Ranger
In 1967, Ranger 7 transmitted close-up pictures of the moon for about 13 minutes before crashing into the Moon's surface. (Grolier Interactive Inc.)
Ranger was a series of U.S. spacecraft that were designed to provide, in the 20 minutes before impact on the
The Spacecraft
The prime contractor for the Ranger program was the Jet Propulsion Laboratory of
the California Institute of Technology. The spacecraft, which weighed about 365
kg (810 lb), had a hexagonal base about 1.5 m (5 ft) in diameter. A 2.5-m-high
(8.25-ft) telescopelike cone structure, which contained 6 television cameras and
an omnidirectional antenna, extended above this base. Two panels, containing
9,800 solar cells that provided 200 W of electricity, unfolded in flight and
gave the spacecraft a wingspan of 4.6 m (15 ft).
All of the Ranger spacecraft were launched by an Atlas-Agena rocket from Kennedy Space Center. After Earth orbit was attained, the Agena second stage was briefly restarted (prior to separation from the spacecraft) in order to inject Ranger into a lunar trajectory. After midcourse corrections the spacecraft were to crash into the Moon at about 9,700 km/h (6,027 mph), some 68 hours after launch.
The Missions
Only the last three Ranger missions met their objectives, but they did so with
great success. Rangers 1 and 2 (launched Aug. 23 and Nov. 18,
1961) were test models in which the Agena engine failed to restart. Ranger
3 (launched Jan. 26, 1962) missed the Moon and entered solar orbit, as did
Ranger 5 (launched Oct. 18, 1962). Ranger 4 (launched Apr. 23,
1962) curved around the Moon and crashed on its far side, while the television
system aboard Ranger 6 (launched Jan. 30, 1964) failed before it impacted
on the Moon.
Ranger 7 (launched July 28, 1964) impacted successfully at 10.7° S, 20.7° W in the Sea of Clouds, sending back 4,316 photos. Ranger 8 (launched Feb. 17, 1965) struck the Moon at 2.7° N, 24.8° E in the Sea of Tranquillity, taking 7,137 photos at an approach angle that swept a large portion of the lunar surface and provided the first close-up views of its highlands. Ranger 9 (launched Mar. 21, 1965) impacted at 12.9° S, 2.4° W inside the crater Alphonsus, yielding 5,814 photos that were the first close-up views of a lunar crater's interior.
Other Results
The improved resolution of the Ranger photos over their Earth-based counterparts
revealed several previously unknown aspects of the Moon, such as the small-scale
topography. The photos showed striking similarities between mare and crater
floors, a smoothed appearance in numerous shallow depressions, and a relative
absence of rubble over substantial portions of the surface. Ranger 9's
target, the crater Alphonsus, gave signs of a complex history influenced by both
internal and external forces. The mare in the photos showed an absence of large
mountain ranges as well as of impact-saturated areas containing numerous
overlapping craters. This discovery influenced the selection of mare regions as
preferred sites for the Surveyor and Apollo landings.
Bibliography: Breuer, W. B., Race to the Moon (1993); Jet Propulsion Laboratory, The View from Ranger (NASA EP-38; 1966); Ley, Willy, Ranger to the Moon (1965); Wilhelms, D. E., To a Rocky Moon (1994).
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