Data preprocessing for decametre wavelength exoplanet detection: An example of cyclostationary RFI detector

The relatively high contrast between planetary and solar low-frequency radio emissions suggest that the low-frequency radio range may be well adapted to the direct detection of exoplanets. Detection is based on temporal and spectral power integration to remove statistical fluctuations of the sky background noise. However, strong limitations, in particular due to radio frequency interference (RFI), may impair such detection. Indeed, if not detected, a RFI may be interpreted as an exoplanet signal or may conceal it. After a short summary of the detection principle in radio astronomy, we describe the algorithms proposed to remove RFI. First method, designed for rather strong RFI, is based on power threshold detection. The second one is based on the cyclostationary properties of amplitude modulation RFI. The main advantages of the latter are the detection of 1) weak RFI, 2) without confusion with potential signal. The statistics of this RFI detector are derived as a function of the integration time and the interference to noise ratio.