Regional remote sensing by near-space vehicle-borne passive radar system

Persistent regional monitoring is particularly valuable in remote sensing applications. Inspired by the advantages of near-space vehicles as compared to satellites and airplanes, this paper presents a regional remote sensing approach by near-space vehicle-borne passive bistatic radars. Note that near-space is defined as the altitude region between 20 and 100 km, which is too high up for conventional airplanes but too low for current satellites. We place passive radar receivers inside near-space vehicles which work in conjunction with opportunistic illuminators such as global positioning system (GPS), spaceborne radar, airborne radar or even ground-based radar as the transmitter, to provide a persistent monitoring. The comparative advantages of near-space vehicle as compared to satellite and airplane are investigated. The system models, signal processing algorithm, synchronization processing technique, and the conceptual design examples are presented. Since experimental data are not available for us, numerical simulation results are provided. Although passive radar is not a new concept, the originality of this paper lies in the matched filter reference signal extraction and synchronization processing algorithms.