the circumstellar envelope can be unveiled. Far-IR line maps would help to trace the spatial variations of the electron density, electron temperature, and relative elemental abundance, which may suggest how much of which material was ejected at what time over the course of the progenitor star’s mass loss history. Also revealed is how PNs are influenced by the passage of the ionization front. While such line diagnostics have been routinely performed in the optical line diagnostics in the far-IR can offer an alternative perspective, because (1) far-IR line ratios are relatively insensitive to the electron temperature due to smaller excitation energies of fine-structure transitions in the far-IR, and (2) far-IR line and continuum measurements are often extinction-independent, permitting probes into dusty PNs. Hence, PN investigations in the far-IR with [*Herschel*]{} should have a bearing on abundance determinations and elemental column densities, and therefore can heavily impact analyses in other wavelength regimes.

With the foregoing as motivation, we have conducted a comprehensive far-IR imaging and spectroscopic survey of PNs, dubbed the Herschel Planetary Nebula Survey (HerPlaNS), using nearly 200hrs of [*Herschel*]{} time by taking advantage of its mapping capabilities – broadband and spectral imaging as well as spatio-spectroscopy – at spatial 