Photos: Atlas 5 rocket aims for International Space Station

The last two spacecraft in a four-satellite constellation of tropical cyclone research platforms took off late Thursday from New Zealand on a Rocket Lab Electron launcher, helping ensure NASA’s TROPICS mission is ready for observations in time for the peak of this year’s Atlantic hurricane season.

SpaceX’s launch team fueled up a Falcon 9 rocket on a California launch pad Thursday, fired the booster’s nine Merlin engines, and passed a key preflight test for the first time since a Falcon 9 exploded during a similar practice countdown in September.

Arianespace has split its third order of Vega rockets from Italy’s Avio between old and new versions of the solid-fueled booster, as officials prepare to build a final batch of around 18 Ariane 5 rockets before switching to the next-generation Ariane 6 in the early 2020s.