Primary Mirror Manufacturing Considerations For A Space Based Coherent Lidar

The measurement of winds from a space borne platform is of significant scientific importance to both weather prediction and climate research. One of the key technologies embodied in coherent detection of winds from space is the use of large aperture, compact, lightweight, high-quality wavefront, photon-efficient optics. This paper discusses the optical design, The mechanical design, material preference, diamond turning issues, polishing requirements, and coating selections for the primary mirror of a 25X afocal beam expander intended for use in space-based coherent lidar systems.Performance requirements levied on a lidar optical system are primarily driven by operational signal to noise budgets, but other factors such as the thermal and launch load environments also factor into the optics design. Therefore, the sensitivity of any coherent lidar is generally limited by the quality of its optical system. Aberrations generated by the optics from manufacturing errors, optical misalignment, or operational thermal activity will substantially affect measurement accuracy's especially when used at the ranges expected from space platforms. The stringent optical performance requirements coupled with demanding physical and environmental constraints have created the need for a design with unique optical and robust mechanical design characteristics. This paper will survey various manufacturing considerations when producing a 25cm diameter f/0.9; 150mm off axis parabola which is associated with the 2-micron SPAce Readiness Coherent Lidar Experiment (SPARCLE). This minor has a final figure of better than 1/4 wave p-v at HeNe and surface roughness of better than 15 angstroms RMS.