LICIACube: the Light Italian Cubesat for Imaging of Asteroids.

Introduction"LICIACube - the Light Italian Cubesat for Imaging of Asteroids"[1] is a CubeSat managed by the Italian Space Agency (ASI), that will be part of the NASA Double Asteroid Redirection Test (DART) mission [2].DART will be the first mission demonstrating the applicability of the kinetic impactor to change to motion of an asteroid in space and prevent the impact of Earth with a hazardous object.After being launched in summer 2021, the DART spacecraft will impact in autumn 2022 Dimorphos, the secondary member of the (65803) Didymos binary asteroid. With a mass of 650 kg and an impact velocity of about 6.6 km/s, DART is expected to change the binary orbital period of the 160-m Dimorphos by about 10 minutes, an effect that can be easily measured by ground-based telescopes.The design, integration and test of the CubeSat have been assigned by ASI to the aerospace company Argotec, while the LICIACube Ground Segment has a complex architecture based on the Argotec Mission Control Centre, antennas of the NASA Deep Space Network and data archiving and processing, managed at the ASI Space Science Data Center. The LICIACube team includes a wide scientific community, involved in the definition of all the aspects of the mission: trajectory design; navigation analysis (and real-time orbit determination during operations); impact, plume and imaging simulation and modelling, in preparation of a suitable framework for the analysis and interpretation of in-situ data. The scientific team is led by National Institute of Astrophysics (OAR, IAPS, OAA, OAPd, OATs) with the support of IFAC-CNR and University Parthenope of Naples. The team is enriched by University of Bologna, for orbit determination and satellite navigation, and Polytechnic of Milan, for mission analysis and optimization.The major technological mission challenge, i.e. the autonomous targeting and imaging of such a small body during a fast fly-by, to be accomplished with the limited resources of a CubeSat, is affordable thanks to a strong synergy of all the mentioned teams in support of the engineering tasks.Nominal missionDART probe will be launched in mid-2021 and LICIACube will be hosted as piggyback during the 15 months of interplanetary cruise, then released 10 days before the impact and autonomously guided along its fly-by trajectory. In Figure 1 the nominal mission is shown. LICIACube downlinks images direct to Earth after the target fly-by.Figure 1- The LICIACube nominal mission.Scientific ObjectivesLICIACube has the aim to testify the main probe impact on Dimorphos, the secondary member of the (65803) Didymos binary asteroid system, and to perform dedicated scientific investigations.Several unique images of the effects of the DART impact on the asteroid, such as the formation and the development of the plume potentially determined by the impact will be collected and transmitted to Earth.The scientific objectives of LICIACube are:Testify and characterize the DART impact; Obtain multiple (at least 3) images of the ejecta plume taken over a span of time and phase angle, that, with reasonable expectations concerning the ejecta mass and particle size distribution, can potentially: Allow measurement of the motion of the slow (< 5 m/s) ejecta: this requirement is intended as the possibility to acquire images at spatial scale better than 5 m/pixel, with the possibility to distinguish the movements of the slowest particles of the plume by the sequence of images. Allow estimation of the structure of the plume, measuring the evolution of the dust distribution; Obtain multiple (at least 3) images of the DART impact site with a sufficient resolution to allow measurements of the size and morphology of the crater. These images will be taken sufficiently late after the impact that the plume can be reasonably expected to have cleared; Obtain multiple (at least 3) images of Dimorphos showing the non-impact hemisphere, hence increasing the accuracy of the shape and volume determination. The whole project and its present status-of-the-art will be presented and discussed together with the in situ observing strategy and the expected performances.