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We propose to use the G102 (0.8 - 1.1 microns) and G141 (1.1 - 1.65 microns) grisms of Hubble.s Wide Field Camera 3 (WFC3) to study an ultra-hot Neptune. Given its size and orbital period comma it is an intriguing target for atmospheric characterisation as it is unclear how the planet has managed to maintain its H-He envelope. These Hubble observations will have the capability to unveil the composition of this atmosphere comma constraining the metallicity and thus providing insights into its formation history comma as well as being able provide initial measurements of the mass loss for this planet via the helium triplet at 1.083 microns.