Editing Viking program (section)

{{short description|Pair of NASA landers and orbiters sent to Mars in 1976}}
{{about|the NASA Mars probes|the Swedish spacecraft|Viking (satellite)}}
{{redirect|Viking Mars|the cruise ship|Viking Cruises}}
{{Use American English|date=January 2014}}
{{Use mdy dates|date=September 2012}}
{{Infobox spacecraft class
| image        = Viking Orbiter releasing the lander.jpg
| caption      = Artist impression of a Viking orbiter releasing a lander descent capsule

| name         = Viking
| manufacturer = [[Jet Propulsion Laboratory]] /  [[Martin Marietta]] 
| country      = [[United States]]
| applications = Mars orbiter/lander
| orbits       = [[Areocentric orbit|Areocentric]]
| operator     = [[NASA]] / [[JPL]]
| lifetime     = Orbiters: 4&nbsp;years at Mars<br/>Landers: 4–6&nbsp;years at Mars

| status       = Retired
| built        = 2
| launched     = 2
| first        = ''[[Viking 1]]''<br/>August 20, 1975<ref name="NASA-20061218" /><ref name="NASA-Viking1">{{Cite web |last=Nelson |first=Jon |title=Viking 1 |url=https://www.jpl.nasa.gov/missions/viking-1 |url-status=live |archive-url=https://web.archive.org/web/20231024145216/https://www.jpl.nasa.gov/missions/viking-1 |archive-date=October 24, 2023 |access-date=February 2, 2014 |publisher=[[JPL]] }}</ref> 
| last         = ''[[Viking 2]]''<br/>September 9, 1975<ref name="NASA-20061218" /><ref name="NASA-Viking2">{{Cite web |last=Nelson |first=Jon |title=Viking 2 |url=https://www.jpl.nasa.gov/missions/viking-2 |url-status=live |archive-url=https://web.archive.org/web/20231008204431/https://www.jpl.nasa.gov/missions/viking-2 |archive-date=October 8, 2023 |access-date=February 2, 2014 |publisher=[[JPL]] }}</ref>
| retired      = ''[[Viking 1]]'' orbiter<br/>August 17, 1980<ref name="NASA-20061218" /><br/>''[[Viking 1]]'' lander<br/>July 20, 1976<ref name="NASA-20061218" /> (landing) to November 13, 1982<ref name="NASA-20061218" /><br/><br />''[[Viking 2]]'' orbiter<br/>July 25, 1978<ref name="NASA-20061218" /><br/>''[[Viking 2]]'' lander<br/>September 3, 1976<ref name="NASA-20061218" /> (landing) to April 11, 1980<ref name="NASA-20061218" />

|autoconvert = off
| mass         = {{convert|3527|kg|lb}}
| power        = Orbiters: 620&nbsp;watts ([[solar array]])<br/>Lander: 70&nbsp;watts (two [[radioisotope thermoelectric generator|RTG]] units)
| batteries    = 
| equipment    =

| dimensions   = 
| x_axis       = 
| y_axis       = 
| z_axis       = 
}}

The '''''Viking'' program''' consisted of a pair of identical American [[space probe]]s, ''[[Viking 1]]'' and ''[[Viking 2]]'' both launched in 1975, and landed on [[Mars]] in 1976.<ref name="NASA-20061218">{{Cite web |last=Williams |first=David R. Dr. |date=December 18, 2006 |title=Viking Mission to Mars |url=https://nssdc.gsfc.nasa.gov/planetary/viking.html |url-status=live |archive-url=https://web.archive.org/web/20231206095644/https://nssdc.gsfc.nasa.gov/planetary/viking.html |archive-date=December 6, 2023 |access-date=February 2, 2014 |publisher=[[NASA]] }}</ref> The mission effort began in 1968 and was managed by the NASA Langley Research Center.<ref name= "SoffenViking1978">Soffen, G. A. (July–August 1978). "Mars and the Remarkable Viking Results." ''Journal of Spacecraft and Rockets''. '''15''' (4): 193-200.</ref> Each [[spacecraft]] was composed of two main parts: an [[orbiter]] spacecraft which photographed the surface of Mars from [[orbit]], and a [[Lander (spacecraft)|lander]] which studied the planet from the surface. The orbiters also served as communication relays for the landers once they touched down.

The Viking program grew from [[NASA]]'s earlier, even more ambitious, [[Voyager program (Mars)|Voyager Mars]] program, which was not related to the successful [[Voyager program|Voyager deep space probes]] of the late 1970s. ''Viking 1'' was launched on August 20, 1975, and the second craft, ''Viking 2'', was launched on September 9, 1975, both riding atop [[Titan IIIE]] rockets with [[Centaur (rocket stage)|Centaur]] upper stages. ''Viking 1'' entered Mars orbit on June 19, 1976, with ''Viking 2'' following on August 7.

After orbiting Mars for more than a month and returning images used for landing site selection, the orbiters and landers detached; the landers then entered the Martian [[atmosphere]] and [[Soft landing (rocketry)|soft-landed]] at the sites that had been chosen. The ''Viking 1'' lander touched down on the surface of Mars on July 20, 1976, more than two weeks before ''Viking 2''{{'}}s arrival in orbit. ''Viking 2'' then successfully soft-landed on September 3. The orbiters continued imaging and performing other scientific operations from orbit while the landers deployed [[Measuring instrument|instrument]]s on the surface. The program terminated in 1982.

The project cost was roughly US$1&nbsp;billion at the time of launch,<ref name="nssdc-viking1orbiter" /><ref name="space.com">{{Cite news |last=Howell |first=Elizabeth |date=October 26, 2012  |title=Viking 1: First U.S. Lander on Mars |url=https://www.space.com/18234-viking-1.html |url-status=live |access-date=December 13, 2016 |archive-url=https://web.archive.org/web/20230906024226/https://www.space.com/18234-viking-1.html |archive-date=September 6, 2023 |newspaper=[[Space.com]] }}</ref> equivalent to about ${{Inflation|US-GDP|1|1970|r=0}}&nbsp;billion in {{Inflation-year|US-GDP}} dollars.{{Inflation-fn|US-GDP}} The mission was considered successful and formed most of the body of knowledge about Mars through the late 1990s and early 2000s.<ref name="cps-viking">{{Cite web |title=The Viking Program |url=https://planetary-science.org/mars-research/mars-landings/the-viking-program/ |url-status=live |archive-url=https://web.archive.org/web/20231120170823/http://planetary-science.org/mars-research/mars-landings/the-viking-program/ |archive-date=November 20, 2023 |access-date=April 13, 2018 |publisher=The Center for Planetary Science }}</ref><ref name="csc-viking-lander">{{Cite web |date=July 3, 2014 |title=Viking Lander |url=https://californiasciencecenter.org/exhibits/air-space/mission-planets/viking-lander |url-status=live |archive-url=https://web.archive.org/web/20230527121521/https://californiasciencecenter.org/exhibits/air-space/mission-planets/viking-lander |archive-date=May 27, 2023 |access-date=April 13, 2018 |publisher=[[California Science Center]] }}</ref>