NASA and SpaceX will try again on Saturday to send the next crew of four astronauts to the International Space Station.

Dubbed Crew-7, the mission will be commanded by American Jasmin Moghbeli and includes Andreas Mogensen of Denmark, Satoshi Furukawa of Japan and Konstantin Borisov of Russia.

Liftoff is planned for 3:27 am (0727 GMT) from Launch Complex 39A at NASA's Kennedy Space Center in Florida, with a backup opportunity on Sunday.

The launch was pushed back to Saturday to give engineers an extra day to review a component of the Crew Dragon capsule's environmental control and life support system, NASA said in a blog post.

One of the precision formation flying Proba-3 satellites as seen from the other during ground testing. The pair will fly in orbit relative to one another down to millimeter scale precision, but in order to do this must keep continuous track of each other in both sunlight and darkness.

To achieve this, Proba-3 combines vision-based detection, as tested here, with radio frequency links, satellite navigation and laser ranging.

The Visual-Based Sensor will be used when the satellites are closer than 250 m to each other. LEDs aboard Proba-3's Coronagraph satellite—seen in the animation below—will be detected by a set of cameras on the other Occulter satellite, appearing as pattens of light in the dark.

Finally, for maximum precision, the Occulter will shine a laser at a retro-reflector mounted on the Coronagraph satellite.

Proba-3 will demonstrate formation flying in the context of a large-scale science experiment. The two satellites will together form a 144-m long solar coronagraph to study the sun's faint corona closer to the solar rim than has ever before been achieved.