View source for Ranger 8

{{Short description|NASA spacecraft to explore the Moon, 1965}}
{{Use mdy dates|date=February 2017}}
{{Infobox spaceflight
| name                  = Ranger 8
| image                 = The Ranger Spacecraft GPN-2000-001979.jpg
| image_caption         = Ranger 8

| mission_type          = [[Moon|Lunar]] impactor
| operator              = [[NASA]]
| website               = 
| COSPAR_ID             = 1965-010A 
| SATCAT                = 1086
| mission_duration      = 65 hours
| spacecraft_type       = 
| manufacturer          = [[Jet Propulsion Laboratory]]
| dimensions            = {{convert|1.52|x|2.51|m|ft|abbr=on}}
| launch_mass           = 366.87 kg<ref name="Ranger 8">{{cite web|url=https://solarsystem.nasa.gov/missions/ranger-8/in-depth/ |title=Ranger 8 |date=December 21, 2017 |publisher=NASA's Solar System Exploration website |access-date=December 1, 2022}}</ref>
| power                 = 200 W

| launch_date           = {{start-date|February 17, 1965, 17:05:00|timezone=yes}}&nbsp;UTC<ref name="Ranger 8"></ref>
| launch_rocket         = [[Atlas-Agena|Atlas LV-3 Agena-B]] 196D/AA13
| launch_site           = [[Cape Canaveral Air Force Station|Cape Canaveral]] [[Cape Canaveral Air Force Station Launch Complex 12|LC-12]]
| launch_contractor     =

| orbit_epoch           = 
| orbit_reference       = <!--transfer orbit-->
| orbit_periapsis       = 
| orbit_apoapsis        = 
| orbit_inclination     = 
| apsis                 = 
|interplanetary         = 
 {{Infobox spaceflight/IP
   |type                = impactor
   |object              = [[Moon|Lunar]]
   |arrival_date        = {{end-date|February 20, 1965, 09:57:36.756|timezone=yes}}&nbsp;UTC
   |location            = {{Lunar coords and quad cat|02.6377|N|24.7881|E}}<br/>([[Mare Tranquillitatis]])
}}
| instruments_list      = 
{{Infobox spaceflight/Instruments
  |name1  = [[Television camera|Vidicon Television Cameras]]
}}

| programme             = ''[[Ranger program|Ranger]]''
| previous_mission      = [[Ranger 7]]
| next_mission          = [[Ranger 9]]
}}
'''Ranger 8''' was a lunar probe in the [[Ranger program]], a [[robotic spacecraft]] series launched by [[NASA]] in the early-to-mid-1960s to obtain the first close-up images of the [[Moon]]'s surface. These pictures helped select landing sites for Apollo missions and were used for scientific study.<ref name="Ranger Facts">
{{cite web
 |last        = Green
 |first       = Nick
 |title       = Ranger 8 Information
 |url         = http://space.about.com/od/rangermissions/p/ranger8info.htm
 |publisher   = About.com
 |access-date  = July 31, 2013
 |archive-url  = https://web.archive.org/web/20130511095307/http://space.about.com/od/rangermissions/p/ranger8info.htm
 |archive-date = May 11, 2013
 |location    = New York
 |url-status     = live
 |year        = 2013
 |df          = mdy-all
}}
</ref>  During its 1965 mission, Ranger 8 transmitted 7,137 lunar surface photographs before it crashed into the Moon as planned. This was the second successful mission in the Ranger series, following [[Ranger 7]]. Ranger 8's design and purpose were very similar to those of Ranger 7.  It had six television [[Video camera tube#Vidicon|vidicon]] cameras: two full-scan and four partial-scan.  Its sole purpose was to document the Moon's surface.<ref name="NSDC Mission Profile">
{{NSSDC|id=1965-010A|access-date=July 31, 2013}}
</ref>

==Spacecraft design==
=== General ===
[[File:Ranger 6789.svg|thumb|left|300px|Diagram of Ranger 8.]]
[[Ranger program|Ranger spacecraft]] were originally designed, beginning in 1959, in three distinct phases called "blocks". Rangers [[Ranger 6|6]], [[Ranger 7|7]], 8, and [[Ranger 9|9]] were the Block 3 versions. The spacecraft consisted of a [[hexagon]]al [[aluminium|aluminum]] frame base 1.5 m across on which was mounted the propulsion and power units, topped by a truncated conical tower that held the television cameras. Two solar panel wings, each 739&nbsp;mm wide by 1537&nbsp;mm long, extended from opposite edges of the base with a full span of 4.6 m, and a pointable high-gain dish antenna was hinge mounted at one of the corners of the base away from the solar panels. A cylindrical quasi-[[omnidirectional antenna]] was seated on top of the conical tower. The overall height of the spacecraft was 3.6 m.<ref name="NSDC Mission Profile" />

Propulsion for the mid-course trajectory correction was provided by a 224 N thrust [[monopropellant]] [[hydrazine]] engine with four jet-vane vector control. Orientation and attitude control about three [[Cartesian coordinate system|axes]] was enabled by twelve nitrogen gas jets coupled to a system of three gyroscopes, four primary Sun sensors, two secondary Sun sensors, and an Earth sensor. Power was supplied by 9,792 silicon [[solar cell]]s contained in the two solar panels, giving a total array area of 2.3 square meters and producing 200 W. Two 1200-watt-hour <abbr title="silver-zinc oxide>AgZnO</abbr> batteries rated at 26.5 V with a capacity for 9 hours of operation provided power to each of the separate communication/TV camera chains. Two 1000-watt-hour AgZnO batteries stored power for spacecraft operations.<ref name="NSDC Mission Profile" />

=== Cameras ===
The spacecraft carried six television [[Video camera tube|vidicon]] cameras&nbsp;—two wide-angle (channel F, cameras A and B) and four narrow-angle (channel P)&nbsp;—to accomplish these objectives.<ref name=Capelotti>
{{cite book
 | pages      = 47–48
 | url        = https://books.google.com/books?id=98qFL5AYIjQC&pg=PA48
 | title      = The Human Archaeology of Space: Lunar, Planetary and Interstellar Relics of Exploration
 | isbn       = 978-0-7864-5994-0 
 | last       = Capelotti
 | first      = Peter Joseph
 | year       = 2010
| publisher=McFarland }}
</ref>  The cameras were arranged in two separate chains, or channels; each was self-contained with separate power supplies, timers, and [[transmitter]]s, to afford the greatest reliability and probability of obtaining high-quality [[television]] pictures. No other experiments were carried on the spacecraft.<ref name="NSDC Mission Profile" />

=== Communications ===
Communications were through the quasiomnidirectional low-gain antenna and the parabolic high-gain antenna. Transmitters aboard the spacecraft included a 60-watt television channel F at 959.52&nbsp;[[Hertz#SI multiples|MHz]], a 60-watt television channel P at 960.05&nbsp;MHz, and a 3-watt transponder channel 8 at 960.58&nbsp;MHz. The telecommunications equipment converted the composite video signal from the camera transmitters into a radio-frequency signal for subsequent transmission through the spacecraft's high-gain antenna. Sufficient video bandwidth was provided to allow for rapid framing sequences of both narrow- and wide-angle television pictures.<ref name="NSDC Mission Profile" />

==Mission profile==
[[File:Ranger8 launch.jpg|thumb|Launch of Ranger 8 by an [[Atlas-Agena]] rocket (Atlas 196D)|200x200px]]
The [[Atlas (rocket family)|Atlas 196D]] and [[RM-81 Agena|Agena]] B 6006 boosters performed nominally, injecting the Agena and Ranger 8 into an [[Earth]] parking [[orbit]] at 185&nbsp;km [[altitude]] after launch. Fourteen minutes later a 90-second burn of the Agena put the spacecraft into lunar transfer [[trajectory]], and several minutes later the Ranger and Agena separated. The Ranger [[solar panel]]s were deployed, [[Spacecraft attitude control|attitude control]] activated, and spacecraft transmissions switched from the omniantenna to the high-gain antenna by 21:30 UT. On February 18, at a distance of 160,000&nbsp;km from Earth, the planned mid-course maneuver took place, involving reorientation and a 59-second rocket burn. During the 27-minute maneuver, spacecraft transmitter power dropped severely, so that lock was lost on all telemetry channels. This continued intermittently until the rocket burn ended, at which time power returned to normal. The telemetry dropout had no serious effects on the mission. A planned terminal sequence to point the cameras more in the direction of flight just before reaching the [[Moon]] was cancelled to allow the cameras to cover a greater area of the Moon's surface.<ref name="NSDC Mission Profile" /> 

Ranger 8 reached the Moon on February 20, 1965.<ref name=Darling>
{{cite book
 | last      = Darling
 | first     = David
 | title     = The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity| page      = [https://archive.org/details/completebookofsp00davi/page/339 339]
 | url       = https://archive.org/details/completebookofsp00davi
 | url-access = registration
 | year      = 2003
 | publisher = John Wiley & Sons
 | location  = Hoboken, New Jersey
 | isbn      = 978-0-471-05649-2
}}
</ref> The first image was taken at 9:34:32 UT at an altitude of 2510&nbsp;km. Transmission of 7,137 [[photograph]]s<ref name=Darling/> of good quality occurred over the final 23 minutes of flight. The final image taken before impact has a resolution of 1.5 meters. <gallery mode="packed" caption="Ranger 8 images">
File:Ranger-moon-image.jpg|Image of the Moon from 302 km, two and a half minutes before impact, showing the craters [[Ritter (crater)|Ritter]] and [[Sabine (crater)|Sabine]].
File:Ranger8-moon.jpg|Image of the Moon from 11 km, 5 seconds before impact, showing  features as small as 4 meters.
</gallery>The spacecraft encountered the lunar surface in a direct [[hyperbolic trajectory]], with incoming [[asymptotic]] direction at an angle of −13.6 degrees from the [[lunar equator]]. The orbit plane was inclined 16.5 degrees to the lunar equator. After 64.9 hours of flight, impact occurred at 09:57:36.756 UT on February 20, 1965, in [[Mare Tranquillitatis]] at approximately 2.67° N, 24.65° E. (The impact site is listed as about 2.72° N, 24.61° E in the initial report "Ranger 8 Photographs of the Moon".) Impact velocity was slightly less than 2.68&nbsp;km/s, approximately 6,000&nbsp;mph. The spacecraft performance was excellent.<ref name="NSDC Mission Profile" />

The impact crater of Ranger 8, approximately 13.5 m wide, was later photographed by ''[[Lunar Orbiter 4]]''.<ref name = "Observing the Moon">
{{cite book
 | last         = North
 | first        = Gerald
 | title        = Observing the Moon
 | date = July 5, 2007
 | page         = 140
 | url          = https://books.google.com/books?id=SA4iUaTIcHsC&pg=PA140
 | isbn         = 978-1-139-46494-9
 | publisher    = Cambridge University Press
 | location     = Cambridge, England, UK
}}
</ref>

==See also==
{{Portal|Solar System|Spaceflight}}
* [[List of artificial objects on the Moon]]
* [[List of missions to the Moon]]
* [[Timeline of Solar System exploration]]

==References==
{{NASA|article=Ranger 8|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1965-010A}}
{{Reflist|30em}}

==External links==
*[https://books.google.com/books/about/Lunar_Impact.html?id=xMIgAAAAIAAJ Lunar impact: A history of Project Ranger (PDF), R. Cargill Hall, 1977]
*[http://nssdc.gsfc.nasa.gov/imgcat/html/mission_page/EM_Ranger_8_page1.html Photographs from ''Ranger 8'']
*[https://www.youtube.com/watch?v=VTh9V-5tOB0 Video from Ranger 8]dead link

{{NASA}}
{{Ranger program | before=[[Ranger 7]] | after=[[Ranger 9]] }}
{{Moon spacecraft}}
{{NASA space program}}
{{Orbital launches in 1965}}

{{Use American English|date=January 2014}}

[[Category:Ranger program|8]]
[[Category:Spacecraft launched in 1965]]
[[Category:Spacecraft that impacted the Moon]]
[[Category:Destroyed space probes]]
[[Category:Impactor spacecraft]]
[[Category:1965 on the Moon]]