Using the Faraday rotation technique, the Deep Space Network of the Jet Propulsion Laboratory (JPL) monitors ionospheric total electron content (TEC) at its three complexes at Goldstone, California, Canberra, Australia, and Madrid, Spain, to correct data used in the orbit determination process for ionospheric effects. With the number of earth satellites suitable for Faraday rotation measurements steadily decreasing, JPL is investigating other ways to determine ionospheric TEC. One promising method has been developed by MacDoran and Spitzmesser. This method exploits the coherent P code modulation of the two L band signals (1575.42 and 1227.60 MHz) transmitted by satellites of the NAVSTAR Global Positioning System (GPS), but does not require knowledge of the code. It has been named SLIC, for satellite L band ionospheric calibration. With the full complement of 18 GPS satellites in operation in 1987, continuous ionospheric sampling in at least four directions will be feasible with SLIC. In this paper, TEC data measured at Goldstone using SLIC are compared with the results of mapping Goldstone Faraday TEC to the five GPS satellite lines of sight. The results of the two methods are in reasonable agreement.

A technique known as SERIES (Satellite Emission Range Inferred Earth Surveying), is a method by which radio signals from artificial satellites already in earth orbit can be exploited for positioning and navigation. The existing satellites of choice are those of the Global Positioning System (GPS). The SERIES technique makes it possible to perform simultaneous pseudo ranging to multiple NAVSTAR‐GPS satellites without knowledge of the codes usually required to make use of these satellites. The accuracy achievable with the SERIES system in a dynamic environment is at the meter level when operated in a differential mode with a single base station which may be several hundred km away. To achieve real time operation, it is necessary to cross‐link the base station receiver output to the dynamic vessel which determines its position and velocity relative to the geodetic position of the base. The demands upon the cross‐link communications are very modest at an average rate of only one byte per second. Since the technique has no requirement for a knowledge of the GPS codes, it is possible to use both of the P‐code channels at L1 and L2 to accomplish the ionospheric calibrations which are essential for achieving one meter accuracy over distances of several hundred kilometers. The conditions under which the SERIES technique will function are compatible with all civilian needs but are not useful in military operations because of electronics‐countermeasures already developed. By the use of a pair of receivers on a single vessel, it is possible to configure an angular orientation measurement system using the NAVSTAR satellites as the frame of reference and with an accuracy of 0.1 degree or better without any moving parts.

No abstract

No abstract