PARIS—Japan’s DSN-1 X-band military communications satellite was damaged during transport from Japan to Europe’s Guiana Space Center spaceport in South America and will miss its planned summer launch aboard a European heavy-lift Ariane 5 rocket, also delaying its intended co-passenger, India’s GSAT-18 telecommunications satellite, industry officials said.

It remained unclear whether the damage is severe enough to require the satellite to be returned to Japan or can be treated at the spaceport facilities. Also unknown is whether the damage occurred during loading or unloading of the satellite, or during its air transport from Japan.

Launch-service provider Arianespace’s chief executive, Stephane Israel, said after the company’s June 18 Ariane 5 launch that the company’s next mission would not occur until Aug. 24 and would carry two Intelsat-owned satellites, IS-33e and IS-36. He made no mention of the planned GSAT-18/DSN-1 launch.

Industry officials said the C- and Ku-band GSAT-18 likely would be paired with Australia’s Sky Muster 2 Ka-band consumer broadband satellite for a launch as early as September, assuming no delays for the Intelsat campaign.

The Japanese Defense Ministry in 2013 agreed to finance the two-satellite DSN project as what was then Japan’s first Private Finance Initiative. A joint venture, called DSN Corp., was created to manage the project from end to end, including ordering and launching the satellites and operating them for 15 years in orbit.

Sky Perfect JSat, Japan’s principal satellite fleet operator, is the project coordinator and owns 65 percent of the joint venture. NEC Corp., with a 17.5 percent share, is prime contractor for the two satellites. NTT Communications, also with a 17.5 percent share in the project, is responsible for ground network management and maintenance. The companies incur the capital investment of the project and then generate annual revenue from the Ministry of Defense until about 2031.

Sky Perfect JSat on June 21 said it was too early to determine the cause of the damage, which appeared to occur while the satellite was inside its transport container. The company issued a financial statement on June 17 saying the launch delay likely would mean no service revenue from DSN-1 before the end of the current fiscal year next March. The company lowered its revenue forecast for the year as a result.

The second satellite, DSN-2, had been scheduled for launch in 2017 by Mitsubishi Heavy Industries aboard a Japanese H-2A rocket. Sky Perfect JSat said this satellite is still on track for a 2017 launch.