A Towed Magnetometer for Vector Field Measurements

P.I.：Jeffery Gee/UCSD Scripps Proposal#：98-19758建议摘要：质子进动磁力仪测量总场强，长期以来一直是海洋地球物理研究的首选仪器。不幸的是，这些仪器受到限制，特别是在赤道附近的N-S方向的脊线上，以及任何存在线状短波长异常或非线状细尺度异常的地方。矢量磁场测量提供了一种减少或克服总场异常数据的这些限制的方法。异常场的水平和垂直分量总是大于总场异常，而这些矢量异常受赤道地区不利几何形状的影响明显较小。PI对船上的矢量磁强计进行了初步测试，但船上的磁场引入了误差。他们还在一辆深拖车上测试了一个系统。这种方法很有前景，但他们没有足够的运动补偿数据。因此，Pi‘s，J.Gee和S.Cande提出了发展一种拖曳矢量场磁强计系统。该系统将使用SeaTex MRU-6运动参考单元，在圆柱形阳极氧化铝压力箱中配备三轴磁强计，适合全海洋深度部署。配备高精度运动传感器的拖曳系统应能消除初始测试中发现的两个重要噪声源。该系统将需要一个RS232数据传输增强器和一条300米长的电缆；它将在SIO组装。PI建议在夏威夷海岸附近的4天巡航中测试该系统，那里存在低幅度异常(100 NT)。这一系统应能够查明海洋盆地相当大一部分地区的扩散相关异常，而现有仪器无法确定这些异常。

P.I.: Jeffery Gee/UCSD Scripps Proposal #: 98-19758Proposal Summary: Proton precession magnetometers, which measure total field intensities, have long been the instrument of choice for marine geophysical studies. Unfortunately, these instruments are subject to limitations, especially over N-S oriented ridges near the equator and anywhere that lineated short-wavelength anomalies or non-lineated fine-scale anomalies exist.Vector magnetic field measurements provide a means to reduce or overcome these limitations of total field anomaly data. Horizontal and vertical components of the anomalous field are always greater than the total field anomaly, and these vector anomalies are significantly less affected by unfavorable geometries in equatorial regions. The PI's made initial tests of a vector magnetometer onboard a ship, but the ship's magnetic field introduced errors. They also tested a system on a deep towed vehicle. This method showed promise, but they did not have adequate motion compensation data. Therefore, the PI's, J. Gee and S. Cande, propose to develop a towed vector field magnetometer system. The system will use a SeaTex MRU-6 motion reference unit with triaxial magnetometers in a cylindrical anodized aluminum pressure case that is suitable for full ocean depth deployment. A towed system with a high precision motion sensor should eliminate the two significant sources of noise found in initial tests. The system will require a RS232 data transmission enhancer and a 300 m cable; it will be assembled at SIO. The PI proposes to test the system during a 4 day cruise off the coast of Hawaii where low amplitude anomalies ( 100 nT) exist. This system should allow identification of spreading related anomalies in significant portions of the ocean basins where such identifications are not possible with existing instrumentation.