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The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense, intended to validate kinetic impact as a means of asteroid deflection. Here we report the first determination of the momentum transferred to an asteroid by kinetic impact. Based on the change in the binary orbit period, we find an instantaneous reduction in Dimorphos's along-track orbital velocity component of 2.70 +/- 0.10 mm/s, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact. For a Dimorphos bulk density range of 1,500 to 3,300 kg/m$^3$, we find that the expected value of the momentum enhancement factor, $\beta$, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg/m$^3$, $\beta$= 3.61 +0.19/-0.25 (1 $\sigma$). These $\beta$ values indicate that significantly more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos., Comment: accepted by Nature

Light Italian Cubesat for Imaging of Asteroids (LICIACube) is an Italian mission managed by the Italian Space Agency (ASI) and part of the NASA Double Asteroid Redirection Test (DART) planetary defense mission. Its main goals are to document the effects of the DART impact on Dimorphos, the secondary member of the (65803) Didymos binary asteroid system, characterizing the shape of the target body and performing dedicated scientific investigations on it. Within this framework, the mission Science Operations Center will be managed by the Space Science Data Center (ASI-SSDC), which will have the responsibility of processing, archiving, and disseminating the data acquired by the two LICIACube onboard cameras. In order to better accomplish this task, SSDC also plans to use and modify its scientific webtool Multi-purpose Advanced Tool for Instruments for the solar system Exploration (MATISSE), making it the primary tool for the LICIACube data analysis, thanks to its advanced capabilities for searching and visualizing data, particularly useful for the irregular shapes common to several small bodies.

The Light Italian Cubesat for Imaging of Asteroids (LICIACube) is part of the NASA Double Asteroid Redirection Test (DART), the first mission aiming to demonstrate the applicability of the kinetic impactor method for planetary defense. The mission was launched on 2021 November 24 to perform the impact experiment on Dimorphos, the small secondary of the binary asteroid (65803) Didymos. The 6U LICIACube, stored as a piggyback of the DART spacecraft, is the first Italian mission operating in deep space managed by the Italian Space Agency that will witness the effects of the DART impact on Dimorphos. On board LICIACube, there is a suite of cameras that will perform imaging of Didymos and Dimorphos to investigate the DART impact effects and study the binary system. Among them, the LICIACube Unit Key Explorer (LUKE), a wide-angle camera coupled to an RGB Bayer pattern filter, will be pivotal to constrain the surface composition and heterogeneity of the binary system due to differences in surface properties linked with possible space weathering effects and/or the presence of exogenous material. Multiband photometric analysis of LUKE data and laboratory experiments in support of data interpretation will provide new insights on the binary asteroid nature and evolution. Moreover, photometric phase curve analysis will reveal the scattering properties of the granular surface medium providing important constraints for the microphysical properties of the Didymos–Dimorphos system. In this work, we will present the state of the art of the LUKE scientific activities with an overview of the instrument setup, science operations, and expected results.

Introduction. Besides being objects of great scientific interest, Near-Earth Asteroids (NEAs) also represent a potential threat to human life and civilization. Several space mission concepts have been proposed to prevent the collision of a NEA on course towards Earth, most of them aiming to slightly deflect it from its catastrophic orbit. Among them, the so-called “kinetic impactor” is currently considered the most mature one. This technique is based on a momentum transfer imparted via an impactor spacecraft launched into an interplanetary intercept trajectory that crashes onto the asteroid at high velocity, changing its orbit. DART will be the first test in real scale of this technique. 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 Dimorphos, the 160-m moon of Didymos (780-m in size), by about 10 min, an effect that can be easily measured by ground-based telescopes (Rivkin et al. 2021; Cheng et al. 2018). LICIACube is the first purely Italian spacecraft to be operated in deep space, it is managed by ASI and it is under development by a large team of engineers and scientists, with the aim to contribute in the NASA DART Planetary Defence objective (Dotto et al. 2021). LICIACube Mission Scenario LICIACube will be launched with DART, hosted as a piggyback and released 10 days before the DART impact and autonomously guided along its fly-by trajectory (see Fig. 1). The aim of this mission is to testify the DART impact and obtain multiple images of the ejecta plume, of the impact site and of the nonimpact hemisphere. After commissioning phase and braking and correction maneuvers LICIACube will approach the target at a minimum distance of about 55 km, and will perform the scientific phase during the asteroid’s fly-by (Capannolo et al. 2021). After that, LICIACube will downlink the obtained images directly to Earth. The architecture of the LICIACube Ground Segment is 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 where images are planned to be integrated in the MATISSE tool (Zinzi et al, 2016; 2019) for visualization and analysis. The LICIACube payload and observing strategy The LICIACube mass is about 13 kg: it is developed by Argotec and equipped with two different payloads named LEIA and LUKE (Fig. 2). LEIA (Liciacube Explorer Imaging for Asteroid) is a narrow FoV camera able to acquire images with a spatial scale close to 1.4 m/px at the minimum distance of about 55 km, while LUKE (Liciacube Unit Key Explorer) is a wide FoV imager with an RGB Bayer pattern filter. LEIA and LUKE will offer the opportunity to obtain a unique science return, investigating for the first time the nature of a binary NEA. Comparing the impact and non-impact regions, as well as studying the nature and the evolution of the produced dust plume, will allow us to deeply investigate the composition and the structure of the material composing a small double NEA. As a general approach each planned observation will be formed by a sequence of different images acquired at the maximum frame rate possible and possibly with different integration times. Starting from about 45 s before T0, the nominal DART impact time, five different acquisition phases have been foreseen (Fig. 3). DART impact observation (red); Ejecta observation (yellow); High resolution observation of the surface properties and the crater (blue); Non-impact hemisphere observation (green); Plume evolution in forward scattering (purple). Data Exploitation The navigation radiometric data acquired during the scheduled tracking passes, along with the images collected before and during the encounter, will be used for an opportunity radio science experiment, to put constraints on the gravity of Didymos. Images acquired by LEIA and LUKE will allow us to constrain the shape and volume of Dimorphos as well as its physical properties. High-resolution images, obtained by LEIA at the closest approach, will allow us to study the surface morphology of Dimorphos and the presence of boulders/large blocks on its surface. By comparing pre- and post-impact surface areas we will have the unique opportunity to witness how the boulders size-frequency distribution and density changed as a result of the DART impact. The LUKE data will give us also the opportunity to investigate the composition of Dimorphos throughout spectrophotometric analyses. So we will be able to map the surface composition of the object and to derive the surface heterogeneity at the observed scale. The images of the plume, compared with numerical models of dust dynamics, will allow us to have measurements of the motion of the slow ejecta and to estimate the structure of the plume. References. Capannolo A., et al. (2021), Acta Astronautica, Volume 182, p. 208. Cheng A. F., et al. (2018) PSS, 157, 104. Dotto E., et al. (2021) PSS, 199, id. 105185 Rivkin A.S., et al. (2021) Planetary Science Journal, in press. Zinzi A. et al. (2016) Astron. Comput., 15, 16-28. Zinzi A. et al. (2019) EPSC-DPS Joint Meeting 2019, id. EPSC-DPS2019-1272. Acknowledgements. The LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP F84I190012600).

In 2021, the DART spacecraft will be launched by NASA to intercept the binary system Didymos and impact the moonlet (Dimorphos), to test the effectiveness of kinetic impactors for the deviation of hazardous asteroids’ trajectories. The impact is expected to generate a cloud of particles, whose study could provide valuable data about asteroid’s properties and impact models. Observations from ground to characterize ejecta and plume evolution after impact would be possible, but the resulting quality would be significantly lower than a short-range imaging. In this framework, ASI (Italian Space Agency) and NASA started a collaboration to embark on the US DART vehicle the LICIA (Light Italian CubeSat for Imaging Asteroid) 6U CubeSat as a piggyback payload. LICIA is devoted to grasp science data by imaging the ejecta plume after the impact, and observe Dimorphos surface while flying by the binary system. The Italian consortium involved in the mission sees ARGOTEC for the platform development, and INAF, Politecnico di Milano and Universita di Bologna to cover the mission science, trajectory design and orbit de-termination tasks, respectively. The paper focuses on the mission analysis and maneuvers design, strongly driven by the science return, under the tight constraints enforced by the platform. In particular, it describes the preliminary procedure followed to derive trajectory constraints and to select the best option for the flyby. Despite the mission is still under development, and subjected to frequent updates of several parameters, the final performances derived in this paper maintain their validity as they represent the desired target values for the mission.

The Asteroid Impact and Deflection Assessment (AIDA) is an international collaboration supported by ESA and NASA to assess the feasibility of the kinetic impactor technique to deflect an asteroid, combining data obtained from NASA’s DART and ESA’s Hera missions [1, 2]. In 2022, DART will perform a kinetic impact on the secondary of the binary near-Earth asteroid (65,803) Didymos, recently named Dimorphos. After 2 years, Hera will follow-up with a detailed post-impact survey of Didymos, to fully characterize this planetary defense technique. Additionally, Hera will deploy two CubeSats around Didymos once the Early Characterization Phase has completed, to complement the observations of the mother spacecraft and increase the scientific return of the mission. The first Cubesat, called Juventas, will complete a low-frequency radar survey of the secondary, to unveil its interior, while the second one has not yet been selected.One of the main objectives of Hera is to characterize the mass and mass distribution of both Didymos primary and secondary by means of radio science investigations. This paper describes the concept of the gravity science investigations to be jointly carried out by the three mission elements, i.e. Hera, Juventas and CubeSat-2. The experiment will combine classical ground-based radiometric measurements, spacecraft-based optical images of Didymos, and Satellite-to-Satellite radiometric tracking between Hera and the Cubesats. Finally, our results and achievable accuracy for the estimation of the mass and gravity field of Didymos and Dimorphos are presented. 1. IntroductionMost of the information about the formation processes of an asteroid lies in its interior structure. One of the very few constraints of the internal mass distribution of a celestial body is given by its gravity field, even if the inversion process is not unique. First, the bulk density can be inferred by measuring the mass of the body, combined to the volume estimated from optical images. In addition, the higher degrees of the gravity field provide information about the internal distribution of mass, such as the moments of inertia.The main scientific goals of the Hera radio science investigations are: Determine the mass and gravity field of Didymos and Dimorphos; Reconstruct the motion of Dimorphos around Didymos; Contribute to the characterization of the energy transfer between DART and Dimorphos. Such objectives are a valuable contribution to the Hera mission objectives, leading to a better understanding of the formation and evolution processes of the Didymos system. 2. TechniqueThe determination of the gravity field of a celestial body is an application of the orbit determination process of deep space spacecraft. In particular, the gravity of Didymos can be estimated precisely reconstructing the trajectory of Hera during a selected number of close encounters (about 10 km at closest approach). The classical observables used in the orbit determination are obtained from the X-band radio link between the spacecraft and the Earth. The microwave signal is sent to spacecraft from a ground antenna and coherently retransmitted back to Earth, where Doppler and range measurements are obtained. A previous study performed for the AIM proposed mission [4] demonstrated that gravity science at Didymos is feasible using radio tracking data only, under realistic assumptions on the technological capabilities of the space and ground segment. Shorter pericenter distances increase the attainable accuracy. However, a significant improvement can be obtained even at relatively large distances processing also optical images of Didymos and Dimorphos taken by the spacecraft.In addition, Hera may track Juventas and CubeSat-2 by means of a space-to-space inter-satellite link (ISL), capable of determining the relative distance (ranging) and the relative line-of-sight velocity (Doppler) between the two bodies. In particular, the latter is expected to represent a very nice add-on to the gravity investigation carried out by the Hera mission, as the Doppler shift that affects the inter-satellite link contains the information on the dynamics of the system, i.e. masses and gravity field of Didymos and Dimorphos.The expected accuracy in the estimation of Didymos gravity fields were obtained through numerical simulations of the orbit determination of Hera and the two Cubesats. Conservative assumptions were made in terms of both radiometric and optical measurement noises, and large a-priori uncertainties for the estimated parameters were used. 3. ResultsAs a result of the numerical simulations, the masses of Didymos and Dimorphos are expected to be estimated with relative uncertainties less than 10-4 and 10-3, respectively. The addition of the ISL measurements improves the achievable accuracies but it is not required to estimate the masses. However, given the relatively large distance of Hera from the system, the higher degree gravity of Didymos and Dimorphos can be estimated only adding the ISL Doppler measurements between the Cubesats and the mother spacecraft. In this case, the gravity field of Didymos can be estimated to at least degree 3, depending on the assumptions about the ISL operations and performance. Similarly, ISL Doppler measurements allows to estimate the extended gravity field of Dimorphos up to degree 2, with an uncertainty of about 10%. Acknowledgements This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870377 (project NEO-MAPP). MZ, IG, ML, EG, RLM, and PT wish to acknowledge Caltech and the Jet Propulsion Laboratory for granting the University of Bologna a license to an executable version of MONTE Project Edition S/W. References[1] Cheng A. F., et al., “AIDA DART asteroid deflection test: Planetary defense and science objectives,” Planet. Space Sci., vol. 157, no. February, pp. 104–115, 2018.[2] Michel, P., et al. “European component of the AIDA mission to a binary asteroid: Characterization and interpretation of the impact of the DART mission”. Adv. Space Res. (2018), Volume 62, Issue 8, pp. 2261-2272.[3] Lasagni Manghi, R., Modenini, D., Zannoni, M., Tortora, P., “Preliminary orbital analysis for a CubeSat mission to the Didymos binary asteroid system”, Adv. Space Res. (2018), Volume 62, Issue 8, pp 2290-2305[4] M. Zannoni, G. Tommei, D. Modenini, P. Tortora, R. Mackenzie, M. Scoubeau, U. Herfort, I. Carnelli, “Radio science investigations with the Asteroid impact mission”, Adv. Space Res. (2018), Vol. 62, Issue 8, pp. 2273-2289.

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 mission DART 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 Objectives LICIACube 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. Acknowledgements: The LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP F84I190012600). References [1] Dotto, E., et al.: LICIACube - the Light Italian Cubesat for Imaging of Asteroids: in support of the NASA DART mission towards asteroid (65803) Didymos, Plan. Space Sci., 2020, submitted. [2] Cheng, A. F., at al.: AIDA DART asteroid deflection test: Planetary defense and science objectives, Plan. Space Sci., Vol. 157, pp. 104-115, 2018.

Hera is ESA’s contribution to an international effort supported by ESA and NASA named Asteroid Impact and Deflection Assessment (AIDA). NASA’s DART mission will first perform a kinetic impact on Didymos secondary, nicknamed Didymoon, then Hera will follow-up with a detailed post-impact survey, to fully characterize this planetary defense technique. Two CubeSats will be deployed by the Hera spacecraft once the Early Characterization Phase has completed.The Hera spacecraft communicates with the ground station on the Earth by means of a standard two-way X-band system. The microwave signal is sent to the S/C from a ground antenna and coherently retransmitted back to Earth, where Doppler (the key observable for gravity science) and range measurements are obtained. In addition, Hera will track the two CubeSats by means of a space-to-space inter-satellite link (ISL). This represents a very nice add-on to the gravity investigation carried out by means of Hera tracking observables as the Doppler effect that affects the inter-satellite link contains the information on the dynamics of the system, i.e. masses and gravity field of Didymos primary and secondary.We describe here the mission scenario for the gravity science experiments to be jointly carried out by the three mission elements, i.e. Hera, CubeSat#1 (named Juventas) and CubeSat#2, via Ground-based and Satellite-to-Satellite Doppler Tracking. Also, our results and achievable accuracy for the estimation of the mass and gravity field of Didymos primary and secondary are presented.

The NASA Double Asteroid Redirection Test (DART) mission will be the first test to check an asteroid deflection by a kinetic impactor. The target of DART mission is the secondary element of the (65803) Didymos binary asteroid system and the impact is expected in late September - early October, 2022. The DART S/C will carry a 6U cubesat called LICIACube (Light Italian Cubesat for Imaging of Asteroid), provided by the Italian Space Agency, with the aim to collect pictures of the impact's effects. The impact of the 610 kg DART spacecraft at 6.58 km/s on the 163 m Didymos B will result in a change of the binary orbital period of about 10 minutes assuming momentum transfer efficiency ? = 1. Values of ? > 1 are expected because the produced ejecta carries momentum, primarily in the direction opposite the DART speed direction. The LICIACube mission profile consists in a flyby of Didymos system with closest approach about 3 minutes after the DART impact. LICIACube will be able to acquire the structure and evolution of the DART impact ejecta plume and will obtain high-resolution images and also in 3 colour of the surfaces of both bodies. The nominal mission foresees also imaging of the Dydymos B non-impact hemisphere. The contributions of LICIACube observations to the DART investigations are important for determination of the momentum transfer efficiency ?, that is a crucial result of the planetary defence test. Moreover, captured images can enable scientific investigations about the main features of the asteroid system. In order to check the imaging capability and to optimize the fast scientific phase of LICIAcube, the LICIA team performed several simulations of pictures' acquisition. In these simulations, considering the specifications of the 2 optical payloads and the foreseen mission design, we reconstructed synthetic images mainly of the plume. As the plume evolution remains the most important uncertainty, since it depends on a very high number of impacting phase parameters, we simulated imaging of different expected evolution behaviours, to obtain instrument operative parameters and to prepare the data analysis.

In Autumn 2022, the NASA Double Asteroid Redirection Test Mission (DART) will impact the surface of asteroid Dimorphos, a ~165 m body orbiting around asteroid (65803) Didymos, with the main aim to demonstrate the kinetic impactor technique for Planetary Defense. During the last minutes of the mission, the DRACO scienti c camera onboard DART will image the surface of both the primary and the secondary asteroids at different spatial scales, allowing the detection of boulders larger than 0.6-1.5 m on the impacted side of Dimorphos and larger than 11-21 m on Didymos. To complement such observations, the ASI "Light Italian Cubesat for Imaging of Asteroids" (LICIACube) will be released from DART ten days before the impact and will be then autonomously guided through a yby with closest approach distance of 55 km from Dimorphos. Through the LEIA (LICIACube Explorer Imaging for Asteroid) narrow angle camera, it will be possible to safely witness the DART redirection test in situ, while its crater and the ejecta and plume are being formed. At closest approach LEIA will image Dimorphos at ~2 m/px: we will therefore be able to identify all boulders larger than 4-7 m located on the imaged side of the asteroid. The analysis of the boulder surface densities and size frequency distributions (SFD) on Didymos and Dimorphos will be important to understand the processes that originated them (impact cratering versus parent body disruption). In addition, we will compare the SFD derived on the binary asteroid with those obtained on other S-type or carbonaceous minor bodies, highlighting the similarities and differences. In this work, the results of the boulder SFD expected from both LICIACube and DART images are presented. Acknowledgments: This research was supported by the Italian Space Agency (ASI) within the LICIACube project (ASI-INAF agreement AC n. 2019-31-HH.0).

“LICIACube – the Light Italian Cubesat for Imaging of Asteroids” is managed by the Italian Space Agency (ASI) and will be part of the NASA DART mission, with the aim of i) documenting the DART impact’s effects on the secondary member of the (65803) Didymos binary asteroid system, ii) characterizing the shape of the target, and iii) performing dedicated scientific investigations on it. DART probe will be launched at the end of 2021 and LICIACube will be hosted as piggyback during the interplanetary cruise, then released 10 days before the impact, and autonomously guided along its fly-by trajectory. The LICIACube payload is composed by LEIA, a narrow FoV camera, and LUKE, a wide FoV imager with an RGB Bayer pattern filter, that will collect and transmit to Earth 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. LICIACube will be the first deep space mission developed and autonomously managed by an Italian team: 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 Center, 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 Italian scientific community, involved in the definition of all the aspects of the mission: trajectory design; mission definition (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 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.

In 2021, the DART spacecraft will be launched by NASA to intercept the binary system Didymos and impact the moonlet (Didymoon), to test the effectiveness of kinetic impactors for the deviation of hazardous asteroids' trajectories. The impact is expected to generate a cloud of particles, whose study could provide valuable data about asteroid's properties and impact models. Observations from ground to characterize ejecta and plume evolution after impact would be possible, but the resulting quality would be significantly lower than a short-range imaging. In this framework, ASI (Italian Space Agency) and NASA started a collaboration to embark on the US DART vehicle the LICIA (Light Italian CubeSat for Imaging Asteroid) 6U CubeSat as a piggyback payload. LICIA is devoted to grasp science data by imaging the ejecta plume just after the impact, while flying by Didymoon. To this end, our analyses underlined that the small vehicle shall be detached from DART several hours before the impact to gain the needed separation from the US spacecraft, and to be on time for impact and ejecta plume imaging, a few minutes after occurrence. Moreover, LICIA scientific goals include imaging the back side of Didymoon, while keeping flying along the binary on its escape leg. The Italian consortium involved in the mission sees ARGOTEC for the platform development, and INAF, Politecnico di Milano and Università di Bologna to cover the mission science, trajectory design and orbit determination tasks, respectively. The paper focuses on the mission analysis and maneuvers design strongly driven by the science return in plume tracking and imaging, under the tight constraints the small platform imposes in terms of agility and control authority. Occurred trade-offs, related to the trajectory design, and navigation and guidance baseline settings to balance the science objectives and the risk mitigation constraints, are discussed in deep. Detailed robustness analysis will show criticalities related to the uncertainties in the flyby trajectory, associated with the cubesat subsystems accuracy. An optimization of correction maneuvers and time windows for Deep Space Networks contacts is finally presented, to show how the deviation of the nominal trajectory can be mitigated to ensure the mission being compliant with the science goals.