Photos: Atlas 5 on the pad for X-37B launch

The fourth and last spacecraft in BlackSky’s initial flock of commercial Earth-imaging microsatellites successfully launched Monday aboard a Rocket Lab Electron rocket with three other payloads, setting the stage for the final assembly and launch of at least 20 more BlackSky orbiting surveillance platforms starting later this year.

Watch the pre-flight news conference that introduces NASA’s OSIRIS-REx spacecraft scheduled to launch from Cape Canaveral atop a United Launch Alliance Atlas 5 rocket on Sept. 8. It will capture a sample of Asteroid Bennu for return to Earth.

Onboard video cameras captured critical events during the 50th Atlas 5 rocket launch, beaming back views in stunning clarity of staging and spacecraft separation.