Toward Vicarious Calibration of Microwave Remote-Sensing Satellites in Arid Environments

Christoph Rudiger, Jeffrey Walker, Yann Kerr, Edward Kim, Jorg Hacker, Robert Gurney, Damien Barrett, John Le Marshall

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    12 Citations (Scopus)


    The Soil Moisture and Ocean Salinity (SMOS) satellite marks the commencement of dedicated global surface soil moisture missions, and the first mission to make passive microwave observations at L-band. On-orbit calibration is an essential part of the instrument calibration strategy, but on-board beam-filling targets are not practical for such large apertures. Therefore, areas to serve as vicarious calibration targets need to be identified. Such sites can only be identified through field experiments including both in situ and airborne measurements. For this purpose, two field experiments were performed in central Australia. Three areas are studied as follows: 1) Lake Eyre, a typically dry salt lake; 2) Wirrangula Hill, with sparse vegetation and a dense cover of surface rock; and 3) Simpson Desert, characterized by dry sand dunes. Of those sites, only Wirrangula Hill and the Simpson Desert are found to be potentially suitable targets, as they have a spatial variation in brightness temperatures of <4 K under normal conditions. However, some limitations are observed for the Simpson Desert, where a bias of 15 K in vertical and 20 K in horizontal polarization exists between model predictions and observations, suggesting a lack of understanding of the underlying physics in this environment. Subsequent comparison with model predictions indicates a SMOS bias of 5 K in vertical and 11 K in horizontal polarization, and an unbiased root mean square difference of 10 K in both polarizations for Wirrangula Hill. Most importantly, the SMOS observations show that the brightness temperature evolution is dominated by regular seasonal patterns and that precipitation events have only little impact.

    Original languageEnglish
    Article number6547697
    Pages (from-to)1749-1760
    Number of pages12
    JournalIEEE Transactions on Geoscience and Remote Sensing
    Issue number3
    Publication statusPublished - Mar 2014


    • Calibration
    • environmental monitoring
    • passive microwave remote sensing
    • soil moisture


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