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Ranger 7 Vidicon Television Cameras

NSSDCA ID: 1964-041A-01

Mission Name: Ranger 7
Principal Investigator:Dr. Gerard P. Kuiper

Description

The television system consisted of a six slow-scan vidicon TV cameras capable of transmitting high-resolution, close-up 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 cm 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-mm focal length) designated the A-camera and one narrow angle (8.4 degree field of view and 76-mm focal length) B-camera. These cameras utilized an active image area of 11 sq mm that contained 1150 lines and was scanned in 2.5 sec. Scan and erase cycles were designed to act alternately resulting in intervals of 5 sec 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 area of these four cameras was 2.8 sq mm which contained 300 lines and was scanned in 0.2 sec. The instrument allowed for camera fields of view, ranging from 25 deg to 2.1 deg, to overlap and produce a 'nesting' sequence of pictures.

Electromagnetically driven slit-type shutters exposed the vidicons. Images were focused on the vidicon target, which was made up of a layer of photoconductive material initially charged by scanning with an electron beam. An electron beam then scanned the surface and recharged the photoconductor. The video signal was amplified several thousand times, sent to the transmitter where amplitude variations were converted to frquency variations, and were then transmitted directly to Earth. At the end of the active scan, the camera entered an erase cycle to prepare it for the next exposure. Twelve P-channel pictures were exposed between each F-channel picture.

The video transmissions were sent to a television receiver and recorded on both kinoscope film recorders and magnetic tape recorders. A cathode-ray tube reconstructed the original image, which was then photographed on 35-mm film. The full-scan camera system began transmitting pictures at 1308 UT on July 31, 1964, 17 min 13 sec prior to impact. The partial-scan system initiated transmission of pictures at 1312 UT, 13 min 40 sec prior to impact. The last full-scan transmission occured between 2.5 and 5 sec before impact, while the last partial-scan picture was taken between 0.2 and 0.4 sec before impact and achieved resolution to 0.5 m. Image motion is more severe in the last pictures. The experiment returned 4308 photographs of excellent quality. Selected photographs and a more complete description of the TV experiment are included in data set 64-041A-01B.

Alternate Names

  • Ranger 7 Impact Television Imaging
  • Ranger7/Ranger7VidiconTelevisionCameras

Facts in Brief

Mass: 173 kg

Funding Agency

  • NASA-Office of Advanced Research and Technology (United States)

Discipline

  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams

 

Personnel

NameRoleOriginal AffiliationE-mail
Dr. Eugene M. ShoemakerOther InvestigatorCalifornia Institute of Technology
Dr. Ewen A. WhitakerOther InvestigatorUniversity of Arizona
Dr. Harold C. UreyOther InvestigatorUniversity of California, San Diego
Mr. Raymond L. HeacockOther InvestigatorNASA Jet Propulsion Laboratory
Dr. Gerard P. KuiperPrincipal InvestigatorUniversity of Arizona

Selected References

  • Ranger 7,8, and 9 TV cameras, NASA-GSFC, NSSDC 68-06, Greenbelt, MD, May 1968.
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