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Session A5: Alternative Sensors for Aiding INSs and Precision Timing

Compact Atomic Magnetometer for Navigation (Nav-CAM)
Michael Larsen, Northrop Grumman
Location: Big Sur

The Compact Atomic Magnetometer for Navigation (Nav-CAM) is being developed by the Northrop Grumman Corporation (NGC) with a very similar structure to the Compact Atomic Magnetometer for Magnetic Anomaly Detection (MAD-CAM) being developed under funding from the Office of Naval Research (ONR). Other atom based magnetometers have provided exquisitely low noise scalar field measurement capabilities, but have suffered from absolute accuracy, heading error, and bandwidth issues. Previous attempts to demonstrate absolute global positioning have utilized either low noise and low bandwidth scalar sensors or higher bandwidth and lower accuracy vector sensors. The vector sensors which are traditionally based on separate sensitive elements for each axis have traditionally suffered from issues of measurement orthogonally and unstable scale factor over the three separate axes that do not change in a common mode manner. By combining Electron Paramagnetic Resonance (EPR) and Nuclear Magnetic Resonance (NMR) in a single co-magnetometer implementation the Northrop Grumman Corporation (NGC) approach provides a three axis vector field measurement capability in a single sensitive element with common magnetic coils. This approach is extremely similar to the implementation used for the Nuclear Magnetic Resonance Gyroscope (NMRG) under development by NGC. By utilizing the two axis vector sensitivity of the Rubidium EPR magnetometer to read out the fixed precession rate in inertial space of a nuclear spin in a constant magnetic field as a measurement of the third vector field direction, the EPR-NMR co-magnetometer provides continuous measurement, high bandwidth, stable scale factor, rotation/heading insensitivity, and low sensitivity to vibration and acceleration in a low SWaP package. Real time closed loop implementation of the sensor also provide a large field range capability and consistent operation even at zero field. The higher bandwidth capability of the Nav-CAM system supports alternative velocity aiding capabilities without any prior knowledge of the magnetic field in the region of aircraft navigation. Therefore, the Nav-CAM technology holds great promise for navigation aiding both for the traditional magnetic map based approach and a velocity aiding approach in a low cost and SWaP package. This presentation will describe the history, operation, and design of the Nav-CAM. General sensor performance results and application concepts will also be presented along with recent test results and future development plans.



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