IPA: /ˈreɪdiəʊsɒnd/
KK: /ˈreɪdioʊˌsɒnd/
A device that is sent into the atmosphere, usually by a balloon, to collect and send back weather information.
The scientists launched a radiosonde to measure temperature and humidity at different altitudes.
Radiosonde → It is formed from "radio" (from Latin *radius*, meaning ray or beam) and "sonde" (from French *sonde*, meaning probe or sounding device). The word refers to a device that uses radio signals to probe or measure atmospheric conditions.
Think of a 'ray' ('radio') that is used to 'probe' ('sonde') the atmosphere — that's what a radiosonde does.
No commonly confused words.