Dish-SUCA RaDICAL Passive Radar Using Starlink Downlinks as Spaceborne Illuminators of Opportunity

This paper presents an advanced implementation of the RaDICAL (Ranging, Detection, Imaging, Communications, and Approach & Landing) passive radar architecture that operates without a reference channel, using Starlink downlinks as Spaceborne Illuminators of Opportunity (SIoO). A Sparse Uniform Circular Array (SUCA) placed in the focal plane of a compact parabolic dish is introduced to form a hybrid Dish–SUCA aperture, enabling multifrequency dither across the receive elements. This technique converts a static reflector into a dynamically scanning antenna that intrinsically encodes range and direction-of-arrival (DOA) information within the received waveform. The paper develops a full electromagnetic and signal-processing model incorporating finite-range target-radar spherical-wave propagation, parabolic focusing, and multifrequency dither modulation. Numerical simulations quantify the effective aperture enhancement, received power, and detection probability under realistic Starlink-band conditions (10.7–12.7 GHz). Results show the reliable detection of − 10 dBsm targets at SNR ≥ − 10 dB using simple correlation-based detection. Monte Carlo analysis confirms near-unity detection probability above 10 dB SNR and a 50% threshold near − 2 dB. The proposed system can be realized on standard Starlink hardware with minimal modification, offering low cost, high sensitivity, and full global coverage. These findings demonstrate a feasible technological path toward autonomous, globally distributed passive radar networks that transform commercial satellite infrastructure into a persistent, space-supported sensor grid for continuous situational awareness.