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Ranger 8

Courtesy of NASA's National Space Science Data Center

Launch Date/Time: 1965-02-17 at 17:05:00 UTC
On-orbit dry mass: 361.80 kg
Nominal Power Output: 200.00 W


Description

Ranger 8 was designed to achieve a lunar impact trajectory and to transmit high-resolution photographs of the lunar surface during the final minutes of flight. The spacecraft carried six television cameras, an optical earth sensor and high-gain antenna for optimum communications, and solar panels to provide power, as well as additional engineering equipment. The telecommunications equipment converted the composite video signal from the camera transmitters into an RF signal for subsequent transmission through the spacecraft high-gain antenna. Sufficient video bandwidth was provided to allow for rapid framing sequences of both narrow- and wide-angle television pictures. The spacecraft encountered the lunar surface in a direct hyperbolic trajectory, with incoming asymptotic direction at an angle of -13.6 degrees from the lunar equator. The orbit plane was inclined 16.5 degrees to the lunar equator. After 64.9 hours of flight, impact occurred at in Mare Tranquillitatis. The spacecraft performance was excellent. The spacecraft transmitted 7,137 photographs during the final 23 minutes of flight, 0934 UT to 0957 UT, on February 20, 1965.

Ranger 8 Impact Television Imaging

The television system consisted of six slow scan vidicon TV cameras capable of transmitting high-resolution closeup television pictures of the lunar surface during the final minutes of flight, before the spacecraft impacted the lunar surface. These photographs provided large-scale topographic information needed for the Surveyor and Apollo projects. Vidicons 2.54 centimeters in diameter with an antimony-sulfide oxy-sulfide (ASOS) photoconductor target were used for image sensing in all six cameras.

There were two camera channels which had independent power distribution networks so that the greatest reliability and probability of obtaining highest quality video pictures would be afforded. The first channel had two full-scan cameras, one wide angle (25 degree field of view and 25-millimeter focal length) designated the A-camera and one narrow angle (8.4-degree field of view and 76-millimeter focal length) B-camera. These cameras utilized an active image area of 11 square millimeters that contained 1,150 lines and was scanned in 2.5 seconds. Scan and erase cycles were designed to act alternately, resulting in intervals of 5 seconds between consecutive pictures on a particular camera. The other channel had four partial-scan (p) cameras, two narrow angle and two wide angle. The image a area of these four cameras was 2.8 square millimeters, contained 300 lines, and was scanned in 0.2 seconds. The TV system allowed for camera fields of view, which ranged from 25 degrees to 2.1 degrees, to overlap and produce a 'nesting' sequence of pictures. The video transmissions were recorded on both kinescope film recorders and magnetic tape recorders. A cathode-ray tube reconstructed the original image, which was then photographed on 35-millimeter film.

Both full-scan and partial-scan camera systems operated during the final 23 minutes of flight, 0934 UT to 0957 UT, on February 20, 1965. Resolution was achieved to 1.5 meters (5 feet). The experiment returned 6,597 partial-scan and 540 full-scan pictures giving the desired broad coverage of the lunar surface.

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