Microwave Imaging Radiometers by Aperture Synthesis—Performance Simulator (Part 1): Radiative Transfer Module

Adriano Camps,Jorge Bandeiras,Jose Barbosa,Hyuk Park,Manuel Martin-Neira,Ana Sousa,Salvatore D’Addio

doi:10.3390/jimaging2020017

Abstract

The Synthetic Aperture Interferometric Radiometer Performance Simulator (SAIRPS) is a three-year project sponsored by the European Space Agency (ESA) to develop a completely generic end-to-end performance simulator of arbitrary synthetic aperture interferometric radiometers. This means, on one side, a generic radiative transfer module from 1 to 100 GHz, including land and ocean covers, as well as a fully 3D atmosphere and Faraday ionospheric rotation based on variable TEC. On the other hand, the instrument can have an arbitrary array topology (number of antenna elements, and their time-dependent position and orientation). Receivers’ topology can also be modified, starting from a very generic one to connecting and disconnecting subsystems, whose parameters can be individually configured. These parameters can be defined either by mathematical functions or by input data files, including the frequency and temperature dependence. Generic calibration and image reconstruction algorithms that are suitable for arbitrary array topologies have also been implemented, as well as tools to compute the instrument performance metrics, i.e., radiometric accuracy, sensitivity, angular resolution, etc. This manuscript presents the generic architecture of the SAIRPS, the algorithms implemented in the Radiative Transfer Module, and simulation results showing its performance. A companion manuscript (Part II) describes the instrument and calibration modelling, the image reconstruction algorithms, and the validation tests that were performed.

Highlights

Synthetic aperture radiometry was developed in the 1950s to obtain high-resolution radio images of the sky
The Geometry Module, which is capable of simulating arbitrary antenna positions and orientations in the array, that are defined individually as time-dependent variables
In the previous section a detailed description of the models used to create synthetic brightness temperature (BT) images to be used in the simulation of synthetic aperture interferometric radiometers (SAIRs) was presented

Summary

Introduction

Synthetic aperture radiometry was developed in the 1950s to obtain high-resolution radio images of the sky. J. Imaging 2016, 2, 17 radiometry, brightness temperature maps were obtained by either a mechanical or electrical scan of a large antenna. In synthetic aperture interferometric radiometers (SAIRs), brightness temperature images are formed through a Fourier synthesis process in a snapshot basis, after cross-correlating all the signal pairs collected by the array elements. The mean value of the image is measured using at least one real aperture radiometer connected to one of the antenna elements. Array elements are located in a plane, and the Z-axis is orthogonal to it, but this is not a restriction of the Fourier synthesis process itself

Methods

Results

Conclusion