Abstract: A method and apparatus for detecting and tracking a coded signal within a noisy background environment, wherein the signal is correlated over subintervals of time both in-phase and in quadrature, stored indices which represent all possible paths of the signal phase are retrieved, in-phase and quadrature sums are formed wherein the first term of the in-phase sum is the in-phase correlated signal over the first time subinterval and the first term of the quadrature sum is the quadrature correlated signal over the first time subinterval and wherein successive terms are correlated signals from successive time subintervals which are selected based upon the value of the retrieved index, and the true phase path of the signal is estimated by determining the correlation sum having the maximum absolute value.

Abstract: A retroreflective attitude marker includes at least two intersecting reflecting planes oriented at 90 degrees with respect to one another, and having the property that incident laser beams which are perpendicular to the line of intersection of the two planes are reflected directly back to the laser source. Each retroreflective attitude marker therefore has a single retroreflecting plane perpendicular to line of intersection of the two mutually perpendicular planes. Using three layer illuminator/receivers, directed toward a spinning object, on which a retroreflective attitude marker is located, the rate of spin and the orientation of the spin axis of the object on which the retroreflective marker is located, may be determined mathematically.