Apollo 17 Landing Site Selection

Deliberation on the landing site for Apollo 17 actually began during discussions regarding the landing site for Apollo 16 because the Apollo Site Selection Board (ASSB) considered the last two lunar landing missions complementary in their preference for lunar highlands. When the ASSB met on 3 June 1971 to select the Apollo 16 site, it also wanted to designate a prime site candidate for Apollo 17. The principal debate for the Apollo 16 landing site was between Descartes and Alphonsus on the eastern edge of Mare Nubium. When Descartes was selected as the site for Apollo 16, that moved Alphonsus to Apollo 17 as the prime candidate site. However, the ASSB wanted to wait for the orbital photographs of the highlands from Mare Crisium to Mare Serenitatis from Apollo 15, as well as gamma ray and X-ray data along the spacecraft's orbital path. In October, the Board reviewed the Apollo 15 photographs taken from the Service Module mapping camera, together with the other data. Four of the six potential landing sites considered from this review were eliminated. The two remaining potential sites were added to the three other high-priority contenders. The five sites under consideration for Apollo 17 now included Alphonsus, Copernicus central peaks, Gassendi central peaks on the northern rim of Mare Humorum, a site southwest of Mare Crisium, and a highlands-volcanic site, designated Taurus-Littrow, on the southeastern edge of Mare Senenitatis.

In December 1971, a Site Evaluation Document was issued to thirty-two evaluators, including the principal investigators, co-investigators and other scientists involved with experiment packages, and mission planners. The responses evaluated by the Ad Hoc Site Evaluation Committee in January 1972 established a consensus of objectives that included (1) orbital science coverage, (2) sampling early volcanics, (3) sampling pre-Imbrium highlands as far from the Imbrium basin as possible, (4) traverse geophysics, and (5) the Apollo Lunar Surface Experiments Package with priority placed on the heat flow experiment (lost on Apollo 16). The responses also weighed in with site preferences. From this, the committee narrowed their short list to three potential sites in order of preference. First was Taurus-Littrow, second was Gassendi and a distant third choice was the crater Alphonsus.

Initially, NASA's Mission Planning and Analysis Division (MPAD) doubted that a landing could be achieved at Taurus-Littrow. The key issue was orbital mechanics and, specifically, what MPAD referred to as the three-sigma-error ellipse. The landing site was the farthest east of any lunar landing site. Once the Lunar Module came out from behind the Moon, there was a limited amount of time to enter the state vector into the LM's computer prior to powered descent. There were also issues with guidance, tracking, and modifying the landing techniques to make it feasible. Several months of work between MPAD and Bellcom, Inc. (which was contracted by NASA to advise on this and other issues related to lunar missions) transpired before all the precise factors necessary for landing at Taurus-Littrow fell into place.

On 11 February 1972, the Apollo Site Selection Board met to select the landing site for Apollo 17. Gassendi presented problems; if the Lunar Module touched down outside the landing ellipse, the crew would not be able to reach the prime objective of the central peaks, even with the LRV. For this and other reasons, Johnson Space Center considered Gassendi unacceptable. The ASSB then focused on Alphonsus and Taurus-Littrow. It was felt that superior orbital coverage and better potential for use of the LRV at Taurus-Littrow made the choice relatively easy, so the ASSB recommended Taurus-Littrow as the landing site for Apollo 17 to the NASA Associate Administrator for Manned Space Flight, Dale Myers.

Fotos Sonda China Luna
The Apollo 17 landing site of Taurus-Littrow was named after the Taurus Massifs (mountains) and Littrow Crater. The latter was named in honor of Joseph Johann von Littrow, who was director of the Vienna Observatory in the early 19th century (NASA)

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