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Pixel Level Decorrelation in Service of the \textit{Spitzer} Microlens Parallax Survey

Microlens parallax measurements combining space-based and ground-based observatories can be used to study planetary demographics. In recent years, the Spitzer Space Telescope was used as a microlens parallax satellite. Meanwhile, \textit{Spitzer} IRAC has been employed to study short-period exoplanets and their atmospheres. As these investigations require exquisite photometry, they motivated the development of numerous self-calibration techniques now widely used in the exoplanet atmosphere community. Specifically, Pixel Level Decorrelation (PLD) was developed for starring-mode observations in uncrowded fields. We adapt and extend PLD to make it suitable for observations obtained as part of the \textit{Spitzer} Microlens Parallax Campaign. We apply our method to two previously published microlensing events, OGLE-2017-BLG-1140 and OGLE-2015-BLG-0448, and compare its performance to the state-of-the-art pipeline used to analyses \textit{Spitzer} microlensing observation. We find that our method yields photometry 1.5--6 times as precise as previously published. In addition to being useful for \textit{Spitzer}, a similar approach could improve microlensing photometry with the Nancy Grace Roman Space Telescope.