We propose to map the  far-IR  dust emission  from the small scale
structures within the molecular cloud core L1498.
Recent spectral line  maps (in high density tracers, CCS &
CS) by NASA's facilities at Goldstone, the VLA & OVRO
Millimeter Array show that cores previously thought to be
single objects  are actually composed of fragments
with mass < 0.1 Mo and sizes< 5000 AU. As adjacent
fragments show distinct chemical differences it appears that
they are  at different stages of evolution.
Coalescence of these fragments will lead to the build up of
protostellar material. Our objective is
to study the properties of the gas and dust in a pre-protostellar
environment and to identify an evolutionary sequence among the
fragments leading up to the formation of protostars.
L1498 core is ideal for understanding pre-star-formation evolution:
dust emission in  submm continuum  observed at the 13CO peak in
L1498 suggests its spectral energy distribution has maximum below
400 micron at about 1 to 2 Jy level; therefore, far-IR maps of ISO
are best suited to study the dust distribution.
Goldstone data show at least three fragments in
CCS; the  OVRO interferometric map (in CS) of one fragment
shows structures on smaller scale (< 30"). These fragments are at
varying evolutionary stages as indicated by the chemical differences
(in CCS, HC3N, HC7N, CS, NH3).
ISO maps of L1498 at 100 and 200 micron  will provide data on the dust
emission and its variation from fragment to fragment as a function of
pre-protostellar evolution determined by radio and ISO map at 60micron.
The ISO and radio data will be used to derive the density structure
unambiguously and to model the physical and chemical
properties of the gas and dust in the pre-protostellar phase.