The Faint Intergalactic-medium Redshifted Emission Balloon (FB-2), a collaborative NASA/CNES suborbital balloon telescope, targets the mapping of faint UV emissions from the circumgalactic medium around low-redshift galaxies. The initial September 2018 flight encountered challenges, including a balloon breach and subsequent damage during landing, impacting the two large telescope mirrors and the critical focal corrector. Likely due to landing shock, the focal corrector experienced misalignment beyond tolerance, necessitating reevaluation and realignment. This paper outlines a comprehensive approach to realigning the focal corrector using a computer-generated hologram (CGH) and a Zygo interferometer for feedback. The CGH enables precise alignment corrections in various degrees of freedom, while interferometer feedback aids in reducing aberrations. The paper details the methodology for optical alignment, surface measurement, and performance evaluation of the focal corrector, emphasizing its successful integration into the FB-2 spectrograph in early 2023 for the September 2023 flight.
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