SCIENTIFIC ABSTRACT
With ISO, we propose to study the physical nature and evolutionary
history of dust debris clouds around solar mass stars. These clouds,
discovered by IRAS, are thought to be related to planetary systems. The
program will consist of: (i) A photometric study of selected A, F, G,
and K-type main sequence stars within 20 pc of the Sun. 160 stars have
been selected with various ages and multiplicity. (ii) A study of the
evolutionary history of debris clouds from observations of 174 young
open cluster stars and weak-line T Tauri stars. (iii) Search for excess
emission from 34 known young main sequence field stars beyond 20 pc.
(iv) Search for possible dust disks around 12 degenerate stars. (v)
Search for infrared excess from 23 Bright Star Catalog A & F stars
which were not observed by IRAS. The investigation will clarify the
relationship of the debris clouds, specific properties of stars, and
place the phenomenon in the context of planetary formation.


OBSERVATION SUMMARY
We will investigate the excess emission from main sequence and the
other field stars at 60 micron and 100 micron using C100 in ISOPHOT,
using the triangular chopping mode.

For the cluster stars we will use a sparse map and C100 (PHT37, PHT38,
and PHT39). Each observation consists of a single stare on the object
and then a corresponding stare on an adjacent sky, separated by 2
arcmin. For stability of the detectors, all observations in a sequence
will be done at one wavelength and then a repeated reverse sequence at
a second wavelength; The two sequences are concatenated together.
Integration times on each of the source and sky will be Typically 128
sec at 60 micron and 128 sec at 100 micron. The required signal to
noise for these cluster stars is unknown, since the photosphere will
not be seen and the amount of excess depends on the unknown dust
density.

We expect that the photosphere will be detected for most stars stars
with a S/N > 5.

For the degenerate white dwarfs and pulsars, the S/N will depend on the 
amount of circumstellar dust, which is uncertain. 

Acquisition			180 sec
Initial instrument setup	 15 sec
Stability of detector		 90 sec
Filter change (2 Pos)		 20 sec
FCS exposures (for 2 filters)	 32 sec
Integration at 60 micron	256 sec
Integration at 100 micron	256 sec

Total time			849 sec