Near-space vehicles: Supply a gap between satellites and airplanes for remote sensing

Near-space is defined as the atmospheric region from about 20 kilometer (km) to 100 km above the Earth´s surface; near-space vehicles offer several advantages to Low Earth Orbit (LEO) satellites and airplanes because near-space vehicles are not constrained by orbital mechanics and fuel consumption. Some of the near-space vehicle advantages include their potential for some specific radar applications that require persistentiy monitoring or fast-revisiting frequency which are explained herein. The role of near-space vehicles is reviewed in supplying a gap between satellites and airplanes for microwave remote sensing applications. Several potential applications such as passive surveillance, reconnaissance, and high resolution wide swath imaging are described. The novel multiple-input and multiple-output (MIMO)-based multi-aperture in elevation and space-time coding (STC) synthetic aperture radar (SAR) are presented for high resolution wide swath imaging. Therefore, given their operational flexibility, near-space vehicle-borne radars may supply the gap between space-borne and airborne radars which is the reason we appeal to the systems engineering community for more publications and more support on the research and development of near-space vehicle-borne radars.