Lockheed Martin said that in the environmental tests, the satellite was placed in the company's Dual Entry Large Thermal Altitude chamber, a vacuum chamber that simulates space.
The MUOS was then subjected to intense extremes of hot and cold.
"We are committed to quality, and our rigorous environmental testing regimen ensures this system is ready for the harsh environments of space," said Iris Bombelyn, vice president of Narrowband Communications at Lockheed Martin. "It's important to check out every aspect of the satellite at this stage so we can prepare it for service.
"We are on track for delivering the third MUOS satellite to the Navy this year."
MUOS satellites carry a wideband code division multiple access payload. It uses commercial cell phone technology and provides a 10-fold boost in communications capacity than that of Ultra high-frequency systems.
A total of five satellites will make up the Navy's MUOS constellation -- four operational craft and one on-orbit spare satellite.
The satellite is slated for launch next year.