Multi-satellites precise orbit determination, an adaptable open-source implementation

Abstract

Orbit determination is a major feature in all operational flight dynamics systems. The most accurate research-level tools have been tuned for decades by agencies. They are generally not available to the public and are also very difficult to operate as user-friendliness is not their primary goal. Commercial off-the-shelf systems are available but at a high price tag and without any way for user to add their specificities. This paper describes the fully open-source orbit determination package that has been made available since 2016 in the Orekit space flight dynamics library. It presents first the history of the package and how it started as a tool for regular operations using classical measurements and how it evolved to include finer and finer models and new features like multi-satellites handling and exotic measurement types. The second part explains the philosophy behind some design choices like the adaptive computation of measurement corrections. Then it presents some technical details about the algorithms used under the hood, like partial derivatives computations or implementation of the multi-satellites features. Results and performances are shown. The paper ends with a presentation of a roadmap for future extensions.