Abstract
The European Space Agency (ESA) successfully launched the Soil Moisture and Ocean Salinity (SMOS) mission in November 2, 2009. SMOS uses a new type of instrument, a synthetic aperture radiometer named MIRAS that provides full-polarimetric multi-angular L-band brightness temperatures, from which regular and global maps of Sea Surface Salinity (SSS) and Soil Moisture (SM) are generated. Although SMOS operates in a restricted band (1400–1427 MHz), radio-frequency interference (RFI) appears in SMOS imagery in many areas of the world, and it is an important issue to be addressed for quality SSS and SM retrievals. The impact on SMOS imagery of a sinusoidal RFI source is reviewed, and the problem is illustrated with actual RFI encountered by SMOS. Two RFI detection and mitigation algorithms are developed (dual-polarization and full-polarimetric modes), the performance of the second one has been quantitatively evaluated in terms of probability of detection and false alarm (using a synthetic test scene), and results presented using real dual-polarization and full-polarimetric SMOS imagery. Finally, a statistical analysis of more than 13,000 L1b snap-shots is presented and discussed.
Highlights
The European Space Agency (ESA) mission “Soil Moisture and Ocean Salinity” (SMOS) was successfully launched on November the 2, 2009
The hexagon in the (ξ, η) domain corresponds to the full hexagonal period in which the synthetic image is formed by a kind of Fourier synthesis process from the (u, v) visibility samples acquired over a hexagonal grid determined by the characteristic Y-array of the MIRAS instrument aboard the SMOS
Detection and mitigation algorithm (Section 3.1). This approach throws away half of the data and would not make any use of the polarimetric information contained in Re[TXY] and Im[TXY], which can be very helpful in detecting the presence of radio-frequency interference (RFI)
Summary
The European Space Agency (ESA) mission “Soil Moisture and Ocean Salinity” (SMOS) was successfully launched on November the 2, 2009. 1400–1427 MHz band), which may interfere in an area of 50 km × 92 km (cross-track × alongtrack), for an error level of eμ ≥ 10−2 This behavior was confirmed by SMOS imagery, showing artifacts as North-South stripes (Figure 2). In these figures, the hexagon in the (ξ, η) domain corresponds to the full hexagonal period in which the synthetic image is formed by a kind of Fourier synthesis process from the (u, v) visibility samples (cross-correlations from the signals collected by pairs of antennas) acquired over a hexagonal grid determined by the characteristic Y-array of the MIRAS instrument aboard the SMOS mission [7].
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