NASA has said that it plans to launch four space shuttle missions this year instead of five, due to the delay caused after hail damage sustained by the shuttle Atlantis in February.
"The space shuttle and International Space Station programs agreed to the changes during a meeting to evaluate options following the (Atlantis) mission's delay, which was caused by hail damage to the external fuel tank," it said on Monday.
Atlantis is now to launch by June 8 at the earliest. It is to be the first mission this year, and after its initially scheduled launch was delayed from March 15.
The next launch, of the Endeavour, is planned for August 9 or shortly thereafter. Following that is to be the Discovery, to launch by October 20 at the earliest.
The last of the year is to be Atlantis on or after December 6. NASA agreed on the changes at a meeting on Monday.
The space agency forecasts 13 missions are needed to complete work on the International Space Station by 2010.