Herschel’s cryostat vacuum vessel

The Herschel cryostat vacuum vessel, seen here in the ESTEC cleanroom, stores 2370 litres of superfluid liquid helium (He II) which is used to help cool the various elements of the detector plane. In orbit, the black outer half of the vessel faces away from the Sun and acts as a radiator while the reflective half faces the inside of the sunshade and reflects excess heat.