The CopterSonde: an insight into the development of a smart unmanned aircraft system for atmospheric boundary layer research

Abstract

Abstract. The CopterSonde is an unmanned aircraft system (UAS) developed in house by a team of engineers and meteorologists at the University of Oklahoma. The CopterSonde is an ambitious attempt by the Center for Autonomous Sensing and Sampling 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 CopterSonde is a unique and highly flexible platform for in situ atmospheric boundary layer measurements with high spatial and temporal resolution, suitable for meteorological applications and research. Custom autopilot algorithms and hardware features were developed as solutions to problems identified throughout several field experiments carried out since 2017. In these field experiments, the CopterSonde has been proven capable of safely operating at wind speeds up to 22 m s−1, flying at 3050 m above mean sea level, and operating in extreme temperatures: nearly −20 ∘C in Finland and 40 ∘C in Oklahoma, United States. Leveraging the open-source ArduPilot autopilot code has allowed for seamless integration of custom functions and protocols for the acquisition, storage, and distribution of atmospheric data alongside the flight control data. This led to the development of features such as the “wind vane mode” algorithm, which commands the CopterSonde to always face into the wind. It also inspired the design of an asymmetric airframe for the CopterSonde, which is shown to provide more suitable locations for weather sensor placement, in addition to allowing for improvements in the overall aerodynamic characteristics of the CopterSonde. Moreover, it has also allowed the team to design and create a modular shell where the sensor package is attached and which can run independently of the CopterSonde's main body. The CopterSonde is on the trend towards becoming a smart UAS tool with a wide possibility of creating new adaptive and optimized atmospheric sampling strategies.

Confronting the boundary layer data gap: evaluating new and existing methodologies of probing the lower atmosphere

“…Careful considerations must be made to ensure the true environmental temperature is being measured, as opposed to the modified rwUAS environment. Additionally, proper aspiration of the sensors and shielding from solar radiation is vital to accurate measurements (Tanner et al, 1996;Hubbard et al, 2004;Greene et al, 2018Greene et al, , 2019.…”

Observations of the thermodynamic and kinematic state of the atmospheric boundary layer over the San Luis Valley, CO using remotely piloted aircraft systems during the LAPSE-RATE field campaign

“…CC BY 4.0 License. The RPAS utilized for this field campaign was the CopterSonde 2 ( Figure 1; see Segales et al, 2020a), which was designed and manufactured by the Center for Autonomous Sensing and Sampling (CASS) at the University of Oklahoma. The CopterSonde 2 is a rotary-wing platform that is based on a modified version of the Lynxmotion HQuad500 wide-X type quadcopter with fixed-50 pitch rotors that has been optimized for vertical profiling operations.…”

“…The CopterSonde's technical specifications can be found in Table 1. Additional information regarding the design and development of the CopterSonde series is described in Segales et al (2020a). The CopterSonde RPAS has been proven to be capable of collecting thermodynamic and kinematic profiles of the atmosphere in a variety of environments from summer in the Southern Great Plains in pre-convective environments (Koch et al, 2018) to polar winter conditions in the Artic (Kral et al, 2020, submitted).…”

“…The CopterSonde 2 is outfitted with sensors that enable it to measure atmospheric state variables as it ascends along its flight path (see Table 4 for details). The wind speed and wind direction were calculated indirectly at 10 Hz using the Wind Vane Mode algorithm described in Segales et al (2020a) which utilizes the roll, pitch, and yaw angles measured with the inertial measurement unit (IMU) on-board the RPAS's autopilot system, the Pixhawk CubeBlack. The pressure was measured at 10 Hz with a MS561 capacitive pressure sensor inside the Pixhawk CubeBlack, which is also utilized for altitude.…”

“…CopterSonde missions were programmed to fly a vertical ascent from the surface to 914 m AGL, utilizing the platforms wind vane mode to continuously orient itself into the wind. This permitted the RPAS to sample the vertical structure of pressure, 120 temperature, humidity, wind speed, and wind direction in a controlled and repeatable manner that minimized influences from the platform itself (Segales et al, 2020a). These flights will be referred to as profiles in subsequent text and tables.…”