Editing Ranger program

{{short description|American uncrewed lunar space missions in the 1960s}}

[[Image:Ranger7 PIA02975.jpg|thumb|200px|right|First image of the Moon returned by a Ranger mission (Ranger 7 in 1964)]]The '''Ranger program''' was a series of [[uncrewed space mission]]s by the [[United States]] in the 1960s whose objective was to obtain the first close-up images of the [[surface of the Moon]]. The Ranger spacecraft were designed to take images of the lunar surface, transmitting those images to Earth until the spacecraft were destroyed upon impact. A series of mishaps, however, led to the failure of the first six flights. At one point, the program was called "shoot and hope".<ref>[http://www.jsc.nasa.gov/history/oral_histories/CortrightEM/EMC_8-20-98.pdf Cortright Oral History (p25)]</ref> Congress launched an investigation into "problems of management" at [[NASA]] Headquarters and [[JPL|Jet Propulsion Laboratory]].<ref>{{cite web|last=Dick|first=Steven J.|title=NASA's First 50 Years: Historical Perspectives|url=https://history.nasa.gov/SP-4704.pdf|publisher=NASA|website=history.nasa.gov|access-date=17 June 2019|page=12}}</ref> After two reorganizations of the agencies,{{citation needed|date=October 2012}} [[Ranger 7]] successfully returned images in July 1964, followed by two more successful missions.

Each of the block III Ranger spacecraft had six cameras on board. The cameras were fundamentally the same with differences in exposure times, fields of view, lenses, and scan rates. The camera system was divided into two channels, P (partial) and F (full). Each channel was self-contained with separate power supplies, timers, and transmitters. The F-channel had two cameras: the wide-angle A-camera and the narrow angle B-camera. The P-channel had four cameras: P1 and P2 (narrow angle) and P3 and P4 (wide angle). The final F-channel image was taken between 2.5 and 5 seconds before impact (altitude about {{convert|5|km}}) and the last P-channel image 0.2 to 0.4 seconds before impact (altitude about {{convert|600|m}}). The images provided better resolution than was available from Earth-based views by a factor of 1000. The design and construction of the cameras was led by [[Leonard R Malling]].<ref>

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The Ranger program manager for the first six spacecraft was [[James Burke (space engineer)|James D. Burke]].<ref name="ranger2">{{cite web|title=LUNAR IMPACT: A History of Project Ranger, Part I. The Original Ranger, Chapter Two - ORGANIZING THE CAMPAIGN|url=http://history.nasa.gov/SP-4210/pages/Ch_2.htm#Ch2_R42|work=NASA History|publisher=NASA|access-date=14 July 2016}}</ref>

The camera preamplifiers of the Ranger program used [[Nuvistor]]s.<ref>Nuvistor Valves by Stef Niewiadomski. <!--http://www.r-type.org/articles/art-150.htm--></ref>

[[File:20180328 Ranger restoration Udvar-Hazy.jpg|thumb|ARanger probe undergoing restoration at the [[Udvar-Hazy Center]]]]

*[[Ranger 4]], launched 23 April 1962, lunar probe, spacecraft failed, Moon impact

*[[Ranger 5]], launched 18 October 1962, lunar probe, spacecraft failed, missed Moon

Block 2 of the Ranger project launched three spacecraft to the Moon in 1962, carrying a TV camera, a radiation detector, and a seismometer in a separate capsule slowed by a rocket motor and packaged to survive its low-speed impact on the Moon's surface. The craft weighed 331&nbsp;kg. The three missions together demonstrated good performance of the Atlas/Agena B launch vehicle and the adequacy of the spacecraft design, but unfortunately not both on the same attempt. [[Ranger 3]] had problems with both the launch vehicle and the spacecraft, missed the Moon by about 36,800&nbsp;km, and has orbited the Sun ever since. [[Ranger 4]] had a perfect launch, but the spacecraft was completely disabled. The project team tracked the seismometer capsule to impact just out of sight on the [[Far side (Moon)|lunar far side]], validating the communications and navigation system. [[Ranger 5]] missed the Moon and was disabled. No significant science information was gleaned from these missions.

Around the end of Block 2, it was discovered that a type of diode used in previous missions produced problematic gold-plate flaking in the conditions of space. This may have been responsible for some of the failures.<ref>{{cite web|url=https://history.nasa.gov/SP-480/ch8.htm|title=ch8}}</ref>

*[[Ranger 6]], launched 30 January 1964, lunar probe, Moon impact, cameras failed

Ranger's Block 3 embodied four launches in 1964-65. These spacecraft boasted a television instrument designed to observe the lunar surface during the approach; as the spacecraft neared the Moon, it would reveal detail smaller than the best Earth telescopes could show, and finally [[dishpan]]-sized craters.<ref>{{cite web|url=https://books.google.com/books?id=2sIfAAAAIAAJ&q=showing+dishpan-sized+craters&pg=PA47|title=The View From Ranger|year=1961|publisher=NASA-JPL|page=47}}</ref> The first of the new series, [[Ranger 6]], had a flawless flight, except that the television system was disabled by an in-flight accident and could take no pictures.

In February 1965, [[Ranger 8]] swept an oblique course over the south of [[Oceanus Procellarum]] and [[Mare Nubium]], to crash in [[Mare Tranquillitatis]] about {{convert|70|km|mi|sp=us}} distant from where [[Apollo 11]] would land 4½ years later. It took more than 7,000 images, covering a wider area and reinforcing the conclusions from Ranger 7. About a month later, [[Ranger 9]] came down in the {{convert|90|km|mi|adj=on|abbr=off|sp=us}} diameter crater [[Alphonsus (crater)|Alphonsus]]. Its 5,800 images, nested concentrically and taking advantage of very low-level sunlight, provided strong confirmation of the crater-on-crater, gently rolling contours of the lunar surface.

*[https://web.archive.org/web/20151201201709/http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Ranger Ranger Program Page] by [http://solarsystem.nasa.gov NASA's Solar System Exploration]