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.
Space History
Ranger to the Moon
Views of the Solar System Copyright © 1997 by
Calvin J. Hamilton. All rights reserved.
