NATIONAL HARBOR, Md. – At the request of unspecified users, the U.S. Air Force has twice taken a pair of high-orbiting space surveillance satellites out of test mode to make observations of specific objects in geosynchronous orbit, a senior service official said.

The missions mark the first assignments for the once-classified Geosynchronous Space Situational Awareness Program, or GSSAP, satellites. The requests speak to the Defense Department’s appetite for surveillance of geosynchronous orbit, the operating location many of its most important and expensive satellites.

Two GSSAP satellites have been on orbit since July 2014 and have been going through checkout procedures and operational testing. Air Force Space Command expects to declare initial operational capability for the satellites within the next several weeks, service officials have said.

But during a Sept. 16 press briefing here at the Air Force Association tech expo, Gen. John Hyten, commander of Air Force Space Command, said the satellites had already completed their first tasks and “performed remarkably.”

“The users that requested the information are extremely pleased with the pictures we gave them,” Hyten said.” The pictures we gave them are truly eye-watering. It’s amazing. You don’t often get to see satellites flying.”

He did not elaborate and an Air Force spokesman declined to provide further information on the user.

Air Force officials disclosed the previously classified space surveillance program in February 2014. Since then, they have acknowledged that the satellites would perform rendezvous and proximity maneuvers to allow close-up looks at spacecraft in geosynchronous orbits, some 36,000 kilometers above Earth’s surface. Hyten has described geosynchronous orbit as “our most valuable orbit.”

Among the U.S. military satellites that operate there are those used for missile warning and nuclear command and control. The Air Force disclosed the existence of GSSAP in part to deter what Pentagon officials say are increasingly threatening activities by China and Russia, Hyten said.

“Why do you think it is we released the GSSAP program last year from the black into the white,” Hyten said, referring to the satellite’s declassification. “It was to make sure we send a message to the world that says: Anything you do in the geosynchronous orbit we will know about. Anything.”

The Air Force told SpaceNews earlier this year that a Russian military satellite launched in March has made at least 11 close approaches to the rocket upper stage that released it into orbit, a maneuvering capability that is consistent with, but not necessarily indicative of, an on-orbit anti-satellite weapon.

Another Russian satellite, known as Object E, was among the subjects of a classified briefing on space threats to congressional defense committees earlier this year, a Capitol Hill source said.

China deliberately destroyed one of its own satellites using a ground-based missile in 2007 and since then has conducted additional nondestructive anti-satellite tests, U.S. government officials say.

Hyten said the Defense Department also is worried about a number of other Chinese space-related activities that are less visible.

According to an Air Force fact sheet, GSSAP is a two-satellite system that operates in a “near-geosynchrous orbit regime” to provide accurate tracking and characterization of man-made orbiting objects. Built by Orbital ATK of Dulles, Virginia, the GSSAP satellites are controlled by operators at Schriever Air Force Base in Colorado Springs, Colorado.

Two additional GSSAP satellites are notionally scheduled to launch in 2016.