Enhancing orbit predictions and laser pointing alignment for SLR stations using TLEs and near real-time observations

Space safety is becoming an increasingly important topic for our society, in particular with respect to space debris. According to the ESA’s Space Environment Report 2025, the number of satellites, and, consequently, the amount of space debris, particularly in low Earth orbits (LEOs), is growing rapidly. This poses a significant challenge to the continued safety and functionality of space operations, which requires strategies to overcome. For collision avoidance, it is necessary to implement countermeasures such as tracking and monitoring space debris. The geodetic observation technique Satellite Laser Ranging (SLR) enables the measurement of distances to satellites and space debris with high-range resolution. However, it is essential to know the approximate positions of the space objects to be tracked via SLR in order to align the SLR station’s laser pointing accordingly. Since there are no accurate orbit predictions available for space debris, its approximate position is determined using the so-called two-line elements (TLEs). Unfortunately, TLEs have the disadvantage that they are restricted in their precision. To achieve a more precise laser alignment for space debris tracking, we present an approach to improve the accuracy of orbit predictions based on TLEs, using the SLR functionality of the Gravity Recovery Object Oriented Programming System (GROOPS) software toolkit. Validation using active satellite missions (Swarm-2 and LAGEOS-1) shows that fitting a dynamic orbit to TLE-based positions significantly stabilizes the orbit and reduces the along-track error. Furthermore, we demonstrate that incorporating a small number of near real-time measurements enhances the accuracy of orbit predictions and reduces the remaining time bias for station laser pointing alignment in subsequent passes. Final space debris measurement campaigns highlight the feasibility of using a freely available geodetic toolkit for high-precision space safety applications.