Wide Field of View Microwave Interferometric Radiometer Imaging

Abstract

In microwave interferometric radiometers with a large field of view, as for example the Microwave Imaging Radiometer with Aperture Synthesis (MIRAS) onboard the Soil Moisture and Ocean Salinity (SMOS) satellite, one of the major causes of reconstruction error is the contribution to the visibility of the brightness temperature outside the fundamental period, defined on the basis of reciprocal grids. A mitigation method consisting of estimating this contribution through the application of a brightness temperature model outside the fundamental period is proposed. The main advantage is that it does not require any a posteriori addition of artificial scenes to the reconstructed image. Additionally, a method to avoid the sophisticated matrix regularization and inversion techniques usually applied in microwave interferometry is presented. Image reconstruction algorithms are implemented on a minimum grid size in order to maximize their numerical efficiency. An improved method to apply an apodization window to the reconstructed image for reducing Gibbs oscillations is also proposed. All procedures are generally described considering the single polarization case and successively implemented applying the MIRAS layout in both its single polarization and full polarimetric modes. Results show similar performance of the proposed algorithm with respect to the nominal one applied by SMOS. All algorithms are implemented in the MIRAS Testing Software and have been successfully used for scientific studies by other teams.

First SMOS Sea Surface Salinity dedicated products over the Baltic Sea

“…The up-to-date methods developed by the UPC in the recent years for reducing image reconstruction errors are also included in the MTS. Details on the used image reconstruction strategy can be found in Corbella et al (2009Corbella et al ( , 2019. Corbella et al (2015) showed that the dominant contribution to both Land/Sea Contamination (LSC) and the Ice/Sea Contamination (ISC) comes from residual multiplicative errors and proposed a 2% correction factor to the MIRAS correlator efficiencies (also known as the G kj correction).…”

New SMOS SSS maps in the framework of the Earth Observation data For Science and Innovation in the Black Sea

“…We use the MIRAS Testing Software (MTS) to obtain SMOS brightness temperatures at antenna reference frame from ESA SMOS Level 0 data (Corbella et al, 2008(Corbella et al, , 2009(Corbella et al, , 2019. We use ALL-LICEF mode as a calibration approach (Corbella et al, 2016) because with this calibration mode the measurements of the antenna temperature (zero-baseline visibility) and the rest of the visibility samples are more consistent.…”

A Novel Digital IQ Demodulation for Interferometric Radiometers

“…In an interferometric radiometer such as MIRAS, M kj is measured by a complex correlator, the system temperatures T sys k,j by "Power Measurement Systems" (PMS) included in each receiver, and G kj by internal calibration injecting correlated noise [9,10]. The visibility V kj is then solved from the above equation, and the brightness temperature is finally obtained by inverting the visibility equation [11].…”

“…in which (11) was used. This operation can be carried out for each individual receiver to obtain its corresponding center frequency, which in general are different from each other.…”