Browsing by Author "Machuca, Pablo"

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    ARTEMIS: A complete mission architecture to bridge the gap between humanity and near-Earth asteroids
    (International Astronautical Federation (IAF), 2018-10-01) Cano, Jorge; Cunill, Jordi; Diaz, Albert Josep; Golemis, Aris; Gupta, Subham; Innes, Daniel; Maiden, David; March, Kieran; Rael, Harvey; Shawe, James; Sierra, Victor; Torrents, Alejandro; Zorzoli Rossi, Elena; Machuca, Pablo; Neves, Rita; Sanchez Cuartielles, Joan Pau
    Asteroid retrieval missions have recently attracted increasing interest from the community and could provide opportunities for scienti c exploration, resource utilisation and even the development of planetary defence strategies. This paper was developed as a result of a 6-month MSc group project, realised by a total of 14 students at Cran eld University pursuing the Astronautics & Space Engineering degree. An overall system design is proposed for a technology demonstrator mission to move a near-Earth asteroid into an easily-accessible location where it could be further explored by future missions. The target nal orbit is a southern halo orbit around the Lagrange point (L2) on the Sun-Earth system. ARTEMIS (Asteroid Retrieval Technology Mission) abides by ESAs constraints for a Large (L) mission call: realised in only one launch with Ariane 64, an operational duration of less than 15 years and a cost at completion of at most e1100M. The proposed mission combines the design of optimal trajectories, employs advanced solar electric propulsion and introduces a be tting level of spacecraft autonomy. The target is the 2006 RH120 asteroid, with an approximate diameter of 6.5 m and mass of roughly 350 tons. To re ne existing data, the ARROW CubeSat mission (Asteroid Reconnaissance to Research Object Worthiness) is to be launched a year prior to the main mission to probe the asteroid via a y-by. ARROW will provide valuable information, such as the asteroids spin rate, rotational axis and better mass estimate, increasing the overall chance of mission success. The main mission will then capture and secure the asteroid using a mechanism of arm-like booms with xenon- lled VectranTM bags. To allow for proper adaptability to the objects shape and mass distribution, as well as preserve the asteroid unaltered, the mechanism is fully contained in fabric that encapsulates the asteroid. The paper concludes that such a mission is conditionally feasible, and summarises the design process resulting in the nal overall mission baseline design. It also examines the practicality of the suggested design for future missions such as space debris removal or its ability to retrieve celestial bodies with variable mass and shape. Proper adaptation of the design could allow for retrieval of similar size or smaller objects. The future implementation of this mission may further the understanding of the origin of the solar system and act as a catalyst to a new celestial body exploitation industry.
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    Asteroid flyby opportunities using semi-autonomous CubeSats: mission design and science opportunities
    (Elsevier, 2018-11-10) Machuca, Pablo; Sanchez, Joan-Pau; Greenland, S.
    CubeSat technology has recently attracted great interest from the scientific community, industry and space agencies, and represents today an exciting movement towards a more affordable and accessible space industry. In view of potential applications of CubeSat technology to small-body planetary exploration, this paper studies the feasibility of using autonomous CubeSats to flyby near-Earth asteroids. This work provides an overview of the current state of CubeSat technology and proposes a 3U CubeSat mission using primarily off-the-shelf components. The proposed mission considers a CubeSat is deployed by a larger spacecraft in a periodic orbit around the first (L1) or the second (L2) Sun-Earth Lagrange points (common destinations to observe the Sun and outer space), from where fuel-optimal impulsive trajectories are designed to flyby asteroids between 2019 and 2025. Navigation support and ground operations costs still represent a major challenge for interplanetary CubeSats. As such, Monte Carlo simulations are performed to determine the flyby accuracies that can be accomplished by a 3U CubeSat flying autonomously (i.e., using observations of the Sun during cruise and observations of the asteroid before the flyby to estimate its own trajectory, instead of using ground stations for navigation support). Asteroid flyby opportunities for an autonomous 3U CubeSat are identified between years 2019 and 2025. Flyby altitudes below 500 km are found possible with currently-available CubeSat components. Possible science payloads are also overviewed, and the potential scientific return of such a low-cost mission is discussed.
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    Autonomous navigation and guidance for CubeSats to flyby near-Earth asteroids
    (International Astronautical Federation (IAF), 2019-10-25) Machuca, Pablo; Sanchez Cuartielles, Joan Pau
    Recent advancements in CubeSat technology unfold new mission ideas and the possibility to lower the cost of space exploration. Exploiting the natural dynamics around the Sun-Earth barycentric Lagrange points, minimal-ΔV trajectories to flyby asteroids appear which are compatible with current CubeSat propulsive capabilities. Ground operations costs for an interplanetary CubeSat, however, still represent a major challenge towards low-cost missions; hence certain levels of autonomy are desirable. Considering the limited allocation of sensors and actuators in CubeSats, and their limited performance, Monte Carlo simulations are implemented to understand the flyby accuracies that can be achieved through autonomous navigation and guidance. Primary sources of error analyzed in this study include: (1) uncertainties in the departure conditions, (2) errors in the propulsive maneuvers, (3) errors in the observations, and (4) uncertainties in the ephemeris of the target asteroid. An autonomous navigation and guidance strategy is proposed and evaluated, employing observations of the Sun, visible planets and of the target asteroid, and two trajectory correction maneuvers along the trajectory. Flyby accuracies below 100 km are found possible if the mission characteristics are suitable in terms of available ΔV, on-board asteroid visibility time, mission duration, and asteroid ephemeris uncertainty before the mission. Ultimately, this study assesses the readiness level of current CubeSat technology to autonomously flyby near-Earth asteroids, with realistic component specifications and modeling of relevant errors and uncertainties. The effect of the different mission factors on the final flyby accuracies is evaluated, and a feasible autonomous navigation and guidance strategy is proposed in the effort to reduce ground operations and overall mission costs.
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    Autonomous optical navigation for small spacecraft in cislunar space
    (International Astronautical Federation (IAF), 2022-09-22) Wu, Christian Xianyang; Machuca, Pablo; Felicetti, Leonard; Sanchez, Joan-Pau
    The Earth-Moon system is expected to be increasingly populated especially due to large space missions like the Lunar Gateway. Communication constellations and small spacecraft are also expected to be deployed in the coming years. However, small spacecraft missions are heavily challenged by limited access and high costs of communicating with ground antennas, and constraints on on-board components. Hence, small spacecraft could greatly benefit from the development of autonomous optical navigation, allowing for higher levels of independence, flexibility, and lower operation costs in a complex environment like cislunar space. The scope of this study is to assess the optical navigation (OPNAV) accuracies achievable through horizon-based position estimation algorithms applied to synthetic images of the Moon. The simulation framework is implemented in Python+Vapory+OpenCV, and it simulates the image acquisition process at different solar phase angles and distances (including camera performance), and the processing of images (involving limb-fitting, centroiding and relative position estimation). A conventional ellipse fitting (EF) technique and the recently proposed Christian-Robinson (CR) approach are compared. Lastly, a Monte Carlo analysis allows to assess the effects of different sources of errors and uncertainties and to gain a better understanding of the navigation accuracies that may be obtained in future cislunar scenarios of interest. Preliminary results show that the CR algorithm consistently provides better performance than the EF technique, both in accuracy and computational time. The resulting errors in range estimation depend on distance, with values of approximately 22 km at a distance of 20, 000 km and up to 422 km at a distance of 150, 000 km. In terms of cross-axis distance estimation, the errors present values around 3.55 km (36 arcsec) at 20, 000 km, and 11.85 km (16 arcsec) at 150, 000 km. Furthermore, simulation outcomes show near normally distributed OPNAV performance with standard deviations around 0.68 km and 0.73 arcsec. A power law function is also provided to approximate the trend of OPNAV accuracies as a function of the distance relative to the observed body, is found based on the outcome of this study. Colour maps illustrating OPNAV accuracies as a function of observation geometry provide a comprehensive picture of the expected performance of OPNAV depending on distance and orientation relative to the observed object.
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    CubeSat autonomous navigation and guidance for low-cost asteroid flyby missions
    (American Institute of Aeronautics and Astronautics, 2021-08-18) Machuca, Pablo; Sánchez, Joan-Pau
    Recent 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.
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    High-fidelity trajectory design to flyby near-Earth asteroids using CubeSats
    (Elsevier, 2019-11-05) Machuca, Pablo; Sanchez, Joan-Pau; Masdemont, Josep J.; Gomez, Gerard
    Fast development of CubeSat technology now enables the first interplanetary missions. The potential application of CubeSats to flyby near-Earth asteroids is explored in this paper in consideration of CubeSats' limited propulsive capabilities and systems constraints. Low-energy asteroid flyby trajectories are designed assuming a CubeSat is initially parked around to the Sun-Earth Lagrange points. High-impulse and low-thrust trajectories with realistic thrusting models are computed first in the Circular Restricted Three-Body Problem (CR3BP), and then in a high-fidelity ephemeris model. Analysis in the ephemeris model is used to confirm that trajectories computed in the CR3BP model also exist in a more realistic dynamical model, and to verify the validity of the results obtained in CR3BP analysis. A catalogue of asteroid flyby opportunities between years 2019 and 2030 is provided, with 80 m/s of available ΔV and departure from halo orbits around the first and second Sun-Earth Lagrange points (of similar size to those typically used by scientific missions). Results show that the CR3BP model can serve as an effective tool to identify reachable asteroids and can provide an initial estimation of the ΔV cost in the ephemeris model (with ±15 m/s accuracy). An impulsive maneuver model can also provide an accurate estimation of the ΔV requirement for a CubeSat equipped with a high-impulse thruster (with 4 m/s accuracy), even if its thrust magnitude is small and requires duty cycling; low-thrust ΔV requirements, however, may differ significantly from the impulsive results (±15 m/s).
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    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, Gerard
    In 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.
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    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, Ryu
    Comet 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