* Astronomy

Title: A method for classifying orbits near asteroids
Author: Xianyu Wang, Shengping Gong, Junfeng Li

A method for classifying orbits near asteroids under a polyhedral gravitational field is presented, and may serve as a valuable reference for spacecraft orbit design for asteroid exploration. The orbital dynamics near asteroids are very complex. According to the variation in orbit characteristics after being affected by gravitational perturbation during the periapsis passage, orbits near an asteroid can be classified into 9 categories: (1) surroundingto-surrounding, (2) surrounding-to-surface, (3) surroundingto-infinity, (4) infinity-to-infinity, (5) infinity-to-surface, (6) infinity-to-surrounding, (7) surface-to-surface, (8) surfaceto-surrounding, and (9) surface-to- infinity. Assume that the orbital elements are constant near the periapsis, the gravitation potential is expanded into a harmonic series. Then, the influence of the gravitational perturbation on the orbit is studied analytically. The styles of orbits are dependent on the argument of periapsis, the periapsis radius, and the periapsis velocity. Given the argument of periapsis, the orbital energy before and after perturbation can be derived according to the periapsis radius and the periapsis velocity. Simulations have been performed for orbits in the gravitational field of 216 Kleopatra. The numerical results are well consistent with analytic predictions.

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On Thursday, March 12, 2015, around 01:08 UTC, main-belt asteroid (216) Kleopatra will occult a  8.1mag star in the constellation Crater. 

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In the case of an occultation, the combined light of the asteroid and the star will drop by 3.9 mag to 11.9 mag (the magnitude of the asteroid) for at most 8.0 seconds.
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Asteroid (216) Kleopatra is at Opposition in the constellation Taurus on the 16th November, 2013.

Magnitude: 9.5
Distance to Earth: 1.139 AU
Distance to Sun center: 2.123 AU

Asteroid (216) Kleopatra makes its closest approach to the Earth (2.036 AU) on the 1st July, 2012.