ABSTRACT

Since its inception, the Navy Navigation Satelite System (Transit) has fostered the development of a number of equipments for both shipboard and land-based users. The newest of these equipments the MX!706, has been developed from the experience gained on previous systems and includes several unique features.

The lVIX/706 has been developed as a tool for the oceanographic community and the equipment is intended for use in the marine environment.

This paper discusses the unique design concepts used in the development of the 706 hardware and software, and defines the capabilities of the 706as a navigation tool.

INTRODUCTION

Since its release for commercial use, much has been written about the Navy Navigation Satellite System (Transit) and its application to a wide variety of navigation and position location problems.

This system, in continuous operation since 1964, has provided users with highly precise position information on a world-wide basis regardless of factors such as local weather conditions, time of day, etc., which normally affect other navigation aids.

In fact, the precise nature of the information obtainable from this system has been responsible for much of our present knowledge of the size and shape of the earth. At the present time, this system (Transit) has been declared the primary geodetic satellite system for our Department of Defense applications (Reference 1).

A broad range of applications for the system has been developed. These applications have included use on vessels of all kinds: submarines, aircraft carriers, oceanographic research and survey ships, drill rigs, and several others. other applications have included use on aircraft, floating ice islands, and land-based fixed site surveys.

As would be expected from the broad range of applications, a number of different user equipments have been developed to exploit certain characteristics of the Transit system. The purpose of this paper is to describe the MX!706 - a "second generation" satellite navigation equipment which has been developed by the Magnavox Company.

Figure 1 shows several equipments developed by Magnavox for Transit applications. Included are: the Geoceiver (AN/PRR-14), a geodetic survey tool, the MX!706, and the MX/702;hp (currently widely used for a number of commercial and military projects).

SYSTEM DESCRIPTION

Several excellent and informative descriptions of the details of the Transit system are available (References 2, 4, 5). For the purpose of this discussion it will suffice to say that the system consists of five (at this time) earth orbiting satellites in 600 nautical mile, circular, polar orbits. The orbital period of each satellite is roughly 107 minutes and it is typically within radio line-of-sight of a given user for about 15 minutes.

Each satellite continuously radiates highly stable 150 and 400 MHz signals which are phase modulated with information defining the precise position of the satellite as a function of time. The rapid motion of the satellite (roughly four miles per second) with respect to the user produces a doppler shift in the received 150 and 400 MHz carriers transmitted by the satellite.

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