Large Strategic Science Missions: History
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NASA's Large Strategic Science Missions, formerly known as Flagship missions or Flagship-class missions, are the costliest and most capable NASA science spacecraft. Flagship missions exist within all four divisions of NASA's Science Mission Directorate: the astrophysics, Earth science, heliophysics and planetary science divisions. "Large" refers to the budget of each mission, typically the most expensive mission in the scientific discipline. Within the Astrophysics Division and the Planetary Science Division, the large strategic missions are usually in excess of $1 billion. Within Earth Science Division and Heliophysics Division, the large strategic missions are usually in excess of $500 million. "Strategic" refers to their role advancing multiple strategic priorities set forth in plans such as the Decadal Surveys. "Science" marks these missions as primarily scientific in nature, under the Science Mission Directorate (SMD), as opposed to, e.g., human exploration missions under the Human Exploration and Operations Mission Directorate (HEOMD). The lines can be blurred, as when the Lunar Reconnaissance Orbiter began as a directed mission from the HEOMD, and was later transferred to the SMD. Flagship missions are not under the purview of any larger "Flagship Program", unlike, e.g., Discovery-class missions that are under the purview of the Discovery Program. Unlike these competed classes that tender proposals through a competitive selection process, the development of Flagship missions is directed to a specific institution — usually a NASA center or the Jet Propulsion Laboratory — by the Science Mission Directorate. Flagship missions are developed ad-hoc, with no predetermined launch cadence or uniform budget size. Flagship missions are always Class A missions: high priority, very low risk.

  • planetary science
  • heliophysics
  • astrophysics

1. History

The Voyager probes mark the transition between the original NASA unmanned mission programs, which were funded and organized as a series of related missions to specific targets such as the Mariner probes, Pioneer probes, Surveyor landers, Ranger probes, etc., and the modern NASA system which includes Flagships. In the early 1990s, NASA made the decision that instead of a centrally planned mission approach around pre-selected targets, mission ideas would compete for selection. The competitions would be based in cost categories, eventually turning into the Discovery and New Frontiers programs, as well as Flagship missions. While teams self-assemble to compete for Discovery and New Frontiers missions, Flagship missions are still strongly influenced by NASA headquarters. Also, Discovery and New Frontiers missions are scheduled frequently enough that a standard process has emerged and scientists can expect that process to be followed, but Flagship missions seem to follow a different organizational and development approach every time.

The 2011 Planetary Science Decadal Survey report recommended to NASA that the highest priority Flagship mission for development was a sample-caching rover, called the Mars Astrobiology Explorer-Cacher (MAX-C), as an American contribution to the ExoMars project with the European Space Agency (ESA) and as precursor to a proposed Mars sample return mission. The second highest priority mission was identified as the Jupiter Europa Orbiter, proposed to be part of the NASA-ESA EJSM/Laplace mission, and would have studied Europa in detail as a site of astrobiological interest.[1] Other priorities included the Uranus Orbiter and Probe, the Enceladus Orbiter, and the Venus Climate Mission.[2]

Under the FY2013 budget that President Obama released on February 2012, NASA terminated its participation in ExoMars due to budgetary cuts,[3] in order to pay for the cost overruns of the James Webb Space Telescope.[4] At that time, all proposed NASA Flagship planetary missions were put on hold indefinitely.[5]

In December 2012, the Mars 2020 sample-caching rover, built on the same architecture as the Mars Science Laboratory (Curiosity rover), was announced on a proposed budget of $1.5 billion.[6] In June 2015, the Europa Clipper was approved by NASA and entered the formulation stage.[7]

In 2016, four different space telescopes were being proposed for selection in 2020: Large UV Optical Infrared Surveyor (LUVOIR), Habitable Exoplanet Imaging Mission (HabEx), Origins Space Telescope (OST), and the Lynx X-ray Surveyor.[8] In 2019 the four teams will turn their final reports over to the National Academy of Sciences, whose independent Decadal Survey committee advises NASA on which pace telescope mission should take top priority. Selection would take place in the 2020s, and launch approximately in 2035.[9]

2. Missions

Each of NASA's science divisions (Planetary Science, Heliospheric, Astrophysics and Earth Science) typically fly just one large strategic mission per decade. The 2020s decade will see two planetary launches, the Mars 2020 rover and the Europa Clipper, and a third, a Europa Lander has been studied for possible launch as early as 2024.[10]

NASA Large Strategic Science Missions[11]
Mission name Mission start Mission end
Planetary Science Division
Viking 1, 2[12] 1975 1982
Voyager 1, 2[12] 1977 Operational
Galileo[12] 1989 2003
Cassini[12] 1999 2017
Mars Science Laboratory/Curiosity rover[13] 2011 Operational
Mars 2020 rover[13] In development  
Europa Clipper[13] In development  
Europa Lander[14] Proposed  
Astrophysics Division
Compton Gamma-Ray Observatory[15] 1991 2000
Hubble Space Telescope[15] 1990 Operational
Chandra X-ray Observatory[15][16] 1999 Operational
James Webb Space Telescope[17][18] In development  
Wide-Field Infrared Survey Telescope (WFIRST)[19] In development  
Competing projects for the next Great Observatory: [9]
  • Habitable Exoplanet Imaging Mission (HabEx)
  • Origins Space Telescope
  • Lynx X-ray Surveyor
  • LUVOIR has 2 concepts: ATLAST and HDST
Under study  
Heliophysics Division
Solar Dynamics Observatory [20] 2010 Operational
Van Allen Probes [20] 2012 Operational
Magnetospheric Multiscale Mission (MMS)[21] 2015 Operational
Parker Solar Probe[22] 2018 Operational
Earth Science Division
Terra [23][24] 1999 Operational
Aqua[23][24] 2002 Operational
ICESat [25] 2003 2010
Aura[24] 2004 Operational
Joint Polar Satellite System (JPSS) - a constellation[25] 2011 Operational
Plankton, Aerosol, Cloud, ocean Ecosystem (PACE)[26] In development  

Of the four Great Observatories, only the Spitzer Space Telescope is not a Flagship mission. Despite an initial budget of US$2 billion, Spitzer was downscoped to a medium-size US$720 million mission.[11]

3. Mission Targets

Planetary science Flagship missions will be crucial in allowing the exploration of high-priority targets. These critically important targets could help establish the limits of planetary habitability, not just for the Solar System, but for planetary systems in general. In particular, they potentially provide an opportunity to identify prebiotic organic molecules or even extant life beyond Earth, should it exist, in the Solar System. The targets of Flagship missions may include complex missions to the atmosphere and surface of Venus, the lower atmosphere and surface of Titan, the surface and subsurface of Europa, the stormy atmosphere of Jupiter, the dusty surface of Mars, the ring systems of Saturn, the deep atmospheres of the ice giants Neptune and Uranus, the surface of the moon Triton, the plumes of Enceladus, the surface and magnetosphere of Mercury, and the surface of a comet nucleus in the form of cryogenically preserved samples.[27]

The content is sourced from:


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  3. [1] Aviation Week (February 14, 2012)
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  6. Harwood, William (4 December 2012)."NASA announces plans for new $1.5 billion Mars rover" CNET. Retrieved 5 December 2012.$1.5-billion-mars-rover/
  7. Howell, Elizabeth (20 June 2015). "NASA's Europa Mission Approved for Next Development Stage" Retrieved 2015-06-21.
  8. NASA Considers Its Next Flagship Space Telescope. Scoles. SciAm March 2016
  9. Scoles, Sarah (30 March 2016). "NASA Considers Its Next Flagship Space Telescope". Scientific American. Retrieved 2017-10-15. 
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  12. Solar System Programs: Outer Planets Flagship. NASA
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  14. American Institute of Physics. 21 July 2017.
  15. Powering Science: NASA's Large Strategic Science Missions (2017). The National Academies Press. Page 25.
  16. Powering Science: NASA's Large Strategic Science Missions (2017). The National Academies Press. Page 1.
  17. Powering Science: NASA's Large Strategic Science Missions (2017). The National Academies Press. Page 27.
  18. Flagship U.S. space telescope facing further delays. Daniel Clery, Science Magazine. 1 March 2018.
  19. Astronomers Will Fight to Save WFIRST Space Telescope from Being Axed. Calla Cofield, Space. 15 February 2018.
  20. Powering Science: NASA's Large Strategic Science Missions (2017). The National Academies Press. Page 17.
  21. Powering Science: NASA's Large Strategic Science Missions (2017). The National Academies Press. Page 2.
  22. Powering Science: NASA's Large Strategic Science Missions (2017). The National Academies Press. Page 16.
  23. Terra: Earth Observing System Flagship. Space Today
  24. Earth Science: NASA's Mission to Our Home Planet. Edward S. Goldstein and Tabatha Thompson, NASA.
  25. NASA Missions: From Concept to Launch. (PDF.) Michael Amato, NASA. March 2013.
  26. Powering Science: NASA's Large Strategic Science Missions (2017). The National Academies Press. Page 14.
  27. Visions and Voyages for Planetary Science 2013 - 2022 (Published on 19 October 2011)
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