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Ranger Program

the first U.S. attempt to obtain close-up images of the lunar surface

The Ranger spacecraft were designed to fly straight down towards the Moon and send images back until the moment of impact, to rough-land a seismometer capsule on the Moon, to collect gamma-ray data in flight, and to study radar reflectivity of the Lunar surface. All this was being done in order to "scout" locations for a planned manned landing on the Moon.

A total of nine Rangers were launched, beginning on August 23, 1961, five of which were successful. The last one was launched on March 24, 1965.

The basic spacecraft was 3.1 m high and consisted of a lunar capsule 65 cm in diameter, a mono-propellant mid-course motor, a 5,080-pound thrust retrorocket, and a gold- and chrome-plated hexagonal base 1.5 m in diameter. A large high-gain dish antenna was attached to the base. Two wing-like solar panels, each 5.2 m across, were attached to the base and deployed early in the flight. Power was generated by 8,680 solar cells.

image of a Ranger spacecraft

Each Ranger spacecraft had 6 cameras on board, each of which provided better resolution than was available from Earth-based views by a factor of 1000. Other apparatus carried by the spacecraft were a gamma-ray spectrometer, a radar altimeter, and a seismometer to be rough-landed on the Lunar surface.

The first image below was taken by Ranger 7 about 17 minutes before impact; the second was taken immediately before impact.

image of Lunar surface about 17 minutes before impact

image of Lunar surface just before impact

Ranger Mission Launch Date Impact Date Mission Notes
Ranger 1 August 23, 1961   Failed to leave Earth parking orbit
Ranger 2 November 18, 1961   Failed to leave Earth parking orbit
Ranger 3 January 26, 1962   Earth contact lost; missed the Moon by ~36,800 km
Ranger 4 April 23, 1962 April 26, 1962 Sequencer failed
Ranger 5 October 18, 1962   Earth contact lost; missed the Moon by 725 km
Ranger 6 January 30, 1964 February 2, 1964 Cameras failed
Ranger 7 July 28, 1964 July 31, 1964 impacted in the Mare Cognitum (Sea That Has Become Known)
Ranger 8 February 17, 1965 February 20, 1965 impacted in the Mare Tranquillitatis (Sea of Tranquility)
Ranger 9 March 21, 1965 March 24, 1965 impacted in the Alphonsus crater

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The Robinson Library >> Technology >> Astronautics >> Unmanned Programs and Missions

This page was last updated on 04/14/2017.