Abstract
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 3.0 × 10−13τ−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.
Highlights
Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards
A variety of cold atom clocks (CACs) have been demonstrated on the ground, notably atomic fountain clocks[2,3,4] and optical frequency standards based on neutral atoms in a lattice or trapped ions[5,6]
Other space applications in cold atom physics such as cold atom interferometry, optical clocks, and cold atom sensors benefit from the techniques used in space CACs14
Summary
Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. The atoms are first cooled by lasers, and interrogated by a microwave field typically with the Ramsey method.
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