CAPE CANAVERAL - NASA started the countdown again yesterday to launch shuttle Discovery after extensive troubleshooting to fix the faulty sensor that scuttled the first attempt.
Liftoff is set for 10:39 a.m. Tuesday from the Kennedy Space Center, with forecasters predicting a 60 percent chance of favorable weather.
Discovery's astronauts arrived in Florida on Friday, saying they hope for dry skies when they climb aboard their spaceship again.
"We hope we can give you a good show," said Discovery commander Eileen Collins. "We're really excited about getting this launch off, we're very prepared, and we'll be talking to you from space."
The main weather issues for Tuesday are isolated showers and clouds in the launch area, said shuttle weather officer Kathy Winters. She said Tropical Storm Franklin has been written off as a threat for the launch.
Once in orbit, Discovery's crew is to dock at the International Space Station to deliver supplies and make a series of spacewalks. The mission is NASA's first shuttle flight in the more than 2 1/2 years since seven astronauts died aboard Columbia in 2003.
Discovery was fueled and just hours from liftoff July 13 when a fuel sensor failed to respond to computer commands during routine pre-launch testing. NASA called off the launch to fix the sensor.
The agency has not been able to figure out the glitch definitively, but engineers suspect that electromagnetic interference from subtle grounding problems caused the sensor to fail.
The sensor is one of four that alerts the shuttle's computers when the external tank is about to run out of hydrogen.
The sensors are a precautionary device and are not needed during a normal launch because the tank carries more hydrogen than is needed to get to orbit.
NASA test director Pete Nickolenko said the agency is confident that the problem will not stand in the way of Discovery's next launch attempt.
"We believe our flight systems and ground-support hardware are ready, we know our flight crew and support teams are ready," Nickolenko said. "We're all eagerly anticipating and looking forward to a successful launch and mission."
NASA has until the beginning of August to launch Discovery to the International Space Station, or it must wait until September to ensure good lighting throughout the ascent. The space agency is insisting on a daylight liftoff for good camera views in case the shuttle is hit by fuel-tank foam insulation, ice or other debris.
Columbia was brought down by a 1 1/2 -pound chunk of foam that pierced the left wing.
The Orlando Sentinel is a Tribune Publishing newspaper. The Associated Press contributed to this article.