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Carbonaceous chondrite compositions could be an order of magnitude more abundant in comets than in asteroids; future observations of comets will calibrate this proportion. Even adopting the full reduction factor of HT ht associated with the value of I N i from Desch et al.[1], a cometary Chicxulub impactor would be up to HT ht times more likely than an asteroid Chicxulub impactor[2]. A cometary Chicxulub impactor remains more likely than an asteroid Chicxulub impactor if the fraction of CC-like comets is HT ht . [Extracted from the article]

The target asteroid of the OSIRIS-REx asteroid sample return mission, (101955) Bennu (formerly 1999 RQ36), is a half-kilometer near-Earth asteroid with an extraordinarily well constrained orbit. An extensive data set of optical astrometry from 1999 to 2013 and high-quality radar delay measurements to Bennu in 1999, 2005, and 2011 reveal the action of the Yarkovsky effect, with a mean semimajor axis drift rate da / dt = (- 19.0 ± 0.1) × 10 - 4 au/Myr or 284 ± 1.5 m/year. The accuracy of this result depends critically on the fidelity of the observational and dynamical model. As an example, neglecting the relativistic perturbations of the Earth during close approaches affects the orbit with 3σ significance in da / dt. The orbital deviations from purely gravitational dynamics allow us to deduce the acceleration of the Yarkovsky effect, while the known physical characterization of Bennu allows us to independently model the force due to thermal emissions. The combination of these two analyses yields a bulk density of ρ = 1260 ± 70 kg/m3, which indicates a macroporosity in the range 40 ± 10 % for the bulk densities of likely analog meteorites, suggesting a rubble-pile internal structure. The associated mass estimate is (7.8 ± 0.9) × 1010 kg and GM = 5.2 ± 0.6 m3 / s2.Bennu's Earth close approaches are deterministic over the interval 1654-2135, beyond which the predictions are statistical in nature. In particular, the 2135 close approach is likely within the lunar distance and leads to strong scattering and numerous potential impacts in subsequent years, from 2175 to 2196. The highest individual impact probability is 9.5 × 10 - 5 in 2196, and the cumulative impact probability is 3.7 × 10 - 4, leading to a cumulative Palermo Scale of -1.70. © 2014 Elsevier Inc.

The target asteroid of the OSIRIS-REx asteroid sample return mission, (101955) Bennu (formerly 1999 RQ36), is a half-kilometer near-Earth asteroid with an extraordinarily well constrained orbit. An extensive data set of optical astrometry from 1999 to 2013 and high-quality radar delay measurements to Bennu in 1999, 2005, and 2011 reveal the action of the Yarkovsky effect, with a mean semimajor axis drift rate da / dt = (- 19.0 ± 0.1) × 10 - 4 au/Myr or 284 ± 1.5 m/year. The accuracy of this result depends critically on the fidelity of the observational and dynamical model. As an example, neglecting the relativistic perturbations of the Earth during close approaches affects the orbit with 3σ significance in da / dt. The orbital deviations from purely gravitational dynamics allow us to deduce the acceleration of the Yarkovsky effect, while the known physical characterization of Bennu allows us to independently model the force due to thermal emissions. The combination of these two analyses yields a bulk density of ρ = 1260 ± 70 kg/m3, which indicates a macroporosity in the range 40 ± 10 % for the bulk densities of likely analog meteorites, suggesting a rubble-pile internal structure. The associated mass estimate is (7.8 ± 0.9) × 1010 kg and GM = 5.2 ± 0.6 m3 / s2.Bennu's Earth close approaches are deterministic over the interval 1654-2135, beyond which the predictions are statistical in nature. In particular, the 2135 close approach is likely within the lunar distance and leads to strong scattering and numerous potential impacts in subsequent years, from 2175 to 2196. The highest individual impact probability is 9.5 × 10 - 5 in 2196, and the cumulative impact probability is 3.7 × 10 - 4, leading to a cumulative Palermo Scale of -1.70. © 2014 Elsevier Inc.

The paper presents the results of identifying secular resonances that act on objects moving in the LEO–MEO regions. The results were obtained from the processing of data of an extensive numerical experiment on the study of the orbital evolution of objects moving in the range of the semi-major axes from 8000 km to the operation zone of the GLONASS navigation systems (25 500 km), with inclinations from 0° to 180° outside the zones of orbital resonances. The distribution maps of the identified secular resonances are given. The analysis of the orbital evolution of the objects is presented. [ABSTRACT FROM AUTHOR]

Near-Earth object (NEO) in-situ exploration can provide invaluable information for science, possible future deflection actions and resource utilisation. This is only possible with space missions which approach the asteroid from its vicinity, i.e. rendezvous. This paper explores the use of solar sailing as means of propulsion for NEO rendezvous missions. Given the current state of sail technology, we search for multiple rendezvous missions of up to ten years and characteristic acceleration of up to 0.10 mm/s2. Using a tree-search technique and subsequent trajectory optimisation, we find numerous options of up to three NEO encounters in the launch window 2019–2027. In addition, we explore steerable and throttleable low-thrust (e.g. solar-electric) rendezvous to a particular group of NEOs, the Taurid swarm. We show that an acceleration of 0.23 mm/s2 would suffice for a rendezvous in approximately 2000 days, while shorter transfers are available as the acceleration increases. Finally, we show low-thrust options (0.3 mm/s2) to the fictitious asteroid 2019 PDC, as part of an asteroid deflection exercise. [ABSTRACT FROM AUTHOR]

In this study, we investigate the ablation properties of bolides capable of producing meteorites. The casual dashcam recordings from many locations of the Chelyabinsk superbolide associated with the atmospheric entry of an 18 m in diameter near-Earth object (NEO) have provided an excellent opportunity to reconstruct its atmospheric trajectory, deceleration, and heliocentric orbit. In this study, we focus on the study of the ablation properties of the Chelyabinsk bolide on the basis of its deceleration and fragmentation. We explore whether meteoroids exhibiting abrupt fragmentation can be studied by analyzing segments of the trajectory that do not include a disruption episode. We apply that approach to the lower part of the trajectory of the Chelyabinsk bolide to demonstrate that the obtained parameters are consistent. To do that, we implemented a numerical (Runge–Kutta) method appropriate for deriving the ablation properties of bolides based on observations. The method was successfully tested with the cases previously published in the literature. Our model yields fits that agree with observations reasonably well. It also produces a good fit to the main observed characteristics of Chelyabinsk superbolide and provides its averaged ablation coefficient σ = 0.034 s2 km−2. Our study also explores the main implications for impact hazard, concluding that tens of meters in diameter NEOs encountering the Earth in grazing trajectories and exhibiting low geocentric velocities are penetrating deeper into the atmosphere than previously thought and, as such, are capable of producing meteorites and even damage on the ground. [ABSTRACT FROM AUTHOR]

In this paper we present a two-step neural network model to separate detections of solar system objects from optical and electronic artifacts in data obtained with the "Asteroid Terrestrial-impact Last Alert System" (ATLAS), a near-Earth asteroid sky survey system. A convolutional neural network is used to classify small "postage-stamp" images of candidate detections of astronomical sources into eight classes, followed by a multi-layered perceptron that provides a probability that a temporal sequence of four candidate detections represents a real astronomical source. The goal of this work is to reduce the time delay between Near-Earth Object (NEO) detections and submission to the Minor Planet Center. Due to the rare and hazardous nature of NEOs, a low false negative rate is a priority for the model. We show that the model reaches 99.6% accuracy on real asteroids in ATLAS data with a 0.4% false negative rate. Deployment of this model on ATLAS has reduced the amount of NEO candidates that astronomers must screen by 90%, thereby bringing ATLAS one step closer to full autonomy. [ABSTRACT FROM AUTHOR]

It has been 20 years since planning began for the 1995 United Nations International Conference on Near-Earth Objects. The conference proceedings established the scientific basis for an international organizational framework to support research and collective actions to mitigate a potential near-Earth object (NEO) threat to the planet. Since that time, researchers have conducted telescope surveys that should, within the coming decade, answer many questions about the size, number, and Earth impact probability of these objects. Space explorations to asteroids and comets have been successfully carried out, including sample recovery. Laboratory experiments and computer simulations at Sandia National Laboratories have analyzed the effects of high-energy-density soft x-ray radiation on meteorites--which might help researchers develop a way to redirect an incoming asteroid by vaporizing a thin layer of its surface. An Action Team on NEOs, established in 2001 in response to recommendations of the Third United Nations Conference on the Exploration and Peaceful Uses of Outer Space, identified the primary components of NEO mitigation and emphasized the value of finding potentially hazardous NEOs as soon as possible. Recommendations from the action team are meant to ensure that all nations are aware of the NEO danger, and to coordinate mitigation activities among nations that could be affected by an impact, as well as those that might play an active role in any eventual deflection or disruption campaign. [ABSTRACT FROM AUTHOR]

Terrestrial accelerator facilities can generate ion beams which enable the testing of the resistance of materials and thin film coatings to be used in the space environment. In this work, a TiO 2 /Al bi-layer coating has been irradiated with a He + beam at three different energies. The same flux and dose have been used in order to investigate the damage dependence on the energy. The energies were selected to be in the range 4–100 keV, in order to consider those associated to the quiet solar wind and to the particles present in the near-Earth space environment. The optical, morphological and structural modifications have been investigated by using various techniques. Surprisingly, the most damaged sample is the one irradiated at the intermediate energy, which, on the other hand, corresponds to the case in which the interface between the two layers is more stressed. Results demonstrate that ion energies for irradiation tests must be carefully selected to properly qualify space components. [ABSTRACT FROM AUTHOR]

This paper provides the first-ever survey of the implications of violent conflict risk for planetary defense program decisions. Arguably, the aim of planetary defense should be to make Earth safer from all threats, including but not limited to threats from near-Earth objects (NEOs). Insofar as planetary defense projects affect other risks besides NEOs, these other risks should be taken into account. This paper evaluates three potential effects of planetary defense programs on violent conflict risk. First, planetary defense may offer a constructive model for addressing a major global risk. By documenting the history of its successes and failures, the planetary defense community can aid efforts to address other global risks, including but not limited to violent conflict. Second, the proposed use of nuclear explosions for NEO deflection and disruption could affect the role of nuclear weapons in violent conflict risk. The effect may be such that nuclear deflection/disruption would increase aggregate risks to human society. However, the effect is difficult to assess, mainly due to ambiguities in violent conflict risk. Third, planetary defense could reduce violent conflict risk by addressing the possibility of NEO collisions being mistaken as violent attacks and inadvertently triggering violent conflict. False alarms mistaken as real attacks are a major concern, especially as a cause of nuclear war. Improved awareness of NEOs and communication between astronomers and military officials could help resolve NEO false alarms. Each of these three effects of planetary defense programs on violent conflict risk can benefit from interaction between the communities that study and address NEO and violent conflict risks. • This paper assess three implications of violent conflict risk for planetary defense. • First is the value of planetary defense as a model for other global risks. • Second is the use of nuclear explosives for near-Earth object (NEO) deflection. • Third is the possibility of NEO collision being mistaken as a violent attack. [ABSTRACT FROM AUTHOR]

Previous work has demonstrated orbital stability for 100 Myr of initially near-circular and coplanar small bodies in a region termed the 'Earth–Mars belt' from 1.08 < a < 1.28 au. Via numerical integration of 3000 particles, we studied orbits from 1.04–1.30 au for the age of the Solar system. We show that on this time-scale, except for a few locations where mean-motion resonances with Earth affect stability, only a narrower 'Earth–Mars belt' covering a ∼ (1.09, 1.17) au, e < 0.04, and I < 1° has over half of the initial orbits survive for 4.5 Gyr. In addition to mean-motion resonances, we are able to see how the ν 3, ν 4, and ν 6 secular resonances contribute to long-term instability in the outer (1.17–1.30 au) region on Gyr time-scales. We show that all of the (rather small) near-Earth objects (NEOs) in or close to the Earth–Mars belt appear to be consistent with recently arrived transient objects by comparing to a NEO steady-state model. Given the <200 m scale of these NEOs, we estimated the Yarkovsky drift rates in semimajor axis and use these to estimate that a diameter of ∼100 km or larger would allow primordial asteroids in the Earth–Mars belt to likely survive. We conclude that only a few 100-km sized asteroids could have been present in the belt's region at the end of the terrestrial planet formation. [ABSTRACT FROM AUTHOR]

The Transiting Exoplanet Survey Satellite (TESS) is a NASA Explorer-class mission designed for finding exoplanets around nearby stars. TESS image data can also serve as a valuable resource for asteroid and comet detection, including near-Earth objects (NEOs). In order to exploit the TESS image data for moving object detection and potential object discovery, our team has developed an image processing pipeline as part of the Lincoln Near-Earth Asteroid Research (LINEAR) program, sponsored by the NASA NEO Observations Program. The LINEAR-TESS pipeline is currently in operation and reporting asteroid observations to the Minor Planet Center. In this paper we discuss the algorithms and methodology utilized to push the limits of the astrometric accuracy and photometric sensitivity of the TESS instrument for asteroid detection without a priori information on the ephemerides of the objects, and report on observation statistics from the first two years of TESS mission data. [ABSTRACT FROM AUTHOR]

The specification and prediction of density fluctuations in the thermosphere, especially during geomagnetic storms, is a key challenge for space weather observations and modeling. It is of great operational importance for tracking objects orbiting in near-Earth space. For low-Earth orbit, variations in neutral density represent the most important uncertainty for propagation and prediction of satellite orbits. An international conference in 2018 conducted under the auspices of the NASA Community Coordinated Modeling Center (CCMC) included a workshop on neutral density modeling, using both empirical and numerical methods, and resulted in the organization of an initial effort of model comparison and evaluation. Here, we present an updated metric for model assessment under geomagnetic storm conditions by dividing a storm in four phases with respect to the time of minimum Dst and then calculating the mean density ratios and standard deviations and correlations. Comparisons between three empirical (NRLMSISE-00,JB2008 and DTM2013) and two first-principles models (TIE-GCM and CTIPe) and neutral density data sets that include measurements by the CHAMP, GRACE, and GOCE satellites for 13 storms are presented. The models all show reduced performance during storms, notably much increased standard deviations, but DTM2013, JB2008 and CTIPe did not on average reveal a significant bias in the four phases of our metric. DTM2013 and TIE-GCM driven with the Weimer model achieved the best results taking the entire storm event into account, while NRLMSISE-00 systematically and significantly underestimates the storm densities. Numerical models are still catching up to empirical methods on a statistical basis, but as their drivers become more accurate and they become available at higher resolutions, they will surpass them in the foreseeable future. [ABSTRACT FROM AUTHOR]

In the course of the NE ar real-time MO nitoring (NEMO) project an information system for bright fireballs on a global scale has been developed. It analyses and combines as much available data as possible from different sources to monitor fireball events, from witness reports via meteor networks to infrasound data. One of near real-time monitoring system's main goals is to deliver information about events in near real-time. For this purpose, the project is supplemented by an alert system. This system is based on Social Media, predominantly on Twitter. Its detection procedure and working principle are presented in this study. • NEMO is an information collection and distribution system for bright fireballs. • It is a near real-time monitoring system on a global scale. • It analyses and combines as much available data as possible from different sources. • NEMO's alert system is based on Social Media. [ABSTRACT FROM AUTHOR]

This study is focused on the relationships between the κ-Cygnid meteor shower and different groups of asteroids crossing the Earth's orbit (the so-called near-Earth objects (NEOs)). The analysis is based on the visible structure of the meteor shower and a comprehensive strategy for estimating the proximity of orbits of two bodies. The κ-Cygnid meteor shower (abbreviated as KCG) is observed from August 3 to August 25 every year; it is classified as a minor shower, and the size of its mean orbit is around 3.2 AU, while the geocentric velocity is 20.9 km/s. No parent body (PB) of the shower has been found among comets so far. Relationships between the shower and asteroids, as potential PBs of the shower, are under active examination; some hypotheses on this subject can be found on the website of the Meteor Data Center (MDC) of the International Astronomical Union (IAU). [ABSTRACT FROM AUTHOR]

The locations of the fully despun, double synchronous end states of tidal evolution, where the rotation rates of both the primary and secondary components in a binary system synchronize with the mean motion about the center of mass, are derived for spherical components. For a given amount of scaled angular momentum J/. J', the tidal end states are over-plotted on a tidal evolution diagram in terms of mass ratio of the system and the component separation (semimajor axis in units of primary radii). Fully synchronous orbits may not exist for every combination of mass ratio and angular momentum; for example, equal-mass binary systems require J/. J' > 0.44. When fully synchronous orbits exist for prograde systems, tidal evolution naturally expands the orbit to the stable outer synchronous solution. The location of the unstable inner synchronous orbit is typically within two primary radii and often within the radius of the primary itself. With the exception of nearly equal-mass binaries, binary asteroid systems are in the midst of lengthy tidal evolutions, far from their fully synchronous tidal end states. Of those systems with unequal-mass components, few have even reached the stability limit that splits the fully synchronous orbit curves into unstable inner and stable outer solutions.Calculations of material strength based on limiting the tidal evolution time to the age of the Solar System indicate that binary asteroids in the main belt with 100-km-scale primary components are consistent with being made of monolithic or fractured rock as expected for binaries likely formed from sub-catastrophic impacts in the early Solar System. To tidally evolve in their dynamical lifetime, near-Earth binaries with km-scale primaries or smaller created via a spin-up mechanism must be much weaker mechanically than their main-belt counterparts even if formed in the main belt prior to injection into the near-Earth region. Small main-belt binaries, those having primary components less than 10. km in diameter, could bridge the gap between the large main-belt binaries and the near-Earth binaries, as, depending on the age of the systems, small main-belt binaries could either be as strong as the large main-belt binaries or as weak as the near-Earth binaries. The inherent uncertainty in the age of a binary system is the leading source of error in calculation of material properties, capable of affecting the product of rigidity μ and tidal dissipation function Q by orders of magnitude. Several other issues affecting the calculation of μQ are considered, though these typically affect the calculation by no more than a factor of two. We also find indirect evidence within all three groups of binary asteroids that the semimajor axis of the mutual orbit in a binary system may evolve via another mechanism (or mechanisms) in addition to tides with the binary YORP effect being a likely candidate. © 2011 Elsevier Inc.

In this paper we retrace the course of near-Earth astronomy from its beginnings.We emphasize the problem of space debris, which has arisen somewhat unexpectedly, and only keeps on growing and growing.We also cast a glance over the conferences, held by our Institute biennially.

Aims. The Euphrosyne asteroid family occupies a unique zone in orbital element space around 3.15 au and may be an important source of the low-albedo near-Earth objects. The parent body of this family may have been one of the planetesimals that delivered water and organic materials onto the growing terrestrial planets. We aim to characterize the compositional properties as well as the dynamical properties of the family. Methods. We performed a systematic study to characterize the physical properties of the Euphrosyne family members via low-resolution spectroscopy using the NASA Infrared Telescope Facility. In addition, we performed smoothed-particle hydrodynamics (SPH) simulations and N-body simulations to investigate the collisional origin, determine a realistic velocity field, study the orbital evolution, and constrain the age of the Euphrosyne family. Results. Our spectroscopy survey shows that the family members exhibit a tight taxonomic distribution, suggesting a homogeneous composition of the parent body. Our SPH simulations are consistent with the Euphrosyne family having formed via a reaccumulation process instead of a cratering event. Finally, our N-body simulations indicate that the age of the family is 280−80+180 Myr $280^{+180}_{-80}\,\mathrm{Myr}$ 280 − 80 + 180   Myr , which is younger than previous estimates. [ABSTRACT FROM AUTHOR]

As staples of science fiction, space technologies, much like outer space itself, have often been regarded as being 'out there' objects of international security analysis. However, as a growing subset of security scholarship indicates, terrestrial politics and practices are ever more dependent on space technologies and systems. Existing scholarship in 'astropolitics' and 'critical astropolitics' has tended to concentrate on how such technologies and systems underpin and impact the dynamics of military security, but this article makes the case for wider consideration of 'orbital infrastructures' as crucial to conceptions and governance of planetary security in the context of the 'Anthropocene'. It does so by outlining and analysing in detail Earth Observation (EO) and Near-Earth Object (NEO) detection systems as exemplary cases of technological infrastructures for 'looking in' on and 'looking out' for forms of planetary insecurity. Drawing on and extending recent theorisations of technopolitics and of Large Technical Systems, we argue that EO and NEO technologies illustrate, in distinct ways, the extent to which orbital infrastructures should be considered not only part of the fabric of contemporary international security but as particularly significant within and even emblematic of the technopolitics of planetary (in)security. [ABSTRACT FROM AUTHOR]

The thermal inertia of an asteroid's surface can provide insight into regolith properties, such as the presence of a layer of fine dust, the density and thermal conductivity of a rocky surface, and, together with other observational data, mineralogy. Knowledge of the surface characteristics of asteroids is important for planetary defense initiatives and the extraction of resources ("asteroid mining"). A simple means of estimating asteroid thermal inertia has been proposed by Harris & Drube, which is suitable for application to large sets of thermal-infrared observational data, such as those obtained by infrared space telescopes. We compare results from the Harris–Drube estimator with recently published values of asteroid thermal inertia from detailed thermophysical modeling, and provide an explanation in terms of reduced surface roughness for some discrepant results. Smooth surfaces covered in fine dust may provide an explanation for the unexpectedly low values of thermal inertia derived from thermophysical modeling for some slowly rotating main-belt asteroids. In the case of near-Earth objects (NEOs) we show that results from the estimator are in good agreement with those from thermophysical modeling, with just a few exceptions. We discuss the special cases of the NEOs (101955) Bennu, (162173) Ryugu, and (29075) 1950 DA in the context of results from our estimator. Given the data requirements and complexity of thermophysical modeling, data-analysis tools based on relatively simple concepts can play an important role in allowing "quick-look" assessment of thermal-infrared data of asteroids, especially NEOs. [ABSTRACT FROM AUTHOR]

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The article offers information on How to avoid an asteroid apocalypse. It mentions effort of European Space Agency (ESA), National Aeronautics and Space Administration and other agencies to detect asteroids, know that about large asteroids that are bigger than diameter are not expected to collide with Earth in the coming centuries.

Telescopes with a small aperture and a wide field of view are widely used and play a significant role in large-scale state-of-the-art sky survey applications, such as transient detection and near-Earth object observations. However, owing to the specific defects caused by optical aberrations, the image quality and efficiency of source detection are affected. To achieve high-accuracy position measurements, an innovative technique is proposed. First, a large number of raw images are analysed using principal component analysis. Then, the effective point spread function is reconstructed, which reflects the state of the telescope and reveals the characteristics of the imaging process. Finally, based on the point spread function model, the centroids of star images are estimated iteratively. To test the efficiency and reliability of our algorithm, a large number of simulated images are produced, and a telescope with small aperture and wide field of view is utilized to acquire the raw images. The position measurement of sources is performed using our novel method and two other common methods on these data. Based on a comparison of the results, the improvement is investigated, and it is demonstrated that our proposed technique outperforms the others on position accuracy. We explore the limitations and potential gains that may be achieved by applying this technique to custom systems designed specifically for wide-field astronomical applications. [ABSTRACT FROM AUTHOR]

We compare the number of lunar craters larger than 15 km across and younger than 1.1 Ga to the estimates of the number of craters that could have been formed for 1.1 Ga if the number of near-Earth objects and their orbital elements during that time were close to the corresponding current values. The comparison was performed for craters over the entire lunar surface and in the region of the Oceanus Procellarum and maria on the near side of the Moon. In these estimates, we used the values of collision probabilities of near-Earth objects with the Moon and the dependences of the crater diameters on the impactor sizes. According to the estimates made by different authors, the number density of known Copernican craters with diameters D ≥ 15 km in mare regions is at least double the corresponding number for the remaining lunar surface. Our estimates do not contradict the growth in the number of near-Earth objects after probable catastrophic fragmentations of large main-belt asteroids, which may have occurred over the recent 300 Ma; however, they do not prove this increase. Particularly, they do not conflict with the inference made by Mazrouei et al. (2019) that 290 Ma ago the frequency of collisions of near-Earth asteroids with the Moon increased by 2.6 times. The number of Copernican lunar craters with diameters not smaller than 15 km is probably higher than that reported by Mazrouei et al. (2019). For a probability of a collision of an Earth-crossing object (ECO) with the Earth in a year equaled to 10–8 , our estimates of the number of craters agree with the model, according to which the number densities of the 15-km Copernican craters for the whole lunar surface would have been the same as that for mare regions if the data by Losiak et al. (2015) for D < 30 km were as complete as those for D > 30 km. With this collision probability of ECOs with the Earth and for this model, the cratering rate may have been constant over the recent 1.1 Ga. [ABSTRACT FROM AUTHOR]

Observations of the large superfast rotator (436724) 2011 UW158 were carried out at the Observatório Astronômico do Sertão de Itaparica (OASI, Brazil) between May and October 2015, before and after it made a close approach to Earth in July 2015. These observations allowed us to obtain 11 light curves, and additional observations at the San Pedro Mártir Observatory (Baja California, Mexico) in March 2017 provided a light curve. From the obtained light curves we could confirm the fast rotation, 0.61071 h, of the near-Earth object (NEO) and by applying the inversion method, we derived a prograde sense of rotation and a quite elongated shape model with rough dimensions a/b  = 2.0, a/c  = 4.2, and b/c  = 2.1. The best determined pole directions suggest that the maximum amplitude of the light curves was obtained from an equatorial view. The reconstructed shape models are in good agreement with the shape elongation and asymmetric shape reported by radar observations. As 2011 UW158 has an uncommon rotation period for asteroids larger than ∼200 m, we used the determined parameters to calculate the minimum internal cohesion strength required to keep its structure intact. We have found that a minimum cohesion ranging from 176 to 295 Pa is required in case the NEO has a composition similar to that of C-type asteroids, and from 364 to 451 Pa for the E-type. Therefore, we suggest that 2011 UW158, if not monolithic, requires a significant cohesion force to keep it spinning so fast. [ABSTRACT FROM AUTHOR]

The first experience in application of artificial neural networks to a study of the dynamic structure of a selected region of the near-Earth orbital space is described. An analysis of time series describing the evolution of the resonant characteristics of the dynamic structure of the region is usually performed manually. However, a study of the dynamic structure of a large region of the orbital space requires consideration of several tens of thousands of such time series. As an alternative approach, technologies of deep learning can be used, namely, design of architecture of one-dimensional convolutional neural network for supervised learning. [ABSTRACT FROM AUTHOR]

Radar observations can be used to obtain accurate orbital elements for near-Earth objects (NEOs) as a result of the very accurate range and range rate measureables. These observations allow the prediction of NEO orbits further into the future and also provide more information about the properties of the NEO population. This study evaluates the observability of NEOs with the EISCAT 3D 233 MHz 5 MW high-power, large-aperture radar, which is currently under construction. Three different populations are considered, namely NEOs passing by the Earth with a size distribution extrapolated from fireball statistics, catalogued NEOs detected with ground-based optical telescopes and temporarily captured NEOs, i.e. mini-moons. Two types of observation schemes are evaluated, namely the serendipitous discovery of unknown NEOs passing the radar beam and the post-discovery tracking of NEOs using a priori orbital elements. The results indicate that 60–1200 objects per year, with diameters D>0.01 m, can be discovered. Assuming the current NEO discovery rate, approximately 20 objects per year can be tracked post-discovery near the closest approach to Earth. Only a marginally smaller number of tracking opportunities are also possible for the existing EISCAT ultra-high frequency (UHF) system. The mini-moon study, which used a theoretical population model, orbital propagation, and a model for radar scanning, indicates that approximately seven objects per year can be discovered using 8 %–16 % of the total radar time. If all mini-moons had known orbits, approximately 80–160 objects per year could be tracked using a priori orbital elements. The results of this study indicate that it is feasible to perform routine NEO post-discovery tracking observations using both the existing EISCAT UHF radar and the upcoming EISCAT 3D radar. Most detectable objects are within 1 lunar distance (LD) of the radar. Such observations would complement the capabilities of the more powerful planetary radars that typically observe objects further away from Earth. It is also plausible that EISCAT 3D could be used as a novel type of an instrument for NEO discovery, assuming that a sufficiently large amount of radar time can be used. This could be achieved, for example by time-sharing with ionospheric and space-debris-observing modes. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the dynamic structure of near-Earth orbital space in the 1 : 2 resonance region with Earth's rotation speed. The results of an extensive numerical-analytical experiment to study the orbital evolution of objects moving in the semimajor axis range from 26 550 to 26 570 km, with inclinations from 0° to 180°. In this region, the zones of action of the five components of the orbital resonance and aspidal–nodal secular resonances of low orders are revealed. The distribution maps of the revealed resonances are constructed. The dynamic structure of the orbital space was also investigated using the fast Lyapunov characteristic of MEGNO and represented by a MEGNO map of the region in the section by the plane (inclination of the orbit, major axis). It is shown that a feature of the dynamic evolution of most of the studied orbits is randomness arising under the influence of overlapping resonances of various types. [ABSTRACT FROM AUTHOR]

The distribution of professional observatories around the world is quite biased toward the Northern Hemisphere, and this tendency is even more pronounced when considering those dedicated only to the study of small solar system bodies. In the Southern Hemisphere, the IMPACTON project deployed the Observatório Astronômico do Sertăo de Itaparica (OASI), dedicated to the observation of minor bodies of the solar system with emphasis on Near-Earth Objects (NEOs). The observatory is located at the county of Itacuruba, in the Pernambuco State of Brazil, and operate a 1 m Cassegrain telescope. Here, we present a complete characterization of the OASI instruments and the sky conditions during the first eight years of operations. The limiting magnitudes are determined in the different available filters. The median seeing results to be 1.″22, with a higher number of photometric nights from April to October. We also give an overview of the results obtained from the OASI observations and discuss them in the light of similar data from the literature. In particular, the rotational periods of 23 NEOs, and the spin directions and shapes of 9 NEOs, have been determined for the very first time using our observations. Analyzing rotational periods, sizes and taxonomic classification from the literature and OASI, we conclude that the fast rotating NEOs are predominantly S-type objects. However, rotational periods obtained at the OASI and with similar value from LCDB database allowed to identify the first fast rotator C-type NEO: asteroid 436724. With an estimated tensile strength as low as 0.5 KPa, this asteroid allows us to suggest that it defines the border between the C- and S-type fast rotators in the size versus period diagram. Although this hypothesis is based on a very small sample it is compatible with all presently available data. Only new observations, however, can prove if this hypothesis is correct. [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]

This paper proposes a novel approach to the solution of optimal control problems under uncertainty (OCPUUs). OCPUUs are first cast in a general formulation that allows the treatment of uncertainties of different nature, and then solved with a new direct transcription method that combines multiple shooting with generalised polynomial algebra to model and propagate extended sets. The continuity conditions on extended sets at the boundary of two adjacent segments are directly satisfied by a bounding approach. The Intrusive Polynomial Algebra aNd Multiple shooting Approach (IPANeMA) developed in this work can handle optimal control problems under a wide range of uncertainty models, including nonparametric, epistemic, and imprecise probability ones. In this paper, the approach is applied to the design of a robust low-thrust trajectory to a Near-Earth Object with uncertain initial conditions. It is shown that the new method provides more robust and reliable trajectories than the solution of an analogous deterministic optimal control problem. • A general formulation of optimal control problems under uncertainty is proposed. • A generalised multiple shooting transcription approach is developed. • The novel transcription relies on polynomial algebra for uncertainty propagation. • The approach is applied to the robust optimisation of a low-thrust trajectory. • The robust control results greatly more reliable than the deterministic one. [ABSTRACT FROM AUTHOR]

Any near-Earth object (NEO) following an Earth-like orbit may eventually be captured by Earth's gravity during low-velocity encounters. This theoretical possibility was first attested during the fly-by of 1991 VG in 1991–1992 with the confirmation of a brief capture episode – for about a month in February 1992. Further evidence was obtained when 2006 RH120 was temporarily captured into a geocentric orbit from July 2006 to July 2007. Here, we perform a numerical assessment of the orbital evolution of 2020 CD3, a small NEO found recently that could be the third instance of a meteoroid temporarily captured by Earth's gravity. We confirm that 2020 CD3 is currently following a geocentric trajectory although it will escape into a heliocentric path by early May 2020. Our calculations indicate that it was captured by the Earth in 2016 |$_{-4}^{+2}$|⁠ , median and 16th and 84th percentiles. This episode is longer (4 |$_{-2}^{+4}$|  yr) than that of 2006 RH120. Prior to its capture as a minimoon, 2020 CD3 was probably a NEO of the Aten type, but an Apollo type cannot be excluded; in both cases, the orbit was very Earth-like, with low eccentricity and low inclination, typical of an Arjuna-type meteoroid. A few clone orbits remained geocentric for nearly a century, opening the door to the existence of yet-to-be-detected minimoons that are relatively stable for time-scales comparable to those of unbound quasi-satellites such as (469219) Kamo'oalewa 2016 HO3. In addition, nearly 10 per cent of the experiments led to brief moon–moon episodes in which the value of the selenocentric energy of 2020 CD3 became negative. [ABSTRACT FROM AUTHOR]

Every year near-Earth object (NEO) surveys discover hundreds of new asteroids, including the potentially hazardous asteroids (PHA). The possibility of impact with the Earth is one of the main motivations to track and study these objects. This paper presents a tether assisted methodology to deflect a PHA by connecting a smaller asteroid, altering the center of mass of the system, and consequently, moving the PHA to a safer orbit. Some of the advantages of this method are that it does not result in fragmentation, which could lead to another problem, and also the flexibility to change the configuration of the system to optimize the deflection according to the warning time. The dynamics of the PHA-tether-asteroid system is analyzed, and the amount of orbit change is determined for several initial conditions. Only motion in the plane of the orbit of the PHA around the Sun is considered, thus the PHA chosen for the simulations has low orbit inclination. Analysis of the dynamics of the system shows that the method is feasible for planetary defense. [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]

In this paper, we discuss the possible disruption of a prolate ellipsoidal small body by the Earth's tidal forces during a close flyby. An exact expression for the stress tensor under the action of gravity, rotation, and tidal forces is obtained using the analytical solution of the elastic problem. Constraints for the critical distance are derived taking into account the size, shape, density, mechanical properties (material strength and Poisson ratio), rotation, and two variants of the body orientation. Asteroid 433 Eros is considered as a case study. The results are important for methods for assessing the asteroid hazard of near-Earth objects (NEO) and the evolution of terrestrial planets. [ABSTRACT FROM AUTHOR]

We describe an artificial neural network model of the near‐Earth space radiation environment. The geomagnetic activity index Kp and low‐earth‐orbit (LEO) electron flux measurements from the National Oceanic and Atmospheric Administration Polar‐orbiting Operational Environmental Satellite (POES) operational spacecraft are used as model training inputs. Electron fluxes from National Aeronautics and Space Administration's Van Allen Probe spacecraft form the training outputs. We demonstrate that the model can accurately specify outer radiation belt (L∼3–7) electron fluxes at two energies, 350 keV and 1 MeV. Various performance metrics are calculated using out‐of‐sample data, and we find high correlations and low errors between the model specification and the observed flux. We emphasize that once the model is trained, the Van Allen Probes data are no longer needed at model run time; only the POES fluxes and the Kp index are required to specify the outer electron belt using the model. Key Points: A demonstration neural network model is presented that specifies (nowcasts) the outer electron radiation belt at 350 keV and 1 MeV energyThe model only requires the Kp index and electron flux measurements from low‐altitude operational sensors as inputsExcellent model performance is demonstrated on out‐of‐sample data [ABSTRACT FROM AUTHOR]

Typically, near-Earth space objects are observable for a small fraction of the orbit revolution. In this paper, we consider the problem of identification and fusion of two short optical tracks of near-Earth space objects, as well as the problem of estimation of the parameters of the corresponding orbits directly from these tracks in the absence of a priori information. The popular approach to solving these problems is based on admissible regions of orbital parameters, which is typically computationally demanding. It is shown that the solution of these problems does not require admissible regions and computationally and algorithmically difficult operations with admissible regions. A new, purely statistical method for solving these problems is proposed. [ABSTRACT FROM AUTHOR]

Though rare, asteroid impacts are inevitable, and with the current state of technology, kinetic impactors are the preferred but not the complete solution. If the time to impact is short, or the threatening body too large, nuclear deflection serves as a final option. This work is part of an integrated study by National Aeronautics and Space Administration (NASA) and the National Nuclear Security Administration (NNSA) to better determine the relative efficacy of these complimentary approaches. In particular, we examine the important material properties that affect each approach, to improve critical characterization efforts, and reduce uncertainty in the limits of the impactor technology. Impact speeds for kinetic impactors on Near-Earth Object (NEO) intercept trajectories commonly range from 5 to 20 km/s, resulting in significant crater ejecta and a momentum enhancement above that carried by the impactor. This enhancement depends substantially on the strength and porosity of the asteroid, as well as the impact speed. Here simulations from different codes are presented, along with constraints from experimental measurements. The uncertainties due to ignorance of the strength and porosity of the impact point are significant in determining the limits of impactor sufficiency. The nuclear approach is considered within the context of current capabilities, posing no need to test, as extant and well-understood devices are sufficient for the largest known Potentially Hazardous Objects (PHOs). Results of x-ray sources with realistic spectra as well as blackbody spectra are given, along with some assessment on composition dependence. • Asteroid Bennu can be successfully deflected by extant nuclear devices. • Kinetic impact, even with large momentum enhancement, is unlikely to deflect Bennu. • Nuclear deflection efficacy depends upon the x-ray source spectrum. • Nuclear deflection efficacy is enhanced by near-surface, unbound volatiles. • Code comparisons for kinetic and nuclear deflection simulations show good agreement. [ABSTRACT FROM AUTHOR]

The subject of the study are space threats - Near-Earth Objects (NEO) and Potentially Hazardous Asteroids (PHA). The research methods employed in this article included the classic theoretical methods used in security sciences and a practical method - a quantitative study of social media. At present, space threat studies aim to resolve the terminological confusion related to NEOs, to determine current and potentially hazardous space objects and estimate the potential threats from them. The research is also expected to come up with two methods for estimating NEO threats, the Palermo and Torino scales. The practical result is to evaluate the public mood regarding NEO threats. Studies have shown that certain active space objects are capable of reaching the Earth's surface and colliding with human-made in-space objects and devices, such as communication satellites. Should this happen, it could cause substantial social damage and destabilise state security, particularly if elements of critical infrastructure of the state were to be affected. Continuous monitoring of NEOs may play a central role in the provision of security. Furthermore, the public should be kept abreast of the threats. [ABSTRACT FROM AUTHOR]