Test of the gravitational redshift effect at Saturn

Abstract
The results of a test of the gravitational redshift effect at Saturn are reported. Measurements of the redshift were obtained with the Voyager 1 spacecraft during its encounter with Saturn in 1980. Because the spacecraft was equipped with an ultrastable crystal oscillator (USO), it is possible to test the redshift effect at an interesting level of accuracy. Assuming that radiation in the Saturn magnetosphere has had a negligible effect on the USO, we verify the prediction of general relativity to an accuracy of one percent. This limit could be of interest for constraining possible alternative theories of gravity.