Radio Interferometer Phase-Channel Combiner Mod. II for the Navy Space Surveillance System

Abstract

The Space Surveillance System developed at the U. S. Naval Research Laboratory, Washington, D. C., for the detection of earth satellites forms a fence across the southern part of the United States. Four receiving sites are alternated with three transmitting sites which illuminate satellites with radio energy as they traverse the fence. The angle of arrival of the reflected energy is measured at each receiving station by a compound radio interferometer. These signals yield a multiplicity of channels which are normally recorded on paper, read and resolved by using slide rules and/or mathematical tables. Operationally the resolution is done by a computer. With the increasing satellite population the number of fence crossings has increased considerably. Automation in the detection process is needed to facilitate identification and sorting of satellites from each other if a large backlog of data is to be avoided. The purpose of this report is to describe an electronic system which automatically combines several noisy ambiguous radio interferometer phase channels into one unambiguous quiet channel. This technique results in that given a multi-baseline radio interferometer system, normally having high angular resolution capability accompanied with the usual interferometer ambiguity problem associated with deciphering the multiple phase signal outputs it can be instrumented directly into a single unambiguous signal output which has an accuracy and resolution proportional to the longest baseline in the interferometer and whose noise content is inversely proportional to this baseline.