Hollow fibre filter cartridge and header.

A variable conductance thermal insulation blanket regulates the temperature of a component (20) on the surface (32) of a spacecraft. The blanket comprises a sealed container (2) and a pressurized gas tank (10). When gas is introduced from the tank (10) into the sealed container (20), heat is conducted away from the component (20) into outer space via conduction through the gas molecules. Thus, component (20) is cooled. When gas is evacuated from within sealed container (2) and there is a vacuum there-within, heat conduction is thwarted, and the primary means of heat escape from component (20) is via radiation. However, radiation is also thwarted by means of a set of stacked radiation sheilds (24) having low emissivity but high thermal conductivity.