Optical Iodine Clocks for future GNSS

Abstract

The clock technology in Global Navigation Satellite Systems is one major driver of the achievable position accuracy. While high performance terrestrial optical lattice clocks outperform current microwave clocks deployed on satellites, they are not feasible for space applications due to their size, weight and power budget. Meanwhile clocks based on Doppler-free spectroscopy of optical transitions are promising candidates for next generation space clocks in the near future. The COMPASSO mission by the German Aerospace Center (DLR) will demonstrate optical key technologies including an optical clock and a laser communication and ranging terminal on the International Space Station. Especially it features two independent optical frequency references based on the spectroscopy of molecular iodine and an optical frequency comb for the transfer from the optical domain to the radio frequency domain. In addition, the next iteration of the iodine clock with SpaceTech GmbH aims at the full space qualification of an optical clock meeting the stringent requirements of GNSS.