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

A small communications satellite built by the German company OHB — a payload so secret that no one has officially disclosed its name or end user — is set to ride a Rocket Lab Electron launcher into orbit Saturday from New Zealand.

The second fully commercial astronaut flight to the International Space Station will have just two opportunities to launch Sunday and Monday, or else wait until after an upcoming SpaceX resupply mission next month to deliver a new set of high-priority solar arrays to the complex.

SpaceX’s Falcon 9 rocket flew its 300th mission on Thursday Feb. 16, lifting off from Vandenberg Space Force Base in California at 1:34 p.m. PST (4:34 p.m. EST, 2134 UTC) carrying another batch of satellites for the company’s Starlink internet service.