Simulation of the Soyuz launch. Photo: ESA

The launch of the European Space Agency's first pair of Cluster 2 satellites has been pushed back three days to make way for the launch of the next major part of the International Space Station, an ESA spokesman said.

Both major missions were scheduled for launch from Russia's Baikonur Cosmodrome in Kazakhstan on July 12. Cluster 2 on a Starsem Soyuz and the station's Zvezda living quarters aboard a Proton.

"We cannot do both on the same day," said Franco Bonacina at ESA Headquarters in Paris. "We are announcing a new launch date."

Artist's impression of the Cluster spacecraft in orbit. Photo: ESA

The Starsem Soyuz carrying the first two Cluster spacecraft is now scheduled to liftoff on July 15 at 1240 GMT (8:40 a.m. EDT). The second Cluster pair will follow into orbit on August 9 as previously planned.

The four drum-shaped Cluster 2 satellites will fly in formation to study the interaction of the solar wind with the Earth's magentic field in unprecedented detail.

The Cluster 2 mission was assembled after the first quartet of Cluster spacecraft were destroyed when Europe's Ariane 5 rocket exploded on its maiden flight.