Disclosed is a spacecraft including a casing having a face, a radiator borne by the face, and a thermal insulation device borne by the radiator. The thermal insulation device includes: —a first screen device able to cover a first zone of the radiator, the first screen device including a thermally insulating and flexible sheet, and at least two springs capable of producing a constant reaction force, the springs being preformed in such a way as to wind up on themselves at rest and being fixed to the insulating sheet, the springs each having an end fixed to the radiator and a free end; and—a traction device able to pull on the free end of the springs to make the sheet cover the first zone and to release the free end in order to expose the first zone to space.