S. B. Peschke 1, M. Stickel 2, I. Heinrichsen 3, H. Böhnhardt 4, C. M. Lisse 5, E. Grün 6, & D.J. Osip 7
1 MPI für Kernphysik, D-69117 Heidelberg, Germany
2 MPI für Astronomie, D-69117 Heidelberg, Germany
3 IPAC, Pasadena, USA
4 ESO, Santiago, Chile
5 University of Maryland, College Park, USA
6 MPI für Kernphysik, D-69117 Heidelberg, Germany
7 MIT, Cambridge, USA
First maps of a comet at 60 and 175
were obtained using
ISOPHOT, the photometer of the Infrared Space Observatory(ISO).
The observations were carried out on December 30, 1997 , mapping
an area of 9'
9' centered on comet Hale-Bopp at both filters.
Each measurement consisted of 3 individual submaps offset by a third of
a pixel in both directions to increase the final resolution of the maps.
The final maps were composed of the submaps with
the use of a drizzle algorithm.
Within the same orbit 3-175
filter photometry on comet Hale-Bopp
was performed as well as multi-aperture photometry near the peak
wavelength
of the thermal emission. The same photometric sequence was repeated
as 'shadow observation' at the same position as that tracked in the
initial sequence for precise background subtraction.
Quasi-simultaneous observations in the near-IR were obtained with
the 3.6m at La Silla/Chile.
>From the 60 and 175,
radial intensity profiles have been derived
which are compared to the ones obtained from the near-IR data and to
the results of multi-aperture photometry.
Since dust grains have the highest thermal emitting efficiency
closest to their own size, the emission in the maps observed with the two
filters are dominated by the the thermal emission of different size grains.
Grain size distribution modeling has been carried out for the spectral
energy distribution derived with multi-filter photometry to get an
indication
of the coma composition which will in turn be used as input for dynamical
modelling. First results will be presented.