Towards the Optimization of Atmospheric Sampling using Unmanned Aerial Systems: A Review of the Latest CopterSonde Design Improvements

The CopterSonde (CS) Unmanned Aerial System (UAS) was developed in-house by a team of engineers and meteorologists at the University of Oklahoma. The CS is an ambitious attempt by the Center for Autonomous Sensing and Sampling (CASS) to address the challenge of filling the observational gap present in the lower atmosphere among the currently used meteorological instruments such as towers and radiosondes. The CASS team is making efforts to further improve upon and integrate atmospheric sensors that effectively exploit the UAS capabilities in order to close the gap between the state of the art UAS engineering and the meteorological research.

Custom autopilot algorithms and hardware features were developed as solutions to problems identified throughout several field experiments carried out since 2017, which made the CS a unique platform for meteorological applications and research. Leveraging the open-source ArduPilot autopilot code allowed for seamless integration of custom functions and protocols for atmospheric data collection along with the flight control data. This led to the creation of scripts such as the “wind vane mode” algorithm which has led to an asymmetric design of the CS. The latter allowed for more convenient locations to place the sensor package as well as improving the overall aerodynamic characteristics of the UAS. Moreover, it also allowed the team to design a modular shell, in which the sensor package is attached and runs independently of the UAS main body. This feature is particularly useful for calibration and maintenance purposes.

In addition to the previously mentioned proven features, further improvements were developed and added to the CS in the past year. First, a cutting-edge smart battery was incorporated into the design for a more user-friendly experience and longer flight times. Second, a precision landing system was successfully implemented and tested; such system will be used as part of a future autonomous charging box system. Third, an improved aspiration scoop for the thermodynamic sensors was designed and built for better sun radiation shielding and adaptability to different wind conditions. Finally, an adaptive sampling algorithm for vertical profiling of temperature was added to the flight control code. It consists in varying the ascent and descent rates based on the conditions sensed by the CS. These developments put the CS on the trend towards a smart UAS tool with a wide possibility of creating new adaptive and optimal atmospheric sampling strategies.

The presentation will provide an overview of the CS, its different features, and the motivation for their respective implementation. Although the focus will be on the new features of the CS, existing capabilities of the system will also be discussed. This will allow the audience to develop a complete picture of the CS and its capabilities. Finally, sample data will be shown and discussed with an emphasis on the quality of the measurements rather than the meteorological conditions in which the samples were collected.