Atmospheric trajectory and orbit of the Omolon meteorite

The Omolon meteorite fell on 1981 May 15 at 17:10 U.T. to a point with the coordinates phi = 64 degrees 01'08 " N, lambda = 161 degrees 48'30 " E. This is the fifth pallasite that was observed at the moment of its fall and the largest of the pallasites known worldwide (250 kg). The history of the observation, search, and finding of the meteorite is briefly described. From the size of the meteorite and the funnel that it produced, the velocity of its encounter with the ground is estimated by aerodynamic formulas to be 220 mis. An attempt at estimating the meteorite's initial velocity and mass from its terminal values (which yielded the mass range of 390-490 kg that corresponds to the velocity range of 12-15 km/s) was successful for the mass but unsuccessful for the velocity and the incidence angle, because the problem was ill posed. The position of the radiant is determined from the available observations to be alpha = 176.4 degrees, delta = +24.1 degrees (Leo). The radiant was situated at an elongation of 29 degrees from the antapex, which means that this was an overtaking meteorite and its entry velocity did not exceed 16 km/s. Three variants of the calculation of the orbital elements-for an entry velocity of 12, 14, and 16 km/s-are presented. In all the three cases, the meteoroid's orbit is close to the orbits of Apollo asteroids and to the orbits of iron meteoroids observed as fireballs with bright iron lines in their spectra. The Omolon meteorite was probably a fragment of an Apollo M-type asteroid. This study is the first attempt at calculating the orbit of a pallasite.