Update for 10:30 a.m. EDT on March 30: SpaceX aborted an attempted launch of the Tranche 0 satellites on Thursday (March 30) with three seconds left in the countdown clock. The next possible launch opportunity comes Friday (March 31) at 10:29 a.m. EDT (1429 GMT).
SpaceX will launch a set of satellites for the U.S. Space Force Friday (March 31), and you can watch the action live.
A Falcon 9 rocket topped with 10 spacecraft for the Space Force's Space Development Agency (SDA) is scheduled to lift off from California's Vandenberg Space Force Base Friday at 10:29 a.m. EDT (1429 GMT; 7:29 a.m. local California time.
Watch it live here at Space.com, courtesy of SpaceX, or directly via the company. Coverage is expected to begin about 15 minutes before liftoff.
Related: What is the U.S. Space Force and what does it do?
If all goes according to plan, the Falcon 9's first stage will come back to Earth safely, touching down at Vandenberg's Landing Zone 4 just under eight minutes after liftoff.
It will be the second launch and landing for this particular booster, according to a SpaceX mission description. The rocket previously helped launch a batch of SpaceX's Starlink satellites to orbit.
The Falcon 9's upper stage, meanwhile, will continue carrying the Tranche 0 satellites to orbit. The SpaceX mission description doesn't say when the spacecraft are scheduled to be deployed. That's not terribly surprising; details about national security missions such as this one are often hard to come by.
We do know a bit about the Tranche 0 spacecraft going up on Friday, however. For example, they'll be the first members of the Proliferated Warfighter Space Architecture (PWSA), a constellation the SDA will assemble in low Earth orbit.
"Under the plan, the Space Force will have hundreds of small satellites, with new ones launched every few years to increase resilience and capabilities in orbit," Air and Space Forces Magazine wrote about the PWSA.
The 10 Tranche 0 satellites cost about $15 million apiece, the magazine added. Eight of the spacecraft going up Friday will relay data and two will track missiles, though this first set is intended primarily to demonstrate capabilities that future SDA satellites will take operational.
Another Tranche 0 set is expected to launch in June, according to Air and Space Forces Magazine.
"The entire tranche consists of 28 satellites — 20 for data transport and eight for missile tracking," the outlet wrote.
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 @Spacedotcom, or on Facebook and Instagram.
