One of the most exciting moments in a landing mission is when the first images from the surface of another world are returned back to Earth. This was no less true for the Viking 2 landing on Mars even though it had been preceded by the successful landing of its sister, Viking 1, on July 20, 1976. Viking 2 landed on a fairly smooth northern plain known as Utopia Planitia at 47.64° N, 225.71° W on September 3, 1976 at 22:37:50 GMT. Minutes after landing, Viking 2 used one of its pair of cameras to acquire a black and white image of a 70° by 20° strip in front of the lander about 1.4 meters from the camera which included a view of the footpad. Although superficially similar to the first image returned 45 days earlier by Viking 1 (see “First Pictures: Viking 1 on Mars – July 20, 1976“), the 10 to 20-centimeter rocks in the scene had vesicles or pits suggesting erosion by wind action.
The first image of the surface of Mars returned by Camera 1 on the Viking 2 Lander shortly after its touchdown on September 3, 1976. Click on image to enlarge. (NASA/JPL)
After transmission of its first image showing the foreground was completed, the Lander’s second camera started work on a much larger 330° panorama providing a fuller view of the landing site. Taken at about 10 AM local Martian time, the Viking 2 landing site appeared similar to that of Viking 1 save for the pitted rocks and the lack of any dune-like features. The left side of the panorama, looking towards the northwest, shows a featureless horizon about four kilometers distant. On the right side towards the southwest, nearby rocks are silhouetted against the skyline suggesting that they are on a slight rise closer to the Lander. The curved appearance of the horizon is an artifact caused by an 8° tilt of the Lander towards the west and how the camera scanned the scene. Viking 2 took its first color image of the Red Planet on Sol 2 of its mission.
The second image returned by Viking 2 using Camera 2 provided a panoramic view of the landing site on Utopia Planitia. Click on image to enlarge. (NASA/JPL)
The first color image of Mars taken by Viking 2 on September 5, 1976. Click on image to enlarge. (NASA/JPL)
The Viking landers each sported a pair of 7.3-kilogram cameras on their upper deck mounted 0.822 meters apart to provide stereo views of the landscape. Unlike the vidicon-based cameras used on NASA’s robotic Surveyor lunar landers a decade earlier which returned individual frames of the scene (see “Surveyor 1: America’s First Moon Lander”), the Viking Lander cameras used a scanning mirror to reflect the scene onto a set of a dozen light-sensitive photodiodes. The nodding motion of the mirror allowed one column of the scene to be scanned before the camera turret rotated stepwise in azimuth to allow the adjacent columns to be scanned one at a time. Each camera could scan up to 342.5° in azimuth and from 40° above to 60° below the horizon. Earlier Soviet Luna, Mars and Venera landers used telephotometers operated on a similar principle (see “Luna 9: The First Lunar Landing” and “Venera 9 & 10 to Venus“).
Cutaway diagram showing the major components of the cameras carried by the Viking Landers. Click on image to enlarge. (NASA)
The array of a dozen detectors allowed the scene to be scanned in six spectral bands for color and near infrared imaging at an image scale of 0.12° per pixel or black and white images with a finer image scale of 0.04° per pixel with four different focus steps ranging from 1.9 to 13.3 meters. Each image column scan was broken up into 512 pixels digitized to 6 bits. The scanning rate was synchronized with the 16,000 bits per second transmission rate using the Viking Orbiters as a relay or the 250 bits per second rate for direct transmission to Earth via the Lander’s high gain antenna (seen on the right side of the first panorama returned by Viking 2). The images could also be stored on a 40 megabit tape recorder for later transmission.
This schematic shows the operation of the Viking Lander camera from scanning the scene to the reconstruction of the image back on Earth. Clcik on image to enlarge. (NASA)
The Viking 2 lander continued operating far beyond the end of its primary mission on October 5, 1976 returning images and other scientific data for years to come (see Related Reading below). The Viking 2 lander was finally shutdown on April 11, 1980 after 1281 Sols on the surface because of battery failure.
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Related Reading
“First Pictures: Viking 1 on Mars – July 20, 1976”, Drew Ex Machina, July 20, 2021 [Post]
“Viking & The First Seismometers on Mars”, Drew Ex Machina, November 21, 2018 [Post]
“NASA’s Viking Mission and the Search for Life on Mars: The Experiments”, Drew Ex Machina, July 28, 2022 [Post]
General References
Michael M. Mirabito, The Exploration of Outer Space with Cameras, McFarland, 1983
Andrew Wilson, Solar System Log, Jane’s Publishing, 1987
The Martian Landscape, NASA SP-425, 1978