Chlorophyll fluorescence sensors represent a key tool for the remote-sensing community. Light re-emitted after being absorbed by chlorophyll molecules of plant leaves is an indicator of ecological conditions and overall plant physiology. The spectral range of interest is roughly 754 to 775 nanometers (Near-Infrared, or NIR). The need is not only for a sensor that covers this range (others can), but one that exhibits very high spatial/spectral resolution (0.1-0.2nm across the range) plus high SNR for excellent low-light performance.
During photosynthesis, plants convert light energy from the sun into chemical energy that is used to fuel organism growth. During that process plants basically absorb one color and emit another (fluorescence). Measured fluorescence using this type of airborne sensor can be used as an indicator of photosynthetic activity of the plant (and thus telling its vitality). It is this type of analysis that can help unlock secrets around crop health and climatology…the former being key to global economies and the latter key to the health of our planet.
Key environmental secrets can be unlocked through chlorophyll fluorescence spectroscopy, but Headwall has been able to ‘tune’ the sensor for the key range of interest while keeping package size, weight, and cost all below those of other systems tackling the same task. Mostly, these sensors are deployed aboard small aircraft and commercial satellites which are often space constrained with respect to payload. The smaller size and weight of Headwall’s sensor allows it to coexist with other instrumentation without impacting the overall payload budget. And the affordable price point of the sensor allows it to be deployed in more applications.
This sensor is small and light thanks to the novel use of a totally reflective concentric optical design enabling simultaneous high spectral and spatial resolution across a wide scan swath. The sensor can be tuned in advance to image any 20-30 nm wide passband within the interval 460-800 nm without any loss of imaging performance. And within that 20-30nm passband, hundreds of spectral bands can be imaged. Residual smile and keystone distortions are also minimized to the maximum extent possible in a compact, high dispersion instrument. Incorporation of Headwall’s holographic diffraction grating technology means every sensor contains a high-efficiency master grating, simultaneously maximizing signal throughput while minimizing stray light. State of the art opto-mechanics create a rugged, passively athermalized platform optimized for imaging in real-world environments such as aircraft, UAVs, and satellites. The net result is that data products will exhibit best in-class SNR and camera-limited spatial resolution across a wide field of view.
• slit image (FWHM) of ≤ 0.15nm within entire slit image
• Slit image (spatial x spectral): 13.3mm x 7.45mm (image format spanning 755-775nm)
• Pixel binning: Yes, depending on chosen camera
• Residual smile: (μm) ≤ 2.5
• Residual keystone: (μm) ≤ 7.0