(FOX 11/CNS) - The launch clock remained set to 7:21 p.m. for SpaceX's launch of a satellite into orbit from Vandenberg Air Force Base, and planned landing of the rocket booster 100 miles west of Los Angeles.
"Sonic boom warning. This won't be subtle" advised SpaceX founder Elon Musk on his Twitter feed on Sunday.
Booms from the Falcon 9 booster's re-entry into the atmosphere were predicted to shake the Pacific Coast as far southeast as Ventura County, but officials said the noise pattern cannot be accurately predicted given varying upper-atmospheric weather patterns.
This will mark the first time SpaceX has attempted a ground landing of the Falcon 9 on the West Coast. Previous re-capture missions from Vandenberg have landed the rocket on a barge floating in the Pacific Ocean, about 400 miles out to sea.
The company has landed rockets on the ground before, but always at Cape Canaveral in Florida.
The launch, employing the upgraded Block 5 version of the Falcon 9 rocket, remained scheduled for 7:21 p.m. The Block 5 is considered more durable than previous Falcon 9 varieties, capable of flying as many as 10 missions.
The rocket being used in Sunday's mission was previously employed in a June launch.
Air Force officials have issued a warning that residents in San Luis Obispo, Santa Barbara and Ventura counties could potentially hear one or more sonic booms due to the launch.
The mission could also create a spectacular light show visible across the Southland, depending on weather conditions.
The rocket will be carrying an Argentinian Earth-observing satellite, known as SAOCOM-1A, into orbit. The satellite is one of a planned six-satellite array.