Nation IN BRIEF : FLORIDA : Countdown Begins for Shuttle Launch

NASA cleared the space shuttle Discovery for flight and started the countdown for its trip Thursday into orbit with an atmosphere research satellite. Discovery’s five astronauts arrived at Florida’s Kennedy Space Center in training jets. Mission commander John Creighton said most of their shuttle flight training has been in the dark because of the middle-of-the-night landing planned at the Kennedy Space Center for the end of the mission. Shuttle test director Mike Leinbach said a leak in a helium line valve in Discovery’s orbital steering system was too small to be of concern.