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Session A2a: Quantum Inertial Sensor Technologies and Applications

Quantum Inertial Sensors for Gravimetry and Inertial Navigation in the Field
M. Cashen, J. Kohler, C. Corder, M. Everton, J. Wolf, N. Crescimanno, A. Vitouchkine, A. Rakholia, G. Skulason, A. Dowd, J. Abo-Shaeer, Vector Atomic; S.A. Keyes, and C. Parks, Honeywell
Location: Deer Valley 1-3
Date/Time: Tuesday, Apr. 29, 1:50 p.m.

Quantum inertial sensors based on atom interferometry have the potential to provide new capabilities in inertial navigation, guidance systems, geodesy, and geophysical exploration. Vector Atomic has developed milliGal-class gravity sensors for strapdown operation in marine environments and microGal-class sensors for static operation in terrestrial environments. [1,2] The prototype gravimeters have been fielded and tested under operational conditions on relevant platforms and test sites. In addition to the gravimeter efforts, Vector Atomic and Honeywell have partnered to develop, integrate, and test a quantum IMU. A prototype quantum gyroscope payload has been delivered for flight testing [3].
(1) Under the Gravity-Aided Inertial Navigation System (GAINS) program [1], Vector Atomic has developed a robust, portable absolute atomic gravimeter for strapdown operation aboard marine vessels. To extend mission duration in GPS-denied environments, GAINS measures local gravity to bound inertial navigation error via gravity map-matching.
To reduce mechanical complexity and size, weight, and power (SWaP), the GAINS gravimeter operates in a strapdown configuration. The gravimeter measures the body-frame specific force along a single axis using laser-cooled rubidium-87 atoms in free fall and established atom interferometry techniques [4-5]. A suite of conventional inertial sensors and a co-mounted high-performance inertial navigation system (INS) enable strapdown operation through multi-axis platform dynamics and recovery of the gravity anomaly under ship motion. GAINS is readily transportable, with quick start-up, and contains no moving or cryogenic components, providing a clear path for integration into a low-SWaP INS.
To date, GAINS has operated at-sea for 36 days, with > 99% uptime through mild to heavy ship dynamics. Previously reported GAINS surveys performed during RIMPAC 2022 demonstrated gravity measurements consistent with the best publicly available gravity maps [6-7]. However, the comparison results were limited by the error and uncertainty in the maps. To better characterize GAINS performance for navigation purposes, the gravity anomaly was surveyed along the ship’s track and compared to simultaneous measurements from other state-of-the-art marine gravimeters aboard the ship. In addition, to facilitate self-comparison of GAINS results, the survey route retraced multiple 100-200 nmi segments.
The comparison results confirm that GAINS measurements are more accurate than the publicly available gravity maps, with performance surpassing 1 mGal gravimeter precision and accuracy for all relevant navigation timescales. Currently, the recovered gravity estimates are limited by residual ship motion dynamics experienced by the strapdown sensor. Advanced compensation algorithms show promise to better reject ship motion and improve the stability off the gravity result.
(2) In addition to a strapdown gravimeter targeting marine platforms, Vector Atomic has recently developed a portable atomic gravimeter and gravity gradiometer for terrestrial applications [2]. MAGIC is designed for real-world operability, providing man-portability, quick setup and data collection by a non-expert user, and long-term autonomous operation in the field. To operate in seismically noisy environments, MAGIC includes a co-sensor to mitigate aliasing high frequency noise in the real time gravity measurement output. By focusing on reduced complexity and size, the compact absolute gravimeter provides robust operation in an easily transportable sensor.
As built, MAGIC is a fully integrated device, requiring no external computers, electronics, or laser systems. The total package weighs < 35 kg and operates from a single 12V power source consuming < 100 W, making it capable of operating over 12 h off a single battery. In this talk, we will present initial results from our MAGIC sensor demonstrating µGal-level observations during autonomous multi-day operation in the laboratory and at a field site. Capable of continuous autonomous measurements without scheduled maintenance and with low power draw, our absolute gravimeter design will simplify field measurements; enable longer gravity survey missions; and provide a new measurement capability for gravity science and applications.
(3) Satellites, spacecraft, and aircraft often rely on onboard IMUs to compute position and orientation. Navigation systems continuously calculate position using IMU data from three gyroscopes and three accelerometers. More accurate inertial sensors can enhance capabilities and extend missions. In particular, bias stability of the gyroscope is a key parameter in determining IMU quality. Traditional technologies such as the ring laser gyro (RLG) and fiber optic gyro (FOG) are expertly engineered and approaching maturity, leaving little headroom for improvement. Atomic inertial sensors have demonstrated superior performance over conventional inertial technologies owing to the intrinsic stability of the atom.
Laboratory-based atomic gyroscopes have demonstrated unmatched ARW (3 microdeg/h1/2) and bias instability (68 microdeg/h) [10], capable of supporting 5 m/h-scale position error. Despite demonstrable performance improvements, however, atomic inertial sensors have yet to be deployed in military or commercial systems. Current-generation laboratory devices come with large and costly overhead, built upon commercial lasers and optics, ultra-high vacuum (UHV) systems, and complex electronics. More importantly, these devices do not meet the practical requirements for widespread deployment: cost, reliability, and the ability to operate in challenging dynamic and thermal environments.
In this presentation we will discuss the development, integration, and testing of a pathfinder atomic sensor payload for testing in space [3]. The payload consists of a single-axis atomic gyroscope and a triad of ring laser gyroscopes; a reference quartz accelerometer; and a star tracker to provide a rotation rate reference under test platform dynamics. The payload was designed and built over an 18-month period. The size, weight, and power for the entire payload is 100 liters, 74 kg, and 125 W during steady state operation. Orbital experiments will be conducted to test the ARW, acceleration sensitivity, and bias and scale factor stability of the atomic sensor outputs.
The atomic sensor, comprised of a physics package, laser system, and electronics subsystems, has undergone rigorous testing. The subsystems have been tested under vibration, shock, thermal, and radiation conditions relevant for launch survival and operation in a space for > 1 year. The integrated payload has undergone extensive performance and thermal testing under static conditions and on a two-axis rate table. We will present the overall system design and test results, with the goal of establishing the viability of high-performance, low-cost atomic sensors for space and airborne applications.
References
1. Contract N00014-18-C-1052, POC: Richard Willis, Office of Naval Research
2. Mobile Atomic Gravimeter for Intelligence Collection (MAGIC); Contract NGA-PLA-0012; POC: Tom Johnson, NGA
3. Funded by Defense Innovation Unit (DIU); POC Lt. Col. Nicholas Estep
4. C. Freier et al. Mobile quantum gravity sensor with unprecedented stability. Journal of Physics: Conference Series 723 (2016) 012050
5. Y. Bidel et al. Absolute marine gravimetry with matter-wave interferometry. Nature Communications. 9:627 (2008)
6. D. T. Sandwell, et al. New global marine gravity model from CryoSat-2 and Jason-1 reveals buried tectonic structure, Science, Vol. 346, no. 6205, pp. 65-67
7. Andersen, O.B., Knudsen, P. (2019). The DTU17 Global Marine Gravity Field: First Validation Results. Fiducial Reference Measurements for Altimetry. International Association of Geodesy Symposia, vol 150.
8. A. Peters et al, “High Precision Gravity Measurements Using Atom Interferometry”, Metrologia, Vol. 38, 1
9. T. L. Gustavson et al, "Rotation sensing with a dual atom-interferometer Sagnac gyroscope," Class. Quantum Grav., Vol. 17, p. 2385, 2000.
10. D.S. Durfee, et al. 2006 Long-term stability of an area-reversible atom interferometer sagnac gyroscope, Physical Review Letters 97 240801 (2006)

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