Results

Since Surveyors 1, 3, 5, and 6 successfully fulfilled requirements in support of Apollo, NASA opted to use the last remaining Surveyor for a purely scientific mission outside of a potential landing site for the early Apollo flights.

After an uneventful coast to the Moon (including one of two planned mid-course corrections), Surveyor 7 successfully set down at 01:05:36.3 UT on Jan. 10, 1968 on the ejecta blanket emanating from the bright Tycho crater in the south of the nearside.

Landing coordinates were 40.97 degrees south latitude and 11.44 degrees west longitude, about 18 miles (29 kilometers) north of Tycho’s rim, and 1.5 miles (2.4 kilometers) from its target.

Initial photos from the surface showed surprisingly few craters, much like the mare sites, although the general area was rougher.

About 21 hours after landing, ground controllers fired pyrotechnic charges to drop the alpha-scattering instrument on the lunar surface. When the instrument failed to move beyond an intermediate position, controllers used the surface sampler (robot arm) to force it down.

The sampler was then used to pick up the alpha-scattering instrument after its first chemical analysis and move it to two additional locations. About 66 hours of alpha-scattering data were obtained during the first lunar day on three samples: the undisturbed lunar surface, a Moon rock, and an area dug up by the surface sampler. The alpha-scattering instrument collected 34 more hours of data during the second lunar day.

The scoop on the sampler’s arm was used numerous times for picking up soil and digging trenches, and for conducting at least 16 surface-bearing tests.

Apart from taking 21,274 photographs (20,993 on the first lunar day and 45 during the second), Surveyor 7 also served as a target for Earth-based lasers (of 1 watt power) to accurately measure the distance between Earth and the Moon.

Communications were paused with Surveyor 7 at 14:12 UT on Jan. 26, 1968, about 80 hours after sunset. Second lunar day operations began at 19:01 UT on Feb. 12, 1968, and extended to 00:24 UT on Feb. 21, 1968 effectively ending the mission.

In total, the five successful Surveyors returned more than 87,000 photos of the lunar surface and operated for about 17 months total on the lunar surface, and most important, demonstrated the feasibility of soft-landing a spacecraft on the lunar surface.

Originally planned as a 7-spacecraft series, in 1963, NASA added 3 more missions (Surveyors H, I, and J) for a total of 10 missions. These later Surveyors, each weighing 2,500 pounds or 1,134 kilograms (as opposed to the 2,200 pound or 998-kilogram model), were, however, canceled in Dec. 1966 based on the successful results of the Ranger missions, Lunar Orbiters, and Surveyors already launched by then.

Source

Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.

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