Chlorophyll Fluorometer for Intelligent Water Sampling by a Small Uncrewed Aircraft System (sUAS)

Area of Science:

• Environmental monitoring
• Instrumentation
• Remote sensing

Background:

• Accurate in-situ chlorophyll measurement is crucial for assessing aquatic ecosystem health.
• Existing methods can be labor-intensive or lack real-time data acquisition capabilities.
• Small uncrewed aircraft systems (sUAS) offer a versatile platform for environmental data collection.

Purpose of the Study:

• To develop and evaluate a lightweight, low-power fluorometer for deployment on an sUAS.
• To enable autonomous, in-situ chlorophyll detection and trigger water sampling.
• To assess the performance and detection limits of the sUAS-mounted fluorometer.

Main Methods:

• A waterproof, 1.3 kg, low-power (1.1 W) fluorometer operating at 5 V DC was designed.
• Excitation was achieved using a 450 nm modulated laser, with fluorescence detected by a photodiode and transimpedance amplifier.
• Control and data logging were managed by an Arduino microcontroller and Raspberry Pi 4B using the Robot Operating System (ROS).
• Calibrations used dissolved chlorophyll standards from Chlorella powder.

Main Results:

• The fluorometer achieved a detection limit of 0.2 μg/L for chlorophyll with a 0.1 s measurement.
• Detection limits improved with longer integration times, as expected.
• Electrical noise from the sUAS increased detection limits by 2-3x, while acoustic noise and vibration had minimal impact.

Conclusions:

• The developed sUAS-based fluorometer system is effective for in-situ chlorophyll measurement.
• The system demonstrates potential for automated environmental water quality monitoring and targeted sampling.
• Further optimization is needed to mitigate electrical noise interference for improved detection limits.