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Orbiter Imaging

NSSDC ID: 1975-083A-01
Mission Name: Viking 2 Orbiter
Principal Investigator: Dr. Michael H. Carr


The Viking visual imaging subsystem (VIS) consisted of twin high-resolution, slow-scan television framing cameras mounted on the scan platform of each orbiter with the optical axes offset by 1.38 deg. The two cameras, including their housing, were 21.8 x 21.8 x 94.0 cm in size and had a mass of 40 kg. Each of the two identical cameras on each orbiter had mechanical shutters; a 475-mm focal length telescope; a 37-mm diameter vidicon, the central section of which was scanned in a raster format of 1056 lines by 1182 samples. A filter wheel between the lens and shutter held six color filter positions: blue (0.35 to 0.53 micrometers), minus-blue (0.48 - 0.70), violet (0.35 - 0.47), green (0.50 - 0.60), red (0.55 - 0.70), and clear (no filter) to restrict the spectral bandpass of an image to limited portions of the near-visual response characteristics. Each field of view was 1.54 deg x 1.69 deg with each picture element (pixel) subtending 25 microradians. This translates to an image area on the surface of roughly 40 x 44 km from an altitude of 1500 km. The slight offset of the optical axes and the alternate shuttering mode of operation (the interval between frames being 4.48 s) provided overlapping, wide-swath coverage of the surface. Exposure duration was adjustable from 0.003 to 2.66 seconds. Each pixel was digitized as a 7-bit number (0 to 127) stored in the onboard tape-recorder, and later transmitted to Earth and converted to an 8-bit number by multiplying by 2. The two cameras were completely redundant, each with its own control, electronics, and power systems.

The VIS had four primary functions: to aid in the selection of landing sites that were both safe and scientifically interesting, to observe large scale features of the landing sites for correlation with lander data from the surface, to observe and map the planet for subsequent study of the geologic features of the planet, and to investigate the atmosphere of Mars. Individual images are identified by picture number (PICNO), which is a unique identifier of the scene. Elements of the PICNO are as follows: the first three digits denote the revolution (REV) during which the image was shuttered; the letter A is Viking Orbiter 1, B is Viking Orbiter 2; and the last two digits are the frame number. The Viking 2 Orbiter camera returned approximately 15,600 images.

Alternate Names

  • VIS
  • Visual Imaging Subsystem

Facts in Brief

Mass: 40.0 kg

Funding Agency

  • NASA-Office of Space Science (United States)


  • Planetary Science: Atmospheres
  • Planetary Science: Geology and Geophysics

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. John E. GuestTeam MemberUniversity of London 
Dr. Joseph F. VeverkaTeam MemberCornell
Dr. James A. CuttsTeam MemberScience Applications,
Dr. Karl R. BlasiusTeam MemberScience Applications, Inc 
Prof. Ronald GreeleyTeam MemberArizona State University 
Dr. Bradford A. SmithTeam MemberUniversity of Arizona 
Dr. Geoffrey S. BriggsTeam MemberNASA
Mr. John B. WellmanTeam MemberNASA Jet Propulsion
Mr. Thomas C. DuxburyTeam MemberNASA Jet Propulsion
Dr. William A. BaumTeam MemberLowell Observatory 
Dr. Michael H. CarrTeam LeaderUS Geological
Dr. Harold MasurskyTeam MemberUS Geological Survey 
Dr. Keith A. HowardTeam MemberUS Geological
Dr. Lawrence A. SoderblomTeam MemberUS Geological

Selected References

Carr, M. H., et al., Imaging experiment - The Viking Mars Orbiter, Icarus, 16, 17-33, 1972.

Blasius, K. R., et al., Geology of the Valles Marineris: First analysis of imaging from the Viking 1 Orbiter primary mission, J. Geophys. Res., 82, No. 28, 4067-4091, Sept. 1977.

Ruiz, R. M., et al., IPL processing of the Viking Orbiter images of Mars, J. Geophys. Res., 82, No. 28, 4189-4202, Sept. 1977.

Duxbury, T. C., and J. Veverka, Viking imaging of Phobos and Deimos: An overview of the primary mission, J. Geophys. Res., 82, No. 28, 4203-4211, Sept. 1977.

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