Analysis of impact of radar antenna mispointing for the WIVERN doppler wind radar ESA Earth Explorer Mission

Earth observation satellites are an increasingly important tool for studying the behavior of the Earth's atmosphere and even more for the behavior of climatological phenomena. In these cases, the critical point of modern science and engineering is effectivily the monitoring and development of increasingly accurate predictive models. WIVERN (Wind Velocity Radar Nephoscope) mission aims to measure atmospheric winds with innovative precision in the field. This is done employing a Doppler radar, characterized by a section of the electromagnetic spectrum in the W band, which is a region with a wavelength of approximately 4 – 2.7 mm and covers the respective range between 110 GHz and 75 GHz. It is also necessary to calculate the reflectivity of the Earth's surface to obtain these measurements. This helps to decouple from the taken measurements every contribution that is not related to hydrometeors. This work proposes a MATLAB-simulator to precisely calculate this quantity, integrating the reflected power of the radar signal from the surface. The western part of Piedmont has been chosen as a region of interest to test the simulator with an accurate and very particular orographic profile. All the georeferenced information, including the elevation value, is included in a matrix of points known as the Digital Elevation Model (DEM), obtained from the website EarthData (supplied by NASA). These data are the starting point for calculating the power equation and transmission power, wavelength, and other constants. The software model computes and processes variables such as the point-satellite distance, the projection of the antenna gain on the surface, the backscattering cross-section of the radar, and the area of the projected surface for each pixel. However, since each pixel is characterized by different georeferenced information, a vectorization process has been developed and used to obtain all the values required for analysis. Moreover, part of the model calculates which points are in the shadow of the satellite so as not to calculate their contribution to the final integral. Once the integral has been calculated, the corresponding reflectivity value is obtained through an equation that links the different quantities. Many of the variables evaluated and examined during the program are then schematized in tables and figures to describe better how the tool works.