Unmanned Aerial Sunlight Induced Chlorophyll Fluorescence System

GaiaSky-SP-SIFUnmanned Aerial Sunlight Induced Chlorophyll Fluorescence SystemBasic principle:

The combination of daylight induced chlorophyll fluorescence monitoring system and rotary wing unmanned aerial vehicles has opened up a new application for precision agricultural monitoring. Chlorophyll fluorescence contains rich photosynthetic information. By extracting fluorescence information from reflected spectral signals that can characterize vegetation, crops, leaves, tree canopies, etc., combined with physiological and biochemical parameters such as fluorescence parameters and chlorophyll (measured under instantaneous ground environmental conditions), the chlorophyll fluorescence spectral characteristics of crops in different environments (fertilizers, water, disease stress, pests and diseases, etc.) and the relationship between their fluorescence indicators and other parameters (such as canopy temperature, surface irradiance, chlorophyll content measurement) can be determined. Therefore, airborne chlorophyll fluorescence monitoring technology is an ideal monitoring technology for efficient, timely, rapid, sensitive, and non-destructive detection of the physiological status of crop vegetation and its relationship with the surrounding environment. It can be widely applied to evaluate the health status of vegetation, etc.

GaiaSky-SP-SIFUnmanned Aerial Sunlight Induced Chlorophyll Fluorescence SystemTechnical specifications for configuration:

System architecture introduction:

Modular integration, standardized structure, no need to debug or adjust the system structure. Simply install it on the drone according to requirements, and achieve interoperability between the system, drone, and ground monitoring platform through wireless image transmission data cables. Provide independent power supply to the system through the drone gimbal. The downstream fiber and independent module are fixed for easy switching of imaging lenses, and the auxiliary camera is integrated on the independent module for observation and monitoring of the acquisition area. The uplink cosine correction function is modularized to collect real-time sunlight signals, with high transmittance, good homogenization effect, and wide adaptability to a wide range of frequency bands. GPS information can accurately locate the location information of the collection area.

Technical advantages:

·High system integration;

·Good system controllability and simple operation;

·Assist in monitoring and accurately locate the collection area;

·One click collection;

·Reflection, fluorescence spectrum display and output;

·Fixed-point cruise;

·Absolute radiation calibration;

·Real time cosine correction module for sunlight;

·GPS module;

·35mm/50mm imaging lens and bare fiber mode switching;

·Special fiber optic structure enables fast switching of uplink and downlink signals, ensuring synchronous acquisition of both signals;

·Can be used for both unmanned aerial vehicles and ground operations;

·The high-definition image transmission and data transmission integrated structure ensures system control (manipulation, data transmission, etc.);

·Multiple data processing models.

Basic principle:

The hardware components of the unmanned aerial vehicle daylight induced chlorophyll fluorescence (SIF) automatic observation system (Special Number: 2020202517297) (GaiaSky SIF) include fiber optic spectrometer, fiber optic, optical path switching module and switch, monitoring camera, acquisition control unit, and calibration module. At present, high-sensitivity fiber optic spectrometers and their accessories are mainly used for continuous and stable high-frequency observation of vegetation chlorophyll fluorescence and hyperspectral field. The system can achieve high-frequency high/hyperspectral observation of vegetation canopy under unmanned aerial vehicle platform. The observation frequency can reach 10s/time, and multiple spectra can be observed in one flight. At the same time, the system has two channels for dual cosine observation in the up and down directions, greatly improving the detection range of ground objects and commercializing the product in the market.

Sunlight induced chlorophyll fluorescence (SIF) is a spectral signal (650-800nm) emitted by the photosynthetic center of plants under sunlight conditions. It has two peaks, red light (around 690nm) and near-infrared light (around 760nm), and can directly reflect the dynamic changes of actual photosynthesis in plants.

SIF remote sensing is a rapidly developing vegetation remote sensing technology in recent years, which can make up for the shortcomings of current vegetation remote sensing observations and provide new ideas and technologies for carbon cycling and vegetation monitoring of terrestrial ecosystems.

Vegetation remote sensing, represented by vegetation indices based on "greenness" observations (such as NDVI), has greatly promoted the understanding and recognition of the Earth's biosphere at a macro scale in the past 30 years. However, it can only detect the "potential photosynthesis" of plants through "greenness".

Chlorophyll fluorescence has special technical advantages in the detection of vegetation photosynthetic physiology and is a direct detection method for "actual photosynthesis".

It can be said that vegetation chlorophyll fluorescence remote sensing is a breakthrough research frontier in the field of vegetation remote sensing in the past 10 years. With the development of research and technology, SIF remote sensing has made significant progress in the past decade.

Radiation calibration:

The entire optical system needs to undergo radiometric calibration to convert the DN values collected by the spectrometer into units of irradiance (mW/m2/nm) or radiance (mW/m2/nm/sr). Radiation calibration requires separate calibration of the bare fiber and the optical path connected to the cosine corrector. Radiometric calibration refers to calibrating the response intensity of a spectrometer at each pixel using a lamp with a known spectral output power. Absolute radiometric calibration changes the shape and size of the entire spectrum, corrects the individual instrument response function (IRF) of the instrument, and converts the Digital Number (DN) measured by the spectrometer into a physical quantity. The calibration coefficient is calculated using the following formula:

Among them, α is the calculated radiometric calibration coefficient, L is the radiance or irradiance of the standard light source, and DC is the dark current value measured by the spectrometer without light input. The unit of the spectrum calibrated by radiation is the power output per unit area per unit wavelength. The standard light source is usually expressed in units of µ W/cm2/nm, and it is best to multiply its value by 10 to convert the unit to mW/m2/nm. The radiance conversion relationship is the same.

Large scale, high-throughput imaging measurement and analysis of plant chlorophyll fluorescence provide suitable solutions for land and air dual base hyperspectral remote sensing analysis. Mainly applied in the following fields:

● Plant photosynthesis and fluorescence measurement

● Plant mapping and vegetation health characteristics

● Forest resource survey and assessment

● Crop growth assessment

Land air dual base hyperspectral remote sensing monitoring