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We propose for one orbit of WFC3 UVIS-IR imaging comma and one non-disruptive ToO orbit of WFC3 IR grism spectroscopy of a nearby superluminous supernova (SLSN) 2020wnt to discern whether it is a pair-instability (PI) SN. PISNe are the theoretical death of a 140-260 solar mass stars comma and they may be a dominant contributor to nucleosynthesis in the early universe. A direct observation of a bona fide PISN does not yet exist in the literature. SN 2020wnt is the best candidate for a PISN yet discovered. It has a long rise from a large ejecta mass (virgul60 Msun) to a peak luminosity of -20.5 mags both consistent with some PISN models. The light curve declines post-maximum with a rate of 0.01 mag-day comma consistent with the radioactive decay of Co-56. Lastly comma latest near-IR spectrum shows shows features associated with Fe-group elements. These features point to an explosion that produces a copious amount of nickel comma like a PISN. Our imaging observations will (i) determine whether the SN is still bright enough for the grism observations and (ii) probe the host properties local to the SN site. If the SN is brighter than 22 mags in the F140W filter comma we will trigger a non-disruptive ToO to obtain grism spectroscopy. The particular lines we aim to observe are the CORCHETE_OPENS ICORCHETE_CLOSE comma CORCHETE_OPENSi ICORCHETE_CLOSE and CORCHETE_OPENFe IICORCHETE_CLOSE line complexes around 1.1 comma 1.25 comma and 1.6 micron. The nebular spectrum will measure the nucleosynthetic yield of the SN comma and unambiguously determine whether SN 2020wnt is a PISN or other more common deaths of a massive star.