Lamplight Stabilization for GPS Rb Atomic Clocks via RF-Power Control.

Abstract

Recent evidence indicates that the signal-in-space user-range-error (SIS-URE) for GPS is strongly influenced by the satellite atomic clock's rubidium (Rb) lamplight intensity jumps. Following a proposal by Bloom and Bell, we have implemented RF-power control of an RF-discharge lamp of the type employed in Rb atomic frequency standards (RAFS). Since Rb lamplight intensity jumps are mapped onto the clock's output frequency via the light-shift effect, stabilization of the Rb light emitted by the lamp has the potential to significantly improve the RAFS' long-term frequency stability, and hence the GPS SIS-URE. Here, we not only demonstrate that RF-power control of the discharge lamp is possible, but also that by employing such control the fluctuations in Rb lamplight intensity can be reduced by orders of magnitude, providing a pathway for significant improvement in global navigation satellite systems.