Abstract
A novel mission concept applying satellite formation flight to passive microwave interferometry was recently proposed to significantly improve the interferometer’s spatial resolution. This concept was shown to sample the visibility in a hexagonal tile of polar grids, and to recover the brightness map, this visibility must be inverted via a discrete polar inverse Fourier transform. For a fast and accurate solution, this letter develops a modified hexagonal variant of the pseudo-polar fast Fourier transform (PPFFT) and its inverse and explores its performance when applied to the proposed formation-flight radiometer. Compared to the conventional rectangular PPFFT, we find approximately a fivefold improvement in the recovered radiometric accuracy, where the rms radiometric error is in the order of $10^{-2}$ K. The impact of visibility interpolation method is also explored, showing that an FFT-based interpolation technique leads to the most accurate final image recovery.
Highlights
A Hexagonal Pseudo-polar FFT for Formation-Flying Interferometric RadiometryAhmed Kiyoshi Sugihara El Maghraby , Angelo Grubišic , Camilla Colombo , and Adrian Tatnall
M ICROWAVE radiometers are highly versatile Earth observation instruments which map the brightness temperature of the Earth at specific microwave frequency bands
Choosing the frequency allows the observation of different features of the Earth; for example, the L-band (1.4 GHz) is most sensitive to ocean salinity and soil moisture, and radiometry at the resonance frequencies of oxygen and water molecules is the basis of atmospheric sounding
Summary
Ahmed Kiyoshi Sugihara El Maghraby , Angelo Grubišic , Camilla Colombo , and Adrian Tatnall. Abstract— A novel mission concept applying satellite formation flight to passive microwave interferometry was recently proposed to significantly improve the interferometer’s spatial resolution. This concept was shown to sample the visibility in a hexagonal tile of polar grids, and to recover the brightness map, this visibility must be inverted via a discrete polar inverse Fourier transform. For a fast and accurate solution, this letter develops a modified hexagonal variant of the pseudo-polar fast Fourier transform (PPFFT) and its inverse and explores its performance when applied to the proposed formation-flight radiometer. The impact of visibility interpolation method is explored, showing that an FFT-based interpolation technique leads to the most accurate final image recovery
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