Nanospacecraft fleet for multi-asteroid touring with electric solar wind sails

We propose a distributed close-range survey of hundreds of asteroids representing many asteroid families, spectral types and sizes. This can be implemented by a fleet of nanospacecraft (e.g., 4-5-unit CubeSats) equipped with miniature imaging and spectral instruments (from near ultraviolet to near infrared). To enable the necessary large delta-v, each spacecraft carries a single electric sail tether which taps the momentum from the solar wind. Data are stored in a flash memory during the mission and downlinked at an Earth flyby. This keeps deep-space network telemetry costs down, despite the large number of individual spacecraft. To navigate without the use of the deep-space network, optical navigation is required to track stars, planets and asteroids. The proposed mission architecture is scalable both scientifically and financially. A fleet of 50 spacecraft will be able to obtain images and spectral data from 200 to 300 near-Earth and main belt asteroids. It allows study of those asteroid families and spectroscopic types for which currently no close-range observations are available. This paper presents science objectives, overall science traceability matrix, example targets and technical challenges associated with the mission. We open to discuss preliminary requirements, mission and spacecraft designs.