Design and manufacture of a lightweight reflective baffle for the BepiColombo Laser Altimeter

The BepiColombo Laser Altimeter (BELA), part of the payload of the European Space Agency's BepiColombo mission, is designed to point a telescope with a 200-mm aperture toward a surface that can reach 700 K. Furthermore, direct sunlight can shine into the instrument at angles of 38 deg from the boresight. At Mercury, the solar flux can exceed 14 kW m−2. A baffle for such conditions must both reduce straylight to the best possible extent and minimize the heat load to the spacecraft, i.e., the sum of absorbed visible light and infrared flux. We describe the design and manufacture, including coating, of a reflective baffle. The baffle is made by diamond turning of aluminum and has a clear aperture of 200 mm, about 300-mm length, and a mass of 716 g.