MT LAUREL, New Jersey — The first launch of Russia’s Proton rocket in nearly a year is now scheduled for June 7, a nine-day slip driven by a review of the ground systems at the rocket’s launch site.

When Proton finally lifts off, it will be carrying EchoStar 21, a 6,900-kilogram commercial telecommunications satellite for Englewood, Colorado-based fleet operator EchoStar.

Proton’s manufacturer, Moscow-based Krunichev Space Center, said May 30 that preparations are underway for the launch from Russia’s Baikonur Cosmodrome in Kazakhstan.

Karen Soriano, spokesperson for International Launch Services, Khrunichev’s Reston, Virginia-based commercial launch service division, said Russia’s state space corporation Roscosmos needed extra time to complete a quality audit of Proton’s launch operations.

“The audit was conducted between May 12-19 and [Krunichev] successfully addressed all of the minor audit findings. The Echostar XXI mission campaign resumed on May 19,” Soriano told SpaceNews by email May 30. “The audit focused solely on the ground segment and had no impact on the flight hardware to be used in support of the Echostar XXI mission. All planned processing activities are proceeding along nominally.”

Prior to the audit, the launch had been slated for May 29.

EchoStar 21 is the first mission for Proton since the rocket’s manufacturer discovered that a different solder had been used by the factory that produces Proton’s second and third stage engines. Though the engines passed hot fire tests with thrust levels and durations beyond launch requirements, Russia grounded Proton while the engines were replaced.

EchoStar has been waiting since last spring to launch EchoStar-21, an S-band satellite from manufacturer Space Systems Loral. The satellite will support a mobile satellite service in Europe from its vantage point at the 10.25 degrees east orbital slot.

Soriano said ILS is still planning three commercial missions this year, and Khrunichev still has four government missions, making for seven Proton launches for 2017. Those commercial missions are EchoStar-21, AsiaSat-9 for Hong Kong-based AsiaSat, and Amazonas-5 for Spanish fleet operator Hispasat.