A cold atom clock in absence of gravity

We describe the operation of a cold atom clock in reduced gravity. We have recorded the cesium hyperfine resonance signal at a frequency near 9.2 GHz in the \(\) gravity environment produced by jet plane parabolic flights. With a resonance width of 7 Hz, the device operated in a regime which is not accessible on earth. In the much lower gravity level of a satellite, our cold cesium clock would outperform the fountains with a potential accuracy of \(\). This experiment paves the way to unprecedented performance in space applications such as tests of general relativity, global time dissemination, astronomy and geodesy.