Innovative filter-on-chip technology from the Fraunhofer IST enables high-resolution data for sustainable agriculture and smart-farming applications
Climate change, increasingly frequent extreme-weather events and the growing demand for high-quality food are creating major challenges for agriculture worldwide. In order to secure yields while ensuring the efficient utilization of resources such as water, fertilizer and energy, farmers require ever more precise information regarding the condition of plants and soils. Hyperspectral remote sensing can provide crucial support here; until now, however, it has only been possible with large, complex and cost-intensive systems.
This is precisely where the ESA-funded RAINBOW project comes into play. In collaboration with Airbus Defence & Space, VISTA Geowissenschaftliche Fernerkundung GmbH and the Fraunhofer Institute for Applied Optics and Precision Engineering IOF, the Fraunhofer Institute for Surface Engineering and Thin Films IST has developed a new generation of compact hyperspectral sensors for small satellites.
At the center of the development is an innovative bandpass filter on the basis of filter-on-chip technology, which was manufactured at the Fraunhofer IST and which covers more than 30 spectral channels in the range from 400 to 1700 nanometers. To achieve this, three linearly variable bandpass filters were combined on a glass substrate with a size of only ten millimeters. In order to realize the exceptionally high spectral variation and to separate the individual filter areas from one another with high precision, the Fraunhofer IST applied state-of-the-art microstructuring procedures such as photolithography and lift-off processes. The result is an extremely compact, robust and economical component which is ideally suited for application on small satellites and which enables hyperspectral measurements that were previously reserved exclusively for larger and significantly more expensive systems.
From the filter directly to the chip
The filters manufactured at the Fraunhofer IST are based on high-precision sputtering processes such as those utilized on the institute’s own EOSS®/Opta-X sputtering platform. This technology enables both linearly variable filters with a large spectral bandwidth and pixel-precise structured filter stacks that can be integrated directly in front of the detector. As a result, the need for complex optical setups is eliminated; the size, weight and costs of the instruments are therefore significantly reduced – a decisive advantage not only for applications in space, but also for mobile or industrial systems. “With RAINBOW, we have taken a decisive step at the Fraunhofer IST towards making high-precision hyperspectral data economically available on small satellites for the very first time,” said Dr. Philipp Farr, Group Manager for Precision Optical Coatings at the Fraunhofer IST.
Hyperspectral data as the foundation for precise decisions
For agriculture, this is a significant step forward. The hyperspectral data that can be obtained with RAINBOW allows a considerably more detailed analysis of plant conditions, for example with regard to nutrient supply, stress factors or water content. As a result, precise conclusions can be drawn that are crucial for the optimization of cultivation strategies and sustainable resource management. New perspectives are also being opened up in quality and yield forecasting, for example through the satellite-based assessment of protein or nutrient content. Furthermore, the data can be used to determine the carbon content of soils, thereby making certification processes in the area of carbon sequestration significantly more efficient.
With the successful completion of the filter module, the Fraunhofer IST has concluded its contribution towards the RAINBOW project. The developed and qualified filter components now form the basis for further integration into the overall optical system and for subsequent validation and test campaigns within the project. The Fraunhofer IST has thereby achieved a significant technological milestone for compact hyperspectral remote-sensing systems.
https://www.ist.fraunhofer.de/en/press-media/2025/hyperspectral-earth-observatio...
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