Near-Earth Objects Impact Monitoring System: a Novel Approach

EPSC Abstracts Vol. 13, EPSC-DPS2019-1333-1, 2019 EPSC-DPS Joint Meeting 2019 c Author(s) 2019. CC Attribution 4.0 license.

Near-Earth objects impact monitoring system: a novel approach

Dmitrii E. Vavilov Institute of Applied Astronomy of the Russian Academy of Sciences, Russia ([email protected])

Abstract method takes into account the fact that the uncertainty region of an asteroid (in this case the uncertainty re- When a new near Earth asteroid is discovered it is im- gion of each virtual asteroid) is stretched preferably portant to know if the object can collide with the Earth along its nominal orbit that makes this method useful and cause danger. The monitoring for such possible even if the Earth is extremely far from the nominal po- incidents is an important role in planetary defense. sition of the virtual asteroid at the epoch of collision. Nowadays there are systems that have been working For all these events if the impact probability is on that problem: NEODyS (University of Pisa) and 10 greater than 10− then we are trying to find the orbit Sentry (Jet Propulsion Laboratory NASA). Here we in the confidence ellipsoid at the epoch of observation present an operational system for monitoring colli- that leads to this collision. If the algorithm fails and sions of potentially hazard objects developed in Insti- can not find it then this collision is marked as unveri- tute of Applied Astronomy of the Russian Academy of fied and is not published. Sciences (IAA RAS). 1. Introduction Table 1: Impact probabilities for asteroid 2005 QK76 The probability of a collision of an asteroid with the by three monitoring systems. Earth (different from zero and unity) is a direct conse- quence of poor determined asteroid’s orbit. Since the Date IAA RAS NEODyS Sentry 5 5 5 precise orbit (orbital elements) is unknown there is a 2030-02-26 4.28 10− 3.73 10− 3.6 10− · 6 · 5 · 5 continuum set of possible orbits. If some of these or- 2038-02-26 6.83 10− 1.06 10− 1.5 10− · 9 · · 8 bits lead to a collision the impact probability arises. 2038-02-26 3.58 10− - 1.0 10− · 9 7 · 7 2038-02-26 9.64 10− 1.04 10− 1.7 10− · 9 · 8 · 2. Line of Variation 2041-02-26 1.41 10− 4.14 10− - · 6 · 10 5 2048-02-26 5.93 10− 3.83 10− 1.3 10− The orbit of an asteroid is determined by six param- · 8 · 10 · 6 2048-02-26 3.02 10− 2.93 10− 3.3 10− eters, for instance, coordinates and velocities at a se- · 13 · · 2053-02-26 1.39 10− -- lected epoch. It is assumed that errors of these param- · 12 10 2059-02-26 2.99 10− - 2.5 10− eters have a normal distribution at the epoch of obser- · 9 · 2062-02-26 3.53 10− -- vations. Consequently, the uncertainty region (region · 11 2073-02-26 3.93 10− -- that restricts possible orbits of an asteroid) is repre- · 11 2073-02-26 3.59 10− -- sented as an ellipsoid (confidence ellipsoid). · 11 2073-02-26 2.52 10− -- Monitoring system of IAA RAS also uses the basic · 11 10 2073-02-26 6.78 10− 7.17 10− - idea of LOV method [1] for estimating impact prob- · 10 · 2078-02-26 8.07 10− -- abilities, as Sentry and NEODyS do. In this method · 12 8 8 2083-02-26 2.92 10− 3.02 10− 5.3 10− the longest axis of the confidence ellipsoid is chosen · 13 · · 2083-02-26 3.55 10− -- to be sampled obtaining virtual asteroids. Each virtual · 12 2083-02-26 1.43 10− -- asteroid’s orbit is propagated from the time of discov- · 11 9 2107-02-26 1.63 10− 1.54 10− - ery 100 years ahead. In IAA RAS system if a virtual · · 2107-02-26 2.63 10 11 2.34 10 9 4.2 10 9 asteroid comes closer to the Earth than 0.1 au the im- − − − ’Date’ is a possible collision· date (year-month-day).· · pact probability is computed by a linear method, which uses a special curvilinear coordinate system [2]. This 3. Results Acknowledgements

Here we check our approach by computing impact This work was supported by a grant of Russian Sci- probabilities of 2005 QK76 asteroid. As one can see ence Foundation #16-12-00071. from Table 1 system of IAA RAS found all the possible collisions that are published in NEODyS and Sentry databases. However, some of these probabil- References 10 ities are less than the selected threshold of 10− and would not be published. The results of the systems are [1] Milani, A., Chesley, S.R., Sansaturio, M.E., Tommei, slightly different especially for small chances of col- G., and Valsecchi, G.B.: Nonlinear impact monitoring: lision because of the difference in the nominal orbit line of variation searches for impactors, Icarus, Vol. 173, and the covariance matrix. In this case all three sys- pp. 362-384, 2005. tems would have different sets of possible collisions [2] Vavilov, D.E. and Medvedev, Yu.D.: A fast method for and probability values. estimation of the impact probability of near-Earth objects, MNRAS, Vol. 446, pp. 705-709, 2015. 4. Summary and Conclusions A monitoring system for estimating impact probabilities of asteroids with the Earth was built in Institute of Applied Astronomy of the Russian Academy of Sci- ences. This system uses a basic idea of LOV method while has original techniques inside as well. The results of this system are in good agreement with other impact monitoring systems while they all have differ- ences because of the difference in initial data.