A New Method of tracking Artificial Earth Satellites

Abstract

EXISTING instruments for making precise trajectory observations on artificial Earth satellites generally employ photographic techniques, a good example being the Schmidt–Baker–Nunn cameras of the Smithsonian Astrophysical Observatory. Since the launching of Sputnik 2, we have been experimenting with optical tracking by a photo-electric method which appears capable of adequate sensitivity and a precision comparable with that of astronomical observations, and thus high enough for observing the non-secular perturbations of a satellite orbit. The principal advantage of the method is the simpler design of the optical system since a long focal length can be used, unlike the photographic method where a short-focus lens is required. The correction of lens aberrations is thereby rendered much easier. A performance in many ways comparable with the Schmidt–Baker–Nunn camera has been obtained with a lens having a 5-in. diameter aperture and 14-in. focal length.