Source: nasa.gov

10-20-2007 14:06

The Ranger series was 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. Shown above is the Ranger spacecraft and an image of the Moon taken by the Ranger 7 A series camera immediately before impact. This image has a resolution of .5 meters. Ranger 7 impacted in mare terrain modified by crater rays. Ranger 8 also impacted in mare terrain, but this area contained a complex system of ridges. Ranger 9 impacted in a large crater in the lunar highlands. Below is the first image of the Moon taken by Ranger 7, about 17 minutes before impact.

Ranger 7

Launched 28 July 1964

Impacted Moon 31 July 1964 at 13:25:49 UT

Latitude 10.70 S, Longitude 339.33 E - Mare Cognitum (Sea That Has Become Known)

Ranger 8

Launched 17 February 1965

Impacted Moon 20 February 1965 at 09:57:37 UT

Latitude 2.71 N, Longitude 24.81 E - Mare Tranquillitatis (Sea of Tranquility)

Ranger 9

Launched 21 March 1965

Impacted Moon 24 March 1965 at 14:08:20 UT

Latitude 12.91 S, Longitude 357.62 E - Alphonsus crater

Each Ranger spacecraft had 6 cameras on board. The cameras were fundamentally the same with differences in exposure times, fields of view, lenses, and scan rates. The camera system was divided into two channels, P (partial) and F (full). Each channel was self-contained with separate power supplies, timers, and transmitters. The F-channel had 2 cameras: the wide-angle A-camera and the narrow angle B-camera. The P-channel had four cameras: P1 and P2 (narrow angle) and P3 and P4 (wide angle). The final F-channel image was taken between 2.5 and 5 sec before impact (altitude about 5 km) and the last P-channel image 0.2 to 0.4 sec before impact (altitude about 600 m). The images provided better resolution than was available from Earth based views by a factor of 1000. These highly detailed images showed Apollo planners that finding a smooth landing site was not going to be easy.

The earlier Rangers, 1 through 6, all failed for various reasons. Information on these missions is given below:

Ranger 1

Launched 23 August 1961

Failed to leave Earth parking orbit

Ranger 2

Launched 18 November 1961

Failed to leave Earth parking orbit

Ranger 3

Launched 26 January 1962

Earth contact lost, missed the Moon by ~36,800 km

Ranger 4

Launched 23 April 1962

Sequencer failed, impacted the Moon 26 April 1962

Ranger 5

Launched 18 October 1962

Earth contact lost, missed the Moon by 725 km

Ranger 6

Launched 30 January 1964

Cameras failed, impacted the Moon 2 February 1964

 

Editor:Liu Fang