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Session 64 - Telescopes for the Next Millennium.
Oral session, Thursday, January 08

[64.02] The Zodiacal Emission at Different Places of the Solar System and the Choice of a Site for the NGST

N. Gor'kavyi (Crimean Obs.), L. Ozernoy (GMU and GSFC/NASA), J. Mather (GSFC/NASA), T. Taidakova (Crimean Obs.)

The current computational approach to modelling the interplanetary dust (IPD) usually employs a very small number of dust sources (a few) and a limited number of dust particles (hundreds to thousands). Recently, we have proposed a new quasi-hydrodynamical approach to the dynamics of IPD particles, which is based on the use of the kinetic equation for particle density in the space of orbital coordinates [1,2]. By using that approach, we compute a `reference model' of the IPD cloud produced by 5000 asteroids, 217 short-period, and 213 long-period comets. Our model, in its present form, accounts for basic effects that govern the large-scale structure of the IPD cloud, such as the Poynting-Robertson drag and evaporation of dust particles. By including particle collisions, gravitational scattering of particles by the planets, and resonant effects we are able to describe a smaller-scale structure of the IPD cloud, such as the `dust bands' and resonance rings. Using the inferred n(R,Z) distribution of the IPD in heliocentric distance R and geocentric altitude Z, we compute the thermal emission of the zodiacal cloud as a function of the observer's position.

These results are directly related to a currently discussed issue where the Next Generation Space Telescope (NGST), which will replace the HST in the beginning of the next century, has to be deployed. The optimal NGST orbit will be chosen by NASA based on several criteria, one of which is a minimum in the zodiacal light emission. The results of the present study enable us to exclude several preliminary considerations and pinpoint the possible sites for the NGST, which deserve further analysis with the use of other criteria.

\footnotesize References:

1. Gor'kavyi, N., Ozernoy, L., amp; Mather, J. 1997, ApJ 474, 496 2. Gor'kavyi, N., Ozernoy, L., Mather, J., amp; Taidakova, T. 1997, ApJ 488, Oct. 10

Program listing for Thursday