Global map showing SMAP Radio Frequency Interference during the month of March and April 2023. The height of the bar indicates the maximum RFI contribution to the antenna temperature (Kelvin) observed in horizontal polarization and the color indicates the persistence of the RFI averaged over a four week period (defined below)


SMAP has one of the most advanced Radio Frequency Interference (RFI) detectors currently in orbit. Even though the SMAP mission measures the brightness temperature of the Earth in the protected 1400-1427 MHz spectrum, SMAP measurements are still corrupted by RFI globally. This is an increasing problem for most microwave remote sensing missions, with limited spectrum available for scientific use and increased demand and competition for access. SMAP can detect and filter RFI at the cost of increased radiometric noise due to data excision. The figures below show the global and regional RFI persistence observed over various locations of the world over a period of one month from June to July 2021.

SMAP observed RFI levels are defined as the difference in Kelvin between the measured antenna temperatures before and after RFI detection and filtering. RFI persistence is determined first by gridding SMAP observed RFI levels onto a 0.25 deg x 0.25 deg map. The persistence percentage in a given pixel is then defined as the ratio of the number of measurements in that pixel whose RFI level exceeds 5 Kelvin divided by the total number of SMAP measurements averaged over a 4 week period. As an example, red colors in the Figures indicate persistent RFI observed 100% of the time over the observation period. The maps shown below use data in horizontal polarization.

For historical SMAP RFI data, please see: SMAP radiometer RFI

RFI - Global


RFI - North America


RFI - South America


RFI - Europe


RFI - Middle East


RFI - Asia


RFI - Africa


RFI - Australia


These images are generated by Dr. Alexandra Bringer at NASA Goddard Space Flight Center. Please contact her for further questions.


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