Frontiers in Astronomy and Space Sciences | Fundamental Astronomy section | New and Recent Articles
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RSS Feed for Fundamental Astronomy section in the Frontiers in Astronomy and Space Sciences journal | New and Recent Articlesen-usFrontiers Feed Generator,version:12019-10-19T07:13:51.2887321+00:0060https://www.frontiersin.org/articles/10.3389/fspas.2019.00034
https://www.frontiersin.org/articles/10.3389/fspas.2019.00034
Long-Term Evolution of Highly-Elliptical Orbits: Luni-Solar Perturbation Effects for Stability and Re-entry2019-07-02T00:00:00ZCamilla ColomboThis paper investigates the long-term evolution of spacecraft in Highly Elliptical Orbits (HEOs). The single averaged disturbing potential due to luni-solar perturbations, zonal harmonics of the Earth gravity field is written in mean Keplerian elements. The double averaged potential is also derived in the Earth-centered equatorial system. Maps of long-term orbit evolution are constructed by measuring the maximum variation of the orbit eccentricity to identify conditions for quasi-frozen, long-lived libration orbits, or initial orbit conditions that naturally evolve toward re-entry in the Earth's atmosphere. The behavior of these long-term orbit maps is studied for increasing values of the initial orbit inclination and argument of the perigee with respect to the Moon's orbital plane. In addition, to allow meeting specific mission constraints, quasi-frozen orbits can be selected as graveyard orbits for the end-of-life of HEO missions, in the case re-entry option cannot be achieved due to propellant constraints. On the opposite side, unstable conditions can be exploited to target Earth re-entry at the end-of-mission.]]>https://www.frontiersin.org/articles/10.3389/fspas.2019.00043
https://www.frontiersin.org/articles/10.3389/fspas.2019.00043
Editorial: The Earth–Moon System As a Dynamical Laboratory2019-06-12T00:00:00ZElisa Maria AlessiJosep MasdemontAlessandro Rossihttps://www.frontiersin.org/articles/10.3389/fspas.2019.00037
https://www.frontiersin.org/articles/10.3389/fspas.2019.00037
Stability of a Rotating Asteroid Housing a Space Station2019-05-22T00:00:00ZThomas I. MaindlRoman MikschBirgit LoibneggerToday there are numerous studies on asteroid mining. They elaborate on selecting the right objects, prospecting missions, potential asteroid redirection, and the mining process itself. For economic reasons, most studies focus on mining candidates in the 100–500 m size-range. Also, suggestions regarding the design and implementation of space stations or even colonies inside the caverns of mined asteroids exist. Caverns provide the advantages of confined material in near-zero gravity during mining and later the hull will shield the inside from radiation. Existing studies focus on creating the necessary artificial gravity by rotating structures that are built inside the asteroid. Here, we assume the entire mined asteroid to rotate at a sufficient rate for artificial gravity and investigate its use for housing a habitat inside. In this study we present how to estimate the necessary spin rate assuming a cylindrical space station inside a mined asteroid and discuss the implications arising from substantial material stress given the required rotation rate. We estimate the required material strength using two relatively simple analytical models and discuss applicability to rocky near-Earth asteroids.]]>https://www.frontiersin.org/articles/10.3389/fspas.2019.00008
https://www.frontiersin.org/articles/10.3389/fspas.2019.00008
JWST/NIRSpec Prospects on Transneptunian Objects2019-02-28T00:00:00ZRobin MétayerAurélie Guilbert-LepoutrePierre FerruitFrédéric MerlinBryan J. HollerNahuel CabralCathy Quantin-NatafThe transneptunian region has proven to be a valuable probe to test models of the formation and evolution of the solar system. To further advance our current knowledge of these early stages requires an increased knowledge of the physical properties of Transneptunian Objects (TNOs). Colors and albedos have been the best way so far to classify and study the surface properties of a large number TNOs. However, they only provide a limited fraction of the compositional information, required for understanding the physical and chemical processes to which these objects have been exposed since their formation. This can be better achieved by near-infrared (NIR) spectroscopy, since water ice, hydrocarbons, and nitrile compounds display diagnostic absorption bands in this wavelength range. Visible and NIR spectra taken from ground-based facilities have been observed for ~80 objects so far, covering the full range of spectral types: from neutral to extremely red with respect to the Sun, featureless to volatile-bearing and volatile-dominated (Barkume et al., 2008; Guilbert et al., 2009; Barucci et al., 2011; Brown, 2012). The largest TNOs are bright and thus allow for detailed and reliable spectroscopy: they exhibit complex surface compositions, including water ice, methane, ammonia, and nitrogen. Smaller objects are more difficult to observe even from the largest telescopes in the world. In order to further constrain the inventory of volatiles and organics in the solar system, and understand the physical and chemical evolution of these bodies, high-quality NIR spectra of a larger sample of TNOs need to be observed. JWST/NIRSpec is expected to provide a substantial improvement in this regard, by increasing both the quality of observed spectra and the number of observed objects. In this paper, we review the current knowledge of TNO properties and provide diagnostics for using NIRSpec to constrain TNO surface compositions.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00045
https://www.frontiersin.org/articles/10.3389/fspas.2018.00045
Rendezvous Strategies in the Vicinity of Earth-Moon Lagrangian Points2019-01-22T00:00:00ZStephanie Lizy-DestrezLaurent BeauregardEmmanuel BlazquezAntonino CampoloSara ManglativiVictor QuetIn the context of Human Spaceflight exploration mission scenario, with the Lunar Orbital Platform- Gateway (LOP-G) orbiting about Earth-Moon Lagrangian Point (EML), Rendezvous and Docking (RVD) operational activities are mandatory and critical for the deployment and utilization of the LOP-G (station assembly, crew rotations, cargo delivery, lunar sample return). There is extensive experience with RVD in the two-body problem: in Low Earth Orbit (LEO) to various space stations, or around quasi-circular Low Lunar Orbits (LLO), the latter by Apollo by means of manual RVD. However, the RVD problem in non-Keplerian environments has rarely been addressed and no RVD has been performed to this date in the vicinity of Lagrangian points (LP) where Keplerian dynamics are no longer applicable. Dynamics in such regions are more complex, but multi-body dynamics also come with strong advantages that need to be further researched by the work proposed here. The aim of this paper is to present methods and results of investigations conducted to first set up strategies for far and close rendezvous between a target (the LOP-G, for example) and a chaser (cargo, crew vehicle, ascent and descent vehicle, station modules, etc.) depending on target and chaser orbit. Semi-analytical tools have been developed to compute and model families of orbits about the Lagrangian points in the Circular Restricted Three Body Problem (CR3BP) like NRHO, DRO, Lyapunov, Halo and Lissajous orbits. As far as close rendezvous is concerned, implementation of different linear and non-linear models used to describe cis-lunar relative motion will be discussed and compared, in particular for NRHO and DRO.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00049
https://www.frontiersin.org/articles/10.3389/fspas.2018.00049
Periodic Motion and Stability of Gravitational Planar Triple Systems2019-01-10T00:00:00ZGeorge VoyatzisAthanasios MourtetzikoglouThe stability of gravitational triple systems is a well-known problem in celestial mechanics. The basic model used is the general three body problem (GTBP). Many criteria estimated from the integrals of motion and zero velocity curves or from purely numerical simulations have been given in literature. In this paper, we propose a different approach for the study of stability of triple systems based on the numerical computation of manifolds of periodic orbits and their linear stability. Such an approach has been used for the study of two-planet exosolar systems but here, applying the method of continuation with respect to the masses, we refer to systems where all bodies can have similar mass values. In the present work we apply the proposed approach by starting from the circular family of periodic orbits, which is known to exist for the planetary type problem, and we restrict our computations to the case of two equal masses. By considering that the system has a hierarchical structure, the constructed manifold of periodic solutions can be projected on a plane defined by the relative distance and the relative mass of the system. On such a plane a stability map can be constructed showing the stability limits on the manifold of periodic orbits.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00029
https://www.frontiersin.org/articles/10.3389/fspas.2018.00029
Orbit Design for LUMIO: The Lunar Meteoroid Impacts Observer2018-09-19T00:00:00ZAna M. CiprianoDiogene A. Dei TosFrancesco TopputoThe Lunar Meteoroid Impacts Observer, or LUMIO, is a space mission concept awarded winner of ESA's SysNova Competition “Lunar CubeSats for Exploration,” and as such it is now under consideration for future implementation by the Agency. The space segment foresees a 12U CubeSat, placed at Earth–Moon L_{2}, equipped with an optical instrument, the LUMIO-Cam, which is able to spot the flashes produced by impacts of meteoroids with the lunar surface. In this paper, the work undertaken to design the baseline orbit of LUMIO is documented. The methodology is thoroughly described, both in qualitative and quantitative terms, in support to the mission analysis trade-off activities. The baseline solution is presented with evidence to support the orbit design.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00020
https://www.frontiersin.org/articles/10.3389/fspas.2018.00020
Periodic Orbits Close to That of the Moon in Hill's Problem2018-06-22T00:00:00ZGiovanni B. ValsecchiIn the framework of the restricted, circular, 3-dimensional 3-body problem Sun-Earth-Moon, Valsecchi et al. (1993) found a set of 8 periodic orbits, with duration equal to that of the Saros cycle, and differing only for the initial phases, in which the motion of the massless Moon follows closely that of the real Moon. Of these, only 4 are actually independent, the other 4 being obtainable by symmetry about the plane of the ecliptic. In this paper the problem is treated in the framework of the 3-dimensional Hill's problem. It is shown that also in this problem there are 8 periodic orbits of duration equal to that of the Saros cycle, and that in these periodic orbits the motion of the Moon is very close to that of the real Moon. Moreover, as a consequence of the additional symmetry of Hill's problem about the y-axis, only 2 of the 8 periodic orbits are independent, the other ones being obtainable by exploiting the symmetries of the problem.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00013
https://www.frontiersin.org/articles/10.3389/fspas.2018.00013
Earth's Minimoons: Opportunities for Science and Technology2018-05-24T00:00:00ZRobert JedickeBryce T. BolinWilliam F. BottkeMonique ChybaGrigori FedoretsMikael GranvikLynne JonesHodei UrrutxuaTwelve years ago the Catalina Sky Survey discovered Earth's first known natural geocentric object other than the Moon, a few-meter diameter asteroid designated 2006 RH_{120}. Despite significant improvements in ground-based telescope and detector technology in the past decade the asteroid surveys have not discovered another temporarily-captured orbiter (TCO; colloquially known as minimoons) but the all-sky fireball system operated in the Czech Republic as part of the European Fireball Network detected a bright natural meteor that was almost certainly in a geocentric orbit before it struck Earth's atmosphere. Within a few years the Large Synoptic Survey Telescope (LSST) will either begin to regularly detect TCOs or force a re-analysis of the creation and dynamical evolution of small asteroids in the inner solar system. The first studies of the provenance, properties, and dynamics of Earth's minimoons suggested that there should be a steady state population with about one 1- to 2-m diameter captured objects at any time, with the number of captured meteoroids increasing exponentially for smaller sizes. That model was then improved and extended to include the population of temporarily-captured flybys (TCFs), objects that fail to make an entire revolution around Earth while energetically bound to the Earth-Moon system. Several different techniques for discovering TCOs have been considered but their small diameters, proximity, and rapid motion make them challenging targets for existing ground-based optical, meteor, and radar surveys. However, the LSST's tremendous light gathering power and short exposure times could allow it to detect and discover many minimoons. We expect that if the TCO population is confirmed, and new objects are frequently discovered, they can provide new opportunities for (1) studying the dynamics of the Earth-Moon system, (2) testing models of the production and dynamical evolution of small asteroids from the asteroid belt, (3) rapid and frequent low delta-v missions to multiple minimoons, and (4) evaluating in-situ resource utilization techniques on asteroidal material. Here we review the past decade of minimoon studies in preparation for capitalizing on the scientific and commercial opportunities of TCOs in the first decade of LSST operations.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00018
https://www.frontiersin.org/articles/10.3389/fspas.2018.00018
Proper Motion and Secular Variations of Keplerian Orbital Elements2018-05-23T00:00:00ZAlexey G. ButkevichHigh-precision observations require accurate modeling of secular changes in the orbital elements in order to extrapolate measurements over long time intervals, and to detect deviation from pure Keplerian motion caused, for example, by other bodies or relativistic effects. We consider the evolution of the Keplerian elements resulting from the gradual change of the apparent orbit orientation due to proper motion. We present rigorous formulae for the transformation of the orbit inclination, longitude of the ascending node and argument of the pericenter from one epoch to another, assuming uniform stellar motion and taking radial velocity into account. An approximate treatment, accurate to the second-order terms in time, is also given. The proper motion effects may be significant for long-period transiting planets. These theoretical results are applicable to the modeling of planetary transits and precise Doppler measurements as well as analysis of pulsar and eclipsing binary timing observations.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00016
https://www.frontiersin.org/articles/10.3389/fspas.2018.00016
Analysis of Close Encounters With Ganymede and Callisto Using a Genetic n-Body Algorithm2018-05-22T00:00:00ZPhilip M. WinterMattia A. GaliazzoThomas I. MaindlIn this work we describe a genetic algorithm which is used in order to study orbits of minor bodies in the frames of close encounters. We find that the algorithm in combination with standard orbital numerical integrators can be used as a good proxy for finding typical orbits of minor bodies in close encounters with planets and even their moons, saving a lot of computational time compared to long-term orbital numerical integrations. Here, we study close encounters of Centaurs with Callisto and Ganymede in particular. We also perform n-body numerical simulations for comparison. We find typical impact velocities to be between υ_{rel} = 20[υ_{esc}] and υ_{rel} = 30[υ_{esc}] for Ganymede and between υ_{rel} = 25[υ_{esc}] and υ_{rel} = 35[υ_{esc}] for Callisto.]]>https://www.frontiersin.org/articles/10.3389/fspas.2018.00014
https://www.frontiersin.org/articles/10.3389/fspas.2018.00014
OSSOS: X. How to Use a Survey Simulator: Statistical Testing of Dynamical Models Against the Real Kuiper Belt2018-05-16T00:00:00ZSamantha M. LawlerJ. J. KavelaarsMike AlexandersenMichele T. BannisterBrett GladmanJean-Marc PetitCory ShankmanAll surveys include observational biases, which makes it impossible to directly compare properties of discovered trans-Neptunian Objects (TNOs) with dynamical models. However, by carefully keeping track of survey pointings on the sky, detection limits, tracking fractions, and rate cuts, the biases from a survey can be modeled in Survey Simulator software. A Survey Simulator takes an intrinsic orbital model (from, for example, the output of a dynamical Kuiper belt emplacement simulation) and applies the survey biases, so that the biased simulated objects can be directly compared with real discoveries. This methodology has been used with great success in the Outer Solar System Origins Survey (OSSOS) and its predecessor surveys. In this chapter, we give four examples of ways to use the OSSOS Survey Simulator to gain knowledge about the true structure of the Kuiper Belt. We demonstrate how to statistically compare different dynamical model outputs with real TNO discoveries, how to quantify detection biases within a TNO population, how to measure intrinsic population sizes, and how to use upper limits from non-detections. We hope this will provide a framework for dynamical modelers to statistically test the validity of their models.]]>https://www.frontiersin.org/articles/10.3389/fspas.2017.00028
https://www.frontiersin.org/articles/10.3389/fspas.2017.00028
Is the Recently Proposed Mars-Sized Perturber at 65–80 AU Ruled Out by the Cassini Ranging Data?2017-10-26T00:00:00ZLorenzo IorioRecently, the existence of a pointlike pertuber PX with 1 m_{♂} ≲ m_{X} ≲ 2.4 m_{⊕} (the symbol “♂” denotes Mars) supposedly moving at 65–80 AU along a moderately inclined orbit has been hypothesized in order to explain certain features of the midplane of the Kuiper Belt Objects (KBOs). We preliminarily selected two possible scenarios for such a PX, and numerically simulated its effect on the Earth-Saturn range ρ(t) by varying some of its orbital parameters over a certain time span; then, we compared our results with some existing actual range residuals. By assuming m_{X} = 1 m_{♂} and a circular orbit, such a putative new member of our Solar System would nominally perturb ρ(t) by a few km over Δt = 12 year (2004 − 2016). However, the Cassini spacecraft accurately measured ρ(t) to the level of σ_{ρ} ≃ 100 m. Nonetheless, such a scenario should not be considered as necessarily ruled out since the Cassini data were reduced so far without explicitly modeling any PX. Indeed, a NASA JPL team recently demonstrated that an extra-signature as large as 4 km affecting the Kronian range would be almost completely absorbed in fitting incomplete dynamical models, i.e., without PX itself, to such simulated data, thus not showing up in the standard post-fit range residuals. Larger anomalous signatures would instead occur for m_{X} > 1 m_{♂}. Their nominal amplitude could be as large as 50 − 150 km for m_{X} = 2.4 m_{⊕}, thus making less plausible their existence.]]>https://www.frontiersin.org/articles/10.3389/fspas.2017.00011
https://www.frontiersin.org/articles/10.3389/fspas.2017.00011
Prospects for Measuring Planetary Spin and Frame-Dragging in Spacecraft Timing Signals2017-09-05T00:00:00ZAndreas SchärerRuxandra BondarescuPrasenjit SahaRaymond AngélilRavit HelledPhilippe JetzerSatellite tracking involves sending electromagnetic signals to Earth. Both the orbit of the spacecraft and the electromagnetic signals themselves are affected by the curvature of spacetime. The arrival time of the pulses is compared to the ticks of local clocks to reconstruct the orbital path of the satellite to high accuracy, and implicitly measure general relativistic effects. In particular, Schwarzschild space curvature (static) and frame-dragging (stationary) due to the planet's spin affect the satellite's orbit. The dominant relativistic effect on the path of the signal photons is Shapiro delays due to static space curvature. We compute these effects for some current and proposed space missions, using a Hamiltonian formulation in four dimensions. For highly eccentric orbits, such as in the Juno mission and in the Cassini Grand Finale, the relativistic effects have a kick-like nature, which could be advantageous for detecting them if their signatures are properly modeled as functions of time. Frame-dragging appears, in principle, measurable by Juno and Cassini, though not by Galileo 5 and 6. Practical measurement would require disentangling frame-dragging from the Newtonian “foreground” such as the gravitational quadrupole which has an impact on both the spacecraft's orbit and the signal propagation. The foreground problem remains to be solved.]]>https://www.frontiersin.org/articles/10.3389/fspas.2016.00028
https://www.frontiersin.org/articles/10.3389/fspas.2016.00028
Connecting VLBI and Gaia Celestial Reference Frames2016-09-12T00:00:00ZZinovy MalkinThe current state of the link problem between radio and optical celestial reference frames is considered. The main objectives of the investigations in this direction during the next few years are the preparation of a comparison and the mutual orientation and rotation between the optical Gaia Celestial Reference Frame (GCRF) and the 3rd generation radio International Celestial Reference Frame (ICRF3), obtained from VLBI observations. Both systems, ideally, should be a realization of the ICRS (International Celestial Reference System) at micro-arcsecond level accuracy. Therefore, the link accuracy between the ICRF and GCRF should be obtained with similar error level, which is not a trivial task due to relatively large systematic and random errors in source positions at different frequency bands. In this paper, a brief overview of recent work on the GCRF–ICRF link is presented. Additional possibilities to improve the GCRF–ICRF link accuracy are discussed. The suggestion is made to use astrometric radio sources with optical magnitude to 20^{m} rather than to 18^{m} as currently planned for the GCRF–ICRF link. In addition, the use of radio stars is also a prospective method to obtain independent and accurate orientation between the Gaia frame and the ICRF.]]>https://www.frontiersin.org/articles/10.3389/fspas.2016.00015
https://www.frontiersin.org/articles/10.3389/fspas.2016.00015
Relativistic Time Transfer for Inter-satellite Links2016-04-26T00:00:00ZYi XieInter-Satellite links (ISLs) will be an important technique for a global navigation satellite system (GNSS) in the future. Based on the principles of general relativity, the time transfer in an ISL is modeled and the algorithm for onboard computation is described. It is found, in general, satellites with circular orbits and identical semi-major axes can benefit inter-satellite time transfer by canceling out terms associated with the transformations between the proper times and the Geocentric Coordinate Time. For a GPS-like GNSS, the Shapiro delay is as large as 0.1 ns when the ISL passes at the limb of the Earth. However, in more realistic cases, this value will decrease to about 50 ps.]]>https://www.frontiersin.org/articles/10.3389/fspas.2016.00011
https://www.frontiersin.org/articles/10.3389/fspas.2016.00011
A Study of the Lunisolar Secular Resonance 2ω˙+Ω˙=02016-03-31T00:00:00ZAlessandra CellettiCătălin B. GaleşThe dynamics of small bodies around the Earth has gained a renewed interest, since the awareness of the problems that space debris can cause in the nearby future. A relevant role in space debris is played by lunisolar secular resonances, which might contribute to an increase of the orbital elements, typically of the eccentricity. We concentrate our attention on the lunisolar secular resonance described by the relation 2ω˙+Ω˙=0, where ω and Ω denote the argument of perigee and the longitude of the ascending node of the space debris. We introduce three different models with increasing complexity. We show that the growth in eccentricity, as observed in space debris located in the MEO region at the inclination about equal to 56°, can be explained as a natural effect of the secular resonance 2ω˙+Ω˙=0, while the chaotic variations of the orbital parameters are the result of interaction and overlapping of nearby resonances.]]>https://www.frontiersin.org/articles/10.3389/fspas.2016.00005
https://www.frontiersin.org/articles/10.3389/fspas.2016.00005
Reference Ellipsoid and Geoid in Chronometric Geodesy2016-02-25T00:00:00ZSergei M. KopeikinChronometric geodesy applies general relativity to study the problem of the shape of celestial bodies including the earth, and their gravitational field. The present paper discusses the relativistic problem of construction of a background geometric manifold that is used for describing a reference ellipsoid, geoid, the normal gravity field of the earth and for calculating geoid's undulation (height). We choose the perfect fluid with an ellipsoidal mass distribution uniformly rotating around a fixed axis as a source of matter generating the geometry of the background manifold through the Einstein equations. We formulate the post-Newtonian hydrodynamic equations of the rotating fluid to find out the set of algebraic equations defining the equipotential surface of the gravity field. In order to solve these equations we explicitly perform all integrals characterizing the interior gravitational potentials in terms of elementary functions depending on the parameters defining the shape of the body and the mass distribution. We employ the coordinate freedom of the equations to choose these parameters to make the shape of the rotating fluid configuration to be an ellipsoid of rotation. We derive expressions of the post-Newtonian mass and angular momentum of the rotating fluid as functions of the rotational velocity and the parameters of the ellipsoid including its bare density, eccentricity and semi-major axes. We formulate the post-Newtonian Pizzetti and Clairaut theorems that are used in geodesy to connect the parameters of the reference ellipsoid to the polar and equatorial values of force of gravity. We expand the post-Newtonian geodetic equations characterizing the reference ellipsoid into the Taylor series with respect to the eccentricity of the ellipsoid, and discuss the small-eccentricity approximation. Finally, we introduce the concept of relativistic geoid and its undulation with respect to the reference ellipsoid, and discuss how to calculate it in chronometric geodesy by making use of the anomalous gravity potential.]]>