Watch a live view of the Atlas 5 launch pad with countdown audio (members only)

The last unflown variant of United Launch Alliance’s Atlas 5 launcher — fitted with a five-meter fairing and a single strap-on solid rocket booster — will carry a pair of U.S. military space surveillance satellites toward geosynchronous orbit from Cape Canaveral late this year, according to a Space Force spokesperson.

Launch of an Atlas 5 rocket from Cape Canaveral with a U.S. Air Force infrared surveillance satellite was scrubbed Thursday evening after engineers encountered a balky valve associated with the first stage’s liquid oxygen system.

Rollout of the Atlas 5 rocket from the Vertical Integration Facility to the launch pad at Complex 41 occurred at 10 a.m. on Monday. Liftoff is planned for Tuesday night to deliver the Cygnus resupply ship into orbit en route to the International Space Station.