Browsing by Author "Sánchez, Joan-Pau"
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Item Open Access Analysis of natural landing trajectories for passive landers in binary asteroids: A case study for (65803) 1996GT didymos(2017-05) Celik, Onur; Sánchez, Joan-Pau; Karatekin, Özgür; Ritter, BirgitBinary asteroids are believed to constitute about 15% percent of the near-Earth asteroid (NEA) population. Their abundance and yet-to-be-resolved formation mechanism make them scientifically interesting, but they can also be exploited as a test bed for kinetic impactors, as the Asteroid Impact and Deflection Assessment (AIDA) joint mission proposal suggested. In addition to impactor spacecraft of AIDA, i.e. DART, the observation spacecraft, called Asteroid Impact Mission (AIM) (whose future is now uncertain) is to characterize Didymos, including pre- and post-impact variations. Due to the highly perturbed dynamical environment around asteroids, large, and generally expensive missions are preferred to be operated from a safe distance from target asteroid. Even if advanced remote sensing techniques provide the finest details of the target, surface agents can obtain higher resolution and ground truth data. Lander solutions for small body exploration have already been suggested in various missions/proposals. The most recent example is the AIM proposal, which envisage to deploy MASCOT lander on the surface of Didymoon. Additionally, AIM proposed to carry two CubeSats on board. A team led by Royal Observatory of Belgium (ROB) proposed Asteroid Geophysical Explorer (AGEX) CubeSat to land on Didymoon. CubeSats can be employed much more daringly in small body environments due to their versatile character and low development cost. Nevertheless, they possess only limited AOCS capabilities because of their size, and in most cases they are passive. This research offers novel landing trajectories by exploiting the natural dynamics of binary systems. The framework of Circular Restricted Three-Body Problem is used for this purpose, in which two asteroids orbit each other around their common center of mass, while third body (CubeSat) move under their gravitational field. Landing trajectories are propagated backwards in time; from each latitude-longitude points in densely meshed surface through the low energy gate at L2. A newly developed bisection algorithm ensures to generate the lowest energy trajectory for landing point under given constraints. The results suggest that landing speeds less than 8 cm/s are possible, while coefficient restitutions of over 0.9 for spherical asteroids would ensure a successful landing. Robustness of trajectories is also investigated. Uncertainties in deployment mechanism and GNC errors of mothership are considered. Trajectories that are obtained in backwards time propagation are added pseudo-random errors, then propagated forward to the surface in a Monte Carlo simulation, in which 1000 trajectories are propagated. The deployment altitude is found to be severely degrading the success rate. The GNC velocity errors are also found to be more effective than their position counterparts. The success rate over 99.7% (3) can be achieved, though extra requirements might need to be considered for mothership design.Item Open Access The Castalia mission to Main Belt Coment 133P/Elst-Pizarro(Elsevier, 2017-09-19) Snodgrass, Colin; Jones, G. H.; Boehnhardt, H.; Gibbings, Alison; Homeister, M.; Andre, N.; Beck, P.; Bentley, M. S.; Bertini, I.; Bowles, Neil E.; Capria, M. T.; Carr, C.; Ceriotti, M.; Coates, A. J.; Della Corte, V.; Donaldson Hanna, Kerri L.; Fitzsimmons, A.; Gutiérrez, P. J.; Hainaut, O. R.; Herique, A.; Hilchenbach, M.; Hsieh, H. H.; Jehin, E.; Karatekin, O.; Kofman, W.; Lara, L. M.; Laudan, K.; Licandro, J.; Lowry, S. C.; Marzari, F.; Masters, A.; Meech, K. J.; Moreno, F.; Morse, A.; Orosei, R.; Pack, A.; Plettemeier, D.; Prialnik, D.; Rotundi, A.; Rubin, M.; Sánchez, Joan-Pau; Sheridan, S.; Trieloff, M.; Winterboer, A.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.Item Open Access Comet interceptor: an ESA mission to a dynamically new solar system object(http://www.iafastro.org/events/iac/iac-2020, 2020-10-12) Sánchez, Joan-Pau; Jones, G. H.; Snodgrass, ColinWhile the scientific merits of past comet missions are unquestioned, previously visited comets had all approached the Sun on many occasions and, as a consequence, have also undergone substantial compositional and morphological alterations. Comet Interceptor (Comet-I) was recently selected as ESA’s first fast-track class mission and aims to explore a pristine comet, which will ideally be visiting the inner Solar System for the first time. Comet-I will hitch a ride to a Sun-Earth L2 quasi-halo orbit, as a co-passenger in ESA’s M4 ARIEL’s launch, in 2028. It will then remain there waiting for the right departure conditions to definitively leave the L2 point and intercept a newly discovered comet. Comet-I will be the first mission to be design and, possibly launched, without an identified target. Nevertheless, a Monte Carlo analysis modelling the uncertainties of the long period comet population and the spacecraft transfer capabilities demonstrate the high likelihood of completing the mission within 6 years. A few days before the closest approach Comet-I will release two small independent probes (~30 kg each) into fly-by paths with close approach distances in the order of a few hundred kilometres, while the main spacecraft (~700 kg) will take a safer path (~1000 km) to protect it from the dust environment. Comet-I will thus involve three spacecraft elements working together to ensure a low-risk, bountiful, interdisciplinary scientific return through unprecedented multipoint measurementsItem Open Access A comparative reliability analysis of ballistic deployments on binary asteroids(Elsevier, 2018-03-14) Çelik, Onur; Sánchez, Joan-Pau; Karatekin, Özgür; Ritter, BirgitSmall 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 320o–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.Item Open Access CubeSat autonomous navigation and guidance for low-cost asteroid flyby missions(American Institute of Aeronautics and Astronautics, 2021-08-18) Machuca, Pablo; Sánchez, Joan-PauRecent advancements in CubeSat technology unfold new mission ideas and the opportunity to lower the cost of space exploration. Ground operations costs for interplanetary CubeSats, however, still represent a challenge toward low-cost CubeSat missions: hence, certain levels of autonomy are desirable. The feasibility of autonomous asteroid flyby missions using CubeSats is assessed here, and an effective strategy for autonomous operations is proposed. The navigation strategy is composed of observations of the Sun, visible planets, and the target asteroid, whereas the guidance strategy is composed of two optimally timed trajectory correction maneuvers. A Monte Carlo analysis is performed to understand the flyby accuracies that can be achieved by autonomous CubeSats, in consideration of errors and uncertainties in a) departure conditions, b) propulsive maneuvers, c) observations, and d) asteroid ephemerides. Flyby accuracies better than ±100 km (3σ)" role>±100 km (3σ)±100 km (3σ) are found possible, and main limiting factors to autonomous missions are identified, namely a) on-board asteroid visibility time (Vlim≥11" role=>Vlim≥11Vlim≥11), b) ΔV" role=">ΔVΔV for correction maneuvers (>15 m/s>15 m/s), c) asteroid ephemeris uncertainty (<1000 km><1000 km<1000 km), and d) short duration of transfer to asteroid. Ultimately, this study assesses the readiness level of current CubeSat technology to autonomously flyby near-Earth asteroids, in consideration of realistic system specifications, errors, and uncertainties.Item Open Access ESA F-Class Comet Interceptor: trajectory design to intercept a yet-to-be-discovered comet(Elsevier, 2021-07-16) Sánchez, Joan-Pau; Morante, David; Hermosin, Pablo; Ranuschio, Daniel; Estalella, Alvaro; Viera, Dayana; Centuori, Simone; Jones, Geraint; Snodgrass, Colin; Levasseur-Regourd, Anny Chantal; Tubiana, CeciliaComet Interceptor (Comet-I) was selected in June 2019 as the first ESA F-Class mission. In 2029+, Comet-I will hitch a ride to a Sun-Earth L2 quasi-halo orbit, as a co-passenger of ESA's M4 ARIEL mission. It will then remain idle at the L2 point until the right departure conditions are met to intercept a yet-to-be-discovered long period comet (or interstellar body). The fact that Comet-I target is thus unidentified becomes a key aspect of the trajectory and mission design. The paper first analyses the long period comet population and concludes that 2 to 3 feasible targets a year should be expected. Yet, Comet-I will only be able to access some of these, depending mostly on the angular distance between the Earth and the closest nodal point to the Earth's orbit radius. A preliminary analysis of the transfer trajectories has been performed to assess the trade-off between the accessible region and the transfer time for a given spacecraft design, including a fully chemical, a fully electric and a hybrid propulsion system. The different Earth escape options also play a paramount role to enhance Comet-I capability to reach possible long period comet targets. Particularly, Earth-leading intercept configurations have the potential to benefit the most from lunar swing-by departures. Finally, a preliminary Monte Carlo analysis shows that Comet-I has a 95–99% likelihood of successfully visit a pristine newly-discovered long period comet in less than 6 years of mission timespan.Item Open Access Icarus: In-situ monitoring of the surface degradation on a near-sun asteroid(Elsevier, 2021-05-21) Lehtinen, Tuomas; Granvik, Mikael; Bellome, Andrea; Sánchez, Joan-PauIcarus is a mission concept designed to record the activity of an asteroid during a close encounter with the Sun. The primary science goal of the mission is to unravel the nontrivial mechanism(s) that destroy asteroids on orbits with small perihelion distances. Understanding the destruction mechanism(s) allows us to constrain the bulk composition and interior structure of asteroids in general. The Icarus mission does not only aim to achieve its science goals but also functions as a technical demonstration of what a low-cost space mission can do. The proposed space segment will include a single spacecraft capable of surviving and operating in the harsh environment near the Sun. The spacecraft design relies on the heritage of missions such as Rosetta, MESSENGER, Parker Solar Probe, BepiColombo, and Solar Orbiter. The spacecraft will rendezvous with an asteroid during its perihelion passage and records the changes taking place on the asteroid’s surface. The primary scientific payload has to be capable of imaging the asteroid’s surface in high resolution using visual and near-infrared channels as well as collecting and analyzing particles that are ejected from the asteroid. The payload bay also allows for additional payloads relating to, for example, solar research. The Icarus spacecraft and the planned payloads have high technology readiness levels and the mission is aimed to fit the programmatic and cost constraints of the F1 mission (Comet Interceptor) by the European Space Agency. Considering the challenging nature of the Icarus trajectory and the fact that the next F-class mission opportunity (F2) is yet to be announced, we conclude that Icarus is feasible as an F-class mission when certain constraints such as a suitable launch configuration are met. A larger mission class, such as the M class by the European Space Agency, would be feasible in all circumstances.Item Open Access Landing in binary asteroids: A global map of feasible descend opportunities for unpowered spacecraft(International Astronautics Federation, 2017-09-29) Celik, Onur; Sánchez, Joan-PauAsteroid surface science provides the necessary “ground-truth” to validate and enhance remote sensing from orbiting spacecraft. Yet, due to uncertainties associated with the dynamical environment near asteroids, it is generally prudent for the main spacecraft to remain at a safe distance. Instead, small landers could be used much more daringly. This paper explores the potential for ballistic landing opportunities in binary asteroid systems. The dynamics near a binary asteroid are modelled by means of the Circular Restricted Three Body Problem, which provides a reasonable representation of a standard binary system. Natural landing trajectories are sought that allow for deployment from safe distances and touchdown with minimum local-vertical velocity. The necessary coefficient of restitution to ensure a successful landing and the effects of navigation and deployment errors are also analysed. Assuming deployment errors in the order of 10 meters and 1 cm/s (1-sigma), the results show that ballistic descent landing operations are likely to be successful if targeting near equatorial regions with longitude within 320o to 20o in the secondary of the binary system.Item Open Access Low-energy trajectory design and autonomous navigation to flyby near-Earth asteroids using CubeSats(International Astronautical Federation (IAF), 2018-10-05) Machuca, Pablo; Sánchez, Joan-Pau; Masdemont, Josep J.; Gomez, GerardIn response to the current interest in CubeSats and potential applications for planetary exploration, this work studies the feasibility of using autonomous CubeSats to flyby near-Earth asteroids. Considering the limited performance of current propulsion systems for CubeSats, low-energy (impulsive and low-thrust) trajectories are designed to encounter near-Earth asteroids in the medium-fidelity Circular Restricted Three-Body Problem, and their existence in a high-fidelity ephemeris model is also verified. The use of large ground antennas for deep-space communications might represent a major portion of CubeSat mission budgets, and thus the feasibility of performing optical navigation to autonomously estimate and correct the trajectory of the CubeSat is also evaluated through Monte Carlo simulations. Preliminary results show that approximately 4 asteroids per year could be reached by a 3U CubeSat if deployed around the first or second Sun-Earth Lagrange points. According to the limited performance of current CubeSat components, flyby altitudes of the order of 100–500 kilometers are determined possible using only observations of the Sun and of the target asteroid for autonomous navigation.Item Open Access Low-thrust trajectory design in low-energy regimes using variational equations(Elsevier, 2020-08-13) Neves, Rita; Sánchez, Joan-PauThis paper proposes a novel description of the equations of motion for low-thrust trajectory design in the presence of a third-body perturbation. The framework is formulated using Gauss’ Variational Equations (GVE) with two distinct accelerations: the one produced by the electric engine and the disturbing term of the third-body effect, which is computed using the disturbing potential of the previously studied Keplerian Map. The presented GVE third-body (GVE-3B) framework allows for a simple and intuitive description of the low-thrust optimisation problem. It is accurate until very close to the sphere of influence of the perturbing body, and thus can be used to target trajectories in low-energy regimes. Together with the framework, this paper develops a methodology to generate low-energy first-guess solutions for low-thrust trajectories. Both the methodology and the framework are showcased in the design of two distinct missions: a rendezvous with asteroid 2017 SV19 during its next Earth encounter, after departing from the unstable invariant manifold of the L2" role="presentation" style="display: inline-block; line-height: normal; font-size: 16.2px; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border-width: 0px; border-style: initial; position: relative;">L2 point in the Sun-Earth system, and the capture of asteroid 2018 AV2 to a stable invariant manifold of the same pointItem Open Access Multifidelity design of low-thrust resonant captures for near-Earth asteroids(AIAA, 2018-11-26) Neves, Rita; Sánchez, Joan-PauThe design of a space trajectory is strongly linked to the gravitational and non-gravitational environment and the dynamical frameworks required to model it. These dynamical models may range from low to high fidelity, with corresponding computational costs. This paper proposes a multifidelity approach for the computation of nearly resonant trajectories with the Earth. This framework is used to compute trajectories for the capture of near-Earth asteroids into libration point orbits of the Sun – Earth system. The transfer is first computed in a suitable low-fidelity model, the Keplerian map, and a multifidelity approach is subsequently used to refine the solution from an impulsive approximation into a low-thrust transfer in the circular restricted three-bodyproblem. The entire trajectory follows a nearly resonant motion with the Earth, lasting less than two synodic periods; starting when the retrieval spacecraft attaches itself to the asteroid, they will encounter the Earth twice, being captured into the target orbit at the end of the second encounter. A velocity change maneuver is carried out at the beginning of the motion, so that the first encounter with the Earth provides a gravitational perturbation resulting on a reduction of overall propellant costs of the transfer. The developed framework is very flexible in terms of the desired accuracy and allows for the low computational cost exploration of a vast number of possible trajectories. The obtained low-thrust transfers yield, for six asteroids, a much higher retrievable mass in comparison with direct capture trajectories, which do not undertake Earth-resonant encounters.Item Open Access Optimal sunshade configurations for space-based geoengineering near the Sun-Earth L1 point(PLOS (Public Library of Science), 2015-08-26) Sánchez, Joan-Pau; McInnes, Colin R.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 L1Lagrange 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 L1equilibrium 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.Item Open Access System requirements analysis for JAXA's contribution to Comet Interceptor mission: autonomous navigation, guidance and attitude control for a hyperbolic comet fly-by(IAC, 2020-10-14) Machuca, Pablo; Ozaki, Naoya; Sánchez, Joan-Pau; Felicetti, Leonard; Funase, RyuComet Interceptor, to be launched in 2028, is a recently-selected ESA/JAXA mission aimed to perform the first fly-by of a pristine long-period comet. As part of the mission’s Phases A/B (feasibility analysis and preliminary design), this work preliminarily analyzes the attitude performance of JAXA’s contribution to the mission, SC B1: one of the two small-spacecraft piggybacked along with ESA’s main spacecraft. This study primarily focuses on the characterization of the dust environment, modelization of dust particle impacts, and analysis of attitude performance through the dust environment. Monte Carlo simulations are implemented to assess the performance of the attitude control system within a highly-active dust environment, for various fly-by altitudes and a worst-case 70-km/s fly-by speed. Results evidence the need for a wide-angle camera, and conclude that image acquisition shall tolerate angular velocities of several degrees per second. Solutions for improved attitude performance are also evaluated (i.e., upgrading of reaction wheels and angular momentum pre-loading), and a larger reaction wheels aligned with the camera line of sight is shown to provide largest performance improvements. Such strategies, nevertheless, still result in pointing errors and angular velocities that are only compatible with a short-exposure, wide-angle science camera