After months of struggling with dangerous fuel leaks on two of its three spaceships, NASA will try to launch the space shuttle Atlantis this week with a spy satellite.

It will be Atlantis' first flight since March, when it placed another spy satellite in orbit. It will also be the 37th flight of a shuttle and the fifth flight this year."We've been through a lot of interesting times over the past few months to say the least," said Conrad Nagel, a NASA official in charge of Atlantis' pre-launch operations. "Now that it's here, it's real exciting."

Atlantis is scheduled to blast off Thursday evening, sometime between 6:30 p.m. and 10:30 p.m. EST. The exact time will be kept secret until nine minutes before liftoff because the Pentagon mission is classified.

The flight is expected to last about four days, during which Atlantis' five astronauts will release a satellite that reportedly will spy on Iraq. Experts believe it is either a photographic imaging or an eavesdropping spacecraft.

Information about the mission will be kept secret as with the six previous Defense Department shuttle flights.

Pentagon officials say this should be the last classified shuttle flight because of the expense of maintaining secure operations. Two military missions planned for next year have unclassified cargoes.

Atlantis' upcoming mission is four months late.