It would be difficult. Optical power of the illumination decreases with the inverse square of the distance. Optical power of the reflected light decreases with

It would be difficult. Optical power of the illumination decreases with the inverse square of the distance. Optical power of the reflected light decreases with the inverse square of the distance. The fluorescence in the plastic is not very bright (how bright?), and it's competing with ambient light (use at night?). Need to do everything you can to increase the signal to noise ratio. I'm imagining two ways to tackle this. 1. Illuminate a wide area and use a camera sensor. To compensate, you need very very bright light sources. It's going to be difficult to make a multi-spectrum, precise, very bright, lightweight light source. Probably strobe the lights to manage heat and so each exposure can compensate for changing ambient light. Probably need a way to measure outgoing light or otherwise live-calibrate based on the changing outgoing brightness. For the camera you need something that doesn't have an IR-filter. You need to use IR lenses (not glass). Preferably use a scientific/astronomy sensor optimized for extremely low-noise and long integration times. The very low-noise sensors are not ideal for drone use (vacuum chambers + cryo cooling = large + heavy + high power). Probably also need a very high dynamic range, even if you're running at night. Use a filter wheel to swap which wavelength the sensor is looking at for each exposure. Then you're going to need a lot of signal processing to handle the video. You'll need the drone to be extremely stable so you can stack long exposures, or use some night-photography exposure stacking AI, or both. The challenge is finding the tiny signals within all the noise. 2. Illuminate a narrow area and use a photodiode. Use a set of lasers at different wavelengths and a photodiode+lens system which looks where the laser is pointing. Now you're looking at a tiny spot at a time and you need a system to scan the laser around. However, it's much easier to make a single very sensitive photodiode amplifier and you can focus your illumination in a smaller, more manageable spot. The signal processing is easier now, too.