Researchers at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena, Germany, developed and manufactured a silicon-based double-slit assembly and two high-precision mirrors for the FLEX satellite's spectrometer. ^[1] The European Space Agency's FLEX mission is scheduled to launch into space on September 15, 2026, as planned. ^[2] The European Space Agency (ESA) has launched the FLEX mission to reveal new insights into how plants function by measuring the faint fluorescence they emit when they capture light during photosynthesis. ^[3] The double-slit assembly developed at Fraunhofer IOF consists of two slits exactly 85 micrometers wide over a length of 44.15 millimeters, with a permissible deviation of only plus or minus 1 micrometer. ^[4] The FLEX mission aims to provide global maps of plant fluorescence to improve the monitoring of ecosystems, agriculture, and forests, as well as lay new foundations for climate and vegetation research. ^[5] Although invisible to the human eye, the fluorescence signal changes with environmental conditions and plant health, allowing scientists to assess vegetation health and stress. ^[6] The FLEX satellite is equipped with the Fluorescence Imaging Spectrometer (FLORIS), an instrument designed specifically to detect and map this delicate glow from space. ^[7]