Radar Imaging and Analysis of Orbital Objects

More than positional data: state information in orbit

Reliable decision‑making in Earth orbit requires more than orbital parameters — it depends on understanding an object’s physical state. Structure, orientation, and rotation determine both risk and available courses of action. Radar imaging provides access to this information space over long distances and largely independent of lighting and weather conditions. Fraunhofer FHR relies on its space observation radar TIRA — Tracking and Imaging Radar — which combines precise tracking with high‑resolution imaging. The results are meaningful images and feature extractions of non‑cooperative targets at long ranges, complemented by transparent confidence levels and robust analytical reports. These capabilities strengthen modern space object characterization and advanced radar imaging.

From indication to detailed analysis: interplay between TIRA and GESTRA

Effective space reconnaissance requires the coordinated use of different sensor systems. Radars such as GESTRA provide wide‑area detection and regular monitoring of the visible low‑Earth orbit, delivering indications of relevant objects or anomalies. Building on this information, our large‑scale TIRA system enables precise orbit tracking and targeted high‑resolution analysis of individual objects. The coordinated use of these systems is managed by the German Space Situational Awareness Command, creating a seamless and effective process chain from detection to detailed characterization. This supports robust space surveillance workflows and enhances multi‑sensor fusion.

High‑resolution radar imaging with ISAR

For detailed analysis, we employ the Inverse Synthetic Aperture Radar (ISAR) technique. It uses an object’s own motion to reconstruct high‑resolution two‑dimensional images from sequential measurements. Combined with TIRA’s precise tracking, this enables detailed depictions of satellites and space objects at long distances. These images reveal geometric properties, rotational behavior, and structural features, providing a solid basis for further assessments. For example, TIRA supports the German Space Situational Awareness Center in the WRIS project (Space Identification Sensor) by contributing to the assessment and evaluation of the space environment. This strengthens advanced ISAR imaging and supports rotation state estimation.

Physical modeling

Reliable assessments in Earth orbit require physical models that realistically represent the structure, dynamics, and behavior of objects. Fraunhofer FHR links radar‑based measurement data — particularly from TIRA campaigns — with simulation‑based approaches. This enables the reconstruction of rotation states, geometries, and changes in non‑cooperative objects and their integration into dynamic models. These efforts support missions for active debris removal (ADR) and on‑orbit servicing (OOS), which are gaining importance in the context of the Zero Debris Charter. This strengthens debris removal analysis and dynamic object modeling.

Clients receive a scientifically sound and application‑oriented basis for evaluating proximity operations, risks, and intervention scenarios.

Practical example: analysis of the Aeolus re‑entry

The effectiveness of these methods was demonstrated during the controlled re‑entry of the Aeolus satellite mission. Fragmentation processes were analyzed in detail, providing valuable insights for assessing similar events. In additional measurement campaigns, we continue to develop methods for three‑dimensional reconstruction and techniques that derive reliable statements about object state and structure from limited observation data. These efforts support re‑entry analysis and fragmentation assessment.

Your benefit: reliable foundations for decision‑making

The resulting products — from high‑resolution images and feature analyses to motion parameters — can be directly integrated into existing situational awareness systems and decision‑making processes. Space agencies, security authorities, and industry partners gain a robust information base for risk assessments, mission planning, and operational decisions. Fraunhofer FHR offers measurement campaigns, analytical services, joint development projects, and more.