===================================================================== ==> In this proposal, more time is being requested for MMEIXNER.PROP_AFS and VBUJARRA.PPNA in a joint effort on GL 618. ===================================================================== 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.