"When it’s close to the Earth, it’s close enough to the atmosphere to turn where it is," she said. "Which means our adversaries don’t know—and that happens on the far side of the Earth from our adversaries—where it’s going to come up next. And we know that that drives them nuts. And I’m really glad about that."

Breaking the silence

The Pentagon rarely releases an update on the X-37B spaceplane in the middle of a mission. During previous flights, military officials typically provided some basic information about the mission before its launch, then went silent until the X-37B returned for landing. The military keeps specifics about the spaceplane's activities in orbit a secret.

This made the Space Force's announcement Thursday somewhat of a surprise. When the seventh flight of the X-37B launched, there were indications that the spacecraft would soar into a much higher orbit than it did on any of its six prior missions.

In February, a sleuthing satellite tracking hobbyist spotted the X-37B in orbit by observing sunlight reflected off of the spacecraft as it flew thousands of miles above Earth. Follow-up detections confirmed the discovery, allowing amateur observers to estimate that the X-37B was flying in a highly elliptical orbit ranging between roughly 300 and 38,600 miles in altitude (186-by-23,985 miles). The orbit was inclined 59.1 degrees to the equator.

On its previous missions, the X-37B was confined to low-Earth orbit a few hundred miles above the planet. When it became apparent that the latest mission was cruising at a significantly higher altitude, analysts and space enthusiasts speculated on what the secret spaceplane was doing and how it would come back to Earth. A direct reentry into the atmosphere from the spaceplane's elliptical orbit would expose the craft's heat shield to hotter temperatures than any of its previous returns.

Now, we have an answer to the latter question.

As for what it's doing up there, the Space Force said the spaceplane on this mission has "conducted radiation effect experiments and has been testing space domain awareness technologies in a highly elliptical orbit." The orbit brings the X-37B through the Van Allen radiation belts and crosses several orbital regimes populated by US and foreign communications, navigation, and surveillance satellites.

Military officials have said previous X-37B flights have tested a Hall-effect ion thruster and tested other experimental space technologies without elaborating on their details. X-37Bs have also secretly deployed small military satellites in orbit.