Experimental validation of the Corbella's visibility function using HUT-2D and MIRAS

Abstract

The Corbella's revision of the fundamental equation of the interferometric aperture synthesis radiometry is verified using airborne and spaceborne data. This experimental verification uses the measurements of the airborne instrument HUT-2D from the Aalto University (Helsinki), and the unique spaceborne microwave imaging radiometer by aperture synthesis (MIRAS) from the ESA's Soil Moisture and Ocean Salinity (SMOS) mission. The data acquired with those sensors support the Corbella's revision of the visibility function. The revised function predicts that visibilities depend on the contrast between the target's brightness temperature and the backward noise of the receivers emitted through the antennas.

Detection of a Sea Surface Salinity Gradient Using Data Sets of Airborne Synthetic Aperture Radiometer HUT-2-D and a GNSS-R Instrument

“…The results confirmed the validity and some major consequences of the new visibility equation [Publication I]. Other studies that suggest the validity of the new equation are described in[117], where measurements of airborne HUT-2D over various targets are analyzed. Also measurements of sky by the MIRAS payload are considered there.The new visibility equation twists two essential elements from the instrument's performance point of view.…”

“…Such studies are carried out e.g. in studies of the fringe-washing calibration [151], and for imaging validation [117].…”

“…[125], [126] To cope with the increased influence of antenna pattern errors, and to take advantage of the sky as a strong known source revealed by the new equation, a new calibration method, FTT, was proposed in [Publication The activity for the validation of the Corbella equation is continued beyond [Publication I] using measurements of MIRAS and HUT-2D in [117].…”

SMOS instrument performance and calibration after six years in orbit

“…The Corbella equation, introduced in 2003(Corbella et al, 2004a, involves a fundamental modification to the formulation of interferometry, as used in radio-astronomy, that is necessary to describe the way an aperture synthesis radiometer of the type of MIRAS works. The calibration of SMOS is based on the Corbella equation, and hence, one of the first and most important tasks undertaken in the frame of the calibration of the instrument was its verification (Martín-Porqueras et al, 2010). Such exercise would ideally involve the imaging of two perfectly uniform black body targets at two different physical temperatures.…”