A method of aligning a lens assembly to a focal plane array is provided. The method may comprise the steps of providing an upper cold shield which holds the lens assembly, providing a lower cold shield for holding the focal plane array, mounting the upper cold shield onto the lower cold shield, lowering the temperature of the upper and lower cold shield to a cryogenic level, translating the upper cold shield with respect to the lower cold shield until the lens assembly is aligned to the focal plane array while the upper and lower cold shields are at the cryogenic temperature levels, and fixing the upper cold shield to the lower cold shield while the upper and lower cold shields are maintained at cryogenic levels.