The shuttle Atlantis roared from its pad at Cape Canaveral with only five minutes to spare, carrying five astronauts who will dispatch the Magellan probe to collect the most detailed images ever of cloud-shrouded Venus. The winged space shuttle thundered smoothly into the Florida sky at 12:47 p.m. MDT, after being delayed a nail-biting 59 minutes by shifting rain clouds and winds that had threatened a second postponement in six days. NASA had 64 minutes in which to launch Thursday. (Earlier story on A3.)