A United Launch Alliance Delta 4 rocket carrying a payload for the National Reconnaissance Office lifted off from Space Launch Complex-6 on Feb. 10 at 3:40 a.m. PST. Credit: ULA.

WASHINGTON — A United Launch Alliance Delta 4 rocket  launched Feb. 10 from Vandenberg Air Force Base, California, carrying a classified payload for the U.S. National Reconnaissance Office.

The launch went into a news blackout typical for NRO missions several minutes after its 6:40 a.m. Eastern liftoff. About two hours later, U.S. Air Force officials said the launch was successful.

The NRO has released no details about the NROL-45 mission, but outside observers believe the payload is a radar imaging intelligence satellite.

The NRO, a federal agency based in Chantilly, Virginia,  is responsible for the design, construction and operation of the United States’ network of intelligence-gathering spy satellites.

The launch followed closely on the heals of ULA’s Feb. 5 launch of the Air Force’s final GPS-2F series of timing, positioning and navigation satellites. The Boeing-built satellite launched from Cape Canaveral Air Force Station, Florida, atop an Atlas 5 rocket.

“This is our second successful launch within five days for our U.S. government customer, a testament to our outstanding teamwork and focus on 100 percent mission success, one launch at a time,”  Laura Maginnis, ULA’s vice president of custom services, said following the Feb. 10 launch of NROL-45. “ULA is proud to be entrusted with safely and reliably delivering our nation’s most critical space assets to orbit.”

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.