Small body missions can significantly benefit from deploying small landing systems onto the surface of the visited object. Despite the potential benefit that they may bring, deployments of landers in small body environments may entail significant mission design challenges. This paper thus addresses the potential of ballistic landing opportunities in binary asteroid moons from a mission design perspective, particularly focusing on reliability aspects of the trajectories. Two binaries that were previously identified as target bodies in several missions/proposals, Didymos and 1996 FG3, are considered in this paper. The dynamics near them are modeled by means of the Circular Restricted Three Body Problem (CR3BP), which provides a reasonable representation of a standard binary system. Natural landing trajectories that allow both minimum-velocity local-vertical touchdown and deployment from a safe distance are investigated. Coefficient of restitution values are used as a design parameter to compute the first touchdown speeds that ensure sufficient reliability of landing trajectories. A simple reliability index, which is derived via uncertainty ellipsoid from covariance analysis, is introduced to create a global reliability map across the asteroid surfaces. Assuming 3σ deployment errors on the order of 90 m and 2 cm/s, the results show that ballistic landing operations are likely to be successful for larger binary moons if the deployments target near equatorial regions within longitude range 320 o –20°. It has also been shown that the deployments to smaller binary moons may require higher accuracy in navigation and deployment systems in their mothership, and/or closer deployment distances.@en

Small body missions can significantly benefit from deploying small landing systems onto the surface of the visited object. Despite the potential benefit that they may bring, deployments of landers in small body environments may entail significant mission design challenges. This paper thus addresses the potential of ballistic landing opportunities in binary asteroid moons from a mission design perspective, particularly focusing on reliability aspects of the trajectories. Two binaries that were previously identified as target bodies in several missions/proposals, Didymos and 1996 FG3, are considered in this paper. The dynamics near them are modeled by means of the Circular Restricted Three Body Problem (CR3BP), which provides a reasonable representation of a standard binary system. Natural landing trajectories that allow both minimum-velocity local-vertical touchdown and deployment from a safe distance are investigated. Coefficient of restitution values are used as a design parameter to compute the first touchdown speeds that ensure sufficient reliability of landing trajectories. A simple reliability index, which is derived via uncertainty ellipsoid from covariance analysis, is introduced to create a global reliability map across the asteroid surfaces. Assuming 3σ deployment errors on the order of 90 m and 2 cm/s, the results show that ballistic landing operations are likely to be successful for larger binary moons if the deployments target near equatorial regions within longitude range 320 o –20°. It has also been shown that the deployments to smaller binary moons may require higher accuracy in navigation and deployment systems in their mothership, and/or closer deployment distances.@en

A planetary sunshade is a large, reflecting disk built to shield the Earth from a small fraction of solar irradiance and partly compensate global warming caused by greenhouse gas emissions. As a specific form of solar geoengineering, the sunshade is an emergency solution that would be implemented to prevent catastrophic climate change, while working towards the net-zero emission goal. In this paper, a dynamic sunshade is proposed. The motion of the sunshade is designed as a combination of static permanence at two equilibrium points above and below the ecliptic plane to shade the poles and a time-optimal transfer trajectory to connect these equilibrium points without overshading the tropical regions. Such a system is capable of not only reducing the global mean surface temperature anomaly, but also minimizing regional climate changes by tailoring the sunshade’s motion according to climate requirements, which is the primary goal of this work. A simplified climate model is used to evaluate the results of a given shading pattern, directly related to the sunshade’s trajectory. A dynamic sunshade with a radius of 1434 km and orbiting in the vicinity of the Sun-Earth L1 point is able to reduce the global mean surface temperature from 16.39˝C (scenario with 680 ppm of atmospheric CO2, double the amount with respect to the pre-industrial era) to 14.13˝C until equilibrium is reached. It also reduces the polar mean surface temperature (for latitudinal bands above 65˝) by more than 2˝C with respect to a scenario without sunshade and by 0.06˝C with respect to a static sunshade at the displaced L1 point. The optimal results are achieved when the sunshade is located at a distance equal to 30% of the Earth’s radius above and below the ecliptic plane. In addition, the transfers between the equilibrium points start respectively at day 56 and day 250, both measured from the 1st of January. @en

Remote sensing instrumentation onboard missions to asteroids is paramount to address many of the fundamental questions in modern planetary science. Yet in situ surface measurements provide the “ground truth” necessary to validate and enhance the science return of these missions. Nevertheless, because of the dynamical uncertainties associated with the environment near these objects, most missions spend long periods of times stationed afar. Small landers can be used much more daringly, however, and thus have already been identified as valuable assets for in situ exploration. This paper explores the potential for ballistic landing opportunities enabled by the natural dynamics found in binary asteroid systems. The dynamics near a binary asteroid are modeled by means of the circular restricted three-body problem, which provides a reasonable representation of a standard binary system. Natural landing trajectories are then sought that allow for a deployment from the exterior region and touchdown with minimum local-vertical velocity. The results show that, although landing on the main body of the system would require an effective landing system capable to dissipate excess of energy and avoid bouncing off the asteroid, the smaller companion offers the prospect of simple ballistic landing opportunities.@en