Laser diode benches for the climate satellite MERLIN

The Ferdinand-Braun-Institut has developed and produced extremely reliable LDBs for MERLIN, the Franco-German climate satellite. In addition to LDB deliveries, FBH supports the Fraunhofer ILT in reliability studies and in preparations for the flight of the satellite. MERLIN is due to be launched into space in 2025 to investigate the effect of the greenhouse gas methane on global warming. A radar-like laser system on the satellite will measure natural and man-made methane emissions: The Integrated Path Differential Absorption (IPDA) LiDAR sends laser beams to the Earth's surface and analyzes the backscattered signal.

Six of FBH's LDBs were integrated into three pump modules of the Fraunhofer ILT and delivered to the project partner ready for operation in July 2020. The modules generate the necessary pump energy for the oscillator of a solid-state laser and are integrated into the LiDAR system by ILT. With the laser diode benches, pump powers of more than 60 watts can be generated in double pulses with a repetition rate of 20 hertz and a pulse width of 150 microseconds. Thanks to the fast axis collimation lenses, the laser beam is coupled into an optical fiber with low loss. The laser diode benches were qualified after extensive internal testing by the European Space Research and Technology Centre ESTEC in the Netherlands. Their lifetime tests demonstrated that the power degrades only insignificantly even over a long operating time of more than four billion pulses. T

For the »MERLIN« satellite project, a collaboration between DLR RfM and CNES, the Fraunhofer ILT is developing the laser source - the »Laser Optical Assembly« - of the laser transmitter under contract to Airbus DS GmbH. The required laser diode benches are supplied by FBH. The work is carried out on behalf of the Federal Ministry of Economics and Energy BMWi under the funding reference 50EP1601.