For anyone else wondering: celestial navigation (by the stars) apparently works during the day as well, as the stars' infrared light remains "visible" [0]:

> The new systems use infrared rather than visible light for locating stars, allowing daytime navigation. The stars shine just as brightly in the day sky as they do at night, but their light is masked by sunlight scattered by the atmosphere. The scattering is strongest at short wavelengths... But glimpse that same sky with a filter that allows only infrared light, and the sky suddenly becomes dark - and filled with stars.

[0] https://www.popularmechanics.com/military/research/a36078957...