The BELA Transmitter Baffle Unit (TBU)
The TBU is designed to protect the laser and guarantees that the laser can perform without any limitation. It can withstand harsh environmental conditions at Mercury orbit. The TBU comprises of two main subassemblies:
Transmitter Baffle Unit
The reflecting Stavroudis Baffle is a complex baffle shape formed out of sections of hyperbolas and ellipsoids. It reflects every incoming radiation or light at an average of only 1.1 internal reflections out of the baffle. The Stavroudis shape is made out of diamond turned, optical grade Aluminum with a surface roughness <4 nm.
The filter has a transmission of > 99.5 % at the laser wavelength (1064 nm), but reflects or absorbs most the other wavelengths in the range between 100 nm and 10 µm. It comprises of a Sapphire substrate with dielectrical coatings on both sides.
Comprehensive mathematical models in the fields of mechanics, optics and thermal were established at the institute in order to support and guide the design process of the TBU.