Q&A with Elon Musk, founder and CEO of SpaceX (members only)

Working overnight on Florida’s Space Coast, SpaceX technicians transferred a two-stage Falcon 9 rocket from the company’s commercial hangar a quarter-mile up the ramp to launch pad 39A early Saturday, positioning the kerosene-fueled booster for liftoff Sunday with a classified payload for the U.S. government’s National Reconnaissance Office.

The Earth observing spacecraft will study clouds and aerosols to further our understanding of climate change. Liftoff happened at 3:20 p.m. PDT (6:20 p.m. EDT, 2220 UTC).

SpaceX’s Falcon 9 rocket is again standing on launch pad 39A at NASA’s Kennedy Space Center in Florida, this time with a Dragon supply ship on top ready to head on a resupply run to the International Space Station.