Nasa to keep launches secret

Nasa will give only 24 hours notice of its exact launch times from now on to guard against possible terror attacks.

It is the first time in more than a decade that the space agency is refusing to give out a shuttle launch time well in advance.

Nasa will give out four-hour launch periods and announce the chosen one a day before lift-off.

The next launch, of Atlantis on April 4, will occur sometime between 7pm and 11pm.

Kennedy Space Centre spokesman Bruce Buckingham said: "Nasa is choosing to be extra careful."

Herring said Nasa wants to put out as much information as possible but added: "We also want to protect the national assets, that is the hardware, the crew and the personnel that work for this agency."

The launch times of the last two space shuttle missions were widely known before September 11 and so there was no attempt to make them secret following the terrorist attacks.