A United Launch Alliance (ULA) Delta IV Heavy rocket will launch a U.S. spy satellite on its final flight from California on Saturday (Sept. 24), and you can watch it live.
The powerful Delta IV Heavy is scheduled to lift off from Vandenberg Space Force Base in California Saturday at 5:53 p.m. EDT (2153 GMT; 2:53 local time), on a mission for the U.S. National Reconnaissance Office (NRO) called NROL-91. Watch it live here, courtesy of ULA, or directly via the company.
The NRO builds and operates the nation's fleet of spy satellites. The activities and payloads of those spacecraft tend to be classified, and the NROL-91 mission is no exception; little is known about the satellite that it will loft.
Related: The Delta IV Heavy: Powerful launch vehicle
"We're on track to launch another national capability into space. This will be our sixth national security launch this year. We've worked alongside ULA to prepare this Delta IV Heavy, and in just a few days, we will see the fruits of our labor," Brig. Gen. Stephen Purdy, Space Force program executive officer for assured access to space, said in an emailed statement Thursday (Sept. 22).
"These launches place critical capabilities into orbit for our nation and our allies in a time of increasing risks and threats," Purdy added. "Every member of our launch team understands what's at stake and works with both care and efficiency to prepare for what’s going to be a tremendous launch."
Saturday's launch will be the final Delta IV Heavy liftoff from California. ULA is phasing out the burly rocket in favor of a new vehicle called Vulcan Centaur, which could debut before the end of 2022, company representatives have said.
There are two Delta IV Heavy missions left after Saturday's flight. Both will launch from Florida's Space Coast, in 2023 and 2024 if all goes according to plan.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook.