Update for 6 p.m. EDT on Aug. 28: The launch window is now expected to open at 6:30 p.m. EDT (2230 GMT) on Aug. 28.
Update for 4 p.m. EDT on Aug. 28: The launch window is now expected to open at 5:45 p.m. EDT (2145 GMT) on Aug. 28.
Update for 1:20 p.m. EDT on Aug. 28: Astra announced via Twitter that the next launch attempt for Rocket 3.3 will come today (Aug. 28), with the window expected to open at 5 p.m. EDT (2100 GMT).
Update for 6:30 p.m. EDT on Aug. 27: Astra's Rocket 3.3 aborted its orbital test launch at the last second today (Aug. 27). Astra has not yet announced when the next attempt will be; daily launch opportunities run through Sept. 11.
Update for 4 p.m. EDT: Astra is targeting a 5 p.m. EDT (2100 GMT) launch for today's Rocket 3.3 launch of a test payload for the U.S. military. Today's launch window runs through 8 p.m. EDT (0000 GMT).
This story was also updated at 4:45 p.m. EDT on Aug. 27 with new details about the mission — for example, that the payload is a mass simulator that will not be deployed.
California startup Astra aims to reach satellite orbit for the first time ever this afternoon (Aug. 28), and you can watch the milestone mission live.
Astra's Launch Vehicle 006, also known as Rocket 3.3, is scheduled to lift off from the Pacific Spaceport Complex on Alaska's Kodiak Island during a two-week window that runs from today through Sept. 11.
On each available day, liftoff can occur during a 4.5-hour window that opens at 4 p.m. EDT (2000 GMT; 12 p.m. local time on Kodiak Island). You can watch the launch live via Astra here, on YouTube via NASASpaceflight or in the window above.
The 43-foot-tall (13 meters) Launch Vehicle 006 is carrying a mass-simulator test payload for the Department of Defense's Space Test Program, which will not be deployed during the mission. The upcoming launch is the first of two that the U.S. Space Force has booked with Astra; the second is expected to launch later this year.
"We are thrilled to partner with Astra on this mission and believe this showcases critical low-cost, mobile and responsive launch capability," Col. Carlos Quinones, director of the Space Test Program, said in a statement earlier this month, when the contract was announced.
Astra, which was established in 2016, has attempted two orbital test launches to date. The first, in September 2020, failed to reach space after Astra's rocket suffered a guidance issue early in the flight. Three months later, Astra's Rocket 3.2 made it to space but ran out of fuel just before reaching orbital velocity.
Full success on this new mission would therefore tick a very big box for Astra.
Astra will notch additional milestones in rapid succession, if all goes according to plan. The Bay Area company plans to claim a large share of the small-satellite launch market with its mass-produced, cost-effective, ever-evolving rockets.
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 Facebook.