

<HTML><HEAD><TITLE>René Michelsen - Thesis</TITLE>
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<P><FONT color=#000000><FONT size=+1><B>René Michelsen</FONT></P></B>

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<H3> PhD thesis: Near-Earth Asteroids from discovery to characterization (2005) </H3> 


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<H3> Abstract: </H3>


<P>Near-Earth Asteorids (NEAs) are characterised by their Earth-approaching 
orbits. The NEA population has its origin in the asteroid Main Belt via 
dynamical, collisional and thermal mechanisms, and the NEAs are the immediate 
supplier of meteorites. This PhD thesis discusses aspects of dynamical and 
physical observations of NEAs. 
<P>The discovery process of NEAs is constrained by the geometric conditions 
induced by the orbital motion of the Earth and the asteroids. I consider NEAs 
located in mean-motion resonances with the Earth, and by simulating an ideal 
survey program, I illustrate the existence of configurations preventing 
discovery. 
<P>From spectroscopic observations obtained with the Danish 1.54m and the 3.5m 
NTT telescope at ESO, La Silla, I determine the taxonomic classification of 12 
NEAs. Recent detailed classification schemes has been developed based on Main 
Belt asteroids. I find that the application of these schemes on NEAs is 
questionable, as the influence of phase reddening on the features of asteroidal 
spectra is neglected. 
<P>Observing sub-kilometer asteroids is difficult due to their short periods of 
visibility, and then only under technical challenging circumstances. Further 
observational advances warrant the application of autonomous techniques from 
space. Simulations, based on numerical integrations of asteroid populations with 
diameters down to 1m, show agreement with the observed flux of bolide 
detonations in the Earth's atmosphere. From these simulations, I further show 
the scientific rationale for an autonomous mission to the asteroid Main Belt. 
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<!-------->The thesis is available in PDF-format <A 
href="http://www.astro.ku.dk/~rene/michelsen_thesis.pdf">here </A>(5.3 MB). 
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rene at astro.ku.dk 
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Last modified 27-Jan-2010. 
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