Abstract: A computer system and method for accurately transforming multiple returns received by multiple satellites from multiple targets into a set of single accurate tracks for each target. Observations from multiple satellites create partial or resulting tracks. These resulting tracks are then correlated with pre-existing base tracks by a series of steps in which resulting tracks are paired with pre-determined base tracks according to a series of criteria. Pairs based on: common observation points and time spans, common satellites, and lack of common satellite, are considered sequentially. The final attempt at correlation consists of pairing each remaining track with each base track and using profile dependent piece correlation of the pairs. Any remaining resulting tracks are then added to the set of base tracks.

Abstract: A track following servo system for a magnetic disk file employs a buried servo pattern having two types of signals therein. The first is a reference signal of frequency f and the second type are control signals of frequency 2f, adjacent control signals being 180.degree. out of phase with each other.