A Hybrid Atom Interferometer Accelerometer-Gyroscope
Jennifer T. Choy, David M.S. Johnson, Christine Y. Wang, Alexander T. Gill, Steven J. Byrnes, Richard E. Stoner, Krish Kotru, Sungyung Lim, Zachary Smigelski, William Trinkle, Buddy Clemmer, Louis Kratchman, Stephanie Golmon, Matthew Sinclair, Tom Thorvaldsen, Matthew Bottkol, Draper; Grant Biedermann, Akash Rakholia, Sandia National Laboratories; Michael Berarducci, Air Force Research Laboratory
Location: Big Sur
Alternate Number 3
Techniques to probe and manipulate the discrete electronic energy levels in atoms have enabled numerous metrology applications, including precise and stable inertial sensors, time and frequency standards, magnetometers, and test-beds for quantum information protocols. In particular, atom interferometry has been used to demonstrate low noise and highly sensitive inertial sensors that are capable of long-term stability, with the potential to enable an inertial navigation system (INS) that can navigate for long periods of time (e.g. ~20 minutes) without external aids. However, these atomic systems do not have sufficient data rate and dynamic range required in most practical applications.
Our proposed approach to an atom-based INS uses a hybrid architecture based around an atomic inertial reference that disciplines a conventional INS. The conventional INS provides the real-time navigation solution which is presented to the user, and it is periodically disciplined by comparing its output with that of the atomic inertial reference. We have shown that this approach can distinguish between scale-factor and bias errors of the conventional INS, resulting in a hybrid system with the stability characteristics of the atomic inertial reference while maintaining the bandwidth and dynamic range of the conventional sensors.
In our approach, the atomic inertial reference is a light-pulse atom interferometer that sequentially samples the acceleration and rotation rate in each degree-of-freedom. This instrument has a very limited dynamic range (several orders of magnitude below inertial inputs caused by typical platform dynamics) and requires knowledge of the local dynamics to within that range. To that end, the conventional INS provides the initial coarse acceleration and rotation rate estimate to the atomic inertial system. The difference between inertial measurements from the conventional INS and the atomic reference forms the error signal which is fed into a Kalman filter and used to discipline the scale-factor and bias of the conventional INS.
We have developed an atomic accelerometer and gyroscope that operates by running reciprocal cold atom interferometers in a ‘launch-catch’ configuration. The ‘launch-catch’ configuration allows for the recapturing of atoms between measurement cycles, thereby reducing the dead time associated with trapping the atoms. The integrated sensor consists of two atomic sensors with oppositely directed inertial axes for cancellation of common-mode effects. The two sets of atomic sensors and conventional sensors are rigidly mounted on a common platform to ensure that they experience the same inertial inputs and to minimize axis misalignment errors. Since the atomic sensors determine the ultimate long-term stability of the INS, we have tailored the sensor design to address potential instability drivers, including optical beam alignment drifts and sensitivities to changes in light and magnetic fields.
In this talk, we will present an overview of the design and performance results of the integrated system on a pier and two-axis rate table. We will compare the dynamic response of the sensor with that predicted by analytical models, and summarize the benefits and limitations of this hybrid architecture. Finally, advancements in miniaturizing electro-optics and vacuum components will be needed to mobilize and implement these sensors outside of the laboratory. We will summarize the component requirements in this system and discuss potential paths to miniaturization.
This research and development was performed with funding from the Defense Advanced Research Projects Agency (DARPA). The views, opinions and/or findings expressed are those of the authors and should not be interpreted as representing the official views or policies of the Department of Defense or the U.S. Government.
This document has been cleared by DARPA and is designated Distribution A (Public Release, Distribution Unlimited).