WASHINGTON — A United Launch Alliance Atlas 5 rocket on Dec. 7 launched the Space Test Program-3 (STP-3) mission for the U.S. Space Force. The rocket lifted off at 5:19 a.m. Eastern from Space Launch Complex-41 at Cape Canaveral Space Force Station, Florida.

The $1.1 billion STP-3 mission flew to geosynchronous Earth orbit on an Atlas 5 551 with five strap-on solid boosters.

STP-3 carried classified national security payloads and a NASA mission to demonstrate in-space laser communications. 

The launch had been scheduled for Dec. 5 but was postponed to repair a leak discovered in a propellant ground storage system.

This was the 90th flight of the Atlas 5 and the rocket’s longest ever mission that required three upper stage RL10C-1 engine burns. ULA said the secondary payload was released seven hours and 10 minutes after liftoff, and the primary payload successfully separated eight hours and eight minutes after liftoff, at an orbit 22,300 miles above Earth.

The primary payload, STPSat-6, hosted the National Nuclear Security Administration’s Space and Atmospheric Burst Reporting System 3 (SABRS-3), a sensor designed to detect nuclear explosions.

STPSat-6 also carried NASA’s Laser Communication Relay Demonstration (LCRD) payload that will be used to test laser communication in space between Earth and the GEO orbit. The LCRD mission is managed by NASA’s Goddard Space Flight Center. 

Badri Younes, deputy associate administrator for NASA’s space communications and navigation program, said the LCRD was designed to be able to downlink data over optical signals at a rate of 1.2 gigabits per second. Transmitting a map of Mars to Earth might take nine years with current radio systems, but as little as nine weeks with laser communications.

The secondary payload was the Long Duration Propulsive ESPA, or LDPE-1, a small-satellite adapter ring designed to deploy military experiments. On this mission it hosted six U.S. Space Force experiments focused on space weather and situational awareness.

Both the STPSat-6 and LPDE-1 spacecraft were built by Northrop Grumman.

The STP-3 mission was originally scheduled to launch in 2019. Setbacks in the development of NASA’s laser communications payload and scheduling problems caused by the pandemic delayed the mission.

Gary Wentz, ULA’s vice president of government and commercial programs, said the Atlas 5 that launched the STP-3 mission debuted three new items: RUAG’s first five-meter diameter payload fairing made with the out-of-autoclave production process, an in-flight power system to charge the satellites’ batteries, and an advanced GPS navigation system for the Centaur upper stage intended to improve the accuracy of orbit insertions. 

Out-of-autoclave production cures carbon fiber composites using only an oven. Wentz said the company wanted to fly these new features on Atlas 5 to accumulate flight experience before they transition to ULA’s future rocket Vulcan Centaur, which will have a larger 5.4 meter payload fairing.

Sandra Erwin writes about military space programs, policy, technology and the industry that supports this sector. She has covered the military, the Pentagon, Congress and the defense industry for nearly two decades as editor of NDIA’s National Defense...