Determining asteroid properties provides valuable physical insights but inverting them from photometric lightcurves remains computationally intensive.This paper presents a new approach that combines a simplified Celli...Determining asteroid properties provides valuable physical insights but inverting them from photometric lightcurves remains computationally intensive.This paper presents a new approach that combines a simplified Cellinoid shape model with the Parallel Differential Evolution(PDE)algorithm to accelerate inversion.The PDE algorithm is more efficient than the Differential Evolution algorithm,achieving an extraordinary speedup of 37.983 with 64 workers on multicore CPUs.The PDE algorithm accurately derives period and pole values from simulated data.The analysis of real asteroid lightcurves validates the method’s reliability:in comparison with results published elsewhere,the PDE algorithm accurately recovers the rotational periods and,given adequate viewing geometries,closely matches the pole orientations.The PDE approach converges to solutions within 20,000 iterations and under one hour,demonstrating its potential for large-scale data analysis.This work provides a promising new tool for unveiling asteroid physical properties by overcoming key computational bottlenecks.展开更多
As the second of Earth's Trojan asteroids, 2020 XL_(5) is worthy of rendezvous and even sample return missions in many aspects. In this paper, a rendezvous mission to Earth's second Trojan asteroid 2020 XL_(5)...As the second of Earth's Trojan asteroids, 2020 XL_(5) is worthy of rendezvous and even sample return missions in many aspects. In this paper, a rendezvous mission to Earth's second Trojan asteroid 2020 XL_(5) is proposed.However, due to its high inclination and large eccentricity, direct impulsive transfer requires large amounts of fuel consumption. To address this challenge, we explore the benefits of electric propulsion and multi-gravity assist techniques for interplanetary missions. These two techniques are integrated in this mission design. The design of a low-thrust gravity-assist(LTGA) trajectory in multi-body dynamics is thoroughly investigated,which is a complex process. A comprehensive framework including three steps is presented here for optimization of LTGA trajectories in multi-body dynamics. The rendezvous mission to 2020 XL_(5) is designed with this three-step approach. The most effective transfer sequence among the outcomes involves Earth–Venus–Earth–Venus-2020 XL_(5). Numerical results indicate that the combination of electric propulsion and multi-gravity assists can greatly reduce the fuel consumption, with fuel consumption of 9.03%, making it a highly favorable choice for this rendezvous mission.展开更多
The shapes and rotation states(periods and pole orientations)of main-belt asteroids are important for understanding their formation and evolution.In order to obtain sufficient photometric data covering different appar...The shapes and rotation states(periods and pole orientations)of main-belt asteroids are important for understanding their formation and evolution.In order to obtain sufficient photometric data covering different apparitions for asteroid(81)Terpsichore,ground-based photometric observations in 2020 and 2021 were carried out.By combining published and newly obtained photometric data,we calculated the shape and spin parameters for(81)Terpsichore using the convex inversion method.With this method,we have derived a best fitted pole orientation—(22.2±_(3.1)^(3.3°),17.5±_(5.5)^(10.8°))with a spin period of 10.94±_(0.01)^(0.01)h.Based on the derived convex shape of(81)Terpsichore,we have fitted the H,G+1,G_(2)phase function using the calibrated TESS data and Gaia data after accounting for the lightcurve amplitude correction.As a result,we have derived its absolute magnitude H=8.68±_(0.19)^(0.22)mag with corresponding phase function parameters G_(1)=0.82±_(0.10)^(0.09)and G_(2)=0.02±_(0.02)^(0.03).展开更多
We characterize the morphology of the photometric phase curve model of an asteroid with a three- parameter magnitude phase function H - G1 - G2 system by considering the effect of brightness variation arising from a t...We characterize the morphology of the photometric phase curve model of an asteroid with a three- parameter magnitude phase function H - G1 - G2 system by considering the effect of brightness variation arising from a triaxial ellipsoid representing the asteroid＇s shape. Applying this new model and a Markov Chain Monte Carlo method, we refine the photometric phase curve of asteroid （107） Camilla and obtain its absolute magnitude H = 7.026-0.054^＋0.052 mag, and phase function parameters G1=0.489-0.044^＋0.043 and G2 = 0.259-0.023^＋0.023.Meanwhile, we also determine （107） Camilla＇s orientation of pole （74.1°-4.5°^＋4.3°,50.2°-5.0°^＋5.4°）. with rotational period of 4.843928-0.000001^＋0.000001 h, and axial ratios a/b ： 1.409-0.020^＋0.020 And b/c =1.249-0.060^＋0.063. Furthermore, according to the values of phase function parameters G1 and G2, we infer that asteroid （107） Camilla is an X-type asteroid.展开更多
We review previously published and newly obtained crater size-frequency distributions in the inner solar system. These data indicate that the Moon and the ter- restrial planets have been bombarded by two populations o...We review previously published and newly obtained crater size-frequency distributions in the inner solar system. These data indicate that the Moon and the ter- restrial planets have been bombarded by two populations of objects. Population 1, dominating at early times, had nearly the same size distribution as the present-day asteroid belt, and produced heavily cratered surfaces with a complex, multi-sloped crater size-frequency distribution. Population 2, dominating since about 3.8-3.7 Gyr, had the same size distribution as near-Earth objects （NEOs） and a much lower im- pact flux, and produced a crater size distribution characterized by a differential -3 single-slope power law in the crater diameter range 0.02 km to 100 km. Taken to- gether with the results from a large body of work on age-dating of lunar and meteorite samples and theoretical work in solar system dynamics, a plausible interpretation of these data is as follows. The NEO population is the source of Population 2 and it has been in near-steady state over the past ～ 3.7-3.8 Gyr; these objects are derived from the main asteroid belt by size-dependent non-gravitational effects that favor the ejection of smaller asteroids. However, Population 1 was composed of main belt as- teroids ejected from their source region in a size-independent manner, possibly by means of gravitational resonance sweeping during orbit migration of giant planets; this caused the so-called Late Heavy Bombardment （LHB）. The LHB began some time before ～3.9 Gyr, peaked and declined rapidly over the next ～ 100 to 300 Myr, and possibly more slowly from about 3.8-3.7 Gyr to ～2 Gyr. A third crater population （Population S） consisted of secondary impact craters that can dominate the cratering record at small diameters.展开更多
Recently, Near Earth Objects （NEOs） have been attracting great attention, and thousands of NEOs have been found to date. This paper examines the NEOs＇ orbital dynamics using the framework of an accurate solar syste...Recently, Near Earth Objects （NEOs） have been attracting great attention, and thousands of NEOs have been found to date. This paper examines the NEOs＇ orbital dynamics using the framework of an accurate solar system model and a Sun- Earth-NEO three-body system when the NEOs are close to Earth to search for NEOs with low-energy orbits. It is possible for such an NEO to be temporarily captured by Earth; its orbit would thereby be changed and it would become an Earth-orbiting object after a small increase in its velocity. From the point of view of the Sun-Earth- NEO restricted three-body system, it is possible for an NEO whose Jacobian constant is slightly lower than C1 but higher than C3 to be temporarily captured by Earth. When such an NEO approaches Earth, it is possible to change its orbital energy to nearly the zero velocity surface of the three-body system at point L1 and make the NEO become a small satellite of the Earth. Some such NEOs were found; the best example only required a 410 m s^-1 increase in velocity.展开更多
The absorption features of olivine in visible and near-infrared(VNIR)reflectance spectra are the key spectral parameters in its mineralogical studies.Generally,these spectral parameters can be obtained by exploiting t...The absorption features of olivine in visible and near-infrared(VNIR)reflectance spectra are the key spectral parameters in its mineralogical studies.Generally,these spectral parameters can be obtained by exploiting the Modified Gaussian Model(MGM)with a proper continuum removal.However,different continua may change the deconvolution results of these parameters.This paper investigates the diagnostic spectral features of olivine with diverse chemical compositions.Four different continuum removal methods with MGM for getting the deconvolution results are presented and the regression equations for predicting the Mg-number(Fo#)are introduced.The results show that different continua superimposed on the mineral absorption features will make the absorption center shift,as well as the obvious alterations in shape,width and strength of the absorption band.Additionally,it is also found that the logarithm of a second-order polynomial continuum can match the overall shape of the spectrum in logarithmic space,and the improved regression equations applied to estimate the chemical composition of olivine-dominated spectra also have a better performance.As an application example,the improved approach is applied to pulse laser irradiated olivine grains to simulate and study the space weathering effects on olivine diagnostic spectral features.The experiments confirm that space weathering can make the absorption band center shift toward longer wavelength.Therefore,the Fo#estimated from remote sensing spectra may be less than its actual chemical composition.These results may provide valuable information for revealing the difference between the spectra of olivine grains and olivine-dominated asteroids.展开更多
The Yarkovsky-O'Keefe-Radzievskii-Paddack(YORP) effect is a net torque caused by solar radiation directly reflected and thermally re-emitted from the surface of small asteroids and is considered to be crucial in t...The Yarkovsky-O'Keefe-Radzievskii-Paddack(YORP) effect is a net torque caused by solar radiation directly reflected and thermally re-emitted from the surface of small asteroids and is considered to be crucial in their dynamical evolution. By long-term photometric observations of selected near-Earth asteroids, it is hoped to enlarge asteroid samples with a detected YORP effect to facilitate the development of a theoretical framework. Archived light-curve data are collected and photometric observations are made for(1685) Toro and(85989) 1999 JD6,which enables measurement of their YORP effect by inverting the light curve to fit observations from a convex shape model. For(1685) Toro, a YORP acceleration υ =(3.2 ± 0.3) × 10^(-9)rad · day^(-2)(1σ error) is updated,which is consistent with previous YORP detection based on different light-curve data;for(85989) 1999 JD6, it is determined that the sidereal period is 7.667 749 ± 0.000009 hr, the rotation pole direction is located atλ = 232° ± 2°, β =-59° ± 1°, the acceleration is detected to be υ =(2.4 ± 0.3) × 10^(-8)rad · day^(-2)(1σ error) and in addition to obtaining an excellent agreement between the observations and model. YORP should produce both spin-up and spin-down cases. However, including(85989) 1999 JD6, the dω/dt values of 11 near-Earth asteroids are positive totally, which suggests that there is either a bias in the sample of YORP detections or a real feature needs to be explained.展开更多
A rotating mass dipole can be used to understand the dynamical behaviors around elongated asteroids as well as binary asteroids. In this paper an improved dipole model with oblateness in both primaries is investigated...A rotating mass dipole can be used to understand the dynamical behaviors around elongated asteroids as well as binary asteroids. In this paper an improved dipole model with oblateness in both primaries is investigated. The dynamical equations of a particle around the improved model are first derived by introducing the oblateness coefficients. The characteristic equations of equilibrium points are obtained, resulting in the emergence of new equilibria in the equatorial plane and the plane xoz de- pending on the shape of the spheroid. Numerical simulations are performed to illustrate the distribution of these equilibrium points. Significant influence from the oblateness of the primaries on the topological structure is also analyzed via zero-velocity curves.展开更多
A solar collector system is a possible method using solar energy to deflect Earth-threatening near-Earth objects.We investigate the dynamics and control of a solar collector system including a main collector （MC） an...A solar collector system is a possible method using solar energy to deflect Earth-threatening near-Earth objects.We investigate the dynamics and control of a solar collector system including a main collector （MC） and secondary collector （SC）.The MC is used to collect the sunlight to its focal point,where the SC is placed and directs the collected light to an asteroid.Both the relative position and attitude of the two collectors should be accurately controlled to achieve the desired optical path.First,the dynamical equation of the relative motion of the two collectors in the vicinity of the asteroid is modeled.Secondly,the nonlinear sliding-mode method is employed to design a control law to achieve the desired configuration of the two collectors.Finally,the deflection capability of this solar collector system is compared with those of the gravitational tractor and solar sail gravitational tractor.The results show that the solar collector is much more efficient with respect to deflection capability.展开更多
The paper describes observations of fast-moving near-Earth asteroids(NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science(NTSC of CAS) and Research Institute ...The paper describes observations of fast-moving near-Earth asteroids(NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science(NTSC of CAS) and Research Institute "Mykolaiv Astronomical Observatory"(RI MAO) by the rotating-drift-scan CCD(RDS CCD) technique. This technique is used to obtain the point images of both the studied objects and reference stars. The results of ongoing follow-up observations of NEAs are discussed. The residual differences(O-C) between the observed and calculated positions from JPL ephemeris were generally small for these asteroids. The standard deviations of these differences were typically ±(0.2′′-0.3′′) in both coordinates for objects with apparent velocity which substantially exceed FWHM for the given exposure time. The results of comparative statistics for such observations from the MPC database show that this is a good level of precision for NEAs. Moreover, the telescopes with the RDS CCD technique implemented can observe the NEAs that closely approach the Earth and with enough observations can improve the precision of determining their orbital elements and impact predictions.展开更多
Olivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic bodies.The profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically ...Olivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic bodies.The profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically vary with their composition ratios.In our experiments,we combine the RELAB spectral database with new spectral data obtained from some assembled olivine-orthopyroxene mixtures.We found that the commonly-used band area ratio(BAR,Cloutis et al.)does not work well on our newly obtained spectral data.To investigate this issue,an empirical procedure based on fitted results by a modified Gaussian model is proposed to analyze the spectral curves.Following the new empirical procedure,the endmember abundances can be estimated with a 15%accuracy with some prior mineral absorption features.In addition,the mixture samples configured in our experiments are also irradiated by pulsed lasers to simulate and investigate the space weathering effects.Spectral deconvolution results confirm that low-content olivine on celestial bodies is difficult to measure and estimate.Therefore,the olivine abundance of space weathered materials may be underestimated from remote sensing data.This study may be utilized to quantify the spectral relationship of olivine-orthopyroxene mixtures and further reveal their correlation between the spectra of ordinary chondrites and silicate asteroids.展开更多
We carried out low-resolution optical spectroscopy of 51 main-belt asteroids, most of which have highly-inclined orbits. They are selected from D-type candidates in the SDSS-MOC 4 catalog. Using the University of Hawa...We carried out low-resolution optical spectroscopy of 51 main-belt asteroids, most of which have highly-inclined orbits. They are selected from D-type candidates in the SDSS-MOC 4 catalog. Using the University of Hawaii 2.2 m telescope and the Inter-University Centre for Astronomy and Astrophysics 2 m telescope in India, we determined the spectral types of 38 asteroids. Among them, eight asteroids were classified as D-type asteroids. Fractions of D-type asteroids are 3.0 ± 1.1% for low orbital inclination main-belt asteroids and 7.3 ± 2.0% for high orbital inclination main-belt asteroids. The results of our study indicate that some D-type asteroids were formed within the ecliptic region between the main belt and Jupiter, and were then perturbed by Jupiter.展开更多
Celestial mechanics has been a classical field of astronomy. Only a few astronomers were in this field and not so many papers on this subject had been published during the first half of the 20th century. However, as t...Celestial mechanics has been a classical field of astronomy. Only a few astronomers were in this field and not so many papers on this subject had been published during the first half of the 20th century. However, as the beauty of classical dynamics and celestial mechanics attracted me very much, I decided to take celestial mechanics as my research subject and entered university, where a very famous professor of celestial mechanics was a member of the faculty. Then as artificial satellites were launched starting from October 1958, new topics were investigated in the field of celestial mechanics. Moreover, planetary rings, asteroids with moderate values of eccentricity, inclination and so on have become new fields of celestial mechanics. In fact I have tried to solve such problems in an analytical way. Finally, to understand what gravitation is I joined the TAMA300 gravitational wave detector group.展开更多
In asteroid rendezvous missions, the dynamical environment near an asteroid’s surface should be made clear prior to launch of the mission. However, most asteroids have irregular shapes,which lower the efficiency of c...In asteroid rendezvous missions, the dynamical environment near an asteroid’s surface should be made clear prior to launch of the mission. However, most asteroids have irregular shapes,which lower the efficiency of calculating their gravitational field by adopting the traditional polyhedral method. In this work, we propose a method to partition the space near an asteroid adaptively along three spherical coordinates and use Chebyshev polynomial interpolation to represent the gravitational acceleration in each cell. Moreover, we compare four different interpolation schemes to obtain the best precision with identical initial parameters. An error-adaptive octree division is combined to improve the interpolation precision near the surface. As an example, we take the typical irregularly-shaped nearEarth asteroid 4179 Toutatis to demonstrate the advantage of this method; as a result, we show that the efficiency can be increased by hundreds to thousands of times with our method. Our results indicate that this method can be applicable to other irregularly-shaped asteroids and can greatly improve the evaluation efficiency.展开更多
The Damocloids are a group of unusual asteroids that recently added a new member： 2010 EJ104. The dynamical evolution of the Damocloids may reveal a connection from the Main Belt to the Kuiper Belt and beyond the sca...The Damocloids are a group of unusual asteroids that recently added a new member： 2010 EJ104. The dynamical evolution of the Damocloids may reveal a connection from the Main Belt to the Kuiper Belt and beyond the scattered disk. According to our simulations, two regions may be considered as possible origins of the Damocloids： the scattered disk, or a part of the Oort cloud, which will be perturbed to a transient region located between 700 AU and 1000 AU. Based on their potential origin, the Damocloids can be classified into two types, depending on their semi-major axes, and about 65.5% of the Damocloids are classified into type I which mainly originate from the Oort cloud. Whether the Damocloids are inactive nuclei of the Halley Family of Comets may depend on their origin. K展开更多
We determine the proportions of two mixed crater populations distinguishable by size distributions on the Moon. A ＂multiple power-law＂ model is built to formulate crater size distribution N（D） ∝ D-αwhose slope ...We determine the proportions of two mixed crater populations distinguishable by size distributions on the Moon. A ＂multiple power-law＂ model is built to formulate crater size distribution N（D） ∝ D-αwhose slope α varies with crater diameter D. This model is then used to fit size distributions of lunar highland craters and Class 1 craters. The former is characterized by α = 1.17 ± 0.04, 1.88 ± 0.07,3.17 ± 0.10 and 1.40 ± 0.15 for D ranges ~ 10- 49, 49- 120, 120- 251 and ~ 251- 2500 km, while the latter has a single slope α = 1.96 ± 0.14 for about 10- 100 km. They are considered as Population 1 and2 crater size distributions, whose sum is then fitted to the global size distribution of lunar craters with D between 10 and 100 km. Estimated crater densities of Population 1 and 2 are 44 × 10-5and 5 × 10-5km-2respectively, leading to the proportion of the latter being 10%. This result underlines the need for more thoroughly investigating Population 1 craters and their related impactors, the primordial main-belt asteroids, which dominated the late heavy bombardment.展开更多
This paper computed the newest impact solutions of the potentially dangerous asteroid （99942） Apophis based on 4,138 optical observations from March 15.10789 UTC （Universal Time Coordinated）, 2004 to February 28.0...This paper computed the newest impact solutions of the potentially dangerous asteroid （99942） Apophis based on 4,138 optical observations from March 15.10789 UTC （Universal Time Coordinated）, 2004 to February 28.089569 UTC, 2014 and 20 radar observations from January 27, 2005 through March 15, 2013, as of June 20, 2014. Using the freely available the OrbFit software Package, this paper followed its orbit forward in the searching for close approaches with the Earth and possible impacts up to year 2116. With the different A2 non-gravitational parameter in the motion of the asteroid （99942） Apophis, this paper computed possible impact solutions using the JPL DE405 （Jet Propulsion Laboratory Development Ephemeris） and 25 additional massive perturbed asteroids. Additionally, this paper used weighing and selection methods adopted in the OrbFit software as prepared by the NEODyS （Near Earth Objects--Dynamical Side） Team. Moreover, this paper used method of computing the orbit of Apophis taking into account star catalog debiasing and an error model with assumed astrometric errors RMS （root mean square）, deduced from the observational material of the given observatories. JPL＇s Sentry and NEODyS＇s CLOMMON2, two automatic monitoring systems routinely scanning for possible impacts in the next hundred years. Only for several dangerous asteroids presented results are computed with the non-gravitational parameters. This paper detected possible impacts of the asteroid （99942） Apophis only with the non-gravitational parameter, A2 〉 0. It was appeared that impacts in 2068, 2087, 2105 and in 2111 were possible only when Apophis rotated in prograde direction.展开更多
In deriving the physical properties of asteroids from their photometric data, the scattering law plays an important role, although the shape variations of asteroids result in the main variations in lightcurves. By fol...In deriving the physical properties of asteroids from their photometric data, the scattering law plays an important role, although the shape variations of asteroids result in the main variations in lightcurves. By following the physical behaviors of light reflections, Hapke et al. deduced complex functions to represent the scattering process, however, it is very hard to accurately simulate the surface scattering law in reality. For simplicity, other numerical scattering models are presented for efficiently calculating the physical properties of asteroids, such as the Lommel-Seeliger （LS） model. In this article, these two models are compared numerically. It is found that in some numerical applications the LS model in simple form with four parameters can be exploited to replace the Hapke model in complex form with five parameters. Furthermore, the generated synthetic lightcurves by the Cellinoid shape model also show that the LS model can perform as well as the Hapke model in the inversion process. Finally, by applying the Principal Component Analysis （PCA） technique to the parameters of the LS model, we present an efficient method to classify C and S type asteroids, instead of the conventional method using the parameters of the Hapke model.展开更多
基金supported by the Characteristic innovation project of Guangdong Provincial Department of Education(No.2023KTSCX195)Scientific Computing Research Innovation Team of Guangdong Province(No.2021KCXTD052)+2 种基金Guangdong Key Construction Discipline Research Capacity Enhancement Project(No.2022ZD JS049)Technology Planning Project of Shaoguan(No.230330108034184)Science and Technology Development Fund,Macao SAR(No.0096/2022/A)。
文摘Determining asteroid properties provides valuable physical insights but inverting them from photometric lightcurves remains computationally intensive.This paper presents a new approach that combines a simplified Cellinoid shape model with the Parallel Differential Evolution(PDE)algorithm to accelerate inversion.The PDE algorithm is more efficient than the Differential Evolution algorithm,achieving an extraordinary speedup of 37.983 with 64 workers on multicore CPUs.The PDE algorithm accurately derives period and pole values from simulated data.The analysis of real asteroid lightcurves validates the method’s reliability:in comparison with results published elsewhere,the PDE algorithm accurately recovers the rotational periods and,given adequate viewing geometries,closely matches the pole orientations.The PDE approach converges to solutions within 20,000 iterations and under one hour,demonstrating its potential for large-scale data analysis.This work provides a promising new tool for unveiling asteroid physical properties by overcoming key computational bottlenecks.
基金supported by Basic Research Project of China(grant No:JCKY2020110C096)the National Key R&D Program of China (grant No:2020YFC2201202)。
文摘As the second of Earth's Trojan asteroids, 2020 XL_(5) is worthy of rendezvous and even sample return missions in many aspects. In this paper, a rendezvous mission to Earth's second Trojan asteroid 2020 XL_(5) is proposed.However, due to its high inclination and large eccentricity, direct impulsive transfer requires large amounts of fuel consumption. To address this challenge, we explore the benefits of electric propulsion and multi-gravity assist techniques for interplanetary missions. These two techniques are integrated in this mission design. The design of a low-thrust gravity-assist(LTGA) trajectory in multi-body dynamics is thoroughly investigated,which is a complex process. A comprehensive framework including three steps is presented here for optimization of LTGA trajectories in multi-body dynamics. The rendezvous mission to 2020 XL_(5) is designed with this three-step approach. The most effective transfer sequence among the outcomes involves Earth–Venus–Earth–Venus-2020 XL_(5). Numerical results indicate that the combination of electric propulsion and multi-gravity assists can greatly reduce the fuel consumption, with fuel consumption of 9.03%, making it a highly favorable choice for this rendezvous mission.
基金financial support from the Science Research Foundation of Yunnan Education Department of China(grant 2020J0649)the Natural Science Foundation of Yunnan Province(grant 202101AU070010)the financial support from the Hundred Talents Program of Yuxi(grant 2019-003)。
文摘The shapes and rotation states(periods and pole orientations)of main-belt asteroids are important for understanding their formation and evolution.In order to obtain sufficient photometric data covering different apparitions for asteroid(81)Terpsichore,ground-based photometric observations in 2020 and 2021 were carried out.By combining published and newly obtained photometric data,we calculated the shape and spin parameters for(81)Terpsichore using the convex inversion method.With this method,we have derived a best fitted pole orientation—(22.2±_(3.1)^(3.3°),17.5±_(5.5)^(10.8°))with a spin period of 10.94±_(0.01)^(0.01)h.Based on the derived convex shape of(81)Terpsichore,we have fitted the H,G+1,G_(2)phase function using the calibrated TESS data and Gaia data after accounting for the lightcurve amplitude correction.As a result,we have derived its absolute magnitude H=8.68±_(0.19)^(0.22)mag with corresponding phase function parameters G_(1)=0.82±_(0.10)^(0.09)and G_(2)=0.02±_(0.02)^(0.03).
基金funded by the National Natural Science Foundation of China(Grant Nos.11073051 and 11473066)by the Open Project of Key Laboratory of Space Object and Debris Observation,Chinese Academy of Sciences(Title:Photometric study of space debris in near geostationary orbit)
文摘We characterize the morphology of the photometric phase curve model of an asteroid with a three- parameter magnitude phase function H - G1 - G2 system by considering the effect of brightness variation arising from a triaxial ellipsoid representing the asteroid＇s shape. Applying this new model and a Markov Chain Monte Carlo method, we refine the photometric phase curve of asteroid （107） Camilla and obtain its absolute magnitude H = 7.026-0.054^＋0.052 mag, and phase function parameters G1=0.489-0.044^＋0.043 and G2 = 0.259-0.023^＋0.023.Meanwhile, we also determine （107） Camilla＇s orientation of pole （74.1°-4.5°^＋4.3°,50.2°-5.0°^＋5.4°）. with rotational period of 4.843928-0.000001^＋0.000001 h, and axial ratios a/b ： 1.409-0.020^＋0.020 And b/c =1.249-0.060^＋0.063. Furthermore, according to the values of phase function parameters G1 and G2, we infer that asteroid （107） Camilla is an X-type asteroid.
文摘We review previously published and newly obtained crater size-frequency distributions in the inner solar system. These data indicate that the Moon and the ter- restrial planets have been bombarded by two populations of objects. Population 1, dominating at early times, had nearly the same size distribution as the present-day asteroid belt, and produced heavily cratered surfaces with a complex, multi-sloped crater size-frequency distribution. Population 2, dominating since about 3.8-3.7 Gyr, had the same size distribution as near-Earth objects （NEOs） and a much lower im- pact flux, and produced a crater size distribution characterized by a differential -3 single-slope power law in the crater diameter range 0.02 km to 100 km. Taken to- gether with the results from a large body of work on age-dating of lunar and meteorite samples and theoretical work in solar system dynamics, a plausible interpretation of these data is as follows. The NEO population is the source of Population 2 and it has been in near-steady state over the past ～ 3.7-3.8 Gyr; these objects are derived from the main asteroid belt by size-dependent non-gravitational effects that favor the ejection of smaller asteroids. However, Population 1 was composed of main belt as- teroids ejected from their source region in a size-independent manner, possibly by means of gravitational resonance sweeping during orbit migration of giant planets; this caused the so-called Late Heavy Bombardment （LHB）. The LHB began some time before ～3.9 Gyr, peaked and declined rapidly over the next ～ 100 to 300 Myr, and possibly more slowly from about 3.8-3.7 Gyr to ～2 Gyr. A third crater population （Population S） consisted of secondary impact craters that can dominate the cratering record at small diameters.
基金supported by the National Natural Science Foundation of China(Grant No 10832004)
文摘Recently, Near Earth Objects （NEOs） have been attracting great attention, and thousands of NEOs have been found to date. This paper examines the NEOs＇ orbital dynamics using the framework of an accurate solar system model and a Sun- Earth-NEO three-body system when the NEOs are close to Earth to search for NEOs with low-energy orbits. It is possible for such an NEO to be temporarily captured by Earth; its orbit would thereby be changed and it would become an Earth-orbiting object after a small increase in its velocity. From the point of view of the Sun-Earth- NEO restricted three-body system, it is possible for an NEO whose Jacobian constant is slightly lower than C1 but higher than C3 to be temporarily captured by Earth. When such an NEO approaches Earth, it is possible to change its orbital energy to nearly the zero velocity surface of the three-body system at point L1 and make the NEO become a small satellite of the Earth. Some such NEOs were found; the best example only required a 410 m s^-1 increase in velocity.
基金the Foundation of the State Key Laboratory of Lunar and Planetary Sciences,Macao University of Science and Technology,Macao,Chinafunded by The Science and Technology Development Fund,Macao SAR(No.0018/2018/A)+3 种基金Beijing Municipal Science and Technology Commission(No.Z181100002918003)Natural Science Foundation of China(Nos.U1631124,11773023 and 11941001)grants from The Science and Technology Development Fund,Macao SAR(No.0007/2019/A)the support of Brown University,MIT and USGS。
文摘The absorption features of olivine in visible and near-infrared(VNIR)reflectance spectra are the key spectral parameters in its mineralogical studies.Generally,these spectral parameters can be obtained by exploiting the Modified Gaussian Model(MGM)with a proper continuum removal.However,different continua may change the deconvolution results of these parameters.This paper investigates the diagnostic spectral features of olivine with diverse chemical compositions.Four different continuum removal methods with MGM for getting the deconvolution results are presented and the regression equations for predicting the Mg-number(Fo#)are introduced.The results show that different continua superimposed on the mineral absorption features will make the absorption center shift,as well as the obvious alterations in shape,width and strength of the absorption band.Additionally,it is also found that the logarithm of a second-order polynomial continuum can match the overall shape of the spectrum in logarithmic space,and the improved regression equations applied to estimate the chemical composition of olivine-dominated spectra also have a better performance.As an application example,the improved approach is applied to pulse laser irradiated olivine grains to simulate and study the space weathering effects on olivine diagnostic spectral features.The experiments confirm that space weathering can make the absorption band center shift toward longer wavelength.Therefore,the Fo#estimated from remote sensing spectra may be less than its actual chemical composition.These results may provide valuable information for revealing the difference between the spectra of olivine grains and olivine-dominated asteroids.
基金supported by the B-type Strategic Priority Program of the Chinese Academy of Sciences (GrantNo.XDB41010104)the National Natural Science Foundation of China (Grant No.11633009)+2 种基金the Space Debris and NearEarth Asteroid Defense Research Project (Grant Nos. KJSP2020020204,KJSP2020020102)the Civil Aerospace Pre-research Project (Grant Nos.D020304,D020302)Minor Planet Foundation。
文摘The Yarkovsky-O'Keefe-Radzievskii-Paddack(YORP) effect is a net torque caused by solar radiation directly reflected and thermally re-emitted from the surface of small asteroids and is considered to be crucial in their dynamical evolution. By long-term photometric observations of selected near-Earth asteroids, it is hoped to enlarge asteroid samples with a detected YORP effect to facilitate the development of a theoretical framework. Archived light-curve data are collected and photometric observations are made for(1685) Toro and(85989) 1999 JD6,which enables measurement of their YORP effect by inverting the light curve to fit observations from a convex shape model. For(1685) Toro, a YORP acceleration υ =(3.2 ± 0.3) × 10^(-9)rad · day^(-2)(1σ error) is updated,which is consistent with previous YORP detection based on different light-curve data;for(85989) 1999 JD6, it is determined that the sidereal period is 7.667 749 ± 0.000009 hr, the rotation pole direction is located atλ = 232° ± 2°, β =-59° ± 1°, the acceleration is detected to be υ =(2.4 ± 0.3) × 10^(-8)rad · day^(-2)(1σ error) and in addition to obtaining an excellent agreement between the observations and model. YORP should produce both spin-up and spin-down cases. However, including(85989) 1999 JD6, the dω/dt values of 11 near-Earth asteroids are positive totally, which suggests that there is either a bias in the sample of YORP detections or a real feature needs to be explained.
基金supported by the National Natural Science Foundation of China(Nos.11602019 and 11572035)China Postdoctoral Science Foundation(2015T80077)+1 种基金The Excellent Young Teachers Program of Beijing Institute of TechnologyBeijing Institute of Technology Research Fund Program for Young Scholars
文摘A rotating mass dipole can be used to understand the dynamical behaviors around elongated asteroids as well as binary asteroids. In this paper an improved dipole model with oblateness in both primaries is investigated. The dynamical equations of a particle around the improved model are first derived by introducing the oblateness coefficients. The characteristic equations of equilibrium points are obtained, resulting in the emergence of new equilibria in the equatorial plane and the plane xoz de- pending on the shape of the spheroid. Numerical simulations are performed to illustrate the distribution of these equilibrium points. Significant influence from the oblateness of the primaries on the topological structure is also analyzed via zero-velocity curves.
基金funded by the National Natural Science Foundation of China(Grant Nos.10902056 and 10832004)
文摘A solar collector system is a possible method using solar energy to deflect Earth-threatening near-Earth objects.We investigate the dynamics and control of a solar collector system including a main collector （MC） and secondary collector （SC）.The MC is used to collect the sunlight to its focal point,where the SC is placed and directs the collected light to an asteroid.Both the relative position and attitude of the two collectors should be accurately controlled to achieve the desired optical path.First,the dynamical equation of the relative motion of the two collectors in the vicinity of the asteroid is modeled.Secondly,the nonlinear sliding-mode method is employed to design a control law to achieve the desired configuration of the two collectors.Finally,the deflection capability of this solar collector system is compared with those of the gravitational tractor and solar sail gravitational tractor.The results show that the solar collector is much more efficient with respect to deflection capability.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1831133 and 12073062)National Astronomical Data Center of China。
文摘The paper describes observations of fast-moving near-Earth asteroids(NEAs) made with the small ground-based telescopes of National Time Service Center of Chinese Academy of Science(NTSC of CAS) and Research Institute "Mykolaiv Astronomical Observatory"(RI MAO) by the rotating-drift-scan CCD(RDS CCD) technique. This technique is used to obtain the point images of both the studied objects and reference stars. The results of ongoing follow-up observations of NEAs are discussed. The residual differences(O-C) between the observed and calculated positions from JPL ephemeris were generally small for these asteroids. The standard deviations of these differences were typically ±(0.2′′-0.3′′) in both coordinates for objects with apparent velocity which substantially exceed FWHM for the given exposure time. The results of comparative statistics for such observations from the MPC database show that this is a good level of precision for NEAs. Moreover, the telescopes with the RDS CCD technique implemented can observe the NEAs that closely approach the Earth and with enough observations can improve the precision of determining their orbital elements and impact predictions.
基金supported by the Foundation of the State Key Laboratory of Lunar and Planetary Sciences, Macao University of Science and Technology, Macao, Chinafunded by The Science and Technology Development Fund, Macao SAR (No. 0073/2019/A2)+2 种基金the support from The Science and Technology Development Fund, Macao SAR (No. 0007/2019/A)supported by Beijing Municipal Science and Technology Commission (No. Z181100002918003)supported by the National Natural Science Foundation of China (NSFC, Nos. 11773023, 11941001, 12073024 and U1631124)
文摘Olivine and pyroxene are important mineral end-members for studying the surface material compositions of mafic bodies.The profiles of visible and near-infrared spectra of olivine-orthopyroxene mixtures systematically vary with their composition ratios.In our experiments,we combine the RELAB spectral database with new spectral data obtained from some assembled olivine-orthopyroxene mixtures.We found that the commonly-used band area ratio(BAR,Cloutis et al.)does not work well on our newly obtained spectral data.To investigate this issue,an empirical procedure based on fitted results by a modified Gaussian model is proposed to analyze the spectral curves.Following the new empirical procedure,the endmember abundances can be estimated with a 15%accuracy with some prior mineral absorption features.In addition,the mixture samples configured in our experiments are also irradiated by pulsed lasers to simulate and investigate the space weathering effects.Spectral deconvolution results confirm that low-content olivine on celestial bodies is difficult to measure and estimate.Therefore,the olivine abundance of space weathered materials may be underestimated from remote sensing data.This study may be utilized to quantify the spectral relationship of olivine-orthopyroxene mixtures and further reveal their correlation between the spectra of ordinary chondrites and silicate asteroids.
基金partially supported by“the Japan-India Cooperative Science Program”carried out by the Japan Society for the Promotion of Science(JSPS)the Department of Science and Technology(DST),Government of India
文摘We carried out low-resolution optical spectroscopy of 51 main-belt asteroids, most of which have highly-inclined orbits. They are selected from D-type candidates in the SDSS-MOC 4 catalog. Using the University of Hawaii 2.2 m telescope and the Inter-University Centre for Astronomy and Astrophysics 2 m telescope in India, we determined the spectral types of 38 asteroids. Among them, eight asteroids were classified as D-type asteroids. Fractions of D-type asteroids are 3.0 ± 1.1% for low orbital inclination main-belt asteroids and 7.3 ± 2.0% for high orbital inclination main-belt asteroids. The results of our study indicate that some D-type asteroids were formed within the ecliptic region between the main belt and Jupiter, and were then perturbed by Jupiter.
文摘Celestial mechanics has been a classical field of astronomy. Only a few astronomers were in this field and not so many papers on this subject had been published during the first half of the 20th century. However, as the beauty of classical dynamics and celestial mechanics attracted me very much, I decided to take celestial mechanics as my research subject and entered university, where a very famous professor of celestial mechanics was a member of the faculty. Then as artificial satellites were launched starting from October 1958, new topics were investigated in the field of celestial mechanics. Moreover, planetary rings, asteroids with moderate values of eccentricity, inclination and so on have become new fields of celestial mechanics. In fact I have tried to solve such problems in an analytical way. Finally, to understand what gravitation is I joined the TAMA300 gravitational wave detector group.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.11473073,11503091,11661161013 and 11633009)Foundation of Minor Planets of the Purple Mountain Observatory
文摘In asteroid rendezvous missions, the dynamical environment near an asteroid’s surface should be made clear prior to launch of the mission. However, most asteroids have irregular shapes,which lower the efficiency of calculating their gravitational field by adopting the traditional polyhedral method. In this work, we propose a method to partition the space near an asteroid adaptively along three spherical coordinates and use Chebyshev polynomial interpolation to represent the gravitational acceleration in each cell. Moreover, we compare four different interpolation schemes to obtain the best precision with identical initial parameters. An error-adaptive octree division is combined to improve the interpolation precision near the surface. As an example, we take the typical irregularly-shaped nearEarth asteroid 4179 Toutatis to demonstrate the advantage of this method; as a result, we show that the efficiency can be increased by hundreds to thousands of times with our method. Our results indicate that this method can be applicable to other irregularly-shaped asteroids and can greatly improve the evaluation efficiency.
基金Wang S. is supported by the National Natural Science Foundation of China (Grant Nos. 10925313 and 10833001)the China Post doctoral Science Foundation (Grant No. 2011M500962)+4 种基金Z.H.B is supported by the National Natural Science Foundation of China (Grant Nos. 10503013 and 10933004)J.J.H is grateful for support by the National Natural Science Foundation of China (Grant Nos. 11273068, 10973044 and 10833001)the Natural Science Foundation of Jiangsu Province (Grant No. BK2009341)the Foundation of Minor Planets of Purple Mountain Observatorythe innovative and inter disciplinary program by CAS (Grant No. KJZD-EW-Z001)
文摘The Damocloids are a group of unusual asteroids that recently added a new member： 2010 EJ104. The dynamical evolution of the Damocloids may reveal a connection from the Main Belt to the Kuiper Belt and beyond the scattered disk. According to our simulations, two regions may be considered as possible origins of the Damocloids： the scattered disk, or a part of the Oort cloud, which will be perturbed to a transient region located between 700 AU and 1000 AU. Based on their potential origin, the Damocloids can be classified into two types, depending on their semi-major axes, and about 65.5% of the Damocloids are classified into type I which mainly originate from the Oort cloud. Whether the Damocloids are inactive nuclei of the Halley Family of Comets may depend on their origin. K
基金supported by the National Key Basic Research Program of China (973 program, No. 2013CB834900)the National Natural Science Foundation of China (Nos. 11003010 and 11333002)+3 种基金the Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences (Grant No. XDB09000000)the Natural Science Foundation for the Youth of Jiangsu Province (No. BK20130547)the 985 project of Nanjing UniversitySuperiority Discipline Construction Project of Jiangsu Province
文摘We determine the proportions of two mixed crater populations distinguishable by size distributions on the Moon. A ＂multiple power-law＂ model is built to formulate crater size distribution N（D） ∝ D-αwhose slope α varies with crater diameter D. This model is then used to fit size distributions of lunar highland craters and Class 1 craters. The former is characterized by α = 1.17 ± 0.04, 1.88 ± 0.07,3.17 ± 0.10 and 1.40 ± 0.15 for D ranges ~ 10- 49, 49- 120, 120- 251 and ~ 251- 2500 km, while the latter has a single slope α = 1.96 ± 0.14 for about 10- 100 km. They are considered as Population 1 and2 crater size distributions, whose sum is then fitted to the global size distribution of lunar craters with D between 10 and 100 km. Estimated crater densities of Population 1 and 2 are 44 × 10-5and 5 × 10-5km-2respectively, leading to the proportion of the latter being 10%. This result underlines the need for more thoroughly investigating Population 1 craters and their related impactors, the primordial main-belt asteroids, which dominated the late heavy bombardment.
文摘This paper computed the newest impact solutions of the potentially dangerous asteroid （99942） Apophis based on 4,138 optical observations from March 15.10789 UTC （Universal Time Coordinated）, 2004 to February 28.089569 UTC, 2014 and 20 radar observations from January 27, 2005 through March 15, 2013, as of June 20, 2014. Using the freely available the OrbFit software Package, this paper followed its orbit forward in the searching for close approaches with the Earth and possible impacts up to year 2116. With the different A2 non-gravitational parameter in the motion of the asteroid （99942） Apophis, this paper computed possible impact solutions using the JPL DE405 （Jet Propulsion Laboratory Development Ephemeris） and 25 additional massive perturbed asteroids. Additionally, this paper used weighing and selection methods adopted in the OrbFit software as prepared by the NEODyS （Near Earth Objects--Dynamical Side） Team. Moreover, this paper used method of computing the orbit of Apophis taking into account star catalog debiasing and an error model with assumed astrometric errors RMS （root mean square）, deduced from the observational material of the given observatories. JPL＇s Sentry and NEODyS＇s CLOMMON2, two automatic monitoring systems routinely scanning for possible impacts in the next hundred years. Only for several dangerous asteroids presented results are computed with the non-gravitational parameters. This paper detected possible impacts of the asteroid （99942） Apophis only with the non-gravitational parameter, A2 〉 0. It was appeared that impacts in 2068, 2087, 2105 and in 2111 were possible only when Apophis rotated in prograde direction.
基金funded under grant Nos. 095/2013/A3 and 039/2013/A2 from the Science and Technology Development Fundsupported partly by the Key Laboratory of Planetary Sciences+2 种基金supported by the MSAR Science and Technology Fund (Project No. 017/2014/A1)support of the National Natural Science Foundation of China (Grant Nos. 11633009, 11273067 and 10503013)the Minor Planet Foundation of Purple Mountain Observatory
文摘In deriving the physical properties of asteroids from their photometric data, the scattering law plays an important role, although the shape variations of asteroids result in the main variations in lightcurves. By following the physical behaviors of light reflections, Hapke et al. deduced complex functions to represent the scattering process, however, it is very hard to accurately simulate the surface scattering law in reality. For simplicity, other numerical scattering models are presented for efficiently calculating the physical properties of asteroids, such as the Lommel-Seeliger （LS） model. In this article, these two models are compared numerically. It is found that in some numerical applications the LS model in simple form with four parameters can be exploited to replace the Hapke model in complex form with five parameters. Furthermore, the generated synthetic lightcurves by the Cellinoid shape model also show that the LS model can perform as well as the Hapke model in the inversion process. Finally, by applying the Principal Component Analysis （PCA） technique to the parameters of the LS model, we present an efficient method to classify C and S type asteroids, instead of the conventional method using the parameters of the Hapke model.
