At times Rosetta needs to dump waste heat, at others to maintain as much warmth as possible.
These thin reflective metal blades remain open in high temperatures so that heat can radiate away, while in the cold they close. The spacecraft has 14 louvre panels covering 2.25 square metres, placed over its radiators across the side and back of the spacecraft.
The louvres open and close without power, working on a bimetallic thermostat principle – or more accurately TRI-metallic. The blades are moved by coiled springs made of a trio of different metals that expand and contract at differing rates.
The system was designed by Spain’s Sener company for the European Space Agency.