Advanced Sensors for Airborne Magnetic Measurements

Numerous ground tests and platform tests were conducted to evaluate the performance of the POLATOMIC 2000 magnetometer, a laser-pumped helium-4 total magnetic field sensor. These results are compared with those from lamp- pumped helium-4 magnetometers, the ASQ-208 and the ASQ-81. The sensitivity of the digital ANlASQ-208 magnetometer is 3 pTHHz from dc to 216 Hz and, the analog ANlASQ-81 has a slightly higher noise floor. The POLATOMIC 2000 noise floor is less than 0.3 pTl4Hz. For airborne measurements the sensor noise is not usually the limiting noise. In the magnetic anomaly detection MAD band 0.04 Hz to 0.5 Hz, for example, substantial reduction of platform and environmental noise is necessary. Important sources of noise are geology, geomagnetic, platform, gradient, and wave. In order to reduce the effect of these noise sources, a variety of ancillary sensors are used in conjunction with noise models. These sensors are fluxgate magnetometers, accelerometers, and a low-noise C-code GPS. In the talk, performance of the POLATOMIC 2000 will be described. Results of numerous ground tests and flight tests will be summarized, and the noise models and the effectiveness of the ancillary sensors for ambient and platform noise reduction will be discussed and quantified.