Falcon 9 Iridium-1 launch
A SpaceX Falcon 9 lifts off from Vandenberg Air Force Base, California, carrying 10 Iridium Next satellites. Credit: SpaceX

WASHINGTON — Iridium Communications says SpaceX has pushed back the launch of its second batch of next-generation satellites from mid-April to mid-June, a move that shifts the expected completion date for Iridium Next to the middle of 2018.

In a Feb. 15 statement, Iridium said the two-monthly launch delay is “due to a backlog in SpaceX’s launch manifest as a result of last year’s September 1st anomaly.”

Iridium’s satellites are launching 10 at a time on Falcon 9 rockets lifting off from  from Vandenberg Air Force Base in California — part of what Iridium Chief Executive Matthew Desch described last June as a “separate queue” from SpaceX missions launching from the more frequently used Cape Canaveral Air Force Station in Florida. However, that was before a Falcon 9 exploded on the Cape’s Pad 40 during a routine pre-flight test. The accident halted SpaceX launches for four-and-half months. Falcon 9 returned to flight Jan. 14 delivering the first 10 Iridium Next satellites to orbit.

SpaceX launched only eight of the 18 missions it had targeted for 2016, shifting 10 missions onto an already-crowded 2017 manifest. The combination of SpaceX’s tightly packed manifest and limited launch range availability has put pressure on Iridium Next despite its preferred status at Vandenberg.

Iridium expects SpaceX to launch a fresh batch of Iridium satellites every two months starting with the mid-June launch. Iridium has seven more launches to complete: six with 10 satellites each and one with five that will be shared with a pair of U.S.-German science satellites dubbed the Gravity Recovery and Climate Experiment Follow-on mission (GRACE-FO).

“After such a successful first launch, we are eager to maintain the momentum until our network is completed,” Desch said in a prepared statement. “Even with this eight-week shift, SpaceX’s targeted schedule completes our constellation in mid-2018.”

Though launches have been delayed, Iridium said in-orbit testing of the first 10 Iridium Next satellites launched Jan. 14 are ahead of schedule and should start service in the coming days.

“Since their perfect orbit injection and deployment by SpaceX, our satellite testing process has progressed ahead of schedule, a testament to the rigorous development program they’ve undergone on the ground,” said Scott Smith, chief operating officer at Iridium.

Iridium has stitched the new satellites into its existing constellation where they will interoperate until the first-generation satellites are deorbited. The satellite operator’s current plan is to launch 75 out of 81 Iridium Next satellites, with 66 working operationally and nine as on-orbit spares. Iridium spokeswoman Diane Hockenberry told SpaceNews Feb. 15 that the remaining six spares will stay on the ground.

Previously Iridium planned to have only six in-orbit spares — one for each plane of satellites — but increased the number when the GRACE-FO shared launch opportunity became available.

Caleb Henry is a former SpaceNews staff writer covering satellites, telecom and launch. He previously worked for Via Satellite and NewSpace Global.He earned a bachelor’s degree in political science along with a minor in astronomy from...