Komarek, Tomas.

The radio transmitters/receivers aboard spacecraft are used for more than just communicating planetary data and receiving commands. A number of scientific experiments can be conducted by analyzing radio signals sent back from the spacecraft. Radio signals from a spacecraft can be analyzed during the passage of that signal close to a planet. The signal is usually bent, delayed, obscured or reflected by the planet. The measurement of these alterations to the signal allows scientists to extract information about planet size, atmospheric density, and other factors not otherwise observable. An example is measuring the General Theory of Relativity by measuring the delay of the radio signal as it passes near a massive object with a large gravity field, such as the Sun. Einstein's theory predicted an apparent slowing in the speed of a radio signal when the signal passes near any massive body. Radio science experiments have validated this theory.

From the description of Radio Science Collection, 1961-1980. (Jet Propulsion Laboratory Library and Archives). WorldCat record id: 733100171