Gravity Gradiometer Demonstration on an Inertial Platform

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Quantum Science OBJECTIVE: This project will demonstrate the operation of a single-axis gravity gradiometer with a noise floor below at approximately 10 Eotvos (or similar performance if already demonstrated) on a moving platform in environments where vibrations, accelerations, rotations, and temperature swings cannot be neglected. DESCRIPTION: Atomic gravity gradiometers are quantum sensors that offer state-of-the-art performance under laboratory conditions [1]. Compared to existing classical approaches, they offer superior sensitivity and reduced size, weight, and power (SWaP). However, their operation is currently limited to static or quasi-static environments achieved through environmental isolation. Dynamic environments present challenges that have hampered the commercialization of devices for fielded operation [2,3]. This solicitation seeks a robust single-axis gravity gradiometer (GG) prototype with performance and SWaP comparable to state-of-the-art atomic devices (10 Eotvos or similar performance if already demonstrated, where 1 E= 10 9 second 2) but capable of operation in environments where vibrations, acceleration and rotations may be present. In contrast to gravimeters, GGs enable common mode rejection of certain platform motions, reducing the time averaging required to detect anomalous mass distributions. Therefore, GGs offer advantages over gravimeters for certain applications such as the detection of underground features (e.g. tunnels or voids). Furthermore, these devices can augment inertial navigation systems by distinguishing between gravitational and inertial acceleration. Ideally, this sensor will have a clear path to commercialization, relying on few, if any, precision-machined components. While this effort is expected to require integration into an inertially stabilized platform, proposers are encouraged to offer innovative concepts that explore cutting-edge physics to solve the challenges of fielding gravity gradiometers. PHASE I: This topic is accepting Direct to Phase II proposals only. Documentation to determine if Phase I feasibility has been met: Existing operational GG hardware with a path to meet the Phase II metrics Demonstrated acceleration accuracy less than 10 microGal GG integrates to under 200 E within 1000 seconds Total system volume of less than 50 L Weight less than 50 kg Power consumption less than 200 W PHASE II: The gravimeter developed in this effort shall measure the spatial gradient of the vertical component of gravity along the vertical direction (i.e. the Gzz component of the tensor, where z is the surface normal). Phase II Base amount must not exceed $1,450,000 for a 24-month period of performance and the Option amount must not exceed $250,000 for a 12-month period of performance. The base portion of Phase II will develop a device that can operate as a GG in the presence of motion. It should meet or exceed the following metrics: Acceleration measurement precision of 10 microGal / rt(Hz) Short term GG sensitivity of less than 50 E / rt(Hz) GG statistical uncertainty of 5 E within 600 seconds of averaging Total system volume (including any inertial stabilization) less than 40 L Weight less than 30 kg Power consumption less than 150 W These specs must be met under environmental test conditions consisting of: Rotations up to 15 deg/s Accelerations within +/- 0.1 g of local gravity Random vibrations of 0.5 grms Operating temperatures between -10 and 40 degC This will entail a thorough analysis of the sensor performance in the presence of dynamics with the appropriate mitigations in place. The Phase II option period will focus on a vehicle demonstration. The device must therefore be self-contained, and mobile enough to be loaded onto an appropriate vehicle. The vehicle can be assumed to provide standard wall-plug power. PHASE III DUAL USE APPLICATIONS: GG capable of fielded operation on a moving platform would have dual-use applications in mineral, oil, and gas exploration, civil engineering, gravity mapping, hydrology, and geophysics. REFERENCES: 1. M. J. Snadden, J. M. McGuirk, P. Bouyer, K. G. Haritos, and M. A. Kasevich, Measurement of the Earth's Gravity Gradient with an Atom Interferometer-Based Gravity Gradiometer, Phys. Rev. Lett. 81, 971 (1998). 2. B. Stray et al., Quantum sensing for gravity cartography, Nature 602, 590 (2022). 3. C. Janvier, A compact differential gravimeter at the quantum projection noise limit, arXiv 2201.03345 (2022). KEYWORDS: Atom Interferometry; Gravity Gradiometer; Fieldable Quantum Sensor