An Optimum Marine Inertial/Doppler Satellite Navigation System

This thesis is concerned with the study of an optimal navigation system which utilizes an inertial navigation set and an earth orbiting satellite. The principal interest herein is directed toward the marine navigator although the concept is also applicable to airborne navigation. Three basic elements are fundamental to this system. The primary element is a fully autonomous inertial navigation set consisting of an inertial measurement unit and digital computer with associated input/output devices, thermal conditioners and power supplies. This type of equipment has been utilized on both surface and submarine craft for over a decade. The second element in the system is the orbiting satellite which broadcasts navigational data in the form of timing signals, satellite ephemeris and radio frequencies for doppler measurement. The navigator will be provided with equipment for reception and processing of these satellite transmissions. A satellite system of this type, the Navy Navigation Satellite System (NNSS), perhaps better known as TRANSIT has been operated by the U.S. Navy since 1964. The final basic element of this system is the algorithm by which the system can optimally process measurements and thus reduce its error. The basic Kalman filter algorithm has been modified to accommodate the satellite doppler measurement in this study. The necessary system mechanization equations have been developed along with a representative error model. The performance has then been evaluated by co-variance error analysis on a digital computer. The results presented indicate the performance capability of this type of system for several relative geometries between the navigator and satellite