WASHINGTON — SpaceX’s eighth and final Iridium Next launch has been delayed nine days to Jan. 7.

The new launch date, announced Dec. 7 by customer Iridium Communications, was driven by the additional two weeks SpaceX ended up needing to launch Spaceflight Industries’ “SmallSat Express” dedicated rideshare mission. That mission — carrying 64 small satellites aboard a Falcon 9 — finally lifted off Dec. 3 from SpaceX’s launch pad at Vandenberg Air Force Base, California.

SpaceX, which has launched seven batches of Iridium Next satellites from Vandenberg since January 2017, had been targeting a Dec. 30 liftoff for the eighth and final batch of 10 satellites needed to complete deployment of Iridium’s second-generation constellation.

Iridium currently has 65 Iridium Next satellites in orbit. The final launch will give Iridium 66 operational satellites and nine orbiting spares. Iridium has another six spare satellites it is keeping on the ground.

SpaceX is Iridium’s sole launch provider for Iridium Next, having conducted the first launch nearly two years ago on Jan. 14, 2017.

Built by Thales Alenia Space and Northrop Grumman Innovation Systems, Iridium Next provides L-band voice and data services from low Earth orbit. The satellites also carry hosted payloads for Aireon’s flight-tracking service and Harris and exactEarth’s maritime ship-tracking business.

SpaceX has launched 20 times this year, beating last year’s record 18 missions. The company has one more mission still planned for 2018: a Dec. 18 launch of the U.S. Air Force’s first GPS-3 satellite.