Meteorological probe

The probe contains a temperature, humidity and air pressure sensor and a small transmitter for the microwave band. It would be attached to a balloon and carried to great height, possibly over 30 km. The first types used a subminiature vacuum tube, transistors were used later. In the end, the probe would slowly fall down. Instructions for a possible finder were written on its case. The probe could be reused if returned to the meteorological institute.