Theory and Implementation of an End-to-End Radio Occultation Simulator

In this report we present the results of a project aimed at developing an end-to-end radio occultation simulator. The project was a cooperation between Chalmers University of Technology, RUAG Space AB, and OHB Sweden, and financed by the Swedish Space Board within the second National Space Research Program (NRFP-2). The simulator includes a wave optics propagator (WOP) capable of simulating realistic GNSS signals as they propagate through the Earth’s atmosphere using realistic refractivity, a routine for propagating the signal to LEO, a routine for adding noise to the received signal, and a routine for interpreting the signals in the terms of bending angle and impact height (in our case achieved using phase matching). In this report we go through the theory behind each of these techniques, we describe how to implement them in Matlab, and we evaluate the accuracy of each step. In addition to this, and in order to evaluate the results from the code, it was necessary to make a detailed investigation into geometrical optics (GO) and the Abel transform. Mainly to find a fast and accurate way to calculate the results from geometrical optics, but as a spin-off we also present a small investigation into the problem with Abel inversion for super-refractive refractivity profiles.

[1]  M. E. Gorbunov,et al.  Comparative analysis of radioholographic methods of processing radio occultation data , 2000 .

[2]  A. Sommerfeld.  Partial Differential Equations in Physics , 1949 .

[3]  Chi O. Ao,et al.  Effect of ducting on radio occultation measurements: An assessment based on high‐resolution radiosonde soundings , 2007 .

[4]  S. Flatté,et al.  Intensity images and statistics from numerical simulation of wave propagation in 3-D random media. , 1988, Applied optics.

[5]  X. Zou,et al.  Analysis and validation of GPS/MET data in the neutral atmosphere , 1997 .

[6]  H. H. Benzon,et al.  Full Spectrum Inversion of radio occultation signals , 2003 .

[7]  E. Wolf,et al.  Principles of Optics (7th Ed) , 1999 .

[8]  Anthony J. Mannucci,et al.  Lower troposphere refractivity bias in GPS occultation retrievals , 2003 .

[9]  M. Levy.  Parabolic Equation Methods for Electromagnetic Wave Propagation , 2000 .

[10]  J. R. Eyre,et al.  A nonlinear optimal estimation inverse method for radio occultation measurements of temperature, humidity, and surface pressure , 2000, physics/0003010.

[11]  R. A. Silverman,et al.  Wave Propagation in a Turbulent Medium , 1961 .

[12]  D. Knepp.  Multiple phase-screen calculation of the temporal behavior of stochastic waves , 1983, Proceedings of the IEEE.

[13]  M. E. Gorbunov.  Radioholographic Methods for P Rocessing Radio Occultation Data in Multipath Regions , 2001 .

[14]  Sergey Sokolovskiy,et al.  Modeling and inverting radio occultation signals in the moist troposphere , 2001 .

[15]  M. E. Gorbunov,et al.  Canonical transform method for processing radio occultation data in the lower troposphere , 2002 .

[16]  E. Kursinski,et al.  The GPS Radio Occultation Concept: Theoretical Performance and Initial Results , 1997 .

[17]  Christian Rocken,et al.  Detection of high‐altitude ionospheric irregularities with GPS/MET , 2002 .

[18]  Benjamin M. Herman,et al.  The GPS radio occulation technique , 2000 .

[19]  G. Fjeldbo,et al.  Atmosphere of Venus as Studied with the Mariner 5 Dual Radio‐Frequency Occultation Experiment , 1969 .

[20]  M. E. Gorbunov,et al.  Microlab‐1 experiment: Multipath effects in the lower troposphere , 1998 .

[21]  F. Xie.  Development of a GPS Occultation Retrieval Method for Characterizing the Marine Boundary Layer in the Presence of Super-Refraction , 2006 .

[22]  M. Gorbunov,et al.  Linearized Zverev Transform and its application for modeling radio occultations , 2007 .

[23]  M. Gorbunov,et al.  Analysis of wave fields by Fourier integral operators and their application for radio occultations , 2004 .

[24]  Anders Berg,et al.  Metop-GRAS in-orbit instrument performance , 2009 .

[25]  X. Zou,et al.  Use of GPS/MET refraction angles in three‐dimensional variational analysis , 2000 .

[26]  E. Karayel,et al.  Sub‐Fresnel‐scale vertical resolution in atmospheric profiles from radio occultation , 1997 .

[27]  Lennart Bengtsson,et al.  Advanced algorithms of inversion of GPS/MET satellite data and their application to reconstruction of temperature and humidity , 1996 .

[28]  H. Benzon,et al.  Geometrical optics phase matching of radio occultation signals , 2004 .

[29]  S. Sokolovskiy.  Effect of superrefraction on inversions of radio occultation signals in the lower troposphere , 2003 .

[30]  G. M.,et al.  Partial Differential Equations I , 2023, Applied Mathematical Sciences.

[31]  Benjamin M. Herman,et al.  An Approach for Retrieving Marine Boundary Layer Refractivity from GPS Occultation Data in the Presence of Superrefraction , 2005 .

[32]  J. Goodman.  Introduction to Fourier optics , 1969 .