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Abstract
It would be desirable when a missile is sent to the Moon to be able to determine the point of impact. Optical methods are possible.
In this memorandum, the light levels are considered with regard to the photographic requirements. Calculations ore presented of the light reflected by a matt white spherical satellite near the Moon. The brightness of the image of the satellite in a photographic telescope is compared with the brightness of the image of the Moon.
Quantum considerations would in any case set a lower limit to the size of the satellite that could just be detected. Recent work on the granularity of photographic emulsions and on probability criteria for detection of a signal in the presence of noise, shows that a photographic emulsion falls far short of an ideal detector. Nevertheless, as is shown in this memorandum, it would certainly be possible with any of a number of existing telescopes to detect small satellites with a high degree of certainty.
The minimum satellite radii for a number of particular cases for photographic detection against die sunlit side of the disc of the Moon are given in Table II. The more interesting results of minimum satellite radii for detection against, as background, the dark, or earthlit, side of the Moon are given in Table 9. It is shown that with any of a number of existing telescopes, by proper choice of emulsion and exposure conditions, it would be possible to record and detect satellites with radii less than one meter. However, half of this figure would be about the extreme limit.