DNS (v1.0): an open-source ray-tracing tool for space geodetic techniques

Abstract

We have developed an open-source ray-tracing tool for space geodetic techniques. The software uses the geometric optics approximation to calculate the signal travel time delay induced by the atmosphere between two given points. The software called DNS (“Direct Numerical Simulation of signal travel time delay”) is written in Fortran and uses OpenMP to speed up computation. The input to the ray-tracing tool is 3D pressure, temperature and humidity fields. The Earth’s magnetic field and electron density field are optional. For the neutral atmosphere (troposphere) the software accepts the NetCDF files from the atmospheric reanalysis ERA5 and the mesoscale model WRF. For the ionosphere the software accepts electron density fields derived from IRI and NeQuick. We review the current status of the software and test its performance. For example, the one-to-one comparison with the open-source software RADIATE shows the high speed and precision of our ray-tracing tool. We also show how our tool can be used to study higher-order ionospheric effects (L-band frequencies). The two outstanding features of the ray-tracing tool compared to previous model developments, i.e. the ability to handle both the troposphere and the ionosphere and do so efficiently, make it perfectly suited for geoscientific applications.