Summary of Data Analysis of the YES2 Tethered SpaceMail Experiment

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The 2nd Young Engineers' Satellite (YES2) is a 36 kg student-built experiment that piggybacked on the Foton-M3 microgravity platform in September 2007. YES2 intended to demonstrate tethered SpaceMail, a concept for frequent sample return originally proposed for the International Space Station (ISS). This paper summarized the YES2 mission results. The planned tether deployment included a unique two-stage approach, a tether swing of 45 degrees and a capsule release from the bottom of the tether for increased landing precision. After a successful first stage, during the second stage the tether deployed to its full length of 31.7 km rather than the target length of 30 km due to an electrical problem. It was released at the proper time close to the nominal release point, sending Fotino some 1250 km upstream of the nominal landing point. The capsule was not yet recovered. The YES2 mission had the following scientific objectives: reconstruction of the deployment trajectory; estimation of the capsule trajectory and determination of the landing spot; assessment of the closed-loop control performance and potential landing accuracy; assessment of the deployer hardware performance for the SpaceMail application; study of tether physics and suitability of simulations and testing for planning future tether missions. All the tether mission objectives could be achieved, the novel deployment features were successfully demonstrated, any problem occurring was identified and solutions proposed. The quantity and quality of the data allows for improved understanding of tether dynamics and recommendation for future activities. Based on the lessons learned a sequel mission can be defined with promising perspectives.