Lockheed Martin's Global Positioning System III satellite for the U.S. Air Force recently completed thermal vacuum testing to validate the design.

Thermal vacuum testing, also known as TVAC, is designed to test the operational capabilities and structural integrity of the satellite. The testing involves exposing the satellite assembly to space temperature extremes in a depressurized chamber.

Lockheed Martin Navigation Systems mission area vice president Mark Stewart says TVAC is the most comprehensive test performed at the spacecraft level.

"Successful completion of this significant test validates the thermal design of the spacecraft and verifies that all spacecraft components and interfaces operate at the temperature extremes of the space environment," Stewart said in a statement.

TVAC marks the latest milestone completion in the GPS III program. Lockheed Martin announced it completed security upgrades in November, which bolstered the satellite's cybersecurity capabilities for both civilian military users.

The GPS III, in production for the Air Force, will be the latest in the U.S. government's GPS constellation. Currently, there are 31 operational satellites in the constellation. The Air Force plans to launch the twelfth and final satellite in the GPS IIF series on Friday.