Indermuehle and Lourenço present the first results of SNIFFLES, an observational programme to characterize intended emission, unwanted emission, and unintended radiation from non-geostationary satellite orbit (NGSO) systems across common radio astronomy receiver bands from 1 to 26 GHz.  Using the 22m Mopra radiotelescope, with follow-up observations from a single ATCA antenna, they conducted 4629 tracked observations of satellites from four NGSO constellations over 376 hours of telescope time.  Satellite identifications were confirmed by correlating detected Doppler shifts with predicted ephemerides. They detected 2345 instances of intended emission, unwanted emission, and unintended radiation at over 300 unique frequencies.  The detections span all three interference classes affecting radio astronomy: (1) intended emission, including Direct-to-Cell (DTC), (2) unwanted emission (out-of-band emission, often at the harmonics of intended emission), and (3) unintended radiation from satellite platform electronics.  Several detections fall within primary radio astronomy allocations, including 1613.19 MHz within the protected OH line band.  At 2700 MHz, unintended radiation was detected in 76.9 per cent of all observations of the relevant satellite version. ATCA follow-up measurements confirm flux densities up to 11 orders of magnitude brighter than typical astronomical sources, well in excess of levels that saturate radio astronomy receivers.  The SNIFFLES programme aims to provide the empirical basis for evaluating mitigation, supporting the development of electromagnetic interference (EMI) standards for space systems, and to demonstrate that sustainable long-term coexistence of NGSO constellations and ground-based radio astronomy is both necessary and achievable.

The figure above is an example of a waterfall plot showing the received power for Doppler-shifted curves from a satellite constellation. In this study, detections were categorized as being weak, strong, or intermittent based on their received power relative to the noise floor, the continuity of the curve, and the temporal stability across the observation.