P CODELESS GPS IONOSPHERIC CALIBRATION SET

THE OBJECTIVE OF THE PROGRAM IS TO DERIVE A GPS SATELLITE RECEIVER WHICH CAN PERFORM MEASUREMENTS OF THE IONOSPHERE'S DELAY OF RF SIGNALS, ON-LINE, IN A COST EFFECTIVE MANNER. BY MEASURING THE DIFFERENTIAL DELAYS IN EACH SATELLITE'S TRANSMISSIONS ON ITS TWO FREQUENCY CHANNELS, L(1) AND L(2), CONTINUOUS MEASURES OF THE TOTAL ELECTRON CONTENT (TEC) OF THE IONOSPHERE ALONG THE LINES OF SIGHT TO THE SATELLITES MAY BE MADE. THE DEVELOPMENT CONTEMPLATES PERFORMING THE MEASUREMENTS ON EACH OF THE CHANNELS WITHOUT REQUIRING KNOWLEDGE OF THE PRECISION (P) CODE, THEREBY RELIEVING PROBLEMS OF POTENTIAL UNAVAILABILITY OF THAT CODE. THE PROJECT BEGINS WITH A DESIGN FOR SUCH A RECEIVER WHICH GENERATES ONLY REPLICA C/A (CLEAR/ACCESS) CODES BUT WHICH ALSO TRACKS P-CODES DIFFERENTIALLY. OPERATION OF SUCH A RECEIVER ESTABLISHES FEASIBILITY, BUT THE DESIGN REQUIRES REFINEMENTS TO OVERCOME ACCURACY LIMITATIONS IMPOSED BY ANTENNA PROPERTIES, SIGNAL MULTIPATH AND PHASE SHIFT CONTROL WITHIN THE RECEIVER'S CHANNELS. REFINEMENTS TO THE DESIGN INVOLVING THE TIMING OF DATA SAMPLES ARE EXPECTED TO PROVIDE PERFORMANCE GAINS IN WIDER TRACKING BANDWIDTHS AND IN THE ABILITY TO DISCRIMINATE SIGNAL AMPLITUDE VARIATIONS DUE TO SCINTILLATION EFFECTS WITH THE IONOSPHERE.