Two U.S. satellites designed to study the radiation belts hovering above the Earth's atmosphere were successfully launched into orbit on Thursday.
The twins began a two-year, $686-million mission when they blasted off before dawn aboard an unmanned rocket at the U.S. spaceport Cape Canaveral, Florida.
The probes will determine how the identical belts, composed of electrically charged particles from the sun and deep space, are affected by energy disturbances that cause them to expand. The radiation belts, which are trapped in Earth's magnetic field, can wreak havoc with communications satellites and solar panels.
The U.S. space agency NASA
says the probes will fly as close as 161 kilometers near each other, and as far as 38,000 kilometers away from each other.
The radiation belts are named after the late James Van Allen, the physicist who discovered them in 1958, using a simple Geiger counter placed inside Explorer One, the first U.S. science satellite.