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The remnants of planetary systems that survived the metamorphosis of their host stars into white dwarfs are identified in the form of compact debris disks comma formed from the tidal disruption of planetesimals. These disks are detectable as IR flux excess comma and comma in rare occasions comma as metallic emission lines from a gaseous disk component in optical spectra. These gaseous disks are thought to host embedded solid fragments comma maybe the core comma of the disrupted planetesimal comma and represent ideal targets for joint ultraviolet comma optical and infrared observations that provide unrivalled insight into the formation of these disks comma the nature of the disrupting planetesimal comma the elemental abundances of the planetary debris comma and its mineralogical make-up. Here comma we propose COS far-ultraviolet spectroscopy of a new comma bright comma and nearby gaseous disk system that we identified in December 2020 comma to measure the elemental abundances of the planetary material. The far-ultraviolet wavelength range is critically important to access transitions of core (Fe comma Ni) comma mantle (Si comma Mg comma O) comma and crust (Ca comma Al) comma as well as volatiles (C comma N comma S comma P) species that have no transitions at optical wavelengths comma or are contaminated by the disk emission lines. This system is also a prime target for JWST Cycle 2 MIRI spectroscopy of the circumstellar dust comma and this mid-cycle program will ensure that the composition of the debris is known well in time for the next JWST proposal round.