Passive Spacebourne SAR Using Opportunity of Illumination

Synthetic Aperture Radar (SAR) can operate regardless of the weather condition or the availability of sunlight. However, the cost of launching an active SAR satellite is still relatively expensive given the stringent requirements of high radio frequency (RF) power needed to illuminate the target. In this paper, we propose a framework for a passive SAR satellite that opportunistically captures signals transmitted by another nearby active SAR satellite. The idea of such opportunistic configuration is based on bistatic radar, where the passive radar is assumed to be capable of estimating the reference signal originating from the active satellite. The proposed geometry considers the passive satellite to be launched to follow the same orbital plane of the active one but with a small delay. In order to demonstrate the concept, a SAR simulator is utilized to generate the unfocused raw data, which is later on is focused using the range-Doppler (RDA) processing algorithm. According to the achieved results, the proposed technique is feasible to be applied and implemented practically on the future SAR systems to generate a low-cost and high-quality SAR image.