NASA’s EZIE mission captures ‘first light’

NASA’s EZIE (Electrojet Zeeman Imaging Explorer) mission has taken its first measurements.

These “first light” observations show that EZIE is poised to reveal crucial details about Earth’s auroral electrojets—powerful electric currents that flow through our upper atmosphere where auroras glow in the sky. This information will help us better understand Earth’s connection to space and mitigate the negative impacts of space weather on society.

With a trio of CubeSats, EZIE launched in mid-March to map the auroral electrojets up close and in detail for the first time. These intense currents are generated in the northern and southern polar regions of our atmosphere, about 65 miles (105 kilometers) above the ground, when tremendous amounts of energy are transferred into Earth’s upper atmosphere from the solar wind. The same process can also ignite colorful auroras (northern or southern lights) in our skies.

The EZIE spacecraft are designed to map the strength and direction of these currents by studying emission from oxygen molecules about 10 miles (16 kilometers) below the electrojets. The oxygen molecules emit microwaves at a frequency of 118 gigahertz.

But in the presence of magnetic fields, such as those created by the electrojets, this emission line divides in a process called Zeeman splitting. The stronger the magnetic field, the farther apart the 118 GHz line is split. The polarizations, or wave orientations, of the oxygen emission reveal the direction of the magnetic field.

On March 19, one of the three EZIE satellites successfully recorded Zeeman splitting of the 118 GHz oxygen emission line for the first time with its Microwave Electrojet Magnetogram (MEM) instrument. The observations reveal the strength and direction of the responsible magnetic field—in this case, Earth’s own magnetic field near the magnetic equator.

“The EZIE team is very excited about these first-light results,” said Sam Yee of the Johns Hopkins Applied Physics Laboratory, the mission’s principal investigator. “The observations demonstrate that both the spacecraft and the MEM instrument onboard are working as expected.”

The EZIE mission is expected to begin its formal science investigations in about a month, following final checkouts and calibrations.