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==> In this proposal, more time is being requested for MMEIXNER.PROP_AFS
and VBUJARRA.PPNA in a joint effort on GL 618.
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During the last stages of its evolution, low mass stars (<8 Msol) lose about
1 Msol in the form of a cool, low velocity (10 km/s) molecular wind on
the Asymptotic Giant Branch (AGB). This phase is thought to end with a burst
of increasing mass loss rate (the "superwind") which largely exhausts the
star.  The star then moves to the left in the HR diagram (the proto-
planetary nebula phase, PPN). Once the central star becomes hot enough, the
still expanding AGB wind will be ionized. At some point during its evolution,
the central star will start losing mass in a fast (100-1000 km/s) but low
density wind. This fast wind will drive fast shocks into the AGB wind.
The interaction of these winds and the hardening of the UV radiation field
will shape the resulting planetary nebula.  Understanding these mass loss
processes and its evolution during the AGB, PPN and PN phases is a key problem
within astrophysics because most of interstellar gas and dust originates
from these stellar sources.
Here, we propose high resolution spectroscopy  of far-infrared atomic
fine structure lines in  GL 618  using the ISO LWS and SWS FP
spectrometers.  GL 618 is a well known prototypical PPN which, because
of its RA, was not included in our original Autumn launch program but
was included in our Spring program.  GL 618 offers a unique opportunity
to study both the photodissociation region (PDR) surrounding its
expanding HII region  and the shocked gas from  its  fast, bipolar wind
colliding with its circumstellar AGB wind.    The far-infrared atomic
fine  structure lines are the primary coolants of  warm (~500K), dense
(~10^6 cm-3) neutral gas and are important probes of PDRs and shocked
gas  regions.