Tracklet-based correlation of combined radar and optical measurements

The ongoing growth of the space debris population leads to an increasing importance of space surveillance tasks to build and maintain knowledge about the object densities in different Earth orbits. Due to numerous fragmentation events, also the highly elliptical orbits contain increasing amounts of space debris. For standard survey measurements, objects in these orbits are either detected by radar close to their perigee or by telescopes close to their apogee. Usually, one single sequence of measurements, called tracklet, is too short to obtain a reliable orbit and instead two tracklets are combined to test if they originate from the same object. This process is called correlation. If radar and optical measurements are treated separately, only limited information about the orbit is available. To improve the processing of these objects, this paper proposes a method for the correlation and initial orbit determination by combining radar and optical tracklets. The method is based on a previously developed radar-only method, which also includes corrections of the J2-perturbations. Simulated survey measurements are used to test the new method and compare it to the radar-only case. It is shown that the radar-optical correlation achieves satisfying results. It also matches the measurements better and gives more precise orbits compared to the radar-only approach.