MIRAS Calibration and Performance: Results From the SMOS In-Orbit Commissioning Phase

TLDR

The Soil Moisture and Ocean Salinity satellite launched in November 2009 began providing continuous data streams for processing. During the first six months, the satellite underwent an in‑orbit commissioning phase that involved extensive calibration of the Microwave Imaging Radiometer with Aperture Synthesis, including orbit‑based instrument mode checks, temperature characterization, internal calibration updates, and the first external calibration maneuvers to establish absolute calibration. The commissioning results show that the instrument achieves stable, well‑calibrated data with high radiometric accuracy, as evidenced by clear brightness‑temperature images of ocean, ice, and land produced using standard inversion techniques.

Abstract

After the successful launching of the Soil Moisture and Ocean Salinity satellite in November 2009, continuous streams of data started to be regularly downloaded and made available to be processed. The first six months of operation were fully dedicated to the In-Orbit Commissioning Phase, with an intense activity aimed at bringing the satellite and instrument into a fully operational condition. Concerning the payload Microwave Imaging Radiometer with Aperture Synthesis, it was fully characterized using specific orbits dedicated to check all instrument modes. The procedures, already defined during the on-ground characterization, were repeated so as to obtain realistic temperature characterization and updated internal calibration parameters. External calibration maneuvers were tested for the first time and provided absolute instrument calibration, as well as corrections to internal calibration data. Overall, performance parameters, such as stability, radiometric sensitivity and radiometric accuracy were evaluated. The main results of this activity are presented in this paper, showing that the instrument delivers stable and well-calibrated data thanks to the combination of external and internal calibration and to an accurate thermal characterization. Finally, the quality of the visibility calibration is demonstrated by producing brightness temperature images in the alias-free field of view using standard inversion techniques. Images of ocean, ice, and land are given as examples.