## 2 Experiment Description
### Instrumentation
#### 2.1.2 UAV Platforms
It allows for the integration of an additional turbulence sensor package (Aerosonde five-hole probe), significantly higher air speeds (up to 25 m s\({}^{-1}\)), and longer endurance (ca. 90 min). The turbulence sensors are placed in the nose facing forward, whereas the temperature and humidity sensors are mounted on top of the fuselage, well separated from the battery and motor. Aside from these differences, the miniTalon is equipped with the same Paparazzi autopilot system and the same basic sensor package as described above (Table 3). The Bebop2 Met is based on Bebop2 by Parrot, a small, commercially-available multicopter with a weight of about 500 g and a diameter of roughly 50 cm. The system was modified for our purposes by adding meteorological sensors (Table 3) integrated into a 3D-printed frame attached on top of the battery, as well as by running the Paparazzi autopilot software on the original processor. The sensors for \(T\) and \(RH\) are placed a few centimeters above one of the propellers on a thin side arm. Tests have shown that the sensors are well ventilated and that the flow at this location is fairly horizontal. The flight time under cold environmental conditions is typically in the range of 20 min, and it can only be operated safely in weak and moderate wind conditions below 10 m s\({}^{-1}\). Typical flight operations include maneuvers such as hovering at a fixed position and altitude and vertical profiles at a fixed location with a constant vertical speed. The Advanced Mission and Operation Research (AMOR) multicopter UAV was designed to fly in environmental monitoring missions [89], including meteorological campaigns in polar regions. The central airframe, the side arms, the landing gear, and the 15 inch propellers are made of carbon-reinforced plastic. The empty weight of the UAV is 1.5 kg, and the maximum takeoff weight is 4.9 kg. Depending on the environmental conditions, the battery, and the payload, the maximum flight time is approximately 60 min, and the UAV can be operated in winds of up to 15 m s\({}^{-1}\). Due to \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Sensor** & **Acq. Frequency** \\ \hline Temperature, \(T\) & PT100-fine-wire & 100 Hz \\ Temperature, \(T\) & TCE-fine-wire & 100 Hz \\ Relative humidity, \(RH\) & P14-Rapid & 100 Hz \\ Pressure, \(p\) & HCA-BARO & 100 Hz \\ Wind components, \(u,v,w\) & 5-hole probe & 100 Hz \\ Position, \(lat,lon,alt\) & GNSS & 100 Hz \\ Attitude angles, \(\theta,\phi,\psi\) & IMU & 100 Hz \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Specifications for the Multi-purpose Airborne Sensor Carrier (MASC-2) UAV. the cold conditions and the relatively short profiling missions during Hailuoto-I, AMOR flights took typically about 5 min. The Advanced Meteorological Onboard Computer (AMOC) receives the sensor data, fuses the data sets with the IMU and GNSS data sets, and stores them on a \(\upmu\)SD card. A fast temperature sensor based on a 25 \(\upmu\)m thermocouple wire, a factory calibrated HYT 271 RH sensor, and a Digi Pico P14 Rapid RH sensor provide the meteorological standard data sets. A pressure sensor provides the altitude above ground level, and a Melexis thermopile sensor provides the surface temperature data, as shown in Table 5. The sensors are mounted on a horizontal tube well outside the downwash of the propellers.