Drone-based precision atomic gradiometer (FlyG)
Abstract
Environmental structures of interest like mountains, tunnels, and deposits of minerals, oil or gas produce distortions in the local gravitational field. In a naval context, mapping these distortions could help underwater navigation, collision avoidance, terrain estimation, and locating submerged objects. Sensing gravity anomalies and comparing them to a gravity map can provide positioning immune to the drift of purely inertial navigation systems. By contrast to other inputs like GPS, gravity signals are hard to fake, and impossible to shield. Sensing the gravitational field at this level is difficult but measuring the gradient in the gravitational field provides access to the information of interest while being immune to noise caused by motion and vibration of a host vehicle. Gravity gradient anomalies of interest have typical strengths between 0.3-50 E~tv~s(1 E = 10-9 /s2) (Fig. 1), and while ex-isting gradiometers can reach this sensitivity, they occupy a huge (1 m3) volume, are heavy (450 kg), and require speedy manned aircraft and helicopters for their operation. This makes comprehensive high-resolution gravity mapping slow, risky in terrain-hugging (low and slow) flight, and expensive. We propose a sensor capable of reaching a sensitivity of 1 E/Hz1/2, which can survey 25 times the area of the state-of-the-art 5 E/Hz1/2 sensitivity in the same amount of time (or the same area at 5 times the spatial resolution). This sensor is also unmanned and eliminates risk to a flight crew, makes surveying less conspicuous, and allows automated terrain hugging flight. This in turn would enable taking data at high spatial resolution, high sensitivity, and at low cost. Wepropose the first airborne (drone-based) autonomous atomic gravity gradiometer.As a technology enabled by quantum mechanics (the wave-particle duality and the fact that all atoms of a given species are exactly the same), it will reach the ~holy grail~ - being able to sense a change in the Earth~s gravity of one part in ten billion over one meter, within one second. Operation from unmanned vehicles offers substantial economic advantages. A drone in flight is much less expensive than a manned aircraft and can be remotely operated over unsafeterrain. It can fly ~terrain-hugging~, low and slow, at no risk to a flight crew. This strongly improves the ability to resolve tiny gravity gradients over small spatial scales. The drone can fly close lines and provide high-resolution mapping of gravity with a ground crew of two at the most for changing battery packs.Three key features enable this project: First, a drone-sensor system developed jointly from the ground up. It is easier to adapt the sensor to the vibration level of a drone, rather than a noisy manned vehicle. Automated controls can maintain a vertical orientation of the gradiometer even in the face of weather conditions. Second, a highly optimized laser system that allows drastic reductions in complexity, size and weight. While conventional construction requires sixbeams for the trap and at least one for the interferometer, we will use a single laser beam entering the vacuum chamber for both purposes. Third, a lightweight and compact vacuum system requiring two viewports instead of about ten. Taken together, these features allow progress in size, weight, and reliability at a small cost in performance.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 25, 2019
- Source ID
- N000141912228
Entities
People
- Holger Mueller
Organizations
- Office of Naval Research
- United States Navy
- University of California Regents