Editing Mariner 6 and 7

{{Short description|Twin NASA flyby missions to Mars (1969–1970)}}
{{Use mdy dates|date=May 2020}}
{{Infobox spaceflight
| name               = Mariner 6
| image              = Mariner 6-7.png
| image_caption      = Mariner 6 and 7
| mission_type       = [[Mars]] flyby
| operator           = [[NASA]] / [[Jet Propulsion Laboratory|JPL]]
| website            = 
| COSPAR_ID          = 1969-014A
| SATCAT             = 3759
| mission_duration   = {{time interval|25 Feb 1969|23 Dec 1970}}
| spacecraft         = Mariner-F
| spacecraft_type    = 
| manufacturer       = [[Jet Propulsion Laboratory]]
| dry_mass           = 
| launch_mass        = 381 kg<ref name=nasa1/>
| power              = 449 W
| launch_date        = {{start date text|February 25, 1969, 01:29:02|timezone=yes}}&nbsp;UTC<ref name=nssdc1/>
| launch_rocket      = [[Atlas-Centaur|Atlas SLV-3D Centaur-D1A]]
| launch_site        = [[Cape Canaveral Air Force Station|Cape Canaveral]] [[Cape Canaveral Air Force Station Space Launch Complex 36|LC-36B]]
| launch_contractor  = 
| disposal_type      = Decommissioned
| deactivated        = {{end date text|December 23, 1970}}
| interplanetary     = {{Infobox spaceflight/IP
  |type         = flyby
  |object       = [[Mars]]
  |distance     = {{convert|3431|km|mi|sp=us}}
  |arrival_date = July 31, 1969
 }}
| programme          = '''[[Mariner program]]'''
| previous_mission   = [[Mariner 5]]
| next_mission       = Mariner 7
}}
{{Infobox spaceflight
| name               = Mariner 7
| image              = 
| image_caption      = 
| mission_type       = [[Mars]] flyby
| operator           = [[NASA]] / [[Jet Propulsion Laboratory|JPL]]
| website            = 
| COSPAR_ID          = 1969-030A
| SATCAT             = 3837
| mission_duration   = {{time interval|27 Mar 1969|28 Dec 1970}}
| spacecraft         = Mariner-G
| spacecraft_type    = 
| manufacturer       = [[Jet Propulsion Laboratory]]
| dry_mass           = 
| launch_mass        = 381 kg<ref name=nasa2/>
| power              = 449 W
| launch_date        = {{start date text|March 27, 1969, 22:22:00|timezone=yes}}&nbsp;UTC<ref name=nssdc2/>
| launch_rocket      = [[Atlas-Centaur|Atlas SLV-3D Centaur-D1A]]
| launch_site        = [[Cape Canaveral Air Force Station|Cape Canaveral]] [[Cape Canaveral Air Force Station Space Launch Complex 36|LC-36A]]
| launch_contractor  = 
| disposal_type      = Decommissioned
| deactivated        = {{end date text|December 28, 1970}}
| interplanetary     = {{Infobox spaceflight/IP
  |type         = flyby
  |object       = [[Mars]]
  |distance     = {{convert|3430|km|mi|sp=us}}
  |arrival_date = August 5, 1969
 }}
| programme          = '''[[Mariner program]]'''
| previous_mission   = Mariner 6
| next_mission       = [[Mariner 8]]
}}

'''Mariner 6''' and '''Mariner 7''' ('''Mariner Mars 69A''' and '''Mariner Mars 69B''') were two uncrewed [[NASA]] [[robotic spacecraft]] that completed the first dual mission to [[Mars]] in 1969 as part of NASA's wider [[Mariner program]]. Mariner 6 was launched from Launch Complex 36B at [[Cape Canaveral Air Force Station]]<ref name=nssdc1/> and Mariner 7 from Launch Complex 36A.<ref name=nssdc2/> The two craft flew over the [[equator]] and south polar regions, analyzing the atmosphere and the surface with remote sensors, and recording and relaying hundreds of pictures. The mission's goals were to study the surface and atmosphere of Mars during close flybys, in order to establish the basis for future investigations, particularly those relevant to the search for extraterrestrial life, and to demonstrate and develop technologies required for future Mars missions. Mariner 6 also had the objective of providing experience and data which would be useful in programming the Mariner 7 encounter five days later.

==Launch==
[[File:Mariner 7 lift-off.jpg|thumb|Mariner 7 lift-off on March 27, 1969]]
Three Mariner probes were constructed for the mission, with two intended to fly and one as a spare in the event of a mission failure. The spacecraft were shipped to Cape Canaveral with their Atlas-Centaur boosters in December 1968 – January 1969 to begin pre-launch checkouts and testing. On February 14, Mariner 6 was undergoing a simulated countdown on LC-36A, electrical power running, but no propellant loaded in the booster. During the test run, an electrical relay in the Atlas malfunctioned and opened two valves in the pneumatic system which allowed helium pressure gas to escape from the booster's balloon skin. The Atlas began to crumple over, however two pad technicians quickly activated a manual override switch to close the valves and pump helium back in. Although Mariner 6 and its Centaur stage had been saved, the Atlas had sustained structural damage and could not be reused, so they were removed from the booster and placed atop Mariner 7's launch vehicle on the adjacent LC-36B, while a different Atlas was used for Mariner 7.

[[NASA]] awarded the quick-thinking technicians, Bill McClure and Charles (Jack) Beverlin, [[NASA Exceptional Bravery Medal|Exceptional Bravery Medal]]s for their courage in risking being crushed underneath the {{convert|124|ft|adj=on}} rocket. In 2014, an escarpment on Mars which NASA'S ''Opportunity'' rover had recently visited was named the McClure-Beverlin Ridge in honor of the pair, who had since died.{{r|nasa3|508pir|memorial}}

Mariner 6 lifted off from LC-36B at Cape Canaveral on February 25, 1969, using the Atlas-Centaur AC-20 rocket, while Mariner 7 lifted off from LC-36A on March 27, using the Atlas-Centaur AC-19 rocket. The boost phase for both spacecraft went according to plan and no serious anomalies occurred with either launch vehicle. A minor [[Liquid oxygen|LOX]] leak froze some telemetry probes in AC-20 which registered as a drop in [[sustainer engine]] fuel pressure; however, the engine performed normally through powered flight. In addition, {{Abbr|BECO|Booster Engine Cut-Off, the event during launch of a rocket with boosters where they stop firing}} occurred a few seconds early due to a faulty cutoff switch, resulting in longer than intended burn time of the sustainer engine, but this had no serious effect on vehicle performance or the flight path. AC-20 was launched at a 108-degree azimuth.<ref name=nasa4/>

The Centaur stage on both flights was set up to perform a retrorocket maneuver after capsule separation. This served two purposes, firstly to prevent venting propellant from the spent Centaur from contacting the probe, secondly to put the vehicle on a trajectory that would send it into solar orbit and not impact the Martian surface, potentially contaminating the planet with [[Earth]] microbes.

==Spaceflight==
[[File:Mariner Mars mission planners used this model to illustrate the orientation of the planet and the expected path of the Mariner 6 and 7 spacecraft 312-159bc.jpg|thumb|Mission planners used this model to illustrate the orientation of the planet and the expected path of the Mariner 6 and 7]]
On July 29, 1969, less than a week before closest approach, Jet Propulsion Laboratory (JPL) lost contact with Mariner 7. The center regained the signal via the backup low-gain antenna and regained use of the high gain antenna again shortly after Mariner 6's close encounter. Leaking gases from a battery (which later failed) were thought to have caused the anomaly.<ref name=nssdc2/> Based on the observations that Mariner 6 made, Mariner 7 was reprogrammed in flight to take further observations of areas of interest and actually returned more pictures than Mariner 6, despite the battery's failure.<ref name=Pyle2012/>

Closest approach for Mariner 6 occurred July 31, 1969, at 05:19:07 UT at a distance of {{Convert|3431|km|sp=us}}<ref name=nssdc1/> above the martian surface. Closest approach for Mariner 7 occurred August 5, 1969 at 05:00:49 UT<ref name=nssdc2/> at a distance of {{Convert|3430|km|sp=us}} above the Martian surface. This was less than half of the distance used by Mariner 4 on the previous US Mars flyby mission.<ref name=Pyle2012/>

Both spacecraft are now defunct and in [[heliocentric orbit]]s.<ref name=Pyle2012/>

===Science data and findings===
[[File:Mars full disk approach view from Mariner 7.jpg|thumb|Two full disc views of Mars from Mariner 7 as it approached, 1969]]
[[file:Mariner7_19.jpg|thumb|A close-up of the surface of Mars taken by Mariner 7]]
By chance, both spacecraft flew over cratered regions and missed both the [[Tharsis|giant northern volcanoes]] and the [[Valles Marineris|equatorial grand canyon]] discovered later. Their approach pictures did, however, photograph about 20 percent of the planet's surface,<ref name=Pyle2012/> showing the dark features long seen from Earth – in the past, these features had been mistaken for [[Martian canals|canals]] by some ground-based astronomers. When Mariner 7 flew over the Martian south pole on August 4, 1969, it sent back pictures of ice-filled craters and outlines of the [[Martian polar ice caps|south polar cap]].<ref name=tht-19690806/> Despite the communication defect suffered by Mariner 7 earlier, these pictures were of better quality than what had been sent by its twin, Mariner 6, a few days earlier when it flew past the Martian equator.<ref name=nyt-19690806/> In total, 201 photos were taken and transmitted back to Earth, adding more detail than the earlier mission, Mariner 4.<ref name=Pyle2012/> Both crafts also studied the [[atmosphere of Mars]].

Coming a week after [[Apollo 11]], Mariner 6 and 7's flyby of Mars received less than the normal amount of media coverage for a mission of this significance.

The [[ultraviolet]] [[spectrometer]] onboard Mariners 6 and 7 was constructed by the University of Colorado's [[Laboratory for Atmospheric and Space Physics|Laboratory for Atmospheric and Space Physics (LASP)]].<ref name=Pearce1971/>

The engineering model of Mariners 6 and 7 still exists, and is owned by the Jet Propulsion Laboratory (JPL). It is on loan to LASP, and is on display in the lab's lobby.<ref>{{Cite web |last=wire1631 |date=2023-10-11 |title=Looking back at 75: Honoring LASP’s contributions to historic missions |url=https://lasp.colorado.edu/2023/10/11/looking-back-honoring-lasps-contributions-to-historic-missions/ |access-date=2025-03-01 |website=Laboratory for Atmospheric and Space Physics |language=en-US}}</ref><ref>{{Cite web |last=CorrugatedSymphony |date=2016 |title=Mariner 6 & 7 working engineering model |url=https://imgur.com/gallery/mariner-6-7-working-engineering-model-J8Mco |access-date=2025-03-01 |website=Imgur |language=en}}</ref>

Mariner 6 and 7 infrared radiometer observations helped to trigger a scientific revolution in Mars knowledge.{{r|:0|Chase1969}} The Mariner 6 and 7 infrared radiometer results showed that the [[atmosphere of Mars]] is composed mostly of carbon dioxide (CO<sub>2</sub>), and they were also able to detect trace amounts of [[Water on Mars|water on the surface of Mars]].<ref name=:0/>

== Spacecraft and subsystems ==
[[file:Mariner_6_or_7_diagrams.jpg|thumb|Spacecraft and subsystems]]
The Mariner 6 and 7 spacecraft were identical, consisting of an octagonal [[magnesium]] frame base, {{Convert|138.4|cm|abbr=on}} diagonally and {{Convert|45.7|cm|abbr=on}} deep. A conical superstructure mounted on top of the frame held the high-gain {{convert|1|m}} diameter parabolic antenna and four [[Photovoltaic array|solar panels]], each measuring {{Convert|215|cm|abbr=on}} x {{Convert|90|cm|abbr=on}}, were affixed to the top corners of the frame. The tip-to-tip span of the deployed solar panels was {{Convert|5.79|m|abbr=on}}. A low-gain omnidirectional antenna was mounted on a {{Convert|2.23|m|abbr=on|adj=on}} high mast next to the high-gain antenna. Underneath the octagonal frame was a two-axis scan platform which held scientific instruments. Overall science instrument mass was {{Convert|57.6|kg|lb|abbr=on}}. The total height of the spacecraft was {{Convert|3.35|m|abbr=on}}.

The spacecraft was attitude stabilized in three axes, referenced to the Sun and the star [[Canopus]]. It utilized 3 gyros, 2 sets of 6 [[nitrogen]] jets, which were mounted on the ends of the solar panels, a Canopus tracker, and two primary and four secondary [[Sun sensor]]s. Propulsion was provided by a 223-[[newton (unit)|newton]] rocket motor, mounted within the frame, which used the mono-propellant [[hydrazine]]. The nozzle, with 4-jet vane vector control, protruded from one wall of the octagonal structure. Power was supplied by 17,472 [[photovoltaic cell]]s, covering an area of {{Convert|7.7|m2|sp=us}} on the four solar panels. These could provide 800 watts of power near Earth, and 449 watts while near Mars. The maximum power requirement was 380 watts, once Mars was reached. A 1200 watt-hour, rechargeable, [[silver-zinc battery]] was used to provide backup power. Thermal control was achieved through the use of adjustable louvers on the sides of the main compartment.

Three telemetry channels were available for telecommunications. Channel A carried engineering data at {{frac|8|1|3}} or {{frac|33|1|3}} bit/s, channel B carried scientific data at {{frac|66|2|3}} or 270 bit/s and channel C carried science data at 16,200 bit/s. Communications were accomplished through the high- and low-gain antennas, via dual S-band [[traveling wave tube]] amplifiers, operating at 10 or 20 watts, for transmission. The design also included a single receiver. An analog [[tape recorder]], with a capacity of 195 million bits, could store television images for subsequent transmission. Other science data was stored on a digital recorder. The command system, consisting of a central computer and sequencer (CC&S), was designed to actuate specific events at precise times. The CC&S was programmed with both a standard mission and a conservative backup mission before launch, but could be commanded and reprogrammed in flight. It could perform 53 direct commands, 5 control commands, and 4 quantitative commands.

=== Scientific Instruments ===
Both spacecraft carried the same set of instruments:<ref>{{Cite web |date=2017-12-20 |title=Mariner 6 - NASA Science |url=https://science.nasa.gov/mission/mariner-6/ |access-date=2025-03-01 |language=en-US}}</ref><ref>{{Cite web |date=2018-01-25 |title=Mariner 7 - NASA Science |url=https://science.nasa.gov/mission/mariner-7/ |access-date=2025-03-01 |language=en-US}}</ref>

* Imaging System (Two TV cameras)
* Infrared Spectrometer
* Ultraviolet Spectrometer
* Infrared Radiometer
* Celestial Mechanics Experiment
* S-Band Occultation Experiment
* Conical Radiometer

== See also ==
{{Portal|Spaceflight}}
* [[List of missions to Mars]]
* [[Space exploration]]
* [[Uncrewed space mission]]s
* [[Heat Flow and Physical Properties Package]] (included an infrared radiometer for the Martian surface)

{{Clear}}

== References ==
{{Reflist|refs=

<ref name=":0">{{Cite web
| url= https://www.acs.org/content/acs/en/education/whatischemistry/landmarks/mars-infrared-spectrometer.html
| title= Infrared Spectrometer and the Exploration of Mars
| website= American Chemical Society
| access-date= 10 August 2019 }}
</ref>

<ref name="508pir">{{cite web
| url= https://www.508pir.org/obits/obit_text/m/mcclure_bb.htm
| title= Billy McClure obituary
| website= 508th Parachute Infantry Regiment (veterans' association)
| date= 2009
| archive-url= https://web.archive.org/web/20151124055808/https://www.508pir.org/obits/obit_text/m/mcclure_bb.htm
| archive-date= 24 November 2015
| url-status= live }}
</ref>

<ref name="Chase1969">{{Cite journal
| author1= S. C. Chase
| date= 1 March 1969
| title= Infrared radiometer for the 1969 mariner mission to Mars
| journal= Applied Optics
| volume= 8
| issue= 3
| pages= 639
| doi= 10.1364/AO.8.000639
| issn= 1559-128X
| pmid= 20072273
| bibcode= 1969ApOpt...8..639C }}
</ref>

<ref name="memorial">{{cite web
| url= https://www.dignitymemorial.com/obituaries/merritt-island-fl/charles-beverlin-5454230
| title= Charles Beverlin obituary
| website= Dignity Memorial
| date= 2013 }}
</ref>

<ref name="nasa1">{{cite web
| url= https://science.nasa.gov/mission/mariner-6/
| title= Mariner 6 - NASA Science
| website= science.nasa.gov
| publisher= [[NASA]]
| access-date= 30 November 2022 }}
</ref>

<ref name="nasa2">{{cite web
| url= https://science.nasa.gov/mission/mariner-7/
| title= Mariner 7 - NASA Science
| website= science.nasa.gov
| publisher= [[NASA]]
| access-date= 30 November 2022 }}
</ref>

<ref name="nasa3">{{cite web
| url= https://science.nasa.gov/resource/opportunitys-southward-view-of-mcclure-beverlin-escarpment-on-mars?site=insight
| title= Opportunity's Southward View of 'McClure-Beverlin Escarpment'
| work= [[NASA]] / [[Jet Propulsion Laboratory|JPL]]
| date= 2014 }}
</ref>

<ref name="nasa4">{{cite book 
| url= https://ntrs.nasa.gov/search.jsp?R=19700009038
| title= Mariner-Mars 1969: A Preliminary Report
| publisher= [[NASA]]
| id= SP-225
| date= 1969
| page= 21 }}
</ref>

<ref name="nssdc1">{{cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1969-014A 
| title= Mariner 6
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| access-date= 28 December 2011 }}
</ref>

<ref name="nssdc2">{{cite web
| url= https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1969-030A 
| title= Mariner 7
| website= nssdc.gsfc.nasa.gov
| publisher= [[NASA]]
| access-date= 28 December 2011 }}
</ref>

<ref name="nyt-19690806">{{Cite news
| url= https://www.nytimes.com/1969/08/06/archives/mariner-7-sends-sharpest-mars-pictures-mariner-7-sends-sharpest.html
| title= Mariner 7 Sends Sharpest Mars Pictures; Mariner 7 Sends Sharpest Mars Photos So Far
| author1= Walter Sullivan
| date= 6 August 1969
| work= [[The New York Times]]
| access-date= 10 August 2019
| language= en-US
| issn= 0362-4331
| url-access= limited }}
</ref>

<ref name="Pearce1971">{{Cite journal
| author1= J. B. Pearce
| author2= K. A. Gause
| author3= E. F. Mackey
| author4= K. K. Kelly
| author5= W. G. Fastie
| author6= C. A. Barth
| display-authors= 3
| date= 1 April 1971
| title= Mariner 6 and 7 Ultraviolet Spectrometers
| journal= Applied Optics
| volume= 10
| issue= 4
| pages= 805–812
| doi= 10.1364/ao.10.000805
| pmid=20094543
| bibcode= 1971ApOpt..10..805P
| issn= 0003-6935 }}
</ref>

<ref name="Pyle2012">{{cite book
| author1= Rod Pyle
| title= Destination Mars: New Explorations of the Red Planet
| date= 2012
| publisher= [[Prometheus Books]]
| isbn= 978-1-61614-589-7
| pages= 61–66 }}
</ref>

<ref name="tht-19690806">{{Cite news
| url= https://www.thehindu.com/archives/from-the-archives-august-6-1969-ice-filled-craters-on-mars/article28825796.ece
| title= From the Archives (August 6, 1969): Ice-filled craters on Mars
| date= 6 August 2019
| work= The Hindu
| access-date= 10 August 2019
| language= en-IN
| issn= 0971-751X }}
</ref>

}}

== External links ==
* [https://web.archive.org/web/20170507213954/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19690007929.pdf Mariner Mars 1969 Launches - Press Kit]
* [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710017236_1971017236.pdf Tracking and data system support for the Mariner Mars 1969 mission. Volume 1 - Planning phase through midcourse maneuver]
* [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710026698_1971026698.pdf Tracking and data system support for the Mariner Mars 1969 mission. Volume 2: Midcourse maneuver through end of nominal mission]
* [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710026683_1971026683.pdf Tracking and data system support for the Mariner Mars 1969 mission. Volume 3: Extended operations mission]
* [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710008533_1971008533.pdf The Mariner 6 and 7 flight paths and their determination from tracking data]
* [https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710005848_1971005848.pdf Two over Mars - Mariner 6 and Mariner 7, February - August 1969]
* [https://web.archive.org/web/20070905051151/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Mariner_06 Mariner 6 Mission Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [https://web.archive.org/web/20070905051458/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Mariner_07 Mariner 7 Mission Profile] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]
* [https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1969-014A&ds Mariner 6 and 7 Data Set Information] (highly technical)
* [http://members.tripod.com/petermasek/mariner67.html Mariner 6 and 7 Data Viewer Page] (includes many images)
* [https://web.archive.org/web/20071005010835/http://www.strykfoto.org/mariner69/mariner7.htm Page with reprocessed Mariner 7 images]
* [http://petermasek.tripod.com/mariner67.html Mariner 6 and 7 images]

{{Mariner program|before=[[Mariner 5]]|after=[[Mariner 8]]}}
{{Orbital launches in 1969}}
{{Mars spacecraft}}
{{Satellite and spacecraft instruments}}

[[Category:Mariner program]]
[[Category:Missions to Mars]]
[[Category:Spacecraft launched in 1969]]
[[Category:Derelict satellites in heliocentric orbit]]
[[Category:Derelict space probes]]
[[Category:Spacecraft launched by Atlas-Centaur rockets]]

[[de:Mariner#Mariner 6 und 7]]