PARIS — Deployment of Europe’s Galileo satellite navigation constellation is likely to be stalled until late next summer because of software issues on the new batch of satellites, according to officials involved with the program.

These officials said the delays are mainly related to harmonizing the software on the new satellites, made by a team led by OHB AG of Germany, with that on board the four Galileo validation satellites already in orbit, which were built by a consortium led by Astrium and Thales Alenia Space.

Bremen-based OHB in January 2010 contracted with the European Commission to build the next 12 Galileo satellites. The contract, valued at 566 million euros ($736 million), called for the satellites to be ready for launch starting in October 2012.

The OHB-led team in February this year was awarded a second contract, valued at about 255 million euros, for the construction of eight more Galileo spacecraft.

The late-2012 launch date of the first two satellites was delayed early this year to the spring following a contract change notice given to OHB by the European Space Agency (ESA), which is managing the Galileo system development on behalf of the European Commission.

Most of the Galileo satellites will ride into space in pairs aboard European versions of Russia’s Soyuz rocket, operated from Europe’s Guiana Space Center in South America. ESA will be contracting for those launches with the Arianespace consortium of Evry, France.

European Commission officials recently have stressed that what is most important to Galileo’s owner is not the date of a given launch but the goal to have 18 Galileo satellites in orbit and operational by the end of 2014. That means having 14 OHB-built satellites launched by seven Soyuz rockets in about 16 months.

Officials said that goal remains feasible but will be more difficult to reach given the demands on the Soyuz vehicle in 2013 and 2014, and the testing requirements the satellites must undergo before launch.

ESA officials declined to comment on the current Galileo launch schedule.

OHB Chief Executive Marco R. Fuchs declined to speculate on a launch date for the first two of his company’s Galileo satellites, saying OHB is delivering the hardware on the ground to ESA.

In an Oct. 30 interview, Fuchs said talks with ESA are ongoing with respect to the amount of software validation needed before the first two satellites are cleared for shipment to the launch site.

Fuchs said the first OHB Galileo spacecraft is still in Bremen but is expected to be sent soon to ESA’s European Space Research and Technology Centre in Noordwijk, Netherlands, for a battery of tests including a thermal vacuum chamber to observe its comportment in a simulated space environment.

“The big date is the end of 2014 we need 18 Galileo satellites in orbit, including 14 FOC and four IOVs,” Fuchs said, referring to Galileo’s Full Operational Capability satellites, built by OHB, and the four in-orbit validation satellites already in operation.

“ESA is the prime contractor and is discussing a certain number of variables with its partners, including the European Commission,” Fuchs said. “It is common in these kinds of projects to debate how much margin you need before you agree to ship the satellite for launch. Yes, there is obviously time pressure on the program, but we are delivering on the key promise of having 14 satellites up by the end of 2014.”

The four validation satellites were launched in October 2011 and October 2012. ESA officials have said they would like to take these satellites through their operational paces for a certain amount of time before proceeding with the launch of the next batch.

Another issue of potential importance to the European Commission has to do with negotiations with China on the frequencies to be used by Galileo and by China’s Beidou positioning, navigation and timing satellites.

China’s Beidou constellation is proceeding full speed ahead. A dozen satellites have been launched and an initial operating capability over the Asia-Pacific region is scheduled by the end of this year.

Beidou is using frequencies for its encrypted, government-only service that partially overlap frequencies Europe’s Galileo wants to use for its equivalent Public Regulated Service (PRS).

The overlap would create no interference but would make it impossible for either system to jam the other’s encrypted service without jamming its own. China and the European Commission are scheduled to meet in Paris in December to attempt to resolve the issue.

It is unclear whether Galileo satellites would need to be modified on the ground in the event the commission decided to move PRS so that it did not overlap China’s service.

Peter B. de Selding was the Paris Bureau Chief for SpaceNews.