Ranger (space probe program)

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Block I satellite design
Ranger 4 (Ranger Block II)
Ranger 9 (Ranger Block III)

Ranger is the name of a US space program and nine space probes that flew to the moon between 1961 and 1965 and transmitted images from there before impact. It was carried out by NASA and was under the direction of JPL .


Nine US probes already flew to the moon as part of the Pioneer program. The flyby of Pioneer 4 on March 4, 1959 alone was a partial success, the other eight probes were all failures.

After US President John F. Kennedy announced in April 1961 that a man would be put on the moon by the end of the decade, NASA intensified its efforts. The Ranger program was an all-purpose program. It was used to practice maneuvers in space and to prepare for landing on the moon. The ranger project is divided into three blocks:

Block I.
The probes 1–2, weighing 306 kg, were to remain earth satellites, but advance into space near the moon and beyond (with an apogee of around 1 million km). These probes did not carry cameras, but measuring instruments for exploring space near the moon.
Block II
The 330–340 kg heavy probes 3–5 should hit the moon and transmit images immediately beforehand. Before this, the mother probe should eject an instrument capsule weighing around 40 kg, which should be protected in a spherical housing made of balsa wood and withstand the impact after repeated hopping without damage. A simple seismograph was located on board the capsule .
Block III
In the case of probes 6–9 with a weight of 365 kg, after the failure of block II, a “soft” landing instrument capsule was dispensed with and instead, with the help of six cameras, the aim was to obtain high-resolution images before the impact. These cameras worked independently of one another and differed in their sampling rate and focal length.


Block I (system testing in earth orbit)

  • Ranger 1 launched on August 23, 1961 and was unable to exit low Earth orbit due to a failure in the missile . The satellite burned up on August 30, 1961 after communication had been broken three days earlier.
  • Ranger 2 launched on November 18, 1961 and suffered a similar fate as Ranger 1. The satellite burned up on November 20, 1961.

Block II (landing a capsule)

  • Ranger 3 took off on January 26, 1962, but due to excessive speed, the probe flew 36,000 km past the moon into a solar orbit. The probe did not send any images.
  • Ranger 4 launched on April 23, 1962, but lost contact with that probe that same day. The probe hit the back of the moon on April 26, 1962. Despite the failure, Ranger 4 was the first US spacecraft to reach the surface of the moon.
  • Ranger 5 started on October 18, 1962, and communication was lost on the same day. The probe flew past the moon around 700 km away and then entered a solar orbit.

Block III (close-ups of the lunar surface)

18-minute time lapse of Ranger 9's approach to the moon
  • Ranger 6 launched on January 30, 1964 and hit the moon on February 2, 1964. The cameras could not be activated immediately before the impact.
  • Ranger 7 started on July 28, 1964 and hit the moon in Mare Cognitum on July 31, 1964 . The probe transmitted 4,300 images immediately before the impact.
  • Ranger 8 started on February 17, 1965 and hit the moon on February 20, 1965 at Mare Tranquillitatis . The probe transmitted 7,300 images.
  • Ranger 9 launched on March 21, 1965, hit the Alphonsus Crater on March 24, 1965 and transmitted 5800 images, which were also shown live on US television. In these three missions, NASA's promises were fulfilled; the transmitted images offered a resolution that was 1000 times better than images from the earth.


Ranger was more successful than the Pioneer moon program with six failures but a satisfactory success rate of 33% in the end. The program cost the USA a total of 170 million US dollars , at that time about 700 million DM . This corresponds to today's costs of $ 1.315 billion or EUR 1.421 billion.
Successor programs were Surveyor and Lunar Orbiter .

See also

Web links

Commons : Ranger (space probe program)  - album with pictures, videos and audio files