An object in a halo orbit spends most of its time out of Earth's shadow: https://en.wikipedia.org/wiki/Halo_orbit#/media/File:Animation_of_Solar_and_Heliospheri

An object in a halo orbit spends most of its time out of Earth's shadow: https://en.wikipedia.org/wiki/Halo_orbit#/media/File:Animation_of_Solar_and_Heliospheric_Observatory_trajectory_-_Polar_view.gif https://en.wikipedia.org/wiki/Halo_orbit#/media/File:Animati... Hubble used cooled instruments, warm mirror. If you only partially cool a mirror then thermal expansion effects will mess up the focus. In the paper they propose heating segments that are shadowed, to keep the whole mirror at the same temp.