Feasibility Analysis of On-Orbit Debris Detection Using Commercial Star Trackers

Abstract

The U.S. Space Surveillance Network (SSN) currently tracks over 23,000 resident space objects (RSOs) in low- earth orbit (LEO). The SSN uses ground-based radar and optical methods, which are susceptible to variations in atmosphere, weather, and lighting conditions. These barriers limit the surveillance capabilities to objects with characteristic length greater than 10 cm. Consequently, hundreds of thousands of smaller RSOs in LEO remain untracked, reducing overall space situational awareness. Prior research has demonstrated the feasibility of using space-based commercial star trackers (CSTs) to detect and track objects larger than 10 cm in characteristic length. The analysis we present in this paper shows that CSTs can also be used to detect debris particles below 10 cm in size. We model particles as Lambertian spheres with zero phase angle and ten percent reflectivity. The apparent visual magnitude of debris particles is expressed as a function of particle size and RSO-CST distance and compared against the sensitivity levels of a variety of CSTs. We find that, when properly illuminated, debris of characteristic length between 1 cm and 10 cm can be detected by some CSTs even at distances of tens of kilometers. More sensitive CSTs can characterize RSOs at the larger end of this scale (i.e., 10 cm) hundreds of kilometers away; alternatively, they can track objects smaller than 1 cm at closer distances.