Radiosonde

1980, National Research Council (U.S.) Select Committee on the National Weather Service, Technological and Scientific Opportunities for Improved Weather and Hydrological Services in the Coming Decade, page 44, The ultimate limitation of radiosonde networks is the impracticality of global deployment. […] Although, in principle, satellite soundings should be able to match radiosonde accuracies, in practice, they have errors of at least twice those of radiosondes.

Thus, the performance characteristics of radiosondes and the relative accuracy of radiosonde winds have been the subject of a great deal of scrutiny over the last few decades.

Sounding balloons carry a payload, usually a radiosonde, to heights of 30 km or more.