Video: 4K video replay of SpaceX’s CRS-21 launch (members only)

Preparations for the planned liftoff Thursday of a SpaceX Dragon capsule with a four-person crew to the International Space Station cleared another readiness review Tuesday at NASA’s Kennedy Space Center in Florida, but officials are tracking marginal wind and sea conditions in downrange abort zones in the Atlantic Ocean that could force a launch delay.

NASA has formally certified SpaceX’s Falcon 9 rocket to launch all but the space agency’s most costly robotic science missions, beginning with a a U.S.-French oceanography satellite set for liftoff from California in July.

Without any public warning, a Chinese Long March 4B rocket lifted off Sunday with two “environmental monitoring satellites” that the country’s state media said will replace a pair of spacecraft launched in 2008 that collected data to assist in a series of disaster relief efforts over the last decade.