Berkeley, US: University of California, Berkeley, physicists have now come up with a cheaper way to measure the Earth’s magnetic field using only a ground-based laser. The method involves exciting sodium atoms in a layer 90 kilometres (60 miles) above the surface and measuring the light they give off.
Ground-based measurements can avoid several problems associated with satellites, said Dmitry Budker, UC Berkeley professor of physics. Because these spacecraft are moving at high speed, it’s not always possible to tell whether a fluctuation in the magnetic field strength is real or a result of the spacecraft having moved to a new location. Also, metal and electronic instruments aboard the craft can affect magnetic field measurements.
“A ground-based remote sensing system allows us to measure, whenever and wherever we want. It avoids problems of spatial and temporal dependence caused by satellite movement,” he said. “Initially, this is going to be competitive with the best satellite measurements, but it could be improved drastically.”
The work is supported by NGA NURI, the University Research Initiatives programme of the National Geospatial-Intelligence Agency, which is part of the Department of Defense.