Despite predicted bad weather, NASA counted down the seconds toward Tuesday's launch of the space shuttle Discovery and its assortment of "Star Wars" instruments.

Shuttle weather officers said Monday there was a 40 percent chance of favorable weather at 7:05 a.m. EDT, liftoff time, slightly better than Sunday's forecast. The main concerns were low clouds, high wind and possible rain.Officials planned to start loading more than a half-million gallons of liquid oxygen and liquid hydrogen into Discovery late Monday. NASA test director Al Sofge said mission managers have tended to proceed with shuttle fueling despite poor weather predicted for launch time.

The goal of the year's second shuttle flight is to gather data on how an enemy missile's fiery exhaust plume appears against a variety of backdrops ranging from the deep black of space to the brilliant blues and whites of planet Earth.