Portable radar stations help predict space weather

A magnetic cloud generated by the sun can plunge a city into darkness, so SRI International has created mobile radar stations for monitoring space weather.

The Advanced Modular Incoherent Scatter Radar system, or AMISR, is a set of modular radar facilities created by the research organisation that can be deployed together, or sent to different parts of the globe, to track weather in the upper atmosphere and beyond. SRI has created three AMISR units so far and deployed them in Peru and Alaska.

Eventually, SRI will build more mobile units as well as a larger, more permanent version that will be installed at the US' rocket testing range at Poker Flat, Alaska.

Space weather affects you more than you think, says John Kelly, programme director of SRI's Center for GeoSpace Studies. Global Positioning System satellites and satellite TV reception can be impacted by activity from the sun. A magnetic cloud can add electrical current to power grids, and thereby cause a blackout.

"If you can warn a power company of an influx of induced currents, they can protect against it," he said.

The astronauts on the Discovery space shuttle and the International Space Station also need weather updates. If a large solar flare erupts, earth-bound technicians can warn them to stay inside.

Monitoring space weather, however, has been an expensive proposition. Permanent radar installations can sport reflectors measuring 300m in diameter.

The modular units are far smaller, and therefore less sensitive than the permanent radar stations, but they can perform many of the same functions, said Kelly. The units contain eight reflective panels measuring 1 by 1.5m each that can be arranged, depending on the task at hand.

"Because it is built out of these panels, you can build whatever shape and size you need," Kelly said.

Mobility also allows researchers to examine events in the ionosphere from different parts of the globe. Putting one of the units at the Jicamarca Radio Observatory near Lima, Peru, came about because SRI wanted to see how AMISR would function at the equator, while the Alaska test (at the High Frequency Active Auroral Research Program Observatory) was designed to see how the system worked in an arctic environment.