B. M. Shustov

Astronomical and physical aspects of the Chelyabinsk event (February 15, 2013)

Various observational data including infrasound, seismic, optical (onboard) monitoring, ground video and photo records, and evidence from witnesses of the Chelyabinsk event on February 15, 2013, have been analyzed. The extensive material gathered has provided a base for investigations of the physical properties of the object, the results of which are discussed. A bolide light curve is constructed, which shows a multiplicity of flashes. Estimations of the energy of the meteoroid explosion, which took place in the atmosphere at an altitude of about 23 km, show evidence of the formation of a high-power shock wave equivalent to 300–500 kilotons of TNT. The object diameter corresponding to this energy falls within the range 16–19 m. The trajectory of the meteor is outlined. It is preliminarily concluded that the Chelyabinsk meteorite was a representative the Apollo asteroid family.

On the possibility of the guidance of small asteroids to dangerous celestial bodies using the gravity-assist maneuver

In this paper, the method of changing the trajectories of hazardous asteroids with orbits known for some years to be on a possible collision course with the Earth is considered. The method relies on the use of small asteroids (asteroid-projectiles) directed at hazardous celestial bodies by giving the projectile a sufficiently small velocity impulse ensuring the Earth gravity assist. As a result, the asteroid-projectile vector can be controllably changed over a wide range. Apophis is considered as an example of the target asteroid. The technical feasibility of this method is discussed. It is noted that despite the potential use of this elegant method, its practical implementation requires further research and development.

Distribution of the near-earth objects

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.

A concept of a space hazard counteraction system: Astronomical aspects

The basic science of astronomy and, primarily, its branch responsible for studying the Solar System, face the most important practical task posed by nature and the development of human civilization—to study space hazards and to seek methods of counteracting them. In pursuance of the joint Resolution of the Federal Space Agency (Roscosmos) and the RAS (Russian Academy of Sciences) Space Council of June 23, 2010, the RAS Institute of Astronomy in collaboration with other scientific and industrial organizations prepared a draft concept of the federal-level program targeted at creating a system of space hazard detection and counteraction. The main ideas and astronomical content of the concept are considered in this article.

Astronomical aspects of building a system for detecting and monitoring hazardous space objects

In order to meet the practical priority of the mass detection of hazardous celestial bodies (HCBs) during the creation of a system to counteract space hazards (asteroids, comet hazards and space debris), we need clear technical requirements for the detection instruments designed (created). Specially targeted astronomical investigations into the basic properties of the HCB ensemble were conducted to specify such requirements (limitations). The paper presents these findings. As to asteroid and comet hazards, quantitative limitations on the HCB size (50 m) have been introduced and quantitative definitions of threatening and collisional HCB orbits have been proposed for the first time. It is shown that at a lead time of 30 days, it is necessary to detect HCBs at distances of about 1 AU, which corresponds to a telescope’s resolving power of V ∼ 23m. This entails the necessity to design wide-angle large-aperture telescopes. For detecting and monitoring space debris objects and meteoroids in the near-earth space at a time scale of about several days, faster instruments with smaller apertures but larger vision fields are efficient. An example is given of a basic design of a space-based system that takes into account the astronomical requirements discussed.

On the concept of a low-cost space system for detecting hazardous celestial bodies

We present the concept of a space system for detecting hazardous celestial bodies larger than 100 m 15–30 days before their possible collision with the Earth on the base of a wide-angle telescope with the aperture of 0.75 m and a field of view with a diameter of 7°. A preliminary configuration of a spacecraft using the low-sized Lavochkin Association platform is proposed. Preliminary estimates of the main system parameters are given. The main advantage of the system is a combination of high productivity, penetrating force, moderate technical complexity, and low cost of the implementation.

Chelyabinsk event as an astronomical phenomenon

The fall of a meteorite near the town of Chelyabinsk is considered from the viewpoint of astronomy, and the major witness facts and entry characteristics (including the measured entry velocity and the height of the explosion) are analyzed. The aerodynamic phenomena that accompanied the entry of the meteorite in the atmosphere at an ultrasonic velocity and the origin of a shock wave that induced damage on the Earth’s surface are analyzed. The paper also reports the estimated frequency of the falls of celestial bodies depending on their size, and consequences of collisions of these bodies with the Earth. It is emphasized that studies of small bodies in the Solar System can provide insight into the origin of the protoplanetary disk and the processes that produced the planets. The studies of small bodies, such as the Chelyabinsk meteorite, are directly related to the problem of asteroid and comet impact hazard (ACIH). The paper reports the sizes of potentially hazardous celestial bodies whose monitoring requires the deployment of a network of specialized telescopes on the Earth to mitigate ACH and a system of space-based systems for the identification and monitoring of such bodies in near space.

On the arc length of observations of a small solar system body sufficient to classify it as hazardous

This paper analyzes the accuracy of orbit determination calculated by observations of short arcs. In this case, we imposed the condition that the arc length and/or the distribution of arc observations should provide a confident classification of the orbit of a small celestial body allowing one to distinguish a potentially hazardous body, also including a threat of collision.

On population of hazardous celestial bodies in the near-Earth space

In recent years, following the Chelyabinsk event of February 15, 2013, the lower size limit for presumably dangerous near-Earth objects has been decreased manyfold (essentially, from 140 m to ~10 m). This has drawn an increased attention to the properties of the population of decameter-sized bodies, in particular, the bodies that approach the Earth from the sunward side (daytime sky). The current paper is concerned with various properties of this population. The properties of the ensemble are analyzed using both observational data from other authors and theoretical estimates obtained by cloning virtual bodies. This question is of great practical importance, as the means for detecting such bodies (for example, the SODA project) need to be developed with consideration for the requirements imposed by the population properties. We have shown that the average rate of entering near-Earth space (NES), i.e., at distances less than ~1 million km from the Earth, for decameter-sized and larger bodies from the daytime sky (elongation values of entry points less than 90°) is approximately 620 objects per year for elongation angles of the detection point <90° and approximately 220 objects per year for elongation angles of the detection point <45°.

Methods and Means of Information-Analytical Assessment of Asteroid and Comet Hazard

This paper contains a description of methods and software tools for creation of the informationanalytical system for monitoring hazardous space objects. The paper presents the structure of the system and a description of its functional components that enable rapid assessment of the NEO hazard and forecast of the effects of dangerous celestial bodies colliding with the Earth. The results of the system’s operation regarding the modeling the motion of space objects are also included in this work.