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Paolo Farinella - One of the best experts on this subject based on the ideXlab platform.
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The rotation of LAGEOS and its long‐term Semimajor Axis decay: A self‐consistent solution
Journal of Geophysical Research: Solid Earth, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin Axis of LAGEOS and the related long-term Semimajor Axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed Semimajor Axis residuals, provided the correct initial conditions for the direction of the spin Axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin Axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
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the rotation of lageos and its long term Semimajor Axis decay a self consistent solution
Journal of Geophysical Research, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin Axis of LAGEOS and the related long-term Semimajor Axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed Semimajor Axis residuals, provided the correct initial conditions for the direction of the spin Axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin Axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
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optical properties of the earth s surface and long term perturbations of lageos s Semimajor Axis
Journal of Geophysical Research, 1992Co-Authors: David Lucchesi, Paolo FarinellaAbstract:We have reproduced the numerical model of Rubincam et al. (1987) for estimating the maximum along-track orbit-averaged perturbative acceleration 〈T〉 on LAGEOS's orbit due to radiation pressure from sunlight anisotropically reflected by the oceans. For the two optical models discussed by Rubincam et al. we have obtained 〈T〉 = 1.17 and 2.79 × 10−12 m/s2. The latter value is about 3 times larger than the corresponding result of Rubincam et al., who made an error, and shows that a reasonable reflection model can give acceleration peaks of the same order as those observed in the residuals of LAGEOS's orbit. Changing the parameters appearing in the ocean reflection law (in particular, the width of the cone about the specular reflection direction which contains a significant amount of radiation) results into peak values of 〈T〉 ranging between 0 and ≈5 × 10−12 m/s2. The “extreme” assumptions of Rubincam et al. (polar orbit, cloudless Earth surface with a diffusive continent in the northern hemisphere, and a partially reflective ocean in the southern one) are found to overestimate 〈T〉 with respect to more realistic models by a factor of the order of, but probably smaller than, 2. The numerical error due to the finite number of Earth surface elements used to compute the radiation force does not exceed a few percents, provided ≈100 uniformly distributed elements are used; a comparable numerical error is involved in the integral over the orbital anomaly if a step of 5° is adopted. Since the largest observed fluctuations in the anomalous Semimajor Axis decay of LAGEOS correspond to values of 〈T〉 ≈ 3 × 10−12 m/s2, we conclude that radiation pressure from Earth-reflected sunlight cannot be ruled out as an important contributor to them. However, a reliable quantitative model of this effect appears to require a rather detailed knowledge of the optical behavior of the oceans. At present, this problem somewhat degrades our capability to predict (or model in a deterministic way) LAGEOS's orbital evolution over long spans of time.
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Optical properties of the Earth's surface and long‐term perturbations of LAGEOS's Semimajor Axis
Journal of Geophysical Research, 1992Co-Authors: David Lucchesi, Paolo FarinellaAbstract:We have reproduced the numerical model of Rubincam et al. (1987) for estimating the maximum along-track orbit-averaged perturbative acceleration 〈T〉 on LAGEOS's orbit due to radiation pressure from sunlight anisotropically reflected by the oceans. For the two optical models discussed by Rubincam et al. we have obtained 〈T〉 = 1.17 and 2.79 × 10−12 m/s2. The latter value is about 3 times larger than the corresponding result of Rubincam et al., who made an error, and shows that a reasonable reflection model can give acceleration peaks of the same order as those observed in the residuals of LAGEOS's orbit. Changing the parameters appearing in the ocean reflection law (in particular, the width of the cone about the specular reflection direction which contains a significant amount of radiation) results into peak values of 〈T〉 ranging between 0 and ≈5 × 10−12 m/s2. The “extreme” assumptions of Rubincam et al. (polar orbit, cloudless Earth surface with a diffusive continent in the northern hemisphere, and a partially reflective ocean in the southern one) are found to overestimate 〈T〉 with respect to more realistic models by a factor of the order of, but probably smaller than, 2. The numerical error due to the finite number of Earth surface elements used to compute the radiation force does not exceed a few percents, provided ≈100 uniformly distributed elements are used; a comparable numerical error is involved in the integral over the orbital anomaly if a step of 5° is adopted. Since the largest observed fluctuations in the anomalous Semimajor Axis decay of LAGEOS correspond to values of 〈T〉 ≈ 3 × 10−12 m/s2, we conclude that radiation pressure from Earth-reflected sunlight cannot be ruled out as an important contributor to them. However, a reliable quantitative model of this effect appears to require a rather detailed knowledge of the optical behavior of the oceans. At present, this problem somewhat degrades our capability to predict (or model in a deterministic way) LAGEOS's orbital evolution over long spans of time.
David Vokrouhlicky - One of the best experts on this subject based on the ideXlab platform.
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DETECTION OF Semimajor Axis DRIFTS IN 54 NEAR-EARTH ASTEROIDS: NEW MEASUREMENTS OF THE YARKOVSKY EFFECT
The Astronomical Journal, 2012Co-Authors: C. R. Nugent, Jean-luc Margot, Steve Chesley, David VokrouhlickyAbstract:We have identified and quantified Semimajor Axis drifts in near-Earth asteroids (NEAs) by performing orbital fits to optical and radar astrometry of all numbered NEAs. We focus on a subset of 54 NEAs that exhibit some of the most reliable and strongest drift rates. Our selection criteria include a Yarkovsky sensitivity metric that quantifies the detectabilityofSemimajorAxisdriftinanygivendataset,asignal-to-noisemetric,andorbitalcoveragerequirements. In 42 cases, the observed drifts (∼10 −3 AU Myr −1 ) agree well with numerical estimates of Yarkovsky drifts. This agreement suggests that the Yarkovsky effect is the dominant non-gravitational process affecting these orbits, and allows us to derive constraints on asteroid physical properties. In 12 cases, the drifts exceed nominal Yarkovsky predictions, which could be due to inaccuracies in our knowledge of physical properties, faulty astrometry, or modeling errors. If these high rates cannot be ruled out by further observations or improvements in modeling, they would be indicative of the presence of an additional non-gravitational force, such as that resulting from a loss of mass of order a kilogram per second. We define the Yarkovsky efficiency fY as the ratio of the change in orbital energy to incident solar radiation energy, and we find that typical Yarkovsky efficiencies are ∼10 −5 .
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Semimajor Axis mobility of asteroidal fragments
Science (New York N.Y.), 1999Co-Authors: Paola Farinella, David VokrouhlickyAbstract:The Semimajor axes of asteroids up to about 20 kilometers in diameter drift as a result of the Yarkovsky effect, a subtle nongravitational mechanism related to radiation pressure recoil on spinning objects that orbit the sun. Over the collisional lifetimes of these objects (typically, 10 to 1000 million years), orbital Semimajor axes can be moved by a few hundredths of an astronomical unit for bodies between 1 and 10 kilometers in mean radius. This has implications for the delivery of multikilometer near-Earth asteroids, because the Yarkovsky drift drives many small main-belt asteroids into the resonances that transport them to the Mars-crossing state and eventually to near-Earth space. Recent work has shown that, without such a drift, the Mars-crossing population would be depleted over about 100 million years, a time scale much smaller than the age of the solar system. Moreover, the Yarkovsky Semimajor Axis mobility may spread in an observable way the tight Semimajor Axis clustering of small asteroids produced as a consequence of disruptive collisions.
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The rotation of LAGEOS and its long‐term Semimajor Axis decay: A self‐consistent solution
Journal of Geophysical Research: Solid Earth, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin Axis of LAGEOS and the related long-term Semimajor Axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed Semimajor Axis residuals, provided the correct initial conditions for the direction of the spin Axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin Axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
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the rotation of lageos and its long term Semimajor Axis decay a self consistent solution
Journal of Geophysical Research, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin Axis of LAGEOS and the related long-term Semimajor Axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed Semimajor Axis residuals, provided the correct initial conditions for the direction of the spin Axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin Axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
Richard Greenberg - One of the best experts on this subject based on the ideXlab platform.
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TIDAL EVOLUTION OF A SECULARLY INTERACTING PLANETARY SYSTEM
The Astrophysical Journal, 2011Co-Authors: Richard Greenberg, Christa Van LaerhovenAbstract:In a multi-planet system, a gradual change in one planet's Semimajor Axis will affect the eccentricities of all the planets, as angular momentum is distributed via secular interactions. If tidal dissipation in the planet is the cause of the change in Semimajor Axis, it also damps that planet's eccentricity, which in turn also contributes to the evolution of all the eccentricities. Formulae quantifying the combined effects on the whole system due to Semimajor Axis changes, as well as eccentricity damping, are derived here for a two-planet system. The CoRoT 7 system is considered as an example.
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Numerical Evaluation of the General Yarkovsky Effect: Effects on Semimajor Axis
Icarus, 2001Co-Authors: Joseph N. Spitale, Richard GreenbergAbstract:Abstract The Yarkovsky effect may play a key role in the orbital evolution of asteroids and near-Earth objects. To evaluate the acceleration under a wide range of conditions, a three-dimensional finite-difference solution to the heat equation is applied to homogeneous, spherical stony bodies with 1-, 10-, and 100-m diameters. This approach employs neither the linearized boundary conditions, the plane-parallel heat flow approximation, nor the assumption of fast rotation used in earlier work. Thus we can explore a wide range of orbital elements and physical properties. Our work agrees well with earlier results in the regimes where their approximations are valid. We investigate a wide range of spin states, including both the “seasonal” (very fast rotation) and “diurnal” (zero obliquity) extremes of the Yarkovsky effect. We find that, for orbits with high eccentricity, the Semimajor Axis can change much faster than for circular orbits. For such orbits, the orientation of the rotation Axis with respect to the direction of pericenter is critical in determining the evolution. A stony main-belt asteroid of diameter 1 m on a high-eccentricity orbit could change its Semimajor Axis by more than 1 AU in 1.5 Myr.
Shigeru Ida - One of the best experts on this subject based on the ideXlab platform.
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Temporary Capture of Asteroids by an Eccentric Planet
The Astronomical Journal, 2017Co-Authors: Arika Higuchi, Shigeru IdaAbstract:We have investigated the probability of temporary capture of asteroids in eccentric orbits by a planet in a circular or eccentric orbit through analytical and numerical calculations. We found that, in the limit of the circular orbit, the capture probability is ~0.1% of encounters to the planet's Hill sphere, independent of planetary mass and Semimajor Axis. In general, temporary capture becomes more difficult as the planet's eccentricity () increases. We found that the capture probability is almost independent of until a critical value () that is given by 5 times the Hill radius scaled by the planet's Semimajor Axis. For , the probability decreases approximately in proportion to . The current orbital eccentricity of Mars is several times larger than . However, since the range of secular change in Martian eccentricity overlaps , the capture of minor bodies by Mars in the past is not ruled out.
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Theoretical predictions of mass, Semimajor Axis and eccentricity distributions of super-Earths
Proceedings of the International Astronomical Union, 2010Co-Authors: Shigeru IdaAbstract:We discuss the effects of close scattering and merging between planets on distributions of mass, Semimajor Axis and orbital eccentricity, using population synthesis model of planet formation, focusing on the distributions of close-in super-Earths, which are being observed recently. We found that a group of compact embryos emerge interior to the ice line, grow, migrate, and congregate into closely-packed convoys which stall in the proximity of their host stars. After the disk-gas depletion, they undergo orbit crossing, close scattering, and giant impacts to form multiple rocky Earths or super-Earths in non-resonant orbits around ~ 0.1AU with moderate eccentricities of ~ 0.01–0.1. The formation of these planets does not depend on model parameters such as type I migration speed. The fraction of solar-type stars with these super-Earths is anti-correlated with the fraction of stars with gas giants. The newly predicted family of close-in super-Earths makes less clear “planet desert” at intermediate mass range than our previous prediction.
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The Signature of the Ice Line and Modest Type I Migration in the Observed Exoplanet Mass-Semimajor Axis Distribution
The Astrophysical Journal, 2009Co-Authors: Kevin C. Schlaufman, Douglas N. C. Lin, Shigeru IdaAbstract:Existing exoplanet radial velocity surveys are complete in the planetary mass-Semimajor Axis (Mp -a) plane over the range 0.1 AU
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the signature of the ice line and modest type i migration in the observed exoplanet mass Semimajor Axis distribution
The Astrophysical Journal, 2009Co-Authors: Kevin C. Schlaufman, D N C Lin, Shigeru IdaAbstract:Existing exoplanet radial velocity surveys are complete in the planetary mass-Semimajor Axis (Mp -a) plane over the range 0.1 AU
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the signature of the ice line and modest type i migration in the observed exoplanet mass Semimajor Axis distribution
arXiv: Astrophysics, 2008Co-Authors: Kevin C. Schlaufman, D N C Lin, Shigeru IdaAbstract:Existing exoplanet radial velocity surveys are complete in the planetary mass-Semimajor Axis (Mp-a) plane over the range 0.1 AU ~ 100 M_Earth. We marginalize over mass in this complete domain of parameter space and demonstrate that the observed Semimajor Axis distribution is inconsistent with models of planet formation that use the full Type I migration rate derived from a linear theory and that do not include the effect of the ice line on the disk surface density profile. However, the efficiency of Type I migration can be suppressed by both nonlinear feedback and the barriers introduced by local maxima in the disk pressure distribution, and we confirm that the synthesized Mp-a distribution is compatible with the observed data if we account for both retention of protoplanetary embryos near the ice line and an order-of-magnitude reduction in the efficiency of Type I migration. The validity of these assumption can be checked because they also predict a population of short-period rocky planets with a range of masses comparable to that of the Earth as well as a "desert" in the Mp-a distribution centered around Mp ~ 30-50 M_Earth and a < 1 AU. We show that the expected "desert" in the Mp-a plane will be discernible by a radial velocity survey with 1 m/s precision and n ~ 700 radial velocity observations of program stars.
François Barlier - One of the best experts on this subject based on the ideXlab platform.
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The rotation of LAGEOS and its long‐term Semimajor Axis decay: A self‐consistent solution
Journal of Geophysical Research: Solid Earth, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin Axis of LAGEOS and the related long-term Semimajor Axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed Semimajor Axis residuals, provided the correct initial conditions for the direction of the spin Axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin Axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
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the rotation of lageos and its long term Semimajor Axis decay a self consistent solution
Journal of Geophysical Research, 1996Co-Authors: Paolo Farinella, David Vokrouhlicky, François BarlierAbstract:We develop a self-consistent model for the evolution of the spin Axis of LAGEOS and the related long-term Semimajor Axis perturbations, due to asymmetric emission/reflection of radiation from the satellite's surface. We show that the theory developed by Bertotti and Iess [1991] for the evolution of LAGEOS's rotation under magnetic and gravitational torques, which we have somewhat generalized here, can lead to a successful fit of the observed Semimajor Axis residuals, provided the correct initial conditions for the direction of the spin Axis are chosen. The remaining residuals have an rms dispersion of 0.50 × 10−12 m/s2, comparable to that of previous solutions, based on purely empirical fits of the spin Axis direction as a function of time. The spectrum of the residuals indicates that they are probably due to unmodeled radiation forces (e.g., from Earth albedo and/or penumbra passages). Our solution allows us to predict the future evolution of LAGEOS's rotation for about another decade in the future, until the spin rate will become so slow that some basic assumptions of the theory will fail. A similar model can also be used to model/predict the coupled spin-orbit evolution of the LAGEOS II satellite, launched in late 1992, although the available data still cover a span of time too short for reaching significant quantitative conclusions concerning this satellite.
