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We propose WFC3 UVIS-G280 grism observations to measure escaping ionizing photons (LyC) from a galaxy at z=1.43 having nebular conditions similar to reionization era systems. The galaxy is a uniquely bright (rvirgul20) gravitationally lensed system with an extended arc (9d_comma long) allowing ionizing photon escape at a sub-kpc level. Based on a newly developed indirect measure of LyC escape fraction using Mg II emission lines comma the galaxy is inferred to be a strong LyC leaker with ionizing photons escape fraction (dust corrected) of 27+--4%. The proposed observations will (i) directly test the utility of Mg II based measure of LyC escape fraction for a high redshift galaxy comma (ii) provide a sub-kpc map of ionizing photon escape allowing detailed probe of LyC escape. To date comma only one source exists at any redshift where a spatially resolved study of LyC photons is possible. However comma it is not clear whether the source is representative of reionization era galaxies. Our observations will exploit the ultraviolet capability of HST allowing the study of production and escape of ionizing photons from an exceptionally bright z=1.43 galaxy that is representative of reionization epoch.