Abstract: As the “fifth airspace” bridging near space and outer space, the Ultra Low Earth Orbit (ULEO) domain boasts comprehensive advantages unmatched by traditional orbits in ultra-high-resolution remote sensing, low-latency high-signal-to-noise-ratio communication, and civilian emergency backup services for public livelihood, making it a frontier field prioritized by major space powers. However, constrained by unique challenges such as significant atmospheric drag and severe environmental disturbances, ULEO satellites currently face the core bottlenecks of being “difficult to sustain, difficult to stabilize, and difficult to fully utilize.” Targeting the requirements of long-term operational applications, this paper systematically reviews the key technology systems and development pathways for ULEO spacecraft. First, in terms of environmental awareness, multi-modal environmental detection techniques and methods for constructing high-precision atmospheric models are discussed. Second, in terms of platform technology, the analysis focuses on advanced propulsion systems centered on air-breathing electric propulsion, aerodynamic simulation and drag reduction design, intelligent orbit and attitude control strategies addressing strong time-varying nonlinear disturbances, as well as high-flux atomic oxygen protection technologies. Additionally, in terms of payload and information processing, the current development status of low-latency communication, sub-target-level high-resolution remote sensing payloads, and onboard information processing technologies adapted to the ULEO environment is elaborated. Finally, analysis shows that ULEO development urgently needs to bridge the gap from simulation verification to engineering application. Future efforts should focus on key technology breakthroughs such as the development of air-breathing electric propulsion prototypes, integrated aerodynamic drag reduction design, high-precision attitude and orbit control, and onorbit flight verification, to support the construction and application of next-generation space-based systems.

Key words: Ultra Low Earth Orbit (ULEO), Air-Breathing Electric Propulsion (ABEP), aerodynamic drag reduction, atomic oxygen protection, high-resolution remote sensing