Demonstration of a trapped-ion atomic clock in space.

Atomic clocks, which lock the frequency of an oscillator to the extremely stable quantized energy levels of atoms, are essential for navigation applications such as deep space exploration and global navigation satellite systems, and are useful tools with which to address questions in fundamental physics. Such satellite systems use precise measurement of signal propagation times determined by atomic clocks, together with propagation speed, to calculate position. Although space atomic clocks with low instability are an enabling technology for global navigation, they have not yet been applied to deep space navigation and have seen only limited application to space-based fundamental physics, owing to performance constraints imposed by the rigours of space operation.

Allan Deviation of Atomic Clock Frequency Corrections: A New Diagnostic Tool for Characterizing Clock Disturbances.

As atomic clocks and frequency standards are increasingly operated in situations where they are exposed to environmental disturbances, it becomes more necessary to understand how variations of each clock component impact the clock output, in particular the local oscillator (LO). Most microwave atomic clocks in operation today use quartz crystal LOs with excellent short-term noise variation but large unwanted long-term drift. Fortunately, this slow drift is mitigated by repeatedly comparing the atomic reference frequency to the LO and applying corrections each iteration through a control algorithm.

Drifts and Environmental Disturbances in Atomic Clock Subsystems: Quantifying Local Oscillator, Control Loop, and Ion Resonance Interactions.

Linear ion trap frequency standards are among the most stable continuously operating frequency references and clocks. Depending on the application, they have been operated with a variety of local oscillators (LOs), including quartz ultrastable oscillators, hydrogen-masers, and cryogenic sapphire oscillators. The short-, intermediate-, and long-term stability of the frequency output is a complicated function of the fundamental performances, the time dependence of environmental disturbances, the atomic interrogation algorithm, the implemented control loop, and the environmental sensitivity of the LO and the atomic system components.

Mercury Ion Clock for a NASA Technology Demonstration Mission.

There are many different atomic frequency standard technologies but only few meet the demanding performance, reliability, size, mass, and power constraints required for space operation. The Jet Propulsion Laboratory is developing a linear ion-trap-based mercury ion clock, referred to as DSAC (Deep-Space Atomic Clock) under NASA's Technology Demonstration Mission program. This clock is expected to provide a new capability with broad application to space-based navigation and science.

Characterization of light shift below 10(-15) in a cesium fountain frequency standard operated without the use of mechanical shutters.

We characterize the light shift in the interaction region of a laser-cooled frequency standard and demonstrate an approach for its mitigation without the use of mechanical shutters. The light shift is confirmed to be below 10-15 and expected to be orders of magnitude lower. This technique makes use of a master-slave laser configuration where cutting the injection power to a slave laser causes it to lase at its free-running wavelength, often two or more nanometers off from the atomic resonance.