Gerd A. Wagner, German Aerospace Center (DLR), Institute of Technical Physics; Wolfgang Riede, German Aerospace Center (DLR), Institute of Technical Physics; Thomas Dekorsy, German Aerospace Center (DLR), Institute of Technical Physics
Keywords: Optical Systems, Orbital Debris, Space Situational Awareness (SSA) / Space Domain Awareness (SDA)
Abstract:
Todays established radar capabilities are the backbone of satellite monitoring and orbital debris detection for SSA around the world. However, passive and active optical systems using lasers can provide additional and unique object information in terms of orbit, attitude, shape, material composition, and activity status. Within the past 3 years, the Institute of Technical Physics of the German Aerospace Center (DLR) has built an optical observatory at a site located 60 km South of Stuttgart (Germany). The site provided necessary infrastructure and fulfilled security requirements. Furthermore, light pollution is at a much lower level compared to the previously operated station within Stuttgart city. The project started in May 2019 and site acceptance test was successfully completed in October 2021. Three main SSA topics will be addressed at the newly built observatory: passive (camera) observations, active laser ranging, and spectral analysis of satellites and space debris. The observatory building including slit dome is 15 m in height and has 2 levels. Level 1 serves as lab space with 2 optical tables and additional electronic racks and level 2 is the telescope level. The 1.75 m telescope (f/6 Ritchey-Chrétien design) with Coudé path option serves as main component for satellite laser ranging, space debris detection, and SSA technology development in the near-infrared spectral region at the observatory. Four Nasmyth ports at the telescope can be selected by rotation of the tertiary mirror of the telescope and enable object analysis using various detectors during a single object flyover. A piggy-back installed astrograph with an aperture of 40 cm and a field of view of 3° provides additional guidance of the main telescope and supports initial orbit determination of unknown objects. Efficient eye-safe lasers based on solid-state and fiber technology in the near-infrared spectral region (1400-1700 nm) are being deployed for ranging and backscatter measurements. The light of the 1.75 m telescope can be fiber-coupled and guided to a grating spectrograph for object composition measurements and cataloguing. Prior implementation to the observatory, all optical and electronic components including lasers and detectors are tested and specified at the institute labs. Additionally, a transportable laser ranging station is co-located at the observatory site to enable bi-static laser ranging measurements to satellite and space debris. It can be deployed and operated within a few hours to a new location and is fully remotely controllable. The transportable station has the size of a standard ISO-container and features an on-board laser system, a 43 cm aperture receiver telescope, and an electronics system for satellite and space debris laser ranging. Furthermore, synergies of radar and laser ranging SSA technologies are investigated within the course of this project. We believe that radar could provide initial object orbit information followed by a more precise laser ranging measurement (radar to laser handover). This contribution presents the development and current operational status of the observatory and transportable laser ranging station and demonstrates selected object tracking, passive observations, and active laser ranging capabilities of satellite and space debris in low Earth orbit (LEO). Furthermore, radar and laser station handover strategies for initial orbit determination are discussed.
Date of Conference: September 27-20, 2022
Track: Optical Systems & Instrumentation