The monitoring of water vapor dynamics and evapotranspiration provides feedback for vegetation and crop water requirements. Many current evapotranspiration techniques heavily relay on satellite imagery, temperature distribution and incorporated into estimation models. The work presented here is based on a direct water vapor change monitoring using snapshot SWIR and NIR spectrometers utilizing custom fiber bundles. These bundles have dense input and sparse output creating void spaces for spectral information and allow recording of spatial-spectral data cube information in parallel at the CMOS/CCD cameras. SWIR / NIR snapshot spectrometers were packaged and ruggedized for field imaging. The number of spatial samples is adaptable within 8000 ~ 35,000 range and spectral sampling 20-50 values. SWIR system allowed 1050-1300 nm spectral range while NIR 650-1000nm, applying 1130nm and 940nm absorption windows respectively. We performed and present series of experiments including controlled reference measurements and field tests.
KEYWORDS: Short wave infrared radiation, Absorption, Real time imaging, Prisms, Infrared imaging, Spectroscopy, Cameras, Atmospheric monitoring, 3D modeling, Solar radiation
A novel snapshot imaging spectrometer has been developed for short wave infrared monitoring. A custom designed fiber bundle remaps an incoming image to create void spaces on the sensor for a prism to disperse each individual fiber cores. This results in 35,000 spatial samples and each spatial sample providing spectral sampling for over 20 channels in the wavelength range of 1100nm to 1300nm. This spectral region spans the vapor sensitive dip of 1130nm and the vapor insensitive peak of 1260nm in the reflect spectrum of land covers, allowing calculation of a vapor index and the potential for monitoring vapor fluctuations in the atmosphere. Laboratory testing confirms the sensitivity can reach about 42 micrometers of precipitable water, due to the absorption coefficient at 1130 nm. Field testing demonstrates the ability to monitor the temporal and spatial fluctuations of vapor from different land covers such as lawn, concrete surfaces. Real time mapping of the vapor variation - index may provide useful information for atmospheric, environmental, agriculture and solar energy research.
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