View source for Mariner Mark II

{{short description|Planned family of uncrewed NASA spacecraft}}
[[File:CRAF.jpg|right|thumb|Conceptual artwork of the CRAF spacecraft based on Mariner Mark II]]
[[File:Cassini-Huygens planning status in 1988.jpg|right|thumb|SOTP a Mariner Mark II spacecraft concept, drawing from 1988. Later redesigned to the [[Cassini–Huygens]] spacecraft]]

'''Mariner Mark II''' was [[NASA]]'s planned family of uncrewed [[spacecraft]] for the exploration of the [[outer Solar System]] that were to be developed and operated by [[JPL]] between 1980 and 2010.

==Summary==
After the [[Flagship Program|"flagship"]] multibillion-dollar missions of the 1970s, in the 1980s NASA was looking for a new, more affordable direction for the 1990s and beyond. Two projects were conceived by NASA's Solar System Exploration Committee in 1983, the [[Planetary Observer program]], and Mariner Mark II.<ref>{{Cite news |url=https://www.deseret.com/1992/11/6/19014815/nasa-picks-basic-spaceship-over-awesome-alternative/ |agency=Associated Press |title=NASA Picks Basic Spaceship Over Awesome Alternative |publisher=The Deseret News |date=November 6, 1992}}</ref>

The Observer program, starting with the [[Mars Observer]], was envisioned as a series of low-cost missions to the [[inner Solar System]], based on commercial Earth satellites, while the Mariner Mark II was to be a series of large spacecraft for the exploration of the [[outer Solar System]].<ref>{{cite journal|title=Mariner Mark II and the exploration of the solar system|last=Neugebauer |first=M. |url=https://ntrs.nasa.gov/citations/19830039082 |date=February 4, 1983|journal= Science |volume=219 |issue=4584 |pages=443–449 |doi=10.1126/science.219.4584.443 |pmid=17742805 |bibcode=1983Sci...219..443N |access-date=July 5, 2025}}</ref>

Mariner Mark II spacecraft were to use common design, hardware and software solutions, much of it derived from previous missions such as [[Voyager program|Voyager]] and [[Galileo (spacecraft)|Galileo]] as well as select new technologies, such as advanced gyroscopes, all with the aim of cutting costs. It was hoped that this new approach would reduce the mission costs to about $400 million each, about half the price of Galileo.<ref>{{cite journal|title=The Mariner Mark II Program|first=Ronald|last=Draper|url=https://doi.org/10.2514/6.1988-67 |journal=26th Aerospace Sciences Meeting |date=January 1988|location=Reno Nevada |doi=10.2514/6.1988-67 |access-date=July 5, 2025|url-access=subscription}}</ref>

The first two missions of the project were to be a mission to Saturn and its moon Titan, the [[Saturn Orbiter/Titan Probe]], or SOTP (later ''[[Cassini–Huygens|Cassini]]'') and the [[Comet Rendezvous Asteroid Flyby]] (CRAF), both of which were approved by Congress in 1990.<ref>{{cite report|url=http://www7.nationalacademies.org/ssb/crafcassini88.html |title=Assessment of CRAF and Cassini missions |archive-url=https://web.archive.org/web/20090318062429/http://www7.nationalacademies.org/ssb/crafcassini88.html |archive-date=2009-03-18 |first=Dr. Robert O. |last=Pepin |publisher=[[United States National Academy of Sciences|National Academy of Sciences]] |date=1988 }}</ref>

Other planned Mariner Mark II-based spacecraft were an [[ESA]] led follow-on to CRAF, the [[Comet Nucleus Sample Return]] or CNSR (later ''[[Rosetta space probe|Rosetta]]'', without the sample return); ''[[Pluto Fast Flyby]]'', a flyby of Pluto (later ''[[Pluto Kuiper Express]]'', eventually realized as ''[[New Horizons]]''); and a ''[[Neptune Orbiter]]'' with an atmospheric probe.<ref>{{cite report|url=http://www7.nationalacademies.org/ssb/neptch4.html |title=Exploring the Trans-Neptunian Solar System |archive-url=https://web.archive.org/web/20090318064524/http://www7.nationalacademies.org/ssb/neptch4.html |archive-date=2009-03-18 |publisher=National Academy of Sciences|access-date=July 5, 2025}}</ref>

However, congressionally imposed reductions to FY 1992–93 funding requirements forced NASA to terminate the CRAF mission<ref>{{cite journal|title=Bush cancels CRAF, closes out Magellan |first=Stephen |last=Cole |date=11 February 1992 |volume=73 |number=6|page=65-70|url=https://doi.org/10.1029/91EO00058 |journal=Eos, Transactions, American Geophysical Union |doi=10.1029/91EO00058 |bibcode=1992EOSTr..73Q..66C |access-date=July 5, 2025|url-access=subscription }}</ref> and to delay the ''Cassini'' launch from April 1996 to October 1997.<ref>{{cite report|title=Cassini Launch Press Kit |date=October 1997 |url=https://www.jpl.nasa.gov/news/press_kits/cassini.pdf |publisher=NASA |access-date=July 5, 2025}}</ref> In order to save it, NASA was forced to significantly redesign ''Cassini'' to reduce the total program cost, mass and power requirements.<ref>{{cite report|url=http://www7.nationalacademies.org/ssb/crafcassini392.html |title=On the CRAF/Cassini Mission |archive-url=https://web.archive.org/web/20090318060626/http://www7.nationalacademies.org/ssb/crafcassini392.html |archive-date=2009-03-18 |first=Dr. Louis J. |last=Lanzerotti |publisher=[[United States National Academy of Sciences|National Academy of Sciences]] |date=1992}}</ref>

NASA has had to replace the ''Mariner Mark II'' program with the lower-cost [[Discovery Program]].<ref>{{cite journal |title=Transforming solar system exploration: The origins of the Discovery Program, 1989-1993 |first=Michael J. |last=Neufeld |url=https://doi.org/10.1016/j.spacepol.2013.10.002 |journal=Space Policy |volume=30 |number=1 |date=February 2014 |pages=5–12|doi=10.1016/j.spacepol.2013.10.002 |bibcode=2014SpPol..30....5N |access-date=July 5, 2025|url-access=subscription }}</ref>

==See also==
* [[Mariner program]]
* [[Voyager program]]
* [[Pioneer program]]

==References==
{{Reflist|30em}}

{{NASA planetary exploration programs}}
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{{Neptune}}
{{Pluto}}

{{DEFAULTSORT:Mariner Mark Ii}}
[[Category:Proposed NASA space probes]]
[[Category:NASA programs]]
[[Category:Cancelled spacecraft]]
[[Category:Missions to Neptune]]
[[Category:Missions to Pluto]]