Lockheed Martin Space Systems of Sunnyvale, Calif., completed thermal vacuum testing April 25 on the U.S. Navy’s second Mobile User Objective System (MUOS) communications satellite, the company announced in a June 18 press release.

The testing validates satellite performance in a simulated space environment. MUOS-2 was exposed to temperature extremes during the testing, carried out inside Lockheed Martin’s Dual Entry Large Thermal Altitude chamber, according to the press release.

MUOS-2 is scheduled for launch in early 2013.

“With the completion of environmental testing, the MUOS team has illustrated its continued focus on successful program execution and mission success,” Kevin Bilger, Lockheed Martin’s Global Communications Systems vice president and general manager, said in a prepared statement. “The first MUOS satellite is on-orbit and poised to provide significantly improved communications capabilities for the mobile warfighter.”

MUOS-1 was launched Feb. 24 from Cape Canaveral Air Force Station, Fla., aboard a United Launch Alliance Atlas 5 rocket. The Navy expects the MUOS constellation, consisting of four satellites plus an on-orbit spare, to reach initial operational capability in 2015 and provide narrowband service beyond 2025.