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Observations of the ultra-faint dwarfs (UFDs) comma as relics of the epoch of reionization comma allow us to probe the earliest epochs of star formation (SF). In particular comma the UFDs in low density environments for most of their lifetimes provide unique tools to probe the effects of early environmental conditions on the SF histories (SFHs) of the UFDs and their sub-solar initial mass function (IMF) because they likely maintain the best 'fossil. record of early local environments. We propose to obtain deep ACS and UVIS imaging in F606W and F814W for 2 LMC satellite UFDs that are on their first approach to our Galaxy comma and thus resided in the outskirts of the Local Group at high redshift. This program is designed to identify systematic differences in the stellar populations of recently captured UFDs vs. long-term MW satellites (data available from previous programs) by using high-fidelity color-magnitude diagrams constructed from deep HST imaging as well as spectroscopically measured metallicity distribution functions. We willdoublePoint (1) Establish whether SF is quenched at different times with different rate in UFDs in low density environment at early times comma probing the patchiness of reionization by directly comparing with theoretical predictions (2) Identify variations in the sub-Solar IMF across UFDs born in different environments (3) Pave the way for a more accurate constraint on the MW halo mass.