Update 11:15 AM EST: SpaceX has scrubbed the mission for today, and will look to try again tomorrow during a three-hour launch window that opens at 9 AM EST. There was an unusually high pressure reading in the upper-stage liquid oxygen tank that the company will work to resolve.
SpaceX is launching a Falcon 9 today from Kennedy Space Center, with a launch window that spans three hours and opens at 9 AM EST (6 AM PST). The mission will carry a spy satellite for the U.S. National Reconnaissance Office (NRO), and will include a recovery attempt for the first-stage booster used on the Falcon 9 vehicle.
This Falcon 9's first-stage has already flown four times previously, including during two of SpaceX's commercial resupply missions to the International Space Station for NASA, and during a Starlink launch, as well as for SAOCOM 1B, a satellite launch operation for the Argentinian space agency in August.
SpaceX will be attempting a landing back at its landing pad at Cape Canaveral Space Force Station, a rarer occurrence versus its use of its two drone landing ships positioned out in the ocean. SpaceX's at-sea landings were introduced to allow for recovery of rocket boosters that didn't have enough fuel remaining on board to make it all the way back to land -- meaning this NRO mission's parameters allow for a "return to sender" trip back home.
Typically, when there's a longer launch window, SpaceX will aim to launch at the beginning, depending on weather conditions. If that's the case today, the stream above should begin at around 8:45 AM EST (15 minutes prior to the opening of the window).