An analysis of close approaches and probability of collisions between LEO resident space objects and mega constellations

With the undergoing and planned implementations of mega constellations of thousands of Low Earth Orbiting (LEO) satellites, space will become even more congested for satellite operations. The enduring effects on the long-term space environment have been investigated by various researchers using debris environment models. This paper is focused on the imminent short-term effects of LEO mega constellations on the space operation environment concerned by satellite owners and operators. The effects are measured in terms of the Close Approaches (CAs) and overall collision probability. Instead of using debris environment models, the CAs are determined from integrated orbit positions, and the collision probability is computed for each CA considering the sizes and position covariance of the involving objects. The obtained results thus present a clearer picture of the space operation safety environment when LEO mega constellations are deployed. Many mega constellations are simulated, including a Starlink-like constellation of 1584 satellites, four possible generic constellations at altitudes between 1110 km and 1325 km, and three constellations of 1584 satellites each at the altitudes of 650 km, 800 km, and 950 km, respectively, where the Resident Space Object (RSO) spatial density is the highest. The increases in the number of CAs and overall collision probability caused by them are really alarming. The results suggest that highly frequent orbital maneuvers are required to avoid collisions between existing RSOs and constellation satellites, and between satellites from two constellations at a close altitude, as such the constellation operation burden would be very heavy. The study is not only useful for satellite operators but a powerful signal for various stakeholders to pay serious attention to the development of LEO mega constellations.