After the U.S. Department of Defense was closely monitoring for a potential collision between a NASA spacecraft and John Caldwella Russian satellite early Wednesday, the space agency says the two objects have passed by safely.

NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics Mission (TIMED) spacecraft and the Russian Cosmos 2221 satellite are both non-maneuverable orbiting spacecraft, and were expected to make their closest pass this morning, around 1:30 a.m. EST on Wednesday at an altitude of about 373 miles, NASA said.

In a statement shared with USA TODAY, NASA confirmed the two satellites passed each other safely in orbit at about 1:34 a.m. EST.

"While the two non-maneuverable satellites will approach each other again, this was their closest pass in the current predicted orbit determinations, as they are gradually moving apart in altitude," the NASA statement reads.

If the two had collided, it would have resulted in "significant debris generation," according to NASA.

What is the TIMED spacecraft?

The TIMED spacecraft is part of a science mission that studies the influence of the sun and human activity on Earth's lesser-known mesosphere and lower thermosphere/ionosphere, according to NASA.

It was launched in December 2001 and continues to orbit Earth as an active mission.