Space-based visible observation strategy for beyond-LEO objects based on an equatorial LEO satellite with multi-sensors

Many space-based visible observation strategies based on Low Earth Orbit (LEO) satellites for observing Geosynchronous Orbit (GEO) objects were proposed previously. However, there were few studies about other beyond-LEO objects (Geostationary Transfer Orbit (GTO) objects, Medium Earth Orbit (MEO) objects, and Molniya objects). In this paper, a space-based visible observation strategy is proposed for observing GEO objects, GTO objects, MEO objects (especially global navigation satellites), and Molniya objects simultaneously to get more orbital data, using an earth-oriented equatorial LEO satellite with three sensors. This work is focused on the pointing geometry. Brightness of observed objects and sensitivity of sensors are assumed under the relative ideal conditions. First, the distribution characteristics of these beyond-LEO objects are discussed. And in order to observe global navigation satellites efficiently, joint regions formed by the track superposition of two adjacent orbits in a constellation are proposed. To offset the influence of the earth shadow and constraint of sun-target-observer angle, two sensors pointing inside of the equatorial plane are used to observe GEO and GTO objects. The installation angle of the third sensor is optimized to obtain a relative high coverage rate for observing global navigation satellites and Molniya objects based on joint regions. Finally, the coverage rate, the number of observations, and observation duration under different sensors with different field of views (FOVs) are compared and analyzed respectively.