An alternative concept for SMOS-HR: unfolding the brightness temperature map by along-the-track inversion of the Van Cittert-Zernike equation

Launched in 2009, the SMOS satellite [1] produces observations of brightness temperature through passive microwave radiometry in the protected radio astronomy portion of the L-band. Although a given point on the Earth’s surface may be visible for 100 consecutive correlator integration times, brightness temperature measurements are produced one correlation period at a time, producing temperature maps that are both noisy and folded due to the antenna array’s undersampling of the u-v frequency plane. For a potential successor of SMOS, SMOS-HR [2], we show that a global inversion of the observation model (based on the Van Cittert-Zernike theorem) across the orbital trace could simultaneously unfold and denoise the observations. To this end, we take advantage of the shift-invariance of the inversion problem in geodesic coordinates.