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The article considers the mission design problem for removal of large space debris objects from near-Earth orbits. It is assumed that a single active spacecraft-collector (SC) should de/re-orbit several objects. The upper planning level calls for a scenario that specifies the type of repeating operations of an SC. Despite the apparent diversity of these scenarios, they can be reduced to two variants of objects removal to disposal orbits (DOs). In variant I, transfers between objects are effected by an SC with detachable propulsion modules (PMs) onboard. Once the next-in-line object is captured, one module is accommodated on its surface, and, after demating, this PM ensures the relocation of the object to a DO. In variant II, the SC operates as a tug vehicle and transfers the object to DO on its own, and then returns to the next object. A reasonable choice of the removal variant depends on the SC launch mass which should be compared for the same number of de/re-orbited derelict targets. To this end, one should estimate the SC dry mass, the payload mass, and the SC propellant mass. Each of these three terms is nonlinear and depends explicitly on each other, the mass of the captured object, and on the SC maneuvers. Analytical models are proposed for estimation of the SC launch mass for each of the two removal variants. It is also shown that there exists an altitude optimality boundary (the radius of a spherical layer) above which the removal variant II is more advantageous than variant I. Such models are constructed based on several assumptions capable of breaking the iterative search of the SC launch mass. The position of the altitude optimality boundary depends on seven input parameters of the mission: the SC dry mass; the PM dry mass; the mass of the object, the required variation of the semi-major axis Δ a to reach the DO, the number of objects removed by a single SC, the average Δ V for a transfer between two objects, and the effective exhaust velocity of SC main engine. In the present paper, four types of objects are considered: heavy and light LV stages in low orbits, upper stages in GEO and GNSS regions. By choosing concrete objects of study one can substantially reduce the solution space by excluding the impossible combinations of input data. By using the developed SC launch mass models, it is possible to formulate removal recommendations for concrete groups of space debris objects. These models were shown as being adequate on the examples of Elsa-M and MRV projects which are due to be implemented in the next one-two years. • Upper planning level for large space debris active removal is considered. • Analytical models are proposed for estimation of the launch mass of an SC aimed at handling several objects. • Two variants of removal of launch vehicle stages and upper stages to disposal orbits are studied. • It is shown that there exists an altitude optimality boundary between these variants. • Recommendations on removal variant for objects located in low, medium, and high Earth orbits are given. [ABSTRACT FROM AUTHOR]

On 18 May 2024, a superbolide traversed the western part of the Iberian Peninsula, culminating its flight over the Atlantic Ocean and generating significant media attention. This event was caused by a weak carbonaceous meteoroid of 1 m, entering the atmosphere at 40.4 km s |$^{-1}$| with an average slope of 8.5 |$^\circ$|⁠. The luminous phase started at 133 km and ended at an altitude of 54 km. The meteoroid's heliocentric orbit had an inclination of 16.4 |$^\circ$|⁠ , a high eccentricity of 0.952, a semimajor axis of 2.4 au, and a short perihelion distance of 0.12 au. The superbolide was recorded by multiple ground-based stations of the Spanish Fireball and Meteorite Network and the European Space Agency, as well as by the U.S. Government sensors from space. Due to the absence of observable deceleration, we successfully reconciled satellite radiometric data with a purely dynamic atmospheric flight model, constraining the meteoroid's mass and coherently fitting its velocity profile. Our analysis shows a good agreement with the radiant and velocity data reported by the Center for Near-Earth Object Studies, with a deviation of 0.56 |$^\circ$| and 0.1 km s |$^{-1}$|⁠ , respectively. The presence of detached fragments in the lower part of the luminous trajectory suggests that the meteoroid was a polymict carbonaceous chondrite, containing higher-strength macroscopic particles in its interior due to collisional gardening, or a thermally processed C-type asteroid. The orbital elements indicate that the most likely source is the Jupiter-Family Comet region, aligning with the Solar and Heliospheric Observatory comet family, as its sunskirting orbit is decoupled from Jupiter. This event provides important information to characterize the disruption mechanism of near-Sun objects. [ABSTRACT FROM AUTHOR]

In recent years, the escalating risk of natural disasters caused by Near-Earth Objects (NEOs) has garnered heightened scrutiny, particularly in the aftermath of the 2013 Chelyabinsk event. This has prompted increased interest from governmental and supranational entities, leading to the formulation of various measures and strategies aimed at mitigating the potential threat posed by NEOs. This paper delves into the analysis of the 2011 AG5 asteroid within the context of small celestial bodies (e.g., asteroids, comets, or meteoroids) exhibiting resonant orbits with Earth's heliocentric revolution. Initial observations in 2011 raised alarms regarding the asteroid's orbital parameters, indicating a significant risk of Earth impact during its resonant encounter in 2040. Subsequent observations, however, mitigated these concerns. Here, we manipulate the orbital elements of the 2011 AG5 asteroid to simulate its behavior as a virtual impactor (a virtual asteroid whose orbit could impact Earth). This modification facilitates the assessment of impact mitigation resulting from a deflection maneuver utilizing a kinetic impactor. The deflection maneuver, characterized as an impulsive change in the asteroid's momentum, is executed during a resonant encounter occurring approximately two decades before the potential impact date. The paper systematically evaluates the dependence of the deflection maneuver's efficacy on critical parameters, including the position along the orbit, epoch, and momentum enhancement factor. [ABSTRACT FROM AUTHOR]

Fireball monitoring network is the main equipment for monitoring impact from small-size near-Earth objects (NEOs), and determining meteorite fall locations. In this paper, a monitoring system using a multi-station distributed all-sky video camera network is proposed, and a regional prototype system has been constructed in Jiangsu and surrounding areas. The main processes of fireball monitoring were implemented, including network control, video capture, data processing, trajectory determination, and orbit calculation. After running for 1 yr, the results show that the limiting apparent magnitude - 1.0 for meteors in the video, and the absolute magnitude exhaustive detection regime can reach around - 2.5. The flux of fireballs is found to be 2.68 × 10 − 7 km − 2 · h − 1. The percentages of streams and sporadic meteors are 46% and 54%, respectively, and the fraction of cometary orbits equals 72.9%, while for asteroidal-type it is 27.1%. The statistical results are close to those of the international meteor monitoring networks, which verified the monitoring capability of the network system in practical operation. [ABSTRACT FROM AUTHOR]

Recent observations and detections of interstellar objects (ISOs) passing through the Solar system have sparked a wave of interest into these objects. Although rare, these ISOs can be captured into bound orbits around the Sun. In this study, we investigate the novel idea of capture of ISOs into near-Earth orbits and find that a steady population of ISOs exists among the current population of near-Earth objects (NEOs). Using numerical simulations, we find that the capture of ISOs into near-Earth orbits is dominated by Jupiter that is 104 times more efficient in capturing ISOs compared to Earth. Captured ISOs are more likely to be in orbits with high eccentricities and low inclinations. We also investigate the stability of captured ISOs and find that they are generally unstable and have an average survival lifetime of ∼1 Myr, consistent with lifetime of NEOs originating from outer asteroid belt, and are ejected from the Solar system due to interactions with other planets or the Sun. Our results have important implications for understanding the population of ISOs in the Solar system and possible future detection. We find that about one to a few 50–70 m sized captured ISOs among NEOs would be detectable by Vera Rubin Observatory over its lifetime. By detecting and studying captured ISOs, we can learn about the properties and origins of such objects, and the formation and evolution of exoplanetary systems and even our Solar system. [ABSTRACT FROM AUTHOR]

In the characterization of the space debris environment, the computation of the orbit of the debris objects is usually conducted by considering the association of short sequences of observations called tracklets. In case the orbits can be already determined with sufficient accuracy from single tracklets, it is necessary to define a criterion to decide if two calculated orbits correspond to the same object. One possibility is to introduce a definition of distance between orbits and to consider a threshold below which the two orbits are considered to be originating from the same object. The concept of distance is quite general and leaves room to different definitions. There are different ways to describe and to parameterize the space of the possible orbits. In this article, new metrics are proposed which extend distance definitions suggested in previous works. In these metrics in addition to orbital plane and orbital shape, also the position of the object along the orbit is taken into account. The obtained distances are scaled according to the orbit covariance. This has the advantage that the distance between orbits with different accuracy can be evaluated. The proposed metrics are then compared with existing common metrics to assess their applicability. [ABSTRACT FROM AUTHOR]

The paper presents a method for processing positional observations of near-Earth objects using a numerical model of satellite motion developed at the Research Institute of Applied Mathematics and Mechanics of Tomsk State University (NII PMM TSU). The root-mean-square error of orbit improvement without rejection of observations for such objects does not exceed 0.3″ over a seven-day time interval. The results of the presentation of observations for the next occurrence of the object are obtained, which makes it possible to find the object in a time interval of five months. The orbit has been refined in the joint processing of measurements on several occurrences of the object over a six-month time interval. All results were obtained from observations made on the equipment of the Terskol Observatory Shared Use Center. [ABSTRACT FROM AUTHOR]

The Yarkovsky effect causes the semimajor axis drift of near-Earth asteroids. The drift can be detected by a precise orbit determination process. Using the proposed algorithm, 2233 out of 27,078 near-Earth asteroids are chosen as the initial candidates. Out of these initial candidates, 769 have a measurable Yarkovsky effect with a signal-to-noise ratio (S/N) larger than 1, and 166 have a measurable Yarkovsky effect with an S/N larger than 3. The ratio between retrograde and prograde near-Earth asteroids is plotted with respect to their size. An average ratio of 2 is found for asteroids with an absolute magnitude between 14 and 21. The measurement work is carried out based on orbit determination software developed by the authors that considers a high-precision dynamical model. [ABSTRACT FROM AUTHOR]

Asteroids having perihelion distance q < 1.3 AU are classified as near-Earth objects (NEOs), which are divided into different sub-groups: Vatira-class, Atira-class, Aten-class, Apollo-class, and Amor-class. 2020 AV 2, the first Vatira (Orbiting totally inside Venus' orbit) was discovered by the Twilight project of the Zwicky Transient Facility (ZTF) on 2020 January 4. Upon the discovery of 2020 AV 2, a couple of orbital studies of the short-term orbital evolution of 2020 AV 2 have been performed and published (e.g. de la Fuente Marcos & de la Fuente Marcos 2020 ; Greenstreet 2020). In this work, we performed an assessment of the long-term orbital evolution of known near-Earth objects and known Atiras under the Yarkovsky effect by using the Mercury6 N -body code. We considered not only planetary gravitational perturbation but also the non-gravitational Yarkovsky effect. Our calculation shows that the NEOs have generally two dynamical populations, one short-lived and the other long-lived. From our calculation, the transfer probabilities of Atira-class asteroids to Vatira-class asteroids for the first transition are ∼13.1 ± 0.400, ∼13.05 ± 0.005, and ∼13.25 ± 0.450 |${{\ \rm per\ cent}}$| for different values of the Yarkovsky force (i.e. obliquity of 0, 90, and 180 deg), respectively. It suggests that the radiation force may play some role in the long-term evolution of this asteroid population. Finally, our statistical study implicates that there should be 8.14 ± 0.133 Atira-class asteroids and 1.05 ± 0.075 Vatira-asteroids of the S-type taxonomy. [ABSTRACT FROM AUTHOR]

Our previous model (NEOMOD2) for the orbital and absolute magnitude distribution of Near Earth Objects (NEOs) was calibrated on the Catalina Sky Survey observations between 2013 and 2022. Here we extend NEOMOD2 to include visible albedo information from the Wide-Field Infrared Survey Explorer. The debiased albedo distribution of NEOs can be approximated by the sum of two Rayleigh distributions with the scale parameters p V,dark ≃ 0. 03 and p V,bright ≃ 0. 17. We find evidence for smaller NEOs having (on average) higher albedos than larger NEOs; this is likely a consequence of the size-dependent sampling of different main belt sources. These inferences and the absolute magnitude distribution from NEOMOD2 are used to construct the debiased size distribution of NEOs. We estimate 830 ± 60 NEOs with diameters D > 1 km and 20 , 000 ± 2 , 000 NEOs with D > 140 m. The new model, NEOMOD3, is available via the NEOMOD Simulator — an easy-to-operate code that can be used to generate user-defined samples (orbits, sizes and albedos) from the model. • The albedo distribution of NEOs is size and orbit dependent. • There are 830 NEOs larger than 1 km and 20,000 NEOs larger than 140 m. • The average interval between impacts of > 140 m km NEOs is 20,000 yr. [ABSTRACT FROM AUTHOR]

This work provides insights into the possible origin of comet P/2003 T12 (SOHO) and the dynamics of comet fragmentation events. We studied the hypothesis of the origin of the comet P/2003 T12 (SOHO) as a fragment of the Jupiter family comet 169P/NEAT. We studied the recent dynamical evolution of the comet pair and determined the epochs of relative minimum distance and velocity as well as the similarity between the orbits using different criteria following Rożek et al. (2011) and Kholshevnikov et al. (2016). We generated 6000 clones of both comets with orbital elements compatible with the observational uncertainties of the actual orbits and found that their evolution is stable for the past ∼ 5000 years. We found four epochs where the relative distance and velocity exhibit simultaneous minima. We studied possible fragmentation events in these epochs by applying a simple break-up model for the generation of fictitious fragments at different relative speeds. Analyzing the orbital distance between the fragments, we found some fragments that exhibit noticeable stable behavior at a very low mutual orbital distance according to several distance definitions, which suggest that those fragments evolve in orbits very similar to that of the P/2003 T12 (SOHO). We conclude that comet P/2003 T12 (SOHO) could be a fragment of comet 169P/NEAT and the most likely epoch for such fragmentation would be at least 2000 years ago (around 94 A.D.), given that the fragments that best resemblance comet P/2003 T12 (SOHO) are found in this epoch. • Orbits 169P/NEAT and P/2003 T12 (SOHO) remained stable for the latest 10000 years • Four simultaneous relative distance and velocity minima are found in the last 2000 years • Several minima that occurred before 2000 years are found but are not well defined • We found simulated fragments that evolve similar to actual P/2003 T12 (SOHO) orbit [ABSTRACT FROM AUTHOR]

Catalina Sky Survey (CSS) is a major survey of Near-Earth Objects (NEOs). In a recent work, we used CSS observations from 2005–2012 to develop a new population model of NEOs (NEOMOD). CSS's G96 telescope was upgraded in 2016 and detected over 10,000 unique NEOs since then. Here we characterize the NEO detection efficiency of G96 and use G96's NEO detections from 2013–2022 to update NEOMOD. This resolves previous model inconsistencies related to the population of large NEOs. We estimate there are 936 ± 29 NEOs with absolute magnitude H < 17. 75 (diameter D > 1 km for the reference albedo p V = 0. 14) and semimajor axis a < 4. 2 au. The slope of the NEO size distribution for H = 25 –28 is found to be relatively shallow (cumulative index ≃ 2. 6) and the number of H < 28 NEOs (D > 9 m for p V = 0. 14) is determined to be (1. 20 ± 0. 04) × 1 0 7 , about 3 times lower than in Harris & Chodas (2021). Small NEOs have a different orbital distribution and higher impact probabilities than large NEOs. We estimate 0. 034 ± 0. 002 impacts of H < 28 NEOs on the Earth per year, which is near the low end of the impact flux range inferred from atmospheric bolide observations. Relative to a model where all NEOs are delivered directly from the main belt, the population of small NEOs detected by G96 shows an excess of low-eccentricity orbits with a ≃ 1 –1.6 au that appears to increase with H (≃ 30 % excess for H = 28). We suggest that the population of very small NEOs is boosted by tidal disruption of large NEOs during close encounters to the terrestrial planets. When the effect of tidal disruption is (approximately) accounted for in the model, we estimate 0. 06 ± 0. 01 impacts of H < 28 NEOs on the Earth per year, which is more in line with the bolide data. The impact probability of a H < 22 (D > 140 m for p V = 0. 14) object on the Earth in this millennium is estimated to be ≃ 4. 5 %. • Catalina Sky Survey observations (2013–2022) are used to update our NEO model. • There are 936 ± 29 NEOs with absolute magnitude H ¡17.75. • The population of very small NEOs is boosted by tidal disruption of large NEOs. • We estimate 0. 06 ± 0. 01 impacts of H ¡28 NEOs on the Earth per year. • The impact probability of a H ¡22 NEO on the Earth in this millennium is 4.5%. [ABSTRACT FROM AUTHOR]

A modified method for identifying and studying secular resonances in the dynamics of near-Earth objects is described. Unlike the traditionally used approach based on approximate analytical formulas for calculating secular frequencies that are valid only for small eccentricities, the proposed method uses exact values obtained in the process of numerical simulation of the motion from the Newton–Euler equations. This technique can be used to analyze the dynamics of objects with any arbitrary eccentricities of the orbits, but its application to the study of the motion along orbits with large or rapidly growing eccentricities is most interesting. Testing is carried out on the example of research of the Lidov–Kozai resonances in the dynamics of near-Earth objects. [ABSTRACT FROM AUTHOR]

The innermost section of the Solar system has not been extensively studied because minor bodies moving inside Earth's orbit tend to spend most of their sidereal orbital periods at very low solar elongation, well away from the areas more frequently observed by programs searching for near-Earth objects. The survey carried out from the Zwicky Transient Facility (ZTF) is the first one that has been able to detect multiple asteroids well detached from the direct gravitational perturbation of the Earth–Moon system. ZTF discoveries include 2019 AQ3 and 2019 LF6, two Atiras with the shortest periods among known asteroids. Here, we perform an assessment of the orbital evolution of 2020 AV2, an Atira found by ZTF with a similarly short period but following a path contained entirely within the orbit of Venus. This property makes it the first known member of the elusive Vatira population. Genuine Vatiras, those long-term dynamically stable, are thought to be subjected to the so-called von Zeipel–Lidov–Kozai oscillation that protects them against close encounters with both Mercury and Venus. However, 2020 AV2 appears to be a former Atira that entered the Vatira orbital domain relatively recently. It displays an anticoupled oscillation of the values of eccentricity and inclination, but the value of the argument of perihelion may circulate. Simulations show that 2020 AV2 might reach a 3:2 resonant orbit with Venus in the future, activating the von Zeipel–Lidov–Kozai mechanism, which in turn opens the possibility to the existence of a long-term stable population of Vatiras trapped in this configuration. [ABSTRACT FROM AUTHOR]

Significant nonradial, nongravitational accelerations with magnitudes incompatible with radiation-driven effects have been reported in seven photometrically inactive near-Earth objects. Two of these objects exhibit large transverse accelerations (i.e., within the orbital plane but orthogonal to the radial direction), and six exhibit significant out-of-plane accelerations. Here, we find that anisotropic outgassing resulting from differential heating on a nucleus with nonzero spin-pole obliquity, averaged over an eccentric orbit, can explain these accelerations for most of the objects. This balanced outgassing model depends on three parameters — the spin pole orientation (R.A. and Dec.) and an acceleration magnitude. For these "dark comets" (excepting 2003 RM), we obtain parameter values that reproduce the observed nongravitational accelerations. We derive formulae for the component accelerations under certain assumptions for the acceleration scaling over heliocentric distance. Although we lack estimates of these objects' spin axes to confirm our values, this mechanism is nevertheless a plausible explanation for the observed accelerations, and produces accurate perturbations to the heliocentric motions of most of these objects. This model may also be applied to active objects outside of the dark comets group. • Seasonal effects produce anisotropic outgassing on rapidly-rotating minor bodies. • Outgassing anisotropies can result in out-of-plane nongravitational accelerations. • A seasonal outgassing model is explanatory for the accelerations of "dark comets". [ABSTRACT FROM AUTHOR]

Highlights • 2017 XO2 is an NEO which had high-rated possible impact solutions. • We performed archival searches to indirectly exclude its impact risk. • We also directly recovered it in archival data. Abstract We present a search for precovery observations of asteroid 2017 XO 2 , a previously high-rated possible impactor, as an ideal example of how archival searches can be used to clarify, either directly or indirectly, the danger posed by objects whose orbits are poorly known or even lost. In particular, we explore how images which should (but do not) contain the position corresponding to an impacting orbit can provide an indirect way to exclude the impacting solution even in the case of asteroids that are currently lost and therefore not directly observable again. [ABSTRACT FROM AUTHOR]

Meteor shower identification and search for parent bodies of the meteoroid streams are still on-going topics of meteor science. Both problems are often approached by comparing the orbital (and/or geocentric) parameters of the investigated bodies, as is done in the independent identification method developed by Rudawska et al. (2014). In our work we applied the slightly modified version of the method to 3 most numerous years of the EDMOND (The European viDeo MeteOr Network Database) meteor data, and identified 517 meteor showers. Found showers were characterized and the problematic cases of mis-identification and hyperbolic orbits were analysed. The newly determined mean orbital parameters were then compared with known cometary and NEO (near-Earth object) orbits with the goal to get a broader picture of the associations of known and also suggested parent bodies of the meteoroid streams. From our results, 62 of known associations with the parent bodies were confirmed, and 13 new parent comets were proposed. For 7 meteor showers, new seemingly better solutions among the shower-asteroid associations are suggested. [Display omitted] • Independent identification method of meteor showers. • Meteor shower identification in years 2014–2016 of EDMOND database. • Possible parent bodies candidates for meteoroid streams based on the orbital similarities. • Orbital similarities of possible parent bodies and individual stream meteoroids. [ABSTRACT FROM AUTHOR]

Recently, the inner main belt asteroid (152830) Dinkinesh was identified as an additional fly- by target for the Lucy mission. The heliocentric orbit and approximate absolute magnitude of Dinkinesh are known, but little additional information was available prior to its selection as a target. In particular, the lack of color spectrophotometry or spectra made it impossible to assign a spectral type to Dinkinesh from which its albedo could be estimated. We set out to remedy this knowledge gap by obtaining visible wavelength spectra with the Keck telescope on 2022 November 23 and with Gemini-South on 2022 December 27. The spectra measured with the Keck I/Low Resolution Imaging Spectrometer (LRIS) and the Gemini South/Gemini Multi-Object Spectrograph South (GMOS-S) are most similar to the average spectrum of S- and Sq-type asteroids. The most diagnostic feature is the ≈15 ± 1% silicate absorption feature at ≈0.9–1.0 μm. Small S- and Sq-type asteroids have moderately high albedos ranging from 0.17 to 0.35. Using this albedo range for Dinkinesh in combination with measured absolute magnitude, it is possible to derive an effective diameter and surface brightness for this body. The albedo, size and surface brightness are important inputs required for planning a successful encounter by the Lucy spacecraft. • The 0.45 and 1.03 μm spectra of (152830) Dinkinesh resemble the Sq or S taxonomic classes. • (152830) Dinkinesh compared with similar sized S-type asteroids suggests it has an albedo of ∼0.26. • There may be hemispherical variations in the spectrum of Dinkinesh. • We estimate an effective diameter of between 0.67 and 0.96 km for Dinkinesh. [ABSTRACT FROM AUTHOR]

An increasing number of Near Earth Asteroids (NEAs) in the range of a few hundred metres to a few kilometres in size have relatively high spin rates, from less than 4 h, down to ∼ 2.2 h, depending on spectral type. For some of these bodies, local acceleration near the equator may be directed outwards so that lift off of near-equatorial material is possible. In particular, this may be the case for asteroid Didymos, the primary of the (65803) Didymos binary system, which is the target of the DART (NASA) and Hera (ESA) space missions. The study of the dynamics of particles in such an environment has been carried out – in the frame of the Hera mission and the EC-H2020 NEO-MAPP project – according to the available shape model, known physical parameters and orbital information available before the DART impact. The presence of orbiting particles in the system is likely for most of the estimated range of values for mass and volume. The spatial mass density of ejected material is calculated for different particle sizes and at different heliocentric orbit epochs, revealing that large particles dominate the mass density distribution and that small particle abundance depends on observation epoch. Estimates of take off and landing areas on Didymos are also reported. Available estimates of the system mass and primary extents, after the DART mission, confirm that the main conclusions of this study are valid in the context of current knowledge. • Mass can lift off from fast spin top-shape asteroids, including Didymos according to current knowledge. • A dust band around Didymos at low equatorial latitudes can develop. • Most particles land back onto the Didymos surface. • Small mass particle space density is a function of the observing phase. • Cycles of particles land and take-off may happen. [ABSTRACT FROM AUTHOR]

The presence of dust comae on asteroids and centaurs is a phenomenon that became accepted in the last decades and which challenges the traditional definitions of asteroids and comets. A possible way of improving the chances of discovery of active asteroids is to use large multicolour surveys or catalogues, like SDSS Moving Object Catalogue. In this paper, we analyse the effects of faint dust comae on asteroid spectra and then use it to investigate the effects that a faint dust comae would have over the spectrum, magnitude and radial profile of asteroids. [ABSTRACT FROM AUTHOR]

Synchronous binary asteroids can experience libration about their tidally-locked equilibrium, which will result in energy dissipation. This is an important topic to the Asteroid Impact and Deflection Assessment, where excitation caused by the DART kinetic impact in the Didymos binary asteroid system may be reduced through dissipation before Hera arrives to survey the effects of the impact. We develop a numeric model for energy dissipation in binary asteroids to explore how different system configurations affect the rate of energy dissipation. We find tumbling within the synchronous state eliminates a systematic trend in libration damping on short timescales (several years), but not over long times (hundreds of years) depending on the material conditions. Furthermore, damping of libration, eccentricity, and fluctuations in the semimajor axis are primarily dependent on the stiffness of the secondary, whereas the semimajor axis secular expansion rate is dictated by the stiffness of the primary, as expected. Systems experiencing stable planar libration in the secondary can see a noticeable reduction in libration amplitude after only a few years depending on the stiffness of the secondary, and thus dissipation should be considered during Hera's survey of Didymos. For a very dissipative secondary undergoing stable libration, Hera may be able to calculate the rate of libration damping in Dimorphos and therefore constrain its tidal parameters. • We simulate energy dissipation in a librating synchronous binary asteroid. • Eccentricity damps quicker in binary asteroids than predicted by analytic theory. • The tidal evolution of the secondary's rotation and orbit are coupled together. • Tumbling in the synchronous state damps at about the same rate as stable rotation. • The libration caused by the DART impact may decrease by the time of Hera's arrival. [ABSTRACT FROM AUTHOR]

Dormant comets in the near-Earth object (NEO) population are thought to be involved in the terrestrial accretion of water and organic materials. Identification of dormant comets is difficult as they are observationally indistinguishable from their asteroidal counterparts, however, they may have produced dust during their final active stages which potentially are detectable today as weak meteor showers at the Earth. Here we present the result of a reconnaissance survey looking for dormant comets using 13 567 542 meteor orbits measured by the Canadian Meteor Orbit Radar (CMOR). We simulate the dynamical evolution of the hypothetical meteoroid streams originated from 407 near-Earth asteroids in cometary orbits that resemble orbital characteristics of Jupiter-family comets (JFCs). Out of the 44 hypothetical showers that are predicted to be detectable by CMOR, we identify five positive detections that are statistically unlikely to be chance associations, including three previously known associations. This translates to a lower limit to the dormant comet fraction of 2.0 ± 1.7 per cent in the NEO population and a dormancy rate of ∼10−5 yr−1 per comet. The low dormancy rate confirms disruption and dynamical removal as the dominant end state for near-Earth JFCs. We also predict the existence of a significant number of meteoroid streams whose parents have already been disrupted or dynamically removed. [ABSTRACT FROM AUTHOR]

Among 11 673 of near-Earth objects (NEOs), 52 asteroids are identified, which, together with the Eccentrids meteor system, comprise a single population of small bodies of the Solar System with the smallest orbits of high eccentricity. Some features of this unique system of bodies are discussed in this paper. The distribution of perihelion longitudes is studied for the given group of asteroids and compared to that of the Aten asteroids, which are the most similar to the Eccentrids. The dependence is obtained of the character of perihelion longitude distribution on the eccentricities of the NEO orbits. Eight asteroid stream of the Eccentrids are found. The Eccentrids asteroids approaching the Earth's orbit along its whole length in their aphelia can pose a certain hazard for the Earth. [ABSTRACT FROM AUTHOR]

We investigate and discuss the structure of the sporadic meteor background population in the near-Earth space based on video meteor orbits from the SonotaCo database (SonotaCo 2009, WGN, 37, 55). The selection of the shower meteors was done by the Southworth-Hawkins streams-search criterion (Southworth & Hawkins 1963, Smithson. Contr. Astrophys., 7, 261). Of a total of 117786 orbits, 69.34% were assigned to sporadic background meteors. Our analysis revealed all the known sporadic sources, such as the dominant apex source which is splitting into the northern and southern branch. Part of a denser ring structure about the apex source connecting the antihelion and north toroidal sources is also evident. We showed that the annual activity of the apex source is similar to the annual variation in activity of the whole sporadic background. The antihelion source exhibits a very broad maximum from July until January and the north toroidal source shows three maxima similar to the radar observations by the Canadian Meteor Orbit Radar (CMOR). Potential parent bodies of the sporadic population were searched for by comparison of the distributions of the orbital elements of sporadic meteors, minor planets and comets. [ABSTRACT FROM AUTHOR]

Results are presented of a study of the effect of secular resonances on the dynamic evolution of objects moving along polar orbits with eccentricities changing over a wide range and semi-major axes from 8 000 to 55 000 km. It is shown that motion of polar objects with semi-major axes in the range 50 000-55 000 km is most complicated in the examined altitude range. [ABSTRACT FROM AUTHOR]

Highlights: [•] We examine the distribution of the angular orbital elements of known NEOs. [•] The Apollos have an axial distribution of the argument of perihelion. [•] The Amors’ perihelia have a mean direction close to Jupiter’s perihelion longitude. [ABSTRACT FROM AUTHOR]

Highlights: [•] 2012 LA is a small NEO in an Earth-like orbit with low Δv to Earth. [•] We obtained extensive astrometric coverage of the object during two close approaches. [•] We detected the effect of radiation pressure on the dynamics of the object. [•] From the radiation pressure detection we inferred an unexpectedly low bulk density. [Copyright &y& Elsevier]

We study the dynamical evolution of the near-Earth Jupiter family comets (NEJFCs) that came close to or crossed the Earth;s orbit at the epoch of their discovery (perihelion distances qdisc < 1.3 AU). We found a minimum in the time evolution of the mean perihelion distance q of the NEJFCs at the discovery time of each comet (taken as t = 0) and a past-future asymmetry of q in an interval -1000 yr, +1000 yr centred on t = 0, confirming previous results. The asymmetry indicates that there are more comets with greater q in the past than in the future. For comparison purposes, we also analysed the population of near-Earth asteroids in cometary orbits (defined as those with aphelion distances Q > 4.5 AU) and with absolute magnitudes H < 18. We found some remarkable differences in the dynamical evolution of both populations that argue against a common origin. To further analyse the dynamical evolution of NEJFCs, we integrated in time a large sample of fictitious comets, cloned from the observed NEJFCs, over a 20 000 yr time interval and started the integration before the comet;s discovery time, when it had a perihelion distance q > 2 AU. By assuming that NEJFCs are mostly discovered when they decrease their perihelion distances below a certain threshold qthre = 1.05 AU for the first time during their evolution, we were able to reproduce the main features of the observed q evolution in the interval [-1000, 1000] yr with respect to the discovery time. Our best fits indicate that ∼40% of the population of NEJFCs would be composed of young, fresh comets that entered the region q < 2 AU a few hundred years before decreasing their perihelion distances below qthre, while ∼60% would be composed of older, more evolved comets, discovered after spending at least ∼3000 yr in the q < 2 AU region before their perihelion distances drop below qthre. As a by product, we put some constraints on the physical lifetime τphys of NEJFCs in the q < 2 AU region. We found a lower limit of a few hundreds of revolutions and an upper limit of about 10 000-12 000 yr, or about 1600-2000 revolutions, somewhat longer than some previous estimates. These constraints are consistent with other estimates of τphys, based either on mass loss (sublimation, outbursts, splittings) or on the extinction rate of Jupiter family comets (JFCs). [ABSTRACT FROM AUTHOR]

Abstract: We have for the first time calculated the population characteristics of the Earth’s irregular natural satellites (NESs) that are temporarily captured from the near-Earth-object (NEO) population. The steady-state NES size–frequency and residence-time distributions were determined under the dynamical influence of all the massive bodies in the Solar System (but mainly the Sun, Earth, and Moon) for NEOs of negligible mass. To this end, we compute the NES capture probability from the NEO population as a function of the latter’s heliocentric orbital elements and combine those results with the current best estimates for the NEO size–frequency and orbital distribution. At any given time there should be at least one NES of 1-m diameter orbiting the Earth. The average temporarily-captured orbiter (TCO; an object that makes at least one revolution around the Earth in a co-rotating coordinate system) completes (2.88±0.82) rev around the Earth during a capture event that lasts (286±18) d. We find a small preference for capture events starting in either January or July. Our results are consistent with the single known natural TCO, 2006 RH120, a few-meter diameter object that was captured for about a year starting in June 2006. We estimate that about 0.1% of all meteors impacting the Earth were TCOs. [Copyright &y& Elsevier]

This paper analyzes the distribution of the orbits of near-Earth minor bodies from the data on more than 7500 objects. The distribution of large near-Earth objects (NEOs) with absolute magnitudes of H < 18 is generally consistent with the earlier predictions (Bottke et al., 2002; Stuart, 2003), although we have revealed a previously undetected maximum in the distribution of perihelion distances q near q = 0.5 AU. The study of the orbital distribution for the entire sample of all detected objects has found new significant features. In particular, the distribution of perihelion longitudes seriously deviates from a homogeneous pattern; its variations are roughly 40% of its mean value. These deviations cannot be stochastic, which is confirmed by the Kolmogorov-Smirnov test with a more than 0.9999 probability. These features can be explained by the dynamic behavior of the minor bodies related to secular resonances with Jupiter. For the objects with H < 18, the variations in the perihelion longitude distribution are not so apparent. By extrapolating the orbital characteristics of the NEOs with H < 18, we have obtained longitudinal, latitudinal, and radial distributions of potentially hazardous objects in a heliocentric ecliptic coordinate frame. The differences in the orbital distributions of objects of different size appear not to be a consequence of observational selection, but could indicate different sources of the NEOs. [ABSTRACT FROM AUTHOR]

We study the fate of internal gravity waves approaching the centre of an initially non-rotating solar-type star, primarily using two-dimensional numerical simulations based on a cylindrical model. A train of internal gravity waves is excited by tidal forcing at the interface between the convection and radiation zones of such a star. We derive a Boussinesq-type model of the central region of a star and find a non-linear wave solution that is steady in the frame rotating with the angular pattern speed of the tidal forcing. We then use spectral methods to integrate the equations numerically, with the aim of studying at what amplitude the wave is subject to instabilities. These instabilities are found to lead to wave breaking whenever the amplitude exceeds a critical value. Below this critical value, the wave reflects perfectly from the centre of the star. Wave breaking leads to mean flow acceleration, which corresponds to a spin-up of the central region of the star, and the formation of a critical layer, which acts as an absorbing barrier for subsequent ingoing waves. As these waves continue to be absorbed near the critical layer, the star is spun up from the inside out. Our results point to an important amplitude dependence of the (modified) tidal quality factor , since non-linear effects are responsible for dissipation at the centre of the star. If the amplitude of the tidal forcing exceeds the critical amplitude for wave breaking to occur, then this mechanism produces efficient dissipation over a continuous range of tidal frequencies. This requires , for a planet of mass mp in an orbit of period P around the current Sun, neglecting stellar rotation. However, this criterion depends strongly on the strength of the stable stratification at the centre of the star, and so it depends on stellar mass and main-sequence age. If breaking occurs, we find , for the current Sun. This varies by no more than a factor of 5 throughout the range of solar-type stars with masses between , for fixed orbital parameters. This estimate of is therefore quite robust and can be reasonably considered to apply to all solar-type main-sequence stars, if this mechanism operates. The strong frequency dependence of the resulting dissipation means that this effect could be very important in determining the fate of close-in giant planets around G and K stars. We predict fewer giant planets with orbital periods of less than about 2 d around such stars if they cause breaking at the centre, due to the efficiency of this process. Even if the waves are of too low amplitude to initiate breaking, radiative damping could, in principle, lead to a gradual spin-up of the stellar centre and to the formation of a critical layer. This process could provide efficient tidal dissipation in solar-type stars perturbed by less massive companions, but it may be prevented by effects that resist the development of differential rotation. These mechanisms would, however, be ineffective in stars with a convective core, such as WASP-18, WASP-12 and OGLE-TR-56, perhaps partly explaining the survival of their close planetary companions. [ABSTRACT FROM AUTHOR]

Abstract: By virtue of their landing on Earth, meteorites reside in near-Earth object (NEO) orbits prior to their arrival. Thus the population of observable NEOs, in principle, gives important representation of meteorite source bodies. By linking meteorites to NEOs, and linking NEOs to their most likely main-belt source locations, we seek to gain insight into the original Solar System formation locations for different meteorite classes. To forge possible links between meteorites and NEOs, we have developed a three dimensional method for quantitative comparisons between laboratory measurements of meteorites and telescopic measurements of near-Earth objects. We utilize meteorite spectra from the Reflectance Experiment Laboratory (RELAB) database and NEO data from the SpeX instrument on the NASA Infrared Telescope Facility (IRTF). Using the Modified Gaussian Model (MGM) as a mathematical tool, we treat asteroid and meteorite spectra identically in the calculation of 1-μm and 2-μm Geometric Band Centers and their Band Area Ratios (BARs). Using these identical numerical parameters we quantitatively compare the spectral properties of S-, Sq-, Q- and V-type NEOs with the spectral properties of the meteorites in four classes: H, L, LL and HED. For each NEO spectrum, we assign a set of probabilities for it being related to each of these four meteorite classes. Our NEO-meteorite correlation probabilities are then convolved with NEO-source region probabilities to yield a final set of meteorite-source region correlations. While the ν6 resonance dominates the delivery for all four meteorite classes, an excess (significant at the 2.1-sigma level) source region signature is found for the H chondrites through the 3:1 mean motion resonance. This results suggest an H chondrite source with a higher than average delivery preference through the 3:1 resonance. A 3:1 resonance H chondrite source region is consistent with the short cosmic ray exposure ages known for H chondrites. [Copyright &y& Elsevier]

Abstract  A new meteroid stream—October Ursa Majorids—was announced by Japanese observers on Oct. 14–16, 2006 (Uehara et al. 2006). Its weak manifestation was detected among coincidental major meteor showers (N/S Taurids, Orionids), as its meteors radiated from a higher placed radiant on the northern sky. We have tried to find out previous displays of the stream throughout available meteor orbits databases, and among ancient celestial phenomena records. Although we got no obvious identification, there are some indications that it could be a meteor shower of cometary origin with weak/irregular activity, mostly overlayed by regular coincidental meteor showers. With a procedure based on D-criterion (Southworth and Hawkins 1963) we found a few records in IAU MDC database of meteor photographic orbits which fulfill common similarity limits, for October Ursae Majorids. However, their real association cannot be established, yet. With respect to the mean orbit of this stream, we suggest for its parent body a long-period comet. [ABSTRACT FROM AUTHOR]

It is widely believed that cometary orbits contain important clues to both the outer solar system’s current structure and its past dynamical evolution. The first part of this paper summarizes the results of numerical simulations designed to study the dynamical origins of observed comets and to link the observed populations to the reservoirs from which they are currently leaking. The second part reviews simulations which are designed to study the dynamical origin of the reservoirs themselves. The paper concludes with a brief discussion of the currently unresolved issue of where in the primordial solar nebula the different dynamical classes of observed comets originated. [ABSTRACT FROM AUTHOR]

Abstract: In the restricted circular three-body problem, two massive bodies travel on circular orbits about their mutual center of mass and gravitationally perturb the motion of a massless particle. The triangular Lagrange points, and , form equilateral triangles with the two massive bodies and lie in their orbital plane. Provided the primary is at least 27 times as massive as the secondary, orbits near and can remain close to these locations indefinitely. More than 2200 cataloged asteroids librate about the and points of the Sun–Jupiter system, and five bodies have been discovered around the point of the Sun–Neptune system. Small satellites have also been found librating about the and points of two of Saturn''s moons. However, no objects have been discovered around the Earth–Moon and points. Using numerical integrations, we show that orbits near the Earth–Moon and points can survive for over a billion years even when solar perturbations are included, but the further addition of the far smaller perturbations from other planets destabilize these orbits within several million years. Thus, the lack of observed objects in these regions cannot be used as a constraint on Solar System formation, nor on the tidal evolution of the Moon''s orbit. [Copyright &y& Elsevier]

The article provides a discussion on the study of near-earth objects (NEOs). NEOs include comets and asteroids which have the possibility of crashing into earth. NEOs that pass 7.5 million kilometers within the Earth's orbit must be detected immediately. On December 2004, the asteroid Apophis was estimated to collide with Earth on April 2029. Additional studies moved the date to April 13, 2036. The incident prompted the development of measures to track NEOs including the completion of the Panoramic Survey Telescope and Rapid Response System. An overview of efforts to track NEOs is provided.

Abstract: In an effort to identify space mission targets of interest, the association of known meteoroid streams with Near-Earth Objects (NEOs) was investigated. In addition to updating previous searches to include NEOs discovered up to January 1, 2007, a new dissimilarity criterion based on dynamical arguments was applied to evaluate the likelihood of each candidate association. The new criterion is based on the fact that the few established cases, such as 2003 EH1 and the Quadrantid stream, involve parent bodies that fragmented in the most recent nutation cycle of their secular orbital evolution. In established cases, the statistics speak strongly of an association due to the lack of NEOs in the a, e, i phase space occupied by these showers. The newly proposed associations are much more uncertain, because the odds of chance associations greatly increase as orbital inclination of the showers decreases. Forty-two plausible candidate dormant comets were identified, that deserve further scrutiny. Both comet and stream typically lack sufficient data to prove the association. Most candidate parent bodies pertain to NEOs with an aphelion distance just short of Jupiter''s orbit, a perihelion distance near Earth orbit, and an eccentricity in the range 0.5–0.8. Surprisingly many have , which means that most candidate parent bodies are dormant Jupiter family comets that have not yet fully decoupled from Jupiter. Establishing these associations can provide further evidence that (mostly) dormant comets break frequently, making this the dominant mechanism for replenishing the zodiacal cloud. [Copyright &y& Elsevier]

Abstract: Arecibo delay–Doppler measurements of (99942) Apophis in 2005 and 2006 resulted in a five standard-deviation trajectory correction to the optically predicted close approach distance to Earth in 2029. The radar measurements reduced the volume of the statistical uncertainty region entering the encounter to 7.3% of the pre-radar solution, but increased the trajectory uncertainty growth rate across the encounter by 800% due to the closer predicted approach to the Earth. A small estimated Earth impact probability remained for 2036. With standard-deviation plane-of-sky position uncertainties for 2007–2010 already less than 0.2 arcsec, the best near-term ground-based optical astrometry can only weakly affect the trajectory estimate. While the potential for impact in 2036 will likely be excluded in 2013 (if not 2011) using ground-based optical measurements, approximations within the Standard Dynamical Model (SDM) used to estimate and predict the trajectory from the current era are sufficient to obscure the difference between a predicted impact and a miss in 2036 by altering the dynamics leading into the 2029 encounter. Normal impact probability assessments based on the SDM become problematic without knowledge of the object''s physical properties; impact could be excluded while the actual dynamics still permit it. Calibrated position uncertainty intervals are developed to compensate for this by characterizing the minimum and maximum effect of physical parameters on the trajectory. Uncertainty in accelerations related to solar radiation can cause between 82 and 4720 Earth-radii of trajectory change relative to the SDM by 2036. If an actionable hazard exists, alteration by 2–10% of Apophis'' total absorption of solar radiation in 2018 could be sufficient to produce a six standard-deviation trajectory change by 2036 given physical characterization; even a 0.5% change could produce a trajectory shift of one Earth-radius by 2036 for all possible spin-poles and likely masses. Planetary ephemeris uncertainties are the next greatest source of systematic error, causing up to 23 Earth-radii of uncertainty. The SDM Earth point-mass assumption introduces an additional 2.9 Earth-radii of prediction error by 2036. Unmodeled asteroid perturbations produce as much as 2.3 Earth-radii of error. We find no future small-body encounters likely to yield an Apophis mass determination prior to 2029. However, asteroid (144898) 2004 VD17, itself having a statistical Earth impact in 2102, will probably encounter Apophis at 6.7 lunar distances in 2034, their uncertainty regions coming as close as 1.6 lunar distances near the center of both SDM probability distributions. [Copyright &y& Elsevier]

Abstract: Institute of Space and Astronautical Science (ISAS) of Japan Aerospace Exploration Agency (JAXA) is currently planning the missions that the small probe ‘interceptor’ flybys near Earth objects. Interceptor is very small probe. An interceptor observes spectrum, takes close images, and determines mass of an NEO (near earth object) during a flyby. The weight of interceptor is less than 10kg. This paper shows three types of missions. In general, it is impossible to determine the relative orbit during flyby only with optical information. Thus, the optical navigation needs to be combined with the radio navigation that should provide the relative velocity vector information. In this paper, the integrated guidance and navigation strategy of interceptor is proposed. The interceptor needs the thruster for the attitude and orbit control. This paper introduces the development of the gas-thrust equilibrium thruster for small satellites. [Copyright &y& Elsevier]

The article presents a discussion on the Earth's defenses against potential asteroid collisions. In case an asteroid is bound for Earth, preventive measures can aim at changing its speed to prevent a collision. Edward Lu of Google and astronaut Stanley Love suggest that an asteroid can be accelerated or slowed down using a spacecraft called a gravity tractor. Apophis, an asteroid which is estimated to get close too close to Earth in 2009, will take forty days to be diverted out of orbit. Other options in preventing asteroid collision include the use of nuclear detonation.