SCIENTIFIC ABSTRACT
Long-period and Mira variables are important stages in the late stellar 
evolution of low and intermediate mass stars. In fact, they are the main 
sources of galactic dust production and of a large variety of chemical
species originating from their circumstellar shells.
A reliable quantitative diagnostic and interpretation of these objects demands 
both, appropriate theoretical models and specific detailed observations, 
in particular in the infrared regime. 
We propose periodic ISOPHOT observations of long--period variables (LPVs) at 
different wavelengths in the mid-- and far--infrared range.
These measurements will yield informations about the temporal variation 
of the physical conditions in different spatial regions of the circumstellar 
dust shells and will allow a comparison with detailed dynamical model 
calculations. 
It is the aim of this project to study the wavelength--dependence of certain 
structures appearing in already observed near--infrared lightcurves and in 
theoretical lightcurves as well. 
The data obtained with this investigation, combined with ground-based 
monitoring, will also allow an interpretation of the long--term behaviour of 
Miras and LPVs in different wavelength regimes. 

OBSERVATION SUMMARY

                      **** IMPORTANT NOTE:  ****

Photometric observations will be performed for only two objects from the 
list given below. 

We use 3 filters for PHT03 AOT at 25 microns (52'' aperture),
60 microns (120'' aperture), and 100 microns (180'' aperture). 
Each observation is concatenated to a background measurement with the same
instrument setting in order to get a proper reference level. All
observations will be performed in staring mode, because the
source--to--background contrast is high and because the reference
position must be independent of the S/C roll angle. Using 32 s
integration time per filter allows to measure our objects with S/N > 100
so that brightness variations on a few percent level can be sufficiently
well assessed. Both sources will be
observed periodically in the 3 proposed filter bands at 6 fixed dates
(three times during two observation periods). 

The decision as to which 2 objects will be observed can only be made 
once the satallite has been launched, since it depends on the visibility
of the objects at the time required for the observations and we 
anticipate that it will be possible for only 2 from the list to be 
observable. These specialised fixed time observations should not 
preclude more general photometry proposals being accepted. 

The calculations of the time required for the
observations were performed using phtaot v1.3.