(AP) -- NASA began the countdown for its final trip to the Hubble Space Telescope on Friday as the astronauts who will attempt the daunting repairs arrived at the launching site.
Space shuttle Atlantis is scheduled to blast off Monday afternoon, taking up hundreds of millions of dollars' worth of new cameras and replacement equipment for Hubble.
An hour after the countdown clocks began ticking, shuttle commander Scott Altman and his crew flew in from Houston.
The 19-year-old Hubble hasn't had any visitors for seven years. Atlantis and its crew were supposed to show up last fall, but the mission was delayed seven months after a key part of the telescope broke.
Altman said it had been a long road to get there.
"The one thing I can say is we are ready. Let's launch Atlantis!" he said, emphasizing each word and raising his right fist into the air.
His six crewmates, standing in a row behind him, also pumped their fists and shouted in agreement. Altman shook hands with each one. All seven wore black ball caps with "Atlantis" and their mission number, "125," emblazoned on front; the hats were decorated with tiny white stars.
"To say it feels sweet is an understatement," said Altman's co-pilot, Gregory Johnson.
NASA expects good launching weather, but rain in Spain could keep Atlantis on the ground next week. The shuttle will fly due east out of Cape Canaveral and the only emergency landing site available overseas is in Spain.
Unlike the five-minute launch windows for space station missions, Atlantis will have about 40 minutes to get off the ground each day. NASA test director Jeremy Graeber considers that a luxury.
Five spacewalks are planned on consecutive days during the 11-day flight. Not only will the astronauts replace old cameras, they will try to repair two failed instruments, something never before attempted at Hubble. It will be the fifth and last time astronauts visit the orbiting observatory.
Shuttle Endeavour is ready to go at the other launch pad in case Atlantis suffers irreparable damage during the flight and its crew needs to be rescued. The astronauts flew by in their training jets as they arrived for the countdown and took in the rare sight of two occupied pads.
NASA has three tries to get Atlantis off, through Wednesday. Then it will have to wait until May 22 because of a military operation at neighboring Cape Canaveral Air Force Station and the recharging of the new batteries going up for Hubble.
On the Net:
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Image: Orion crew module at the Neil Armstrong Operations and Checkout Building, Kennedy Space Center