The Development of Ultralight Radiosonde and Its Applications in Atmospheric Sciences

This study presents a mini-size (5*3*2cm) and ultralight-weight (15g including battery) radiosonde designed and made by authors from 2016. The motivation of this mini-size radiosonde (called NTUAS tracker) is to treat them as storm trackers into typhoon (hurricane) circulation. The core of NTUAS tracker is MT7688 SoC (System on Chip), which runs under Linux-like operating system (OpenWRT) connected to ATMEGA328 microcontroller (serial port) for reading RF modules. Through time divided multi-access(TDMA) system, ublox’s MAX-7Q GPS module passes data to MT7688 microprocessor unit (MPU) and ATMEGA328 microcontroller unit (MCU). MCU passes all sensors’ measurements (pressure, temperature, humidity variables) to MPU. This MPU has a built-in Web server and using Node.JS code to display real-time measurement on Web page through WIFI antenna. So its flight track could be monitored on Google Map by cellular phone directly. All measuring data is also recorded into internal secure digital memory card (SD) in the ground receiving station. This home-made ~160g weight ground station (9*9*5cm waterproof box with Raspberry-Pi Single board computer, LoRa gateway, Li-ion battery) connects a 6dB gain omnidirectional antenna to receive 8-channel (1 channel for 10 NTUAS trackers) data simultaneously. During the first inter-comparison in December of 2017 at Taichung city of Taiwan, 4-day intensive (3-hour interval) co-flights with Vaisala RS41 radiosonde showed that solar insolation on the no-shade temperature/humidity sensor(HTU21D) in daytime causes ~5.3℃ warming phenomenon. In the second co-flight inter-comparison field test in July of 2018 at same place, the shaded hat on the sensor reduced ~1.5℃ in daytime, but made warmer bias in nighttime. For the wind speed and wind direction retrieval from GPS location, the wind field from NTUAS tracker is well-consistent to Vaisala RS41 calculation. Due to the reasonable performance and cheaper cost (~US$25 for each NTUAS tracker and ~US$150 for ground station), ~500 sets of NTUAS trackers had been used to study in the atmospheric boundary layer (ABL) in TASSE (TAipei Summer Storm Experiment), July of 2018. The hourly wind profile with GPS navigation is not only more efficient and accurate than traditional eye-theodolite, but also provide high resolution of ABL thermodynamic profiles.