Codeless gps sonde

Abstract

Windfinding apparatus is described in which receiver processing of the Global Positioning System (GPS) signals is without knowledge of the spread spectrum codes. The apparatus receiver ignores the bi-phase code and recovers the carrier frequency of all satellites in view of the receiving antenna. Two of these receivers are used in a windfinding system. One of the receivers is located on the ground at a known latitude and longitude. The other receiver is placed on a weather balloon sonde and launched into the atmosphere. A telemetry transmitter aboard the sonde transmits a signal that contains the GPS carrier frequency information to the ground-based telemetry receiver. The telemetry receiver output and the local codeless GPS receiver feed a set of tracking filters. The filtered signals are evaluated to obtain a measurement of the difference between the local GPS receiver carrier frequency and the sonde GPS receiver carrier frequency caused by the velocity of the sonde relative to the ground-based receiver (i.e., doppler effect). The wind velocity is computed based on knowledge of the doppler of the sonde GPS receiver and known GPS satellite positions. The sonde velocity is computed as a three dimensional vector. This vector can then be integrated to obtain the x distance, y distance and z altitude from the sonde launch point.