J.P. Sanchez

Asteroid resource map for near-Earth space

Most future concepts for the exploration and exploitation of space require a large initial mass in low Earth orbit. Delivering this required mass from the Earth’s surface increases cost due to the large energy input necessary to move mass out of the Earth’s gravity well. An alternative is to search for resources in-situ among the near Earth asteroid population. The near Earth asteroid resources that could be transferred to a bound Earth orbit are determined by integrating the probability of finding asteroids inside the Keplerian orbital element space of the set of transfers with an specific energy smaller than a given threshold. Transfers are defined by a series of impulsive maneuvers and computed using the patched-conic approximation. The results show that even moderately low energy transfers enable access to a large mass of resources.

Low Energy, Low-Thrust Capture of Near Earth Objects in the Sun-Earth and Earth-Moon Restricted Three-Body Systems

In this paper a method to retrieve asteroids incorporating low-thrust propulsion into the invariant manifolds technique is investigated. Assuming that a tugboat-spacecraft is in a rendez-vous condition with the candidate Near Earth Object (NEO), the aim is to take the joint spacecraft-asteroid system to selected periodic orbits of the Earth–Moon restricted three-body system: the orbits can be either libration point periodic orbits (LPOs) or distant periodic orbits around the Moon, both prograde (DPOs) and retrograde (DROs). In detail, low-thrust propulsion is used to bring the joint spacecraft-asteroid system from the initial condition to a point belonging to the stable manifold associated to the final periodic orbit: from here onward, thanks to the intrinsic dynamics of the physical model adopted, the flight is purely ballistic. The idea is to couple together the Sun–Earth and the Earth–Moon models following the ”patched restricted three-body problems approximation”, therefore allowing the spacecraft-asteroid system to fly along the interplanetary manifold trajectories, explicitly exploiting the hyperbolic transit orbits flying by L1 and L2. Dedicated capture sets are introduced to exploit the combined use of low-thrust propulsion with stable manifolds trajectories, aiming at defining feasible first guess solutions. An optimal control problem is then formulated to refine them. This approach enables a new class of missions, whose solutions are not obtainable neither through the patched-conics method nor through the classic invariant manifolds technique.

The Castalia mission to Main Belt Comet 133P/Elst-Pizarro

We describe Castalia, a proposed mission to rendezvous with a Main Belt Comet (MBC), 133P/Elst-Pizarro. MBCs are a recently discovered population of apparently icy bodies within the main asteroid belt between Mars and Jupiter, which may represent the remnants of the population which supplied the early Earth with water. Castalia will perform the first exploration of this population by characterising 133P in detail, solving the puzzle of the MBC’s activity, and making the first in situ measurements of water in the asteroid belt. In many ways a successor to ESA’s highly successful Rosetta mission, Castalia will allow direct comparison between very different classes of comet, including measuring critical isotope ratios, plasma and dust properties. It will also feature the first radar system to visit a minor body, mapping the ice in the interior. Castalia was proposed, in slightly different versions, to the ESA M4 and M5 calls within the Cosmic Vision programme. We describe the science motivation for the mission, the measurements required to achieve the scientific goals, and the proposed instrument payload and spacecraft to achieve these.

Optimal Sunshade Configurations for Space-Based Geoengineering near the Sun-Earth L1 Point.

Within the context of anthropogenic climate change, but also considering the Earth’s natural climate variability, this paper explores the speculative possibility of large-scale active control of the Earth’s radiative forcing. In particular, the paper revisits the concept of deploying a large sunshade or occulting disk at a static position near the Sun-Earth L1 Lagrange equilibrium point. Among the solar radiation management methods that have been proposed thus far, space-based concepts are generally seen as the least timely, albeit also as one of the most efficient. Large occulting structures could potentially offset all of the global mean temperature increase due to greenhouse gas emissions. This paper investigates optimal configurations of orbiting occulting disks that not only offset a global temperature increase, but also mitigate regional differences such as latitudinal and seasonal difference of monthly mean temperature. A globally resolved energy balance model is used to provide insights into the coupling between the motion of the occulting disks and the Earth’s climate. This allows us to revise previous studies, but also, for the first time, to search for families of orbits that improve the efficiency of occulting disks at offsetting climate change on both global and regional scales. Although natural orbits exist near the L1 equilibrium point, their period does not match that required for geoengineering purposes, thus forced orbits were designed that require small changes to the disk attitude in order to control its motion. Finally, configurations of two occulting disks are presented which provide the same shading area as previously published studies, but achieve reductions of residual latitudinal and seasonal temperature changes.

Accessibility of the resources of near Earth space using multi-impulse transfers

Most future concepts for exploration and exploitation of space require a large initial mass in low Earth orbit. Delivering this mass requires overcoming Earths natural gravity well, which imposes a distinct obstacle to space-faring. An alternative for future space progress is to search for resources in-situ among the near Earth asteroid population. This paper examines the scenario of future utilization of asteroid resources. The near Earth asteroid resources that could be transferred to a bound Earth orbit are determined by integrating the probability of finding asteroids inside the Keplerian orbital element space of the set of transfers with an specific energy smaller than a given threshold. Transfers are defined by a series of impulsive maneuvers and computed using the patched-conic approximation. The results show that even moderately low energy transfers enable access to a large mass of resources.

Opportunities for Ballistic Soft Landing in Binary Asteroids

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 “gro...

Laplace plane and low inclination geosynchronous radar mission design

This study is inspired by the Laplace orbit plane property of requiring minimal station-keeping and therefore its potential use for long-term geosynchronous synthetic aperture radar (GEOSAR) imaging. A set of GEOSAR user requirements is presented and analysed to identify significant mission requirements. Imaging geometry and power demand are assessed as a function of relative satellite speed (which is determined largely by choice of orbit inclination). Estimates of the cost of station-keeping as a function of orbit inclination and right ascension are presented to compare the benefits of different orbit choices. The conclusion is that the Laplace plane (and more generally, orbits with inclinations up to 15°) are attractive choices for GEOSAR.

Semi-Analytical Approach for Distant Encounters in the Spatial Circular Restricted Three-Body Problem

This paper presents a three-dimensional semi-analytical formulation to model the third-body effect on a massless particle in the circular restricted three-body problem dynamical regime. The final expressions are obtained by means of the classical Lagrange planetary equations, by considering as small parameter of the perturbative approach the mass parameter of the system. The variations of the Keplerian orbital elements of the massless particle over one orbital period are computed as a function of the relative phasing between the massless particle and the secondary, and the overall behavior is described in terms of kick maps. Several applications to mission design are introduced, and the accuracy provided by the methodology is discussed on the basis of different initial conditions and physical systems.

CHAPTER 8:Space-Based Geoengineering Solutions

This chapter provides an overview of space-based geoengineering as a tool to modulate solar insolation and offset the impacts of human-driven climate change. A range of schemes are considered including static and orbiting occulting disks and artificial dust clouds at the interior Sun–Earth Lagrange point, the gravitational balance point between the Sun and Earth. It is demonstrated that, in principle, a dust cloud can be gravitationally anchored at the interior Lagrange point to reduce solar insolation and that orbiting disks can provide a uniform reduction of solar insolation with latitude, potentially offsetting the regional impacts of a static disk. While clearly speculative, the investigation of space-based geoengineering schemes provides insights into the long-term prospects for large-scale, active control of solar insolation.

Optimization of Asteroid Capture Missions Using Earth Resonant Encounters

This paper describes a robust methodology to design Earth-resonant asteroid capture trajectories leading to Libration Point Orbits (LPOs). These trajectories consider two impulsive manoeuvres; one occurring before the first Earth encounter and a final one that inserts the asteroid into a stable hyperbolic manifold trajectory leading to an LPO of the Sun-Earth system. The first manoeuvre is key to exploit the chaotic perturbative effects of the Earth and obtain important reductions on the cost of inserting the asteroid into a manifold trajectory. The perturbative effects caused by the Earth are here modelled by means of a Keplerian Map approximation, and these are a posteriori compared with the dynamics of the Circular Restricted Three-Body Problem. Savings in the order of 50% of total Δv are computed for four different asteroids.