The Radio Science Experiment on Hera, Juventas and Milani

Hera, the European Space Agency’s first planetary defence mission, complements NASA’s DART mission as part of the Asteroid Impact and Deflection Assessment collaboration. Its primary objective is to conduct a detailed post-impact analysis of the Didymos binary asteroid system, with a focus on Dimorphos, the smaller moon impacted by DART. Hera will assess the effectiveness of the kinetic impactor technique for asteroid deflection while investigating the physical and compositional properties of Dimorphos. The mission’s radio science experimental setup includes an X-band radio link enabling two-way range and range-rate measurements as well as Delta-DOR observations, complemented by additional data from inter-satellite ranging with the Juventas and Milani CubeSats, optical navigation imaging, and altimetry. These measurements will enhance the accuracy of the post-impact data analysis. This paper summarizes the existing literature, outlines the experimental configuration and mission operations during the cruise phase and at the Didymos system, and discusses the expected scientific outcomes of Hera’s radio science experiment.