MIRAS (Microwave Imaging Radiometer with Aperture Synthesis), the single payload of the ESA-SMOS mission, consists of a Y-shape interferometric radiometer basically formed by 72 receivers placed along the three arms. Cross-correlations of the signals collected by each receiver pairs "k,j" give the samples of the so-called visibility function, V_kj, which develops into a brightness temperature map by means of a Fourier transform. Therefore, phase errors in the visibility samples are directly translated into image distortion through this Fourier process. The phase is calibrated by injecting correlated noise to its receivers. A method to track phase errors due to temperature gradients has been developed in order to increase the intercalibration period, thus maximizing coverage. Due to the large size of the instrument (arms length around 4 m) and power constraints, moderate thermal swings and thermal gradients within the payload are unavoidable along the orbit. The method presented in this work shows how the visibility phase errors are decoupled into receiver phase errors that can be tracked in temperature. Experimental tests show how decoupling must deal with phase-wrapping problems and cope with the interferometric inherent problem of setting a phase reference in a temperature changing environment.

Date Published: 9 October 2008
PDF: 8 pages
Proc. SPIE 7106, Sensors, Systems, and Next-Generation Satellites XII, 71061U (9 October 2008); doi: 10.1117/12.800118

Published in SPIE Proceedings Vol. 7106:
Sensors, Systems, and Next-Generation Satellites XII
Roland Meynart; Steven P. Neeck; Haruhisa Shimoda; Shahid Habib, Editor(s)