LICIACube: Italian deep space small satellite technology for the Asteroid Redirection Test (DART) mission

The Double Asteroid Redirection Test (DART) mission is part of the plan developed by NASA for the Planetary Defence program, since space mission towards asteroid have become crucial to study their composition. Moreover, these missions are the future of space exploration, providing opportunities for testing novel technologies for extreme conditions. These are some of the many reasons why NASA developed the Double Asteroid Redirection Test (DART) mission and the Italian Space Agency joined the effort. DART is a spacecraft acting as a kinetic impactor that will deflect the orbit of a binary asteroid by crashing itself into the moonlet of the Didymos binary system. In order to increase the accuracy of the deflection measurement, the ASI 6U Light Italian CubeSat for Imaging of Asteroid (LICIACube) will be carried on DART and released by the main probe in proximity of the target. The effects of the impact will be observed also from ground-based telescopes. The small satellite that will be the only witness of this event, LICIACube, is an Italian Space Agency project, and has been designed, integrated and tested by the assigned aerospace company Argotec. The primary objective of LICIACube is to capture photographs of DART impact ejecta plume over a span of times and phase angles in order to confirm the DART impact on the secondary body of the Didymos binary asteroid system and to observe the ejecta plume dynamics. After the deployment from the DART spacecraft, LICIACube will perform braking manoeuvers, to increase the relative velocity with respect to DART spacecraft, allowing LICIACube to perform the scientific phase and fulfil the mission objectives. Following this phase, the LICIACube satellite will continue on its path for few months, transferring scientific data and performing radio-science experiments. Many of the scientific objectives will be accomplished by using the autonomous navigation algorithm and the imaging capabilities provided by the baseline platform, based on the heritage of the Argotec company. The images acquired by LICIACube will help the Italian involved scientific community to obtain relevant discoveries about the binary asteroid system.

The mission is articulated in a series of single critical moments: LICIACube will be deployed by DART 120 hours before the impact on Didymos B; the satellite will fly-by the asteroid with a relative velocity of 6.5 km/s, and it will document the effects of the impact, the crater and the evolution of the plume generated by the collision. To acquire images with the best spatial resolution, LICIACube will aim at fly-bying the asteroid close to the Didymos-B surface: considering the high relative velocity at the close approach, LICIACube will have to maintain the asteroid's pointing at an angular speed of approximately 10 deg/s. Scientific objectives will be accomplished by using the autonomous navigation algorithm and the imaging capabilities provided by the platform, based on the heritage of the Argotec company. The two optical payloads embarked on LICIACube have the duty of acquiring the images that are then processed on board through the navigation algorithm, thus allowing to identify the asteroid system, distinguish the main and secondary bodies and control the satellite attitude in order to keep the asteroid pointing during fly-by. The navigation algorithm is mainly based on neural network trained on ground using photorealistic images of the binary asteroid system and the plume generated by the impact.

The images acquired and downlinked by the LICIACube satellite will help the scientific community to obtain more detailed results about the binary asteroid, and provide feedback to the Planetary Defense program, pioneered by the Space Agencies. The scientific team is enriched by University of Bologna team, supporting the orbit determination and the satellite navigation, Polytechnic of Milan, for mission analysis support and optimization and INAF (National Institute of Astrophysics), providing support in the scientific operations of the satellite. The LICIACube mission will be a challenging opportunity for the entire Italian technical and scientific community leading to the implementation of a deep space mission based on a small scale but highly technological platform.