25..985N|last1 = Nelson|first1 = R. M.|last2 = Horn|first2 = L. J.|last3 = Weiss|first3 = J. R.|last4 = Smythe|first4 = W. D.|year = 1994}}</ref> (similar to the [[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.<ref name="finalists01">{{cite web |url=http://www.spacetoday.net/Summary/7 |title=NASA announces Discovery mission finalists |publisher=Space Today |date=January 4, 2001 |archive-url=https://web.archive.org/web/20030916192235/http://www.spacetoday.net/Summary/7 |archive-date=September 16, 2003 |url-status=live}}</ref> The concept was further matured and implemented as [[Juno (spacecraft)|Juno]] in the [[New Frontiers program]].<ref name="Space Missions Roster 2012">{{cite web |url=http://www.lpl.arizona.edu/research/missions |title=Space Missions Roster |work=Lunar and Planetary Laboratory |publisher=The University of Arizona |url-status=live |archive-date=March 13, 2014 |archive-url=https://web.archive.org/web/20140313171936/http://www.lpl.arizona.edu/research/missions}}</ref>
* The '''Dust Telescope''', a space observatory that would measure various properties of incoming [[cosmic dust]].<ref name="dust">{{cite web |url=http://www.irs.uni-stuttgart.de/cosmicdust/documents/CDB_Dustgroup.pdf |title=Cosmic Dust – Messenger from Distant Worlds |publisher=University Stuttgart |archive-url=https://web.archive.org/web/20140224180419/http://www.irs.uni-stuttgart.de/cosmicdust/documents/CDB_Dustgroup.pdf |archive-date=February 24, 2014 |url-status=live}}</ref> The dust telescope would combine a trajectory sensor and a [[mass spectrometer]], to allow the elemental and even isotopic composition to be analyzed.<ref name="dust" />
* '''OSIRIS''' (Origins Spectral Interpretation, Resource Identification and Security), an asteroid observation and sample return mission concept selected in 2006 for further concept studies.<ref name="select">{{cite web |url=http://www.nasa.gov/home/hqnews/2006/oct/HQ_06342_Discovery_AO.html |title=NASA Announces Discovery Program Selections |work=News Release |publisher=NASA |date=October 30, 2006 |archive-url=https://web.archive.org/web/20090629094310/http://www.nasa.gov/home/hqnews/2006/oct/HQ_06342_Discovery_AO.html |archive-date=June 29, 2009 |url-status=live}}</ref> It further matured and launched September 8, 2016, as [[OSIRIS-REx]] in the [[New Frontiers Program]].<ref name="factsheet">{{cite web |title=OSIRIS-REx Factsheet |url=http://osiris-rex.lpl.arizona.edu/sites/osiris-rex.lpl.arizona.edu/files/pdfs/Technical%20Fact%20Sheet%202013-05-01.pdf |publisher=University of Arizona |archive-url=https://web.archive.org/web/20130722204427/http://osiris-rex.lpl.arizona.edu/sites/osiris-rex.lpl.arizona.edu/files/pdfs/Technical%20Fact%20Sheet%202013-05-01.pdf |archive-date=July 22, 2013 |url-status=dead  }}</ref>
* '''Small Body Grand Tour''', an asteroid rendezvous mission.<ref name=bodies>{{cite journal |bibcode=1993STIA...9581370F |title=Extended-mission opportunities for a Discovery-class asteroid rendezvous mission |last1=Farquhar |first1=Robert |last2=Jen |first2=Shao-Chiang |last3=McAdams |first3=Jim V. |journal=Astrophysics Data System |volume=95 |pages=435 |publisher=Harvard-Smithsonian Centre for Astrophysics |date=September 12, 2000}}</ref> This 1993 concept reviews possible targets for what became NEAR{{mdash}} [[4660 Nereus]] and [[2019 Van Albada]].<ref name=bodies/> Other targets considered for an extended mission included [[Encke's comet]] (2P), [[433 Eros]], [[1036 Ganymed]], [[4 Vesta]], and [[4015 Wilson–Harrington]] (1979 VA).<ref name=bodies/> ([[NEAR Shoemaker]] visited 433 Eros and [[Dawn (spacecraft)|Dawn]] visited 4 Vesta)<ref name=":2" /><ref name=":3" />
* '''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.<ref name="lpi_SaS">{{cite web |url=http://www.lpi.usra.edu/decadal/sbag/topical_wp/ScottASandford.pdf |title=The Comet Coma Rendezvous Sample Return |first1=Scott A. |last1=Sandford |first2=Michael |last2=A'Hearn |first3=Louis J. |last3=Allamandola |first4=Daniel |last4=Britt |first5=Benton |last5=Clark |first6=Jason P. |last6=Dworkin |first7=George |last7=Flynn |first8=Danny |last8=Glavin |first9=Robert |last9=Hanel | first10=Martha | last10=Hanner |first11=Fred |last11=Hörz |first12=Lindsay |last12=Keller |first13=Scott |last13=Messenger |first14=Nicholas |last14=Smith |first15=Frank |last15=Stadermann |first16=Darren |last16=Wade |first17=Ernst |last17=Zinner |first18=Michael E. |last18=Zolensky |publisher=Lunar and Planetary Institute |archive-url=https://web.archive.org/web/20100628104309/http://www.lpi.usra.edu/decadal/sbag/topical_wp/ScottASandford.pdf |archive-date=June 28, 2010 |url-status=live}}</ref> (Similar to [[Stardust (spacecraft)|''Stardust'']])
* '''Micro Exo Explorer''', a spacecraft that would've utilised a new form of micro-electric propulsion, called 'Micro Electro-fluidic-spray Propulsion' to travel to a near Earth object and gather important data.<ref>{{cite web |url=http://lcpm10.caltech.edu/pdf/session-5/9_NEO_Hunter_Seeker13.pdf |title=A Low-Cost NEO Micro Hunter-Seeker Mission Concept |work=Low-Cost Planetary Missions Conference, LCPM-10 |first1=Joseph E. |last1=Riedel |first2=Colleen |last2=Marrese-Reading |first3=Young H. |last3=Lee |publisher=California Institute of Technology |date=June 19, 2013 |archive-url=https://web.archive.org/web/20140301115330/http://lcpm10.caltech.edu/pdf/session-5/9_NEO_Hunter_Seeker13.pdf |archive-date=March 1, 2014 |url-status=dead |access-date=February 25, 2014 }}</ref>

===Mars focused===
[[File:PIA11858 Starburst Spider.jpg|thumb|Mars Geyser Hopper would investigate 'spider' features on Mars, as imaged by an orbiter. Image size: {{convert|1|km|mi|abbr=on}} across.]]
* '''Pascal''', a Mars climate network mission.<ref>{{cite journal |bibcode=2000came.work..135H |last1=Haberle |first1=R. M. |last2=Catling |first2=D. C. |last3=Chassefiere |first3=E. |last4=Forget |first4=F. |last5=Hourdin |first5=F. |last6=Leovy |first6=C. B. |last7=Magalhaes |first7=J. |last8=Mihalov |first8=J. |last9=Pommereau |first9=J. P. | last10=Murphy | first10=J. R. |title=The Pascal Discovery Mission: A Mars Climate Network Mission |journal=Astrophysics Data System |pages=135 |publisher=Harvard-Smithsonian Centre for Astrophysics |year=2000 }}</ref>
* '''MUADEE''' (Mars Upper Atmosphere Dynamics, Energetics, and Evolution), an orbiter mission designed to study Mars's upper atmosphere.<ref name="delft">{{cite web |url=https://discover.tudelft.nl/recordview/view?recordId=Elsevier%3Aelsevier%3ACXT0348A%3A00945765%3A003500S1%3A9400203X |title=MUADEE: A Discovery-class mission for exploration of the upper atmosphere of Mars |publisher=Delft University of Technology |location=Netherlands |access-date=February 28, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20150204180416/https://discover.tudelft.nl/recordview/view?recordId=Elsevier:elsevier:CXT0348A:00945765:003500S1:9400203X |archive-date=February 4, 2015}}</ref> (similar to [[MAVEN]] of the Mars Scout program)
* '''PCROSS''', similar to [[LCROSS]], but directed towards Mars's moon [[Phobos (moon)|Phobos]].<ref>{{cite journal |bibcode=2012LPICo1679.4180C |title=PCROSS – Phobos Close Rendezvous Observation Sensing Satellite |last1=Colaprete |first1=A. |last2=Bellerose |first2=J. |last3=Andrews |first3=D. |journal=Astrophysics Data System |volume=1679 |pages=4180 |publisher=Harvard-Smithsonian Centre for Astrophysics |year=2012 }}</ref>
* '''Merlin''', a mission that would place a lander on Mars's moon [[Deimos (moon)|Deimos]].<ref>{{cite web |url=http://multimedia.seti.org/PhD2011/abstracts/PhD2-11-014.pdf |title=Merlin : Mars-Moon Exploration, Reconnaissance and Landed Investigation |first1=A. S. |last1=Rivkin |first2=N. L. |last2=Chabot |first3=S. L. |last3=Murchie |first4=D. |last4=Eng |first5=Y. |last5=Guo |first6=R. E. |last6=Arvidson |first7=A. |last7=Trebi-Ollennu |first8=F. P. |last8=Seelos |publisher=SETI |archive-url=https://web.archive.org/web/20140228132654/http://multimedia.seti.org/PhD2011/abstracts/PhD2-11-014.pdf |archive-date=February 28, 2014 |url-status=dead}}</ref>
* '''Mars Moons Multiple Landings Mission''' (M4), would conduct multiple landings on Phobos and Deimos.<ref name="lpi_4363">{{cite web |url=http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4363.pdf |title=Phobos and Deimos: Robotic Exploration in Advance of Humans to mars Orbit |first1=Pascal |last1=Lee |first2=Christopher |last2=Hoftun |first3=Kira |last3=Lorbe |work=Concepts and Approaches for Mars Exploration (2012) |publisher=Lunar and Planetary Institute |archive-url=https://web.archive.org/web/20140301114741/http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4363.pdf |archive-date=March 1, 2014 |url-status=live}}</ref>
* '''Hall''', a Phobos and Deimos sample return mission.<ref name="lpi_1633">{{cite web |url=http://www.lpi.usra.edu/meetings/lpsc2010/pdf/1633.pdf |title=HALL: A Phobos and Deimos Sample and Return Mission |first1=Pascal |last1=Lee |first2=Joseph |last2=Veverka |first3=Julie |last3=Bellerose |first4=Marc |last4=Boucher |first5=John |last5=Boynton |first6=Stephen |last6=Braham |first7=Ralf |last7=Gellert |first8=Alan |last8=Hildebrand |first9=David |last9=Manzella | first10=Greg | last10=Mungas |first11=Steven |last11=Oleson |first12=Robert |last12=Richards |first13=Peter C. |last13=Thomas |first14=Michael D. |last14=West |work=41st Lunar and Planetary Science Conference (2010) |publisher=Lunar and Planetary Institute |archive-url=https://web.archive.org/web/20140227183425/http://www.lpi.usra.edu/meetings/lpsc2010/pdf/1633.pdf |archive-date=February 27, 2014 |url-status=live}}</ref>
* '''Aladdin''', a Phobos and Deimos sample return mission.<ref>{{cite journal |bibcode=1997LPI....28.1111P |title=ALADDIN – Phobos-Deimos sample return |last1=Pieters |first1=C. |last2=Murchie |first2=S. |last3=Cheng |first3=A. |last4=Zolensky |first4=M. |last5=Schultz |first5=P. |last6=Clark |first6=B. |last7=Thomas |first7=P. |last8=Calvin |first8=W. |last9=McSween |first9=H. | last10=Yeomans | first10=D. |last11=McKay |first11=D. |last12=Clemett |first12=S. |last13=Gold |first13=R. |journal=Astrophysics Data System |pages=1111 |publisher=Harvard-Smithsonian Centre for Astrophysics |year=1997 }}</ref> It was a finalist in the 1999 Discovery selection, with a planned launch in 2001 and return of the samples by 2006.<ref name="sr">{{cite web |url=http://www.lpi.usra.edu/meetings/LPSC99/pdf/1155.pdf |title=ALADDIN: Exploration and Sample Return of Phobos and Deimos |first1=C. |last1=Pieters |first2=W. |last2=Calvin |first3=A. |last3=Cheng |first4=B. |last4=Clark |first5=S. |last5=Clemett |first6=R. |last6=Gold |first7=D. |last7=McKay |first8=S. |last8=Murchie |first9=J. |last9=Mustard | first10=J. | last10=Papike |first11=P. |last11=Schultz |first12=P. |last12=Thomas |first13=A. |last13=Tuzzolino |first14=D. |last14=Yeomans |first15=C. |last15=Yoder |first16=M. |last16=Zolensky |first17=O. |last17=Barnouin-Jha |first18=D. |last18=Domingue |work=Lunar and Planetary Science |publisher=Lunar and Planetary Institute |archive-url=https://web.archive.org/web/20040905173338/http://www.lpi.usra.edu/meetings/LPSC99/pdf/1155.pdf |archive-date=September 5, 2004 |url-status=live}}</ref> Sample collection was intended to work by sending projectiles into the moons, then collecting the ejecta by means of a collector spacecraft flyby.<ref name="sr" />
* [[Mars Geyser Hopper]], a lander that would investigate the springtime [[carbon dioxide]] [[Martian geyser]]s found in regions around the [[Planum Australe|Martian south pole]].<ref name="Geyser Hopper">{{citation |first1=Geoffrey A. |last1=Landis |first2=Steven J. |last2=Oleson |first3=Melissa |last3=McGuire |contribution=Design Study for a Mars Geyser Hopper |title=50th AIAA Aerospace Sciences Conference |publisher=Glenn Research Center, NASA |date=January 9, 2012 |contribution-url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120004036_2012004260.pdf |contribution-format=PDF |access-date=July 1, 2012}}</ref><ref>{{cite web |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120004036_2012004260.pdf |title=Mars Geyser-Hopper (AIAA2012) |work=NASA Technical Reports |publisher=NASA |access-date=February 28, 2014}}</ref>
* '''MAGIC''' (Mars Geoscience Imaging at Centimeter-scale), an orbiter that would provide images of the Martian surface at 5–10&nbsp;cm/pixel, permitting resolution of features as small as 20–40&nbsp;cm.<ref name="lpi_4325">{{cite web |url=http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4325.pdf |title=Mars Geoscience Imaging at Centimetre-Scale (MAGIC) from Orbit |first1=M. A. |last1=Ravine |first2=M. C. |last2=Malin |first3=M. A. |last3=Caplinger |work=Concepts and Approaches for Mars Exploration (2012) |publisher=Lunar and Planetary Institute |archive-url=https://web.archive.org/web/20131029185914/http://www.lpi.usra.edu/meetings/marsconcepts2012/pdf/4325.pdf |archive-date=October 29, 2013 |url-status=live}}</ref>
* ''[[Red Dragon (spacecraft)|Red Dragon]]'', a Mars lander and sample return.<ref name="8m">{{citation |contribution=Red Dragon |title=Feasibility of a Dragon-derived Mars lander for scientific and human-precursor investigations |url=http://digitalvideo.8m.net/SpaceX/RedDragon/karcz-red_dragon-nac-2011-10-29-1.pdf |publisher=SpaceX |date=October 31, 2011 |archive-url=https://web.archive.org/web/20120616154043/http://digitalvideo.8m.net/SpaceX/RedDragon/karcz-red_dragon-nac-2011-10-29-1.pdf |archive-date=June 16, 2012 |url-status=live}}</ref>

===Lunar focused===
* Lunar sample return from the [[South Pole–Aitken basin]], current geological models don't adequately describe the area and this mission would have attempted to solve this issue.<ref name="lpi_8017">{{cite web |url=http://www.lpi.usra.edu/meetings/moon99/pdf/8017.pdf |title=Sample Return Mission to the South Pole Aitken Basin |first1=M. B. |last1=Duke |first2=B. C. |last2=Clark |first3=T. |last3=Gamber |first4=P. G. |last4=Lucey |first5=G. |last5=Ryder |first6=G. J. |last6=Taylor |work=Workshop on New Views of the Moon II |publisher=Lunar and Planetary Institute |archive-url=https://web.archive.org/web/20041109233513/http://www.lpi.usra.edu/meetings/moon99/pdf/8017.pdf |archive-date=November 9, 2004 |url-status=live}}</ref>
* '''EXOMOON''', ''in situ'' investigation on Earth's Moon.<ref>{{cite web |url=http://www.ri.cmu.edu/publication_view.html?pub_id=6129 |title=Robotics Institute: EXOMOON – A Discovery and Scout Mission Capabilities Expansion Concept |publisher=Robotics Institute, Carnegie Mellon University |date=June 15, 2011 |archive-url=https://web.archive.org/web/20140228020156/http://www.ri.cmu.edu/publication_view.html?pub_id=6129 |archive-date=February 28, 2014 |url-status=dead}}</ref>
* '''PSOLHO''', would use the Moon as an occulter to look for exoplanets.<ref>{{cite journal |bibcode=2003AAS...203.0305C |title=Planetary System Occultation from Lunar Halo Orbit (PSOLHO): A Discovery Mission |last=Clarke |first=T. L. |journal=Astrophysics Data System |volume=203 |pages=03.05 |publisher=Harvard-Smithsonian Centre for Astrophysics |year=2003 }}</ref>
* '''Lunette''', a lunar lander.<ref name="lpi_klaus">{{cite web |url=http://www.lpi.usra.edu/meetings/leag2012/presentations/Klaus.pdf |title=Concepts Leading to a Sustainable Architecture for Cislunar Development |first=K |last=Klaus |work=LEAG |publisher=Lunar and Planetary Institute |date=October 24, 2012 |archive-url=https://web.archive.org/web/20140301113544/http://www.lpi.usra.edu/meetings/leag2012/presentations/Klaus.pdf |archive-date=March 1, 2014 |url-status=live}}</ref>
* '''Twin Lunar Lander''', a double lander mission to better understand the Moon's evolution and geology.<ref name="lpi_2832">{{cite web |url=http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2832.pdf |title=Lunette: A Two-Lander Discovery-Class Geophysics Mission to the Moon |first1=C. R. |last1=Neal |first2=W. B. |last2=Banerdt |first3=L. |last3=Alkalai |work=42nd Lunar and Planetary Science Conference (2011) |publisher=Lunar and Planetary Institute |archive-url=https://web.archive.org/web/20140301115247/http://www.lpi.usra.edu/meetings/lpsc2011/pdf/2832.pdf |archive-date=March 1, 2014 |url-status=live}}</ref>

[[File:Vmpmvenus.gif|thumb|The Venus Multiprobe Mission involved sending 16 atmospheric probes into Venus in 1999.<ref>{{cite web |url=http://nssdc.gsfc.nasa.gov/planetary/discovery3.html |title=Discovery Missions Under Consideration |publisher=Goddard Space Flight Centre, NASA |archive-url=https://web.archive.org/web/20140301113019/http://nssdc.gsfc.nasa.gov/planetary/discovery3.html |archive-date=March 1, 2014 |url-status=live}}</ref>]]

===Venus focused===
* '''Venus Multiprobe''', proposed for a 1999 launch, would have dropped 16 atmospheric probes into Venus, which would fall slowly to the surface, taking pressure and temperature measurements.<ref name="nasa" />
* '''Vesper''', a concept for a Venus orbiter focused on studying the planet's atmosphere.<ref name="finalists">{{cite web |url=http://deepimpact.umd.edu/press/98-203.html |series=Press Releases |title=Deep Impact: Five Discovery Mission Proposals Selected for Feasibility Studies |work=Deep Impact |publisher=University of Maryland |date=November 12, 1998 |archive-url=https://web.archive.org/web/20020620083019/http://deepimpact.umd.edu/press/98-203.html |archive-date=June 20, 2002 |url-status=live}}</ref><ref name="vesper">{{cite web |url=http://www.nasa.gov/centers/goddard/news/topstory/2006/vesper.html |title=NASA – Vesper Could Explore Earth's Fiery Twin |publisher=NASA |archive-url=https://web.archive.org/web/20070823131906/http://www.nasa.gov/centers/goddard/news/topstory/2006/vesper.html |archive-date=August 23, 2007 |url-status=live}}</ref><ref>{{cite journal |title=The VESPER Mission to Venus |volume = 30|pages = 1106|journal=Astrophysics Data System |publisher=Harvard-Smithsonian Centre for Astrophysics |bibcode = 1998BAAS...30.1106A|last1 = Allen|first1 = M.|last2 = Chin|first2 = G.|author3 = VESPER Science Team|year = 1998}}</ref> It was one of three concepts to receive funds for further study in the 2006 Discovery selection.<ref name="vesper" /> Osiris and GRAIL were the other two, and eventually GRAIL was chosen and went on to be launched.<ref name="select" /> 
* '''V-STAR''' (Venus Sample Targeting, Attainment and Return), a Venus sample return mission with a goal of understanding Venus's evolution.<ref name="vsr">{{cite web |url=http://henry.pha.jhu.edu/2007_Academy_Group_Project.pdf |title=Venus Sample Targeting, Attainment, and Return (V-STAR) |work=2007 NASA Academy at the Goddard Space Flight Center |publisher=The Henry Foundation |archive-url=https://web.archive.org/web/20120315021449/http://henry.pha.jhu.edu/2007_Academy_Group_Project.pdf |archive-date=March 15, 2012 |url-status=dead  }}</ref><ref name="trs_0542">{{cite web |url=http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/14139/1/00-0542.pdf |title=Venus Sample Return Missions – A Range of Science, A Range of Costs |first1=Ted |last1=Sweetser |first2=Craig |last2=Peterson |first3=Erik |last3=Nilsen |first4=Bob |last4=Gershman |publisher=California Institute of Technology |archive-url=https://web.archive.org/web/20100526220032/http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/14139/1/00-0542.pdf |archive-date=May 26, 2010 |url-status=dead  }}</ref> The mission would have consisted of a [[Venus]] orbiter with an attached lander. The lander would fall through the Venusian atmosphere, collecting samples along the way, as well as after landing through the use of a "mole". Said lander would launch those samples into a low orbit, where they would rendezvous with the orbiter, returning the samples to Earth.<ref name="vsr" />
* '''VEVA''' (Venus Exploration of Volcanoes and Atmosphere), an atmospheric probe for Venus.<ref name="veva">{{cite journal  |title=VEVA Discovery mission to Venus: exploration of volcanoes and atmosphere |first1=Kenneth |last1=Klaasen |first2=Ronald |last2=Greeley |date=March 31, 2003| doi=10.1016/s0094-5765(02)00151-0 |volume=52 |issue=2–6 |journal=Acta Astronautica |pages=151–158|bibcode=2003AcAau..52..151K }}</ref> The main component is a 7-day balloon flight through the atmosphere accompanied by various small probes dropped deeper into the planet's thick gases.<ref name="veva" />
* '''Venus Pathfinder''', a long-duration Venus lander.<ref>{{cite web |url=http://www.planetaryprobe.org/sessionfiles/session2/papers/lorenz_venus_lander-paper.pdf |title=Venus Pathfinder: A Stand-Alone Long-Lived Venus Lander Mission Concept |first1=Ralph D. |last1=Lorenz |first2=Doug |last2=Mehoke |first3=Stuart |last3=Hill |work=8th International Planetary Probe Workshop (IPPW-8) |publisher=National Institute of Aerospace |archive-url=https://web.archive.org/web/20140227204705/http://www.planetaryprobe.org/sessionfiles/session2/papers/lorenz_venus_lander-paper.pdf |archive-date=February 27, 2014 |url-status=dead  }}</ref> 
* '''RAVEN''', a Venus orbiter radar mapping mission.<ref>{{cite journal |bibcode=2009AGUFM.P31D..04S |title=RAVEN – High-resolution Mapping of Venus within a Discovery Mission Budget |last1=Sharpton |first1=V. L. |last2=Herrick |first2=R. R. |last3=Rogers |first3=F. |last4=Waterman |first4=S. |journal=Astrophysics Data System |volume=2009 |pages=P31D–04 |publisher=Harvard-Smithsonian Centre for Astrophysics |year=2009 }}</ref>
* '''VALOR''', a Venus mission to study its atmosphere with a balloon.<ref name="val">{{cite web |url=https://smartech.gatech.edu/bitstream/handle/1853/26401/65-172-1-PB.pdf |title=Exploring Venus with Balloons: Science Objectives and Mission Architectures for small and Medium-Class Missions |first1=Kevin H. |last1=Baines |first2=Jeffery L. |last2=Hall |first3=Tibor |last3=Balint |first4=Viktor |last4=Kerzhanovich |first5=Gary |last5=Hunter |first6=Sushil K. |last6=Atreya |first7=Sanjay S. |last7=Limaye |first8=Kevin |last8=Zahnle |publisher=Georgia Tech Library |archive-url=https://web.archive.org/web/20140227192352/https://smartech.gatech.edu/bitstream/handle/1853/26401/65-172-1-PB.pdf |archive-date=February 27, 2014 |url-status=live}}</ref> Twin balloons would circumnavigate the planet over 8 Earth-days.<ref name="val" /> 
* '''Venus Aircraft''', a robotic atmospheric flight on Venus's atmosphere using a long-duration solar-powered aircraft system.<ref name="VenusAirplane">{{cite conference |conference=40th AIAA Aerospace Sciences Meeting & Exhibit |citeseerx=10.1.1.195.172 |title=NASA TM-2002-0819 : Atmospheric Flight on Venus |first1=Geoffrey A. |last1=Landis |first2=Christopher |last2=LaMarre |first3=Anthony |last3=Colozza |publisher=American Institute of Aeronautics and Astronautics, The Pennsylvania State University |date=January 14, 2002 |doi=10.2514/6.2002-819 }}</ref> It would carry 1.5&nbsp;kg of scientific payload and would contend with violent wind, heat and a corrosive atmosphere.<ref name="VenusAirplane" />
* [[Venus Landsailing Rover|Zephyr]], a rover concept that would be propelled by the wind force on its vertical wingsail. Conceived in 2012, the project has since made progress in developing electronic components that would allow the vehicle to operate for 50 days on the surface of Venus without a cooling system.<ref name='Zephyr 2015 Report'>[https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150000879.pdf Zephyr: A Landsailing Rover For Venus]. (PDF) Geoffrey A. Landis, Steven R. Oleson, David Grantier, and the COMPASS team. NASA John Glenn Research Center. 65th International Astronautical Congress, Toronto, Canada. February 24, 2015.  Report: IAC-14,A3,P,31x26111</ref>