Proposal Title: Airborne Lidar Induced Fluorescence Transient (LIFT) Method for Measuring Photosynthetic Performance and Primary Productivity in Terrestrial Ecosystems
We will develop an airborne Lidar-based system to measure the photosynthetic performance and primary production in terrestrial ecosystems that will comply with ANSI Z-136.1 guidelines on eye-safe laser radiation. The proposed method is based on measuring laser-induced fluorescence transients (LIFT) in response to a spatially and temporally modulated excitation signal at energy levels of 30 to 50 W/m2. This excitation saturates up to 60% of the photosynthetic electron transport, causing a transient increase in the quantum yield of chlorophyll fluorescence. The amplitude of induced fluorescence transient, and the rate of fluorescence saturation are controlled by a set of photosynthetic parameters, such as the functional absorption cross section, the efficiency of photochemical conversion, and the rates of electron transport in photosystem II.
The LIFT method will be implemented in a prototype instrument capable of airborne operation, which will be used to demonstrate the feasibility of the proposed approach in field applications. To excite chlorophyll fluorescence, we will use an array of laser diodes to produce a spatially and temporally modulated excitation pattern along the flight path. We will also explore the possibility of using a single, non-coherent light source, equipped with a fiberoptic spatial modulator. Moving along a flight path with a typical speed of 135 mph (60 m/s), the beam will "paint" a spatially modulated excitation image on the ground. This excitation pattern will produce a fluorescence image with modulation characteristics controlled by the photosynthetic parameters of exposed plants. The fluorescence image will be collected by a 400 mm telescope, and will be acquired by a red-sensitive intensified CCD camera. Photosynthetic parameters will be calculated by the nume! ! rical fitting of excitation/emission images into a numerical model describing the functional relationship between light, fluorescence, and photosynthesis.