Technical characteristics of the radiosondes.
On September 8 1944 the “service of radiosondes” of the National Observatory of Cuba was formally inaugurated (Millás, 1945). These facilities were at the time the most advanced things as for investigation techniques applied to meteorology.
The devices consisted of two globes of “synthetic rubber” (artificial). The bigger globe was able to support a tension that potentially allowed it to arrive to a height 65 600 feet (»20 km), and it had suspended the classic parachute to assure the soft descent of the recoverable instruments.
Underneath another smaller globe was placed, of red color that carried ballast in its interior consistent in some 300 g of sand, with the purpose of regulating the ascendant speed of the group in the low levels of the troposphere. The two balloons were filled with helium. Finally the radiosonde device or radiometeorograph was suspended.
At about 9 800 feet (»3 km) the secondary globe exploded, and the radiosonde ascended only with the main spheroid. The ascendant speed should be controlled, in order to synchronize it with the inertia or intrinsic response delay of the instruments following the changes in the value of the meteorological variables with height; this situation affected the hygrometer in particular.
The sensibility of the meteorological instruments had limitations, and some error margins were tolerated. The type of aneroid barometer used only two capsules of Vidi, and it was qualified by Millás as “acceptable”; the thermometers, consistent in an electric resistance with ceramic elements, had an error of ±0,5°C; lastly, the hygrometers gave a margin of up to 5% error in their readings.
The radio transmitter operated in the range of ultrashort waves, in the frequency of 72 MHz, and had a power of 0,5 W. The manufacturers had chosen an energy source consisting in a battery “of 3 V on the filament and 90 V at the plates” (Larragoiti, 1945). The device emitted two signals of fixed frequency, called “reference” that served of comparison point with the signals corresponding to the three variables.
In total, the device weighed 1,2 kg approximately, and its dimensions (in cm) were 20,32 for 10,16 for 20,32. In one of the sides of the container a legend was placed that pointed out: “Return to: National Observatory, Casablanca, Havana”, dedicated to whoever found the device after its return to earth.