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New approach to the problem of determination of atmospheric refractivity corrections for space geodetic applications

Prokopov A., Remayev Y.

Reports on Geodesy

2000

z. 9/55

43-48

The effect of troposphere on electromagnetic waves propagation parameters is one of the most essential sources of errors in GPS measurements. The allowing for this effect can be executed by entering the corrections in results of measurements and by estimating the residual tropospheric delays at once from GPS signals [Collins, 1997). The final accuracy is determined in both cases by accuracy of the tropospheric delay dependence of satellite elevation angle - the complement of the zenith angle (this dependence usually is termed mapping function). Unfortunately mapping functions practically used are empirical functions obtaining by computer experiment with models for vertical profiles of refractive index of air. Biases appearing in this procedure decreases the accuracy of mapping functions and this is the cause of errors in tropospheric corrections determination as well as in restoring the parameters of troposphere basing on GPS measurements. To increase the accuracy of tropospheric effects modeling the new method of determination of tropospheric corrections for space geodetic applications in both optical and radio ranges (astronomy, SLR, GPS, VLBI) is proposed. This method is based on integral ray optics approximation (IROA) which was intended specially for the determination of integral characteristics of electromagnetic waves propagation in three-dimensional inhomogeneous mediums |Prokopov, 1994). Below general equations of IROA technique are given and the results of research of new method in particular case of spherically stratified troposphere are presented.

New approach to the problem of determination of atmospheric refractivity corrections for space geodetic applications

Prokopov A., Remayev Y.

Reports on Geodesy

2000

z. 8/54

81-86

The effect of troposphere on electromagnetic waves propagation parameters is one of the most essential sources of errors in GPS measurements. The allowing for this effect can be executed by entering the corrections in results of measurements and by estimating the residual tropospheric delays at once from GPS signals (Collins, 1997). The final accuracy is determined in both cases by accuracy of the tropospheric delay dependence of satellite elevation angle - thecomplement of the zenith angle (this dependence usually is termed mapping function). Unfortunately mapping functions practically used are empirical functions obtaining by computer experiment with models for vertical profiles of refractive index of air. Biases appearing in this procedure decreases the accuracy of mapping functions and this is the cause of errors in tropospheric corrections determination as well as in restoring the parameters of troposphere basing on GPS measurements. To increase the accuracy of tropospheric effects modeling the new method of determination of tropospheric corrections for space geodetic applications in both optical and radio ranges (astronomy, SLR, SLR, GPS, VLBI) is proposed. This method is based on integral ray approximation (IROA) which was intended specialtly for the determination of integral characteristics of electromagntic waves propagation in three-dimensional inhomogenous mediums [Prokopov, 1994]. Below general equations of IROA technique re given and the results of research of new method in particulare method in particular case of spherically stratified troposphere are presented.