Precision optics to make plant health visible from space

The Fraunhofer IOF developed a silicon-based double-slit assembly and two high-precision mirrors for the FLEX mission, which will carry a spectrometer to detect plant fluorescence from space. The spectrometer, called FLORIS, uses two channels to analyze light emissions from plants, providing insights into their health and stress levels. The double-slit assembly is critical for achieving high spectral resolution and broad coverage, with slits precisely manufactured to within 1 micrometer of deviation. The slits are 85 micrometers wide and 44.15 millimeters long, with a permissible deviation of ±1 micrometer. The manufacturing process involved specialized lithography and coating to minimize reflections and ensure optical performance. The mirrors are integrated into the assembly and meet a roughness requirement of 0.3 nanometers rms. The mission aims to provide global maps of plant fluorescence, which can indicate ecosystem health and plant stress. The dual-slit assembly was developed under subcontract from OHB System AG, with integration led by Leonardo S.p.A. and Thales Alenia Space. The FLEX mission is commissioned by ESA and is expected to improve monitoring of ecosystems, agriculture, and forests.

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