The Spacecraft

NASA's EZIE mission will use three small solar-powered satellites, each roughly the size of a shoebox that has been innovatively designed to include a low-power, miniaturized instrument for measuring the auroral electrojets.

Lined up like pearls on a string, the three spacecraft will fly 260-390 miles (420-630 km) above Earth's surface, moving from pole to pole.

During each orbit, each spacecraft will produce a map of the electrojets, providing detailed views over space and time to determine the electrojets' structure and evolution. They partly do this by changing the space between each spacecraft. Typically, that would require a propulsion system, but the EZIE spacecraft won't have that.

No Propulsion? No Problem!

Instead, while traveling at about 5 miles (8 km) per second, the spacecraft will be able to turn individually, using the drag experienced while flying through their upper atmosphere to change how they're spaced. This either brings one or more spacecraft closer together or spaces them farther apart. Consequently, the spacecraft will fly over the same region from 2-10 minutes after each other.

Making Measurements

EZIE's CubeSat trio will fly high above the electrojets, which flow just 60 miles (97 km) above Earth's surface.

But EZIE is actually eying oxygen molecules located 10 miles (16 km)below the electrojets.

Making Measurements

That's because the electrojets create a magnetic field around them that leaves a signature in light released by the oxygen molecules — a magnetic “fingerprint” that EZIE is designed to look for.

Zeeman Splitting

The oxygen molecules are constantly rotating. But when their rotation slows, the molecules release a photon of microwave light with a frequency at exactly 118 Gigahertz.

Although this light is invisible to our eyes, EZIE can “see” it using a spectrometer — an instrument that separates and collects light as individual wavelengths.

When near the magnetic field around the electrojets, however, that 118 Gigahertz line splits apart — a phenomenon called the Zeeman effect.

The stronger the electrojets' magnetic field, the farther the lines split apart.

Scientists have used this phenomenon to measure the magnetic fields of the Sun and other stars. In this case, it allows an indirect measurement of the current flowing in the electrojets.

Thanks to recent technological advancements, the EZIE team has developed a miniaturized instrument just about 3.5 inches (9 cm) tall and 9 inches (23 cm) long and wide to measure this effect.

It's called the Microwave Electrojet Magnetogram or (MEM), and each of EZIE's CubeSats will carry one.

The MEM uses four reflective dishes, each pointed in a different direction, so the instrument can simultaneously collect microwaves from multiple angles before passing the light to a spectrometer.

With these assets combined, the three spacecraft will reveal unprecedented details about the behavior of not just the auroral electrojets but the entire wedge-like system, finally solving these decades-old and much-debated mysteries.