Concepts for detection of extraterrestrial life/Chapter 2
Mars Surface High-Resolution Near-Scan TV
The first thing man generally does in a new and strange environment is to look around. This is exactly what scientists want eventually to do through one of the Voyager-class landing capsules on Mars by using photographs relayed from television cameras. This “eyes on Mars” experiment would offer genuine scientific merit for the following reasons.
1. We want to know the topography immediately surrounding the capsule. There may be both geological and biological surprises in the landscape revealed by a televised survey.
2. We would like to monitor the instrument operations.
3. Scientists and laymen alike could participate in this experiment. All could see what the scenery of the red planet is like.
TV cameras such as those used on Surveyor or Ranger (spacecraft used in lunar missions) might be adapted for use in the exploration of Mars. The Surveyor cameras use zoom lenses having a focal length range of from 25 mm (wide-angle) to 100 mm (narrow-angle). In the narrow-angle mode these cameras can produce a resolution of 0.25 milliradian per TV line. This means that at a distance of 4 meters the resolution is approximately 1 mm per TV line. These cameras are fitted with filters for color separation and polarization studies. Figure 3 shows one of the Surveyor cameras. The vidicon image tube is mounted vertically and looks up into a mirror which can be rotated in elevation and azimuth to provide viewing in virtually all directions.
The Ranger TV cameras, now well described in other reports, are also of the wide- and narrow-angle type. Although possessing a fixed focus, they can photograph in the range of approximately 1,120 miles to about ⅓ mile. Lens apertures vary and are set so that pictures can be taken corresponding to average lighting conditions on Earth from noon to dusk. The vidicon tube for each camera works on a photoconductive principle similar to tubes in commercial television cameras. The light and dark areas of the image on the face plate are scanned by a beam of electrons which differentiate these light and dark areas by their electrical resistance. The scan lines are converted into electrical signals, highly amplified, converted to a frequency-modulated signal, sent to a 60-watt transmitter, and received on Earth. Direct mounting and use of this system on a capsule on the surface of Mars is not now possible. Nevertheless, the Ranger VII photographs of the Moon underscore the potential of the system as soon as technology permits its application to the planets.
A more sophisticated use of television cameras is illustrated by the microscope-television combination described in the next chapter.
Figure 3.—Television survey camera.