LOS ANGELES - A SpaceX rocket carried 10 communications satellites into orbit from California on Sunday, two days after the company launched a satellite from Florida.

The Falcon 9 rocket blasted off through low-lying fog at 1:25 pm from Vandenberg Air Force Base northwest of Los Angeles. It carried a second batch of new satellites for Iridium Communications, which is replacing its orbiting fleet with a next-generation constellation of satellites.

Following stage separation, the first stage of Falcon 9 successfully landed on a droneship in the Pacific Ocean, despite challenging weather conditions.

Billionaire Elon Musk, who founded SpaceX, believes reusing rocket components will bring down the cost of space launches.

Iridium plans to put in place 75 new satellites for its mobile voice and data communications system by mid-2018, requiring six more launches, all by SpaceX.

The $3 billion effort by Iridium involves complex procedures to replace 66 operational satellites in use for many years. Some of the new satellites will be so-called on-orbit spares, or older satellites that remain in orbit on standby for use if the newer ones malfunction.

Swapping out and deorbiting some old satellites has already begun, Iridium CEO Matt Desch said.

Several old satellites have been moved into lower orbits to use up their remaining fuel and configure the solar panels for maximum drag so they will re-enter the atmosphere and burn up.

"It's hard to celebrate something like that, but these satellites have put in almost 20 years of service, and making sure we've cleaned up after ourselves as we deploy our new constellation is a priority," he said.

The new satellites also carry payloads for joint-venture Aerion's space-based, real-time tracking and surveillance of aircraft around the globe, which has implications for efficiency, economy and safety especially in remote airspace over the oceans.

Ap - Xinhua