AN ON-ORBIT CALIBRATION METHOD FOR CORRECTION MICROWAVE RADIOMETER BASED ON PHYSICAL MODEL AND NEURAL NETWORKS
Marzo 25, 2026THE FRONTEND OF THE ICE CLOUD IMAGER ONBOARD THE METOP SATELLITE B
Marzo 25, 2026G. Pomante1, P. Burghignoli1, D. Comite1
1Dipartimento di Ing. Informazioni Elettronica, Sapienza University Rome, Italy
Long-term satellite observation of Earth’s oceans and polar regions relies heavily on microwave radiometric data, particularly from dual-polarized satellite instruments. Polarimetric capabilities offer unique opportunities for retrieving geophysical parameters such as sea ice concentration, ocean surface wind vectors, sea surface temperature, and salinity. In this context, the European Copernicus Imaging Microwave Radiometer (CIMR), currently under development as part of the Copernicus Expansion Missions, is designed for monitoring sea ice parameters, both with relatively high spatial resolution (order of 5 km) and temporal resolution (sub-daily), and high geophysical accuracy.
CIMR is designed as a multi-frequency, conically scanning, polarimetric radiometer operating in the L, C, X, K, and Ka bands. Its architecture aims to also ensure continuity with predecessor missions such as AMSR-E/2, SMOS, and SMAP and to extend capabilities by targeting the retrieval of fully polarimetric data. Whereas the measurement of the first two elements of the Stokes vector is well consolidated, the estimation of the third and fourth remains technologically challenging due to their weak magnitude and a higher sensitivity to systematic effects introduced by the receiver chain and the antenna system.
The research in progress at Sapienza University develops a comprehensive modeling framework for the receiver chain of a polarimetric radiometer. The approach is based on a rigorous Stokes-vector formalism combined with Mueller-matrix representations, enabling an innovative end-to-end description of how the polarization state of incoming radiation is transformed by each component of the receiver. The chain is modeled as a series of interconnected blocks—antenna, ortho-mode transducer, amplification stages, and digitization modules—each represented by a suitable set of scattering matrices, which must be properly transformed into Mueller matrices. This methodology allows for systematically characterizing attenuation, cross-coupling, phase instabilities, and noise contributions of the various blocks. In the first stage, the analysis considers idealized noise-free devices, but it can also include equivalent noise temperatures.
Based on the proposed analytical modeling, we develop numerical simulations and uncertainty analyses. A Monte Carlo technique is employed to quantify the propagation of noise and systematic errors through the chain, providing a robust estimate of the instrument performance under realistic conditions, especially to simulate small magnitude values. These simulations will not only serve to validate the modeling framework but also offer insights into the design trade-offs and calibration requirements of future polarimetric radiometers.
The proposed modeling approach and calibration strategies are conceived to be general and applicable to any multi-frequency polarimetric radiometers. By developing a systematic framework to describe, simulate, and mitigate imperfections in receiver chains, this research aims to significantly enhance the performance assessment of the radiometric accuracy of polarimetric measurements from spaceborne radiometers.
DISCLAIMER: Views and opinion expressed are however those of the author(s) only and the European Commission and/or ESA cannot be held responsible for any use which may be made of the information contained therein.
