System concept and thermo-mechanical design aspects of a robust and efficient Laser Transmitter for the AEOLUS-2 mission

Airbus Defense and Space GmbH, in cooperation with Fraunhofer ILT, is currently developing an engineering model (EM) of the laser transmitter for the AEOLUS-2 mission in frame of the ESA contract ALTA.. For this follow-up mission, a more powerful Laser transmitter is required, to provide single frequency laser pulses of 150 mJ energy. The design focuses on maximizing the use of the heritage from previous space-borne laser designs of the projects FULAS (ESA, EM-like Technology Demonstrator) and MERLIN (DLR/CNES, French-German Climate Mission). The FULAS laser comprises INNOSLAB based MOPA delivering IR laser pulses in the 100 mJ class at 100 Hz PRF. It has undergone a test program demonstrating outstanding thermal insensitivity and robustness and optical and mechanical stability, showing no degradation or misalignment at all after seven years. The laser transmitter of MERLIN, evolved from FULAS, comprises a scaled MOPA, combined with a subsequent Optical Parametric Oscillator (OPO) for frequency conversion. While the Laser opto-mechanical assembly (LASO) is developed by Fraunhofer ILT, Airbus Defence and Space GmbH is in charge of the system concept and the hermetically sealed Laser Housing (LASH) as well as the innovative thermal control system. This publication will provide insight in the transfer of the FULAS and MERLIN system concepts to the Doppler Wind LIDAR Transmitter. Emphasis will be on the robust thermo-mechanical design, with its thermally and mechanically decoupled optical bench and the sophisticated thermal control system based on heat pipes for effective heat removal directly from the individual heat sources of the system. This design is chosen to provide hands off operation of the Transmitter over life time.