“OTV 4 [Orbital Test Vehicle mission No.4] entered the lowest initial altitude of the program. The ground track nearly repeats every two days. This could be an indication of a surveillance mission, or it may offer some operational advantage I have yet to figure out,” Molczan added.
The X-37B craft, already the fourth such probe orbited since the program was launched in 1999, was sent aloft May 20 from Cape Canaveral atop a United Launch Alliance Atlas 5 rocket.
The Air Force revealed two experiments to be conducted on the current mission — an electric propulsion thruster test and materials exposure in the space environment, but much about the flight remains classified, including the orbit and mission duration.
The Boeing X-37, also known as the Orbital Test Vehicle (OTV), is a reusable unmanned spacecraft. It is boosted into space by a launch vehicle, then re-enters Earth's atmosphere and lands as a spaceplane.
Some experts believe the X-37B can be used to inspect and disable space satellites.
The Pentagon denies the claim, insisting that the program is all about testing new technology.