Minor Celestial Bodies Research Articles

Autonomous Robotic Capabilities in Space Exploration: From Mars to Beyond

The historical timeline of automated systems functioning in space settings spans around 75 years, whereas the existence of practical automated equipment to facilitate astronomical observation dates back over 200 years. Over time, physical servomechanisms have seen advancements in both hardware and software capabilities, enabling their successful operation on the Martian surface and even during journeys to the heliopause, which marks the outer boundary of interstellar space. Contemporary spaceflight operations exemplify a growing capacity to provide decentralized coordination across several automated systems, intricate communication networks, and diverse communities of scientists and engineers. This article examines the impact of autonomous robotic functionalities on space explorations, specifically emphasizing the investigation of Mars' surface. The article examines the use of robotic systems in past missions, specifically focusing on their application in activities like as the identification and analysis of water ice deposits, study of geological features, and the deployment of sensor devices. The article further emphasizes the achievements of autonomous operations in missions conducted in Earth's orbit, as well as the progress made in developing autonomy for operations in close vicinity to minor celestial bodies. This research explores the Chang'e 4 lunar mission and the OSIRIS-REx mission as instances of autonomous exploration and sample gathering on minor celestial bodies. The research also encompasses the exploration of prospective autonomy in forthcoming expeditions to oceanic realms and distant locales.

Analysis of prospective flight schemes to Venus accompanied by an asteroid flyby

This paper deals with the problem of constructing a flight scheme to Venus, in which a spacecraft flying to the planet after a gravity assist maneuver and transition to a resonant orbit in order to re-encounter with Venus, makes a passage of a minor celestial body. The 117 candidate asteroids from the NASA JPL catalogue, whose diameter exceeds 1 km, were selected. The flight trajectories which meet the criteria of impulse-free both flyby Venus and asteroid, and the subsequent landing on the surface of Venus were found within the interval of launch dates from 2029 to 2050. The trajectory of the spacecraft flight from the Earth to Venus including flyby of Venus and asteroids with a subsequent landing on the surface of Venus was analyzed.

Impact and stick-slip dynamics in the soft-landing on minor celestial bodies

The soft-landing on the surface of minor celestial bodies has been investigated with considering the impact and stick-slip effect. The polyhedron model is used to analyze the irregular shape and topography and geomorphology of minor celestial bodies. The soft-sphere discrete element method is used to fill the irregular minor celestial body’s polyhedron model and cover the surface of the body; and then the irregular shape, the gravitational environment, as well as the impact and hopping with the surface can be calculated precisely. The dynamical parameters of failed soft-landing and successful soft-landing are calculated and analyzed. In the cases of successful soft-landing, there are two obviously different kinds: firstly, the final position of the lander is near the target position; secondly, the final position of the lander is far from the target position. The difference of these two kinds of results is discussed. This research shows the major dynamical behavior of soft-landing on minor celestial bodies includes impact, hopping, as well as stick-slip effect. If the initial positions of soft-landing are improper chosen, the lander may become orbital motion around minor celestial body after one or more impact and hopping, or turn to quasi-periodic motion around equilibrium points without impact, or perhaps be static far from the initial position after several times of impact and hopping and leads to the failure of the deep space mission. For the successful soft-landing process, after several times of landings on the surface during the soft-landing process, the lander will finally settle on the surface of the minor celestial body. The results show that the soft-landing region should be selected as a flat area or concave region, which is far from the equatorial plane of the minor celestial bodies.

Periodic orbits related to the equilibrium points in the potential of Irregular-shaped minor celestial bodies

Abstract We presented an overview of detailed continuation results of periodic orbit families which emanate from the equilibrium points (EPs) of irregular-shaped minor celestial bodies (hereafter called minor bodies). The generation and annihilation of periodic orbits (POs) related to the EPs are discussed in detail. The branch points of families of POs are also investigated. We presented 3D bifurcation diagrams for periodic orbits families emanating from the EPs of minor bodies which have five EPs totally. Structures of the 3D bifurcation diagrams depend on the distribution of EPs with different topological classifications. We calculated orbit families emanating from the EPs of asteroids 433 Eros and 216 Kleopatra, including the Lyapunov orbit family, the Vertical orbit family, the orbit families bifurcating from the Vertical orbit family, as well as the nonplanar orbit family.

Celestial mechanics and polarization optics of the Kordylewski dust cloud in the Earth–Moon Lagrange point L5 – I. Three-dimensional celestial mechanical modelling of dust cloud formation

Since the discovery in 1772 of the triangular Lagrange points L4 and L5 in the gravitational field of two bodies moving under the sole influence of mutual gravitational forces, astronomers found a large number of minor celestial bodies around these points of the Sun-Jupiter, Sun-Earth, Sun-Mars and Sun-Neptune systems. The L4 and L5 points of the Earth and Moon may be empty due to the gravitational perturbation of the Sun. However, in 1961 Kordylewski found two bright patches near the L5 point, which may refer to an accumulation of interplanetary particles. Since that time this formation is called the Kordylewski dust cloud (KDC). Until now only a very few computer simulations studied the formation and characteristics of the KDC. To fill this gap, we investigated a three-dimensional four-body problem consisting of the Sun, Earth, Moon and one test particle, 1860000 times separately. We mapped the size and shape of the conglomeratum of particles not escaped from the system sooner than an integration time of 3650 days around L5. Polarimetric observations of a possible KDC around L5 are presented in the second part of this paper.

Annihilation of relative equilibria in the gravitational field of irregular-shaped minor celestial bodies

The rotational speeds of irregular-shaped minor celestial bodies can be changed by the YORP effect. This variation in speed can make the numbers, positions, stabilities, and topological cases of the minor body's relative equilibrium points vary. The numbers of relative equilibrium points can be reduced through the collision and annihilation of relative equilibrium points, or increase through the creation and separation of relative equilibrium points. Here we develop a classification system of multiple annihilation behaviors of the equilibrium points for irregular-shaped minor celestial bodies. Most minor bodies have five equilibrium points; there are twice the number of annihilations per equilibrium point when the number of equilibrium points is between one and five. We present the detailed annihilation classifications for equilibria of objects which have five equilibrium points. Additionally, the annihilation classification for the seven equilibria of Kleopatra-shaped objects and the nine equilibria of Bennu-shaped objects are also discussed. Equilibria of different objects fall into different annihilation classifications. By letting the rotational speeds vary, we studied the annihilations and creations of relative equilibria in the gravitational field of ten minor bodies, including eight asteroids, one satellite of a planet, and one cometary nucleus: the asteroids were 216 Kleopatra, 243 Ida, 951 Gaspra, 1620 Geographos, 2063 Bacchus, 2867 Steins, 6489 Golevka, and 101955 Bennu; the satellite of the planet was S16 Prometheus; and the comet was 1682 Q1/Halley. For the asteroid 101955 Bennu, which has the largest number of equilibria among the known asteroids, we find that the equilibrium points with different indices approach each other as the rotational speed varies and thus annihilate each other successively. The equilibrium in the gravitational field and the smooth surface equilibrium collides when the equilibrium touches the surface of the body.

Stable periodic orbits for spacecraft around minor celestial bodies

We are interested in stable periodic orbits for spacecrafts in the gravitational field of minor celestial bodies. The stable periodic orbits around minor celestial bodies are useful not only for the mission design of the deep space exploration, but also for studying the long-time stability of small satellites in the large-size-ratio binary asteroids. The irregular shapes and gravitational fields of the minor celestial bodies are modeled by the polyhedral model. Using the topological classifications of periodic orbits and the grid search method, the stable periodic orbits can be calculated and the topological cases can be determined. Furthermore, we find five different types of stable periodic orbits around minor celestial bodies: A) Stable periodic orbits generated from the stable equilibrium points outside the minor celestial body, B) Stable periodic orbits continued from the unstable periodic orbits around the unstable equilibrium points, C) Retrograde and nearly circular periodic orbits with zero-inclination around minor celestial bodies, D) Resonance periodic orbits, E) Near-surface inclined periodic orbits. We take asteroid 243 Ida, 433 Eros, 6489 Golevka, 101955 Bennu, and the comet 1P/Halley for examples.

PERIODIC ORBIT FAMILIES IN THE GRAVITATIONAL FIELD OF IRREGULAR-SHAPED BODIES

ABSTRACT The discovery of binary and triple asteroids in addition to the execution of space missions to minor celestial bodies in the past several years have focused increasing attention on periodic orbits around irregular-shaped celestial bodies. In the present work, we adopt a polyhedron shape model for providing an accurate representation of irregular-shaped bodies and employ the model to calculate their corresponding gravitational and effective potentials. We also investigate the characteristics of periodic orbit families and the continuation of periodic orbits. We prove a fact, which provides a conserved quantity that permits restricting the number of periodic orbits in a fixed energy curved surface about an irregular-shaped body. The collisions of Floquet multipliers are maintained during the continuation of periodic orbits around the comet 1P/Halley. Multiple bifurcations in the periodic orbit families about irregular-shaped bodies are also discussed. Three bifurcations in the periodic orbit family have been found around the asteroid 216 Kleopatra, which include two real saddle bifurcations and one period-doubling bifurcation.

Generalized flyby trajectories around elongated minor celestial bodies as a rotating mass dipole

The aim of this paper is to understand the common characteristics of the generalized flyby trajectory around natural elongated bodies. Such flyby trajectories provide a short-term mechanism to clear away vicinal objects or temporally capture ejecta into circling orbits. The gravitational potential of elongated bodies is described by a unified approximate model, i.e., the rotating mass dipole which is two point masses connected with a constant massless rod. The energy power is used to illustrate the flyby effect in terms of the instantaneous orbital energy. The essential of the single flyby trajectory is studied analytically, and the relationship between the flyby trajectory and its Jacobi integral is also illustrated. Sample trajectories are given to show the variational trend of the energy increment with respect to different orbital periapsides. The distribution of natural ejecting orbits is presented by varying the parameters of the approximate model.

Estimate of sizes of small asteroids (cosmic bodies) by the method of stroboscopic radiolocation

Radiolocation methods of probing minor celestial bodies (asteroids) by the nanosecond pulses can be used for monitoring of near-Earth space with the purpose of identification of hazardous cosmic objects able to impact the Earth.Development of the methods that allow us to improve the accuracy of determining the asteroids size (i.e. whether it measures tens or hundreds meters in diameter) is important for correctly estimating the degree of damage which they can cause (either regional or global catastrophes, respectively). In this paper we suggest a novel method of estimating the sizes of the passive cosmic objects using the radiolocation probing by ultra-high-resolution nanosecond signals to obtain radar signatures. The modulation envelope of the reflected signal, which is a radar portrait of the cosmic object, is subjected to time scale transformation to carrier Doppler frequency by means of radioimpulse strobing. The shift of a strobe within the probing period will be performed by radial motion of the object which will allow us to forgo the special autoshift circuit used in the oscillographic technical equipment.The measured values of duration of radiolocation portrait can be used to estimate the mean radius of the object by using the average spatial length of the portrait. The method makes it possible to appraise the sizes of cosmic objects through their radiolocation portrait duration, with accuracy that is independent of the objects range.

Analysis of the potential field and equilibrium points of irregular-shaped minor celestial bodies

The equilibrium points of the gravitational potential field of minor celestial bodies, including asteroids, comets, and irregular satellites of planets, are studied. In order to understand better the orbital dynamics of massless particles moving near celestial minor bodies and their internal structure, both internal and external equilibrium points of the potential field of the body are analyzed. In this paper, the location and stability of the equilibrium points of 23 minor celestial bodies are presented. In addition, the contour plots of the gravitational effective potential of these minor bodies are used to point out the differences between them. Furthermore, stability and topological classifications of equilibrium points are discussed, which clearly illustrate the topological structure near the equilibrium points and help to have an insight into the orbital dynamics around the irregular-shaped minor celestial bodies. The results obtained here show that there is at least one equilibrium point in the potential field of a minor celestial body, and the number of equilibrium points could be one, five, seven, and nine, which are all odd integers. It is found that for some irregular-shaped celestial bodies, there are more than four equilibrium points outside the bodies while for some others there are no external equilibrium points. If a celestial body has one equilibrium point inside the body, this one is more likely linearly stable.

Sections/Associated Societies Focus

The community of Italian geoscientists looks like a composite galaxy; there is a major star (eni, the national oil company) and a minor star (OGS, the Italian National Institute for Oceanography and Applied Geophysics) which are surrounded by a few large planets (e.g., polytechnic schools at Milan and Turin, universities in Naples, Rome, Trieste, and Padua), and several minor celestial bodies. Throughout our history, Italian geophysicists have been affiliated with SEG, EAGE, both of them, or none. The only way to get a critical mass was to somehow join all of them together. The solution, which arrived 12 years ago, was unique: a combined EAGE-SEG section. The first executive committee, in 2001, included a president from academia (Alfredo Mazzotti, Pisa University), a vice president from industry (Luca Bertelli, eni), and a treasurer from a research institute (Aldo Vesnaver, OGS). Such “rainbow representation” has been maintained in the succeeding years. The current leadership is headed by Massimo Antonelli (eni) and includes representatives from industry (eni), research (OGS and Aresys), and academia (Naples).

Control of Hovering Spacecraft Near Small Bodies: Application to Asteroid 25143 Itokawa

The small gravitational forces associated with a minor celestial body, such as an asteroid or comet nucleus, allow visiting spacecraft to implement active control strategies to improve maneuverability about the body. One form of active control is hovering, where the nominal accelerations on the spacecraft are canceled by a nearly continuous control thrust. We investigate the stability of realistic hovering control laws in the body-fixed and inertial reference frames. Two implementations of the body-fixed hovering thrust solution are numerically tested and compared with an analytical stability result presented in the previous literature. The perturbation equations for inertial frame hovering are presented and numerically simulated to identify regions of stability. We find that body-fixed hovering can be made stable inside a region roughly approximated by the body's resonance radius and inertial frame hovering is stable in all regions outside the resonance radius. A case study of hovering above Asteroid (25143) Itokawa, target of the Hayabusa mission, is also presented.

On autonomous tracking of a minor celestial body

There is suggested an algorithm of the autonomous tracking of a minor celestial body (comet, asteroid or satellite) by the photo-TV-camera of the spacecraft during its flyby in the vicinity of the celestial body, investigated by the data of images obtained by this camera. This algorithm allows prediction of the celestial body angular position in order to point the onboard camera to the body. The field of applicability for the suggested algorithm taking into account various errors is being investigated. The problems of the optimization of the program of the autonomous tracking in order to decrease the prediction errors or to increase the prediction time interval are considered. The results obtained are illustrated by the example of the autonomous tracking of Halley's comet nucleus.

Large 3,600 R.F.M. turbo-generator is now in operation at Los Angeles

Radiolocation methods of probing minor celestial bodies (asteroids) by the nanosecond pulses can be used for monitoring of near-Earth space with the purpose of identification of hazardous cosmic objects able to impact the Earth.Development of the methods that allow us to improve the accuracy of determining the asteroids size (i.e. whether it measures tens or hundreds meters in diameter) is important for correctly estimating the degree of damage which they can cause (either regional or global catastrophes, respectively). In this paper we suggest a novel method of estimating the sizes of the passive cosmic objects using the radiolocation probing by ultra-high-resolution nanosecond signals to obtain radar signatures. The modulation envelope of the reflected signal, which is a radar portrait of the cosmic object, is subjected to time scale transformation to carrier Doppler frequency by means of radioimpulse strobing. The shift of a strobe within the probing period will be performed by radial motion of the object which will allow us to forgo the special autoshift circuit used in the oscillographic technical equipment.The measured values of duration of radiolocation portrait can be used to estimate the mean radius of the object by using the average spatial length of the portrait. The method makes it possible to appraise the sizes of cosmic objects through their radiolocation portrait duration, with accuracy that is independent of the objects range.