Impact of antenna tuning on SMOS correlation loss

Abstract

The Soil Moisture and Ocean Salinity (SMOS) mission by the European Space Agency (ESA) was launched in 2009 [1]. Since then, it has produced a continuous stream of valuable geophysical data over land, ice and ocean [2] However, a problem which does persist is the so-called land-sea contamination (LSC) effect, an artificial increase of brightness temperature around large land masses that enters into the ocean several hundreds of kilometers. This artifact has been found to be caused by an inconsistency between the multiplicative error that affects the zero baseline (antenna temperature) and the error affecting the rest of baselines (correlations). This inconsistency is related to about 2% measurement overestimation of the correlation efficiency (fringe washing function at the origin) that produces a scene dependent bias in the retrieved brightness temperature [3]. It must be pointed out that correlation efficiency is periodically measured on-board by means of an internal noise injection scheme [4]. Since antenna frequency response is not included in the noise injection loop, this paper is devoted to assess its potential impact in SMOS end-to-end increased correlation loss.