Jianbo Zhao

In-orbit operation of an atomic clock based on laser-cooled 87 Rb atoms

Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth’s radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0u2009×u200910−13τ−1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.Cold atom clocks are among the most precise measuring devices and play key roles in everyday life and scientific explorations. Here the authors demonstrate the first in-orbit atomic clock using cold Rb atoms operating in microgravity and opening possibilities of space surveys and tests of fundamental physics.

Initial Tests of a Rubidium Space Cold Atom Clock

We report the initial test results of a rubidium (87Rb) space cold atom clock (SCAC). The space-qualified 87Rb SCAC is composed of the physical package, the optical bench, the microwave synthesizer and the control electronics. After the system is integrated, about 108 87Rb cold atoms are captured by magneto-optical trap. The linewidth of the Ramsey fringe is about 10 Hz for the free evolution time of 50 ms on the ground, and the signal-to-noise ratio is measured to be larger than 300. We demonstrate a good medium-term fractional frequency stability of 1.5 × 10−14@1000 s in the closed-loop operation on the ground. The main effects of the noise on the stability are also presented, and the optimized operating parameter is analyzed for the operation of SCAC in the microgravity environment.