Upper-air balloon soundings for weather predictions have been made since thebeginning of the 20th century. New radiosonde instruments for in situhumidity-, radiation- and gas-profile measurements in the troposphere and thelower stratosphere, were introduced in recent years for atmospheric researchand climate monitoring, but such instruments are often expensive and it isdesired they be reused on multiple flights. Recovering instruments thatfreely descend with parachutes is time consuming, sometimes difficult andeven dangerous. Here, we introduce the return glider radiosonde (RGR), whichenables flying and retrieving valuable in situ upper-air instruments. The RGRis lifted with weather balloons similar to traditional radiosondes to apreset altitude, at which time a release mechanism cuts the tether string,and a built-in autopilot flies the glider autonomously back to the launchsite or a desired preprogrammed location. Once the RGR reaches the landingcoordinates it circles down and releases a parachute 100 m above ground forlanding. The motivation for this project was to measure radiation profilesthroughout the atmosphere with the same instrument multiple times and with arapid turn-around time. The paper describes technical aspects of the returnglider radiosonde and the built-in radiation instruments and shows testflights up to 24 km altitude that are analyzed in terms of flightperformance and maximal distances covered. Several successive flightsmeasuring radiation profiles demonstrate the reliability and the operationalreadiness of the RGR, allowing new ways for atmospheric in situ research andmonitoring with payloads up to several kg depending on the specific size ofthe glider.
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