Browsing Meteoritics & Planetary Science, Volume 44, Number 12 (2009) by Subjects
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Absolute magnitude and slope parameter G calibration of asteroid 25143 ItokawaWe present results from an observing campaign of 25143 Itokawa performed with the 2.2 m telescope of the University of Hawaii between November 2000 and September 2001. The main goal of this paper is to determine the absolute magnitude H and the slope parameter G of the phase function with high accuracy for use in determining the geometric albedo of Itokawa. We found a value of H = 19.40 and a value of G = 0.21.

Asteroid orbital ranging using MarkovChain Monte CarloWe present a novel MarkovChain MonteCarlo orbital ranging method (MCMC) for poorly observed singleapparition asteroids with two or more observations. We examine the Bayesian a posteriori probability density of the orbital elements using methods that map a volume of orbits in the orbitalelement phase space. In particular, we use the MCMC method to sample the phase space in an unbiased way. We study the speed of convergence and also the efficiency of the new method for the initial orbit computation problem. We present the results of the MCMC ranging method applied to three objects from different dynamical groups. We conclude that the method is applicable to initial orbit computation for nearEarth, mainbelt, and transneptunian objects.

Dynamical constraints on the origin of Main Belt cometsIn an effort to understand the origin of Main Belt comets (MBCs) 7968 ElstPizzaro, 118401, and P/2005 U1, the dynamics of these three icy asteroids and a large number of hypothetical MBCs were studied. Results of extensive numerical integrations of these objects suggest that they were formed in place through the collisional breakup of a larger precursor body. Simulations point specifically to the Themis family of asteroids as the origin of these objects and rule out the possibility of a cometary origin (i.e., inward scattering of comets from outer solar system and their primordial capture in the asteroid belt). Results also indicate that while 7968 ElstPizzaro and 118401 maintain their orbits for 1 Gyr, P/2005 U1 diffuses chaotically in eccentricity and becomes unstable in ~20 Myr. The latter suggest that this MBC used to be a member of the Themis family and is now escaping away. Numerical integrations of the orbits of hypothetical MBCs in the vicinity of the Themis family show a clustering of stable orbits (with eccentricities smaller than 0.2 and inclinations less than 25) suggesting that many more MBCs may exist in the vicinity of this family (although they might have not been activated yet). The details of the results of simulations and the constraints on the models of the formation and origins of MBCs are presented and their implications for the detection of more of these objects are discussed.

KLENOT Project 20022008 contribution to NEO astrometric followupNearEarth object (NEO) research plays an increasingly important role not only in solar system science but also in protecting our planetary environment as well as human society from the asteroid and comet hazard. Consequently, interest in detecting, tracking, cataloguing, and the physical characterizing of these bodies has steadily grown. The discovery rate of current NEO surveys reflects progressive improvement in a number of technical areas. An integral part of NEO discovery is astrometric followup crucial for precise orbit computation and for the reasonable judging of future close encounters with the Earth, including possible impact solutions. The KLENOT Project of the Klet Observatory (South Bohemia, Czech Republic) is aimed especially at the confirmation, early followup, longarc followup, and recovery of nearEarth objects. It ranks among the worlds most prolific professional NEO followup programs. The 1.06 m KLENOT telescope, put into regular operation in 2002, is the largest telescope in Europe used exclusively for observations of minor planets and comets, and full observing time is dedicated to the KLENOT team. In this paper, we present the equipment, technology, software, observing strategy, and results of the KLENOT Project obtained during its first phase from March 2002 to September 2008. The results consist of thousands of precise astrometric measurements of NEOs and also three newly discovered nearEarth asteroids. Finally, we also discuss future plans reflecting also the role of astrometric followup in connection with the modus operandi of the next generation surveys.

OpenOrb: Opensource asteroid orbit computation software including statistical rangingWe are making an opensource asteroid orbit computation software package called OpenOrb publicly available. OpenOrb is built on a wellestablished Bayesian inversion theory, which means that it is to a large part complementary to orbitcomputation packages currently available. In particular, OpenOrb is the first package that contains tools for rigorously estimating the uncertainties resulting from the inverse problem of computing orbital elements using scarce astrometry. In addition to the wellknown leastsquares method, OpenOrb also contains both MonteCarlo (MC) and MarkovChain MC (MCMC; Oszkiewicz et al. [2009]) versions of the statistical ranging method. Ranging allows the user to obtain sampled, nonGaussian orbitalelement probabilitydensity functions and is therefore optimized for cases where the amount of astrometry is scarce or spans a relatively short time interval. Rangingbased methods have successfully been applied to a variety of different problems such as rigorous ephemeris prediction, orbital element distribution studies for transneptunian objects, the computation of invariant collision probabilities between nearEarth objects and the Earth, detection of linkages between astrometric asteroid observations within an apparition as well as between apparitions, and in the rigorous analysis of the impact of orbital arc length and/or astrometric uncertainty on the uncertainty of the resulting orbits. Tools for making ephemeris predictions and for classifying objects based on their orbits are also available in OpenOrb. As an example, we use OpenOrb in the search for candidate retrograde and/or highinclination objects similar to 2008 KV42 in the known population of transneptunian objects that have an observational time span shorter than 30 days.