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Nanosatellite missions represent a promising option for the exploration of the near-Earth asteroid population since they provide low-cost versatile platforms for scientific observations. This paper describes the preliminary orbital and navigation analyses for the DustCube mission, which was pre-selected to reach the binary asteroid system Didymos on-board ESA’s AIM spacecraft. Possible candidate orbits that exploit the binary nature of the system are identified and traded off to produce a preliminary concept of operations. The overall feasibility of the proposed scenario is then addressed by integrating the spacecraft trajectories in a realistic dynamical environment, evaluating their sensitivity to state errors, and estimating the accuracy of the orbit determination system. Preliminary results suggest that autonomous navigation of a Cubesat platform within a binary asteroid system is technically feasible. The proposed solution, which combines an initial parking orbit at the L4 equilibrium point with a Distant Retrograde Orbit for proximity operations, is shown to be consistent with the estimated orbit determination accuracy and allows to fulfil the mission requirements.

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. Together the missions represent the first humankind’s investigations of a planetary defense technique. In 2022, DART will impact Dimorphos, the secondary of the binary near-Earth asteroid (65803) Didymos. After 4 years, Hera will follow-up with a detailed post-impact survey of Didymos, to fully characterize and validate this planetary defense technique. In addition, Hera will deploy two CubeSats around Didymos once the Early Characterization Phase has completed, to augment the observations of the mother spacecraft. Juventas, the first Cubesat, will complete a low-frequency radar survey of the secondary, to unveil its interior. Milani, the second Cubesat, will perform a global mapping of Didymos and Dimorphos, with a focus on their compositional difference and their surface properties. One of the main objectives of Hera is to determine the binary system’s mass, gravity field, and dynamical state using radio tracking data in combination with imaging data. The gravity science experiment includes classical ground-based radiometric measurements between Hera and ground stations on Earth by means of a standard two-way X-band link, onboard images of Didymos, and spacecraft-to-spacecraft inter-satellite (ISL) radiometric tracking between Hera and the Cubesats. The satellite-to-satellite link is a crucial add-on to the gravity estimation of low-gravity bodies by exploiting the Cubesats’ proximity to the binary, as the range-rate measurements carried out by the inter-satellite link contain information on the dynamics of the system, i.e., masses and gravity field of Didymos primary and secondary.We will describe the updated mission scenario for the Hera radio science experiment to be jointly carried out by the three mission elements, i.e., Hera, Juventas and Milani. To conclude, our updated analysis and latest results, as well as the achievable accuracy for the estimation of the mass and gravity field of Didymos and Dimorphos, are presented.

To accurately estimate the mass of a comet, is a challenging task, given the complexity of its dynamical environment, and particularly so while close to perihelion, where the coma emissions are stronger. This study describes an operational approach for simultaneous orbit determination and mass estimation of a cometary target, using detailed dynamical models and combining measurements from multiple instruments. The testbed for the proposed approach is represented by the Proteus mission towards the main belt comets 288P and 238P-Read, for which formal uncertainties for the mass and other parameters of interest are estimated though a covariance analysis. It will be shown that the required relative accuracy of 10% in mass estimation can be achieved for both cometary targets under realistic operational conditions.

Nanosatellite missions represent a promising option for the exploration of the near-Earth asteroid population since they provide low-cost versatile platforms for scientific observations. This paper describes the orbital analysis for the DustCube mission, which was preliminarily selected to reach the binary asteroid system Didymos on-board ESA’s AIM spacecraft. Possible candidate orbits that exploit the binary nature of the system and satisfying the mission requirements and constraints were identified. The overall feasibility of the proposed Concept of Operations was then addressed by integrating the spacecraft trajectories in a realistic dynamical environment, evaluating their sensitivity to state errors, and estimating the accuracy requirements of the Orbit Determination and Control Subsystem (ODCS). The proposed operational concept proved consistent with the maneuvering capabilities of a CubeSat platform in terms of frequency of the station-keeping maneuvers and total delta-v budget. The proposed solution combines an initial parking orbit at the L4 equilibrium point with a Distant Retrograde Orbit for proximity operations, allowing to fulfil all mission requirements. However, this result is strictly coupled with the overall performance of the orbit determination system, which is required to allow for safe operations.