Nation IN BRIEF : FLORIDA : Shuttle Readied for Countdown Restart

Engineers at Florida’s Kennedy Space Center replaced a balky navigation unit aboard the space shuttle Columbia and geared up to restart the ship’s interrupted countdown for a blastoff on Wednesday. Columbia, its seven-member crew, 30 rats and some 2,500 baby jellyfish were grounded Saturday just 45 minutes before the ship’s planned launch on a medical research flight now running 14 days behind schedule. The faulty navigation device, called an inertial measurement unit, was replaced by a spare, and engineers spent the day Sunday putting the device through a series of tests to make sure it would work properly.