WASHINGTON, D.C. The Smithsonian Institution plans a four-day festival with NASA to welcome space shuttle Discovery into its collection in April. The National Air and Space Museum has plans for more than 25 special exhibits, programs and activities to highlight the history of the 30-year space shuttle program and the future of space exploration. Discovery is scheduled to leave NASA's Kennedy Space Center in Florida on the back of a Boeing 747 on April 17 and fly over parts of the Washington area. See nasm.si.edu for more information.