This article is from the Space FAQ, by Jon Leech leech@cs.unc.edu and Mark Bradford tla@surly.org with numerous contributions by others.
The SURVEYOR series were designed primarily to see if an APOLLO lunar
module could land on the surface of the Moon without sinking into the
soil (before this time, it was feared by some that the Moon was covered
in great layers of dust, which would not support a heavy landing
vehicle). SURVEYOR was successful in proving that the lunar surface was
strong enough to hold up a spacecraft from 1966 to 1968.
Only SURVEYOR 2 and 4 were unsuccessful missions. The rest became the
first U.S. probes to soft land on the Moon, taking thousands of images
and scooping the soil for analysis. APOLLO 12 landed 600 feet from
SURVEYOR 3 in 1969 and returned parts of the craft to Earth. SURVEYOR 7,
the last of the series, was a purely scientific mission which explored
the Tycho crater region in 1968.
 
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