US astronauts took off Monday at the start of a high-risk mission to service, for the last time, the Hubble telescope, which has revolutionized humankind's understanding of the universe.
Flight director Mike Leinbach gave the team the go-ahead for takeoff saying: "It's a great day to go to fly," adding he wished the crew "a great mission, good luck and Godspeed and see you back in 11 days."
The mission aims to provide the fifth and final maintenance operation to the Hubble before the shuttle fleet is retired, and if successful NASA has said the fix-up would extend the stargazer's already lengthy life by at least five years.
The Hubble's servicing will entail five space walks, each lasting up to seven hours. Crew members plan to replace the telescope's six gyroscopes and batteries and upgrade its optical instruments.
Launched in 1990, Hubble has long been considered the greatest tool in the history of astronomy.
Orbiting 575 kilometers (360 miles) above Earth and using powerful instruments to peer into deep space, it has provided profound insights into the origins, evolution and mysteries of the universe through hundreds of thousands of photographs.
But not until it shed its reputation as a cosmic joke in its first years, when mirror problems gave the Hubble an embarrassing case of blurry vision.
The flaw was corrected in 1993, and Hubble began beaming back spectacularly sharp images which enabled scientists to better measure the age and origins of the universe, observe distant supernovas, and identify and study bodies in and outside the solar system.
National Aeronautics and Space Administration experts stressed that the Atlantis voyage carries heavy risks.
"This will be the most challenging servicing mission that's been faced by our astronauts in terms of the total amount of work," said Preston Burch, mission manager.
A journey to the 11-ton Hubble carries more risk of being hit by space debris or micrometeorites than a flight to the International Space Station, as the telescope orbits at almost twice the altitude of the ISS.
Officials hope the mission will allow Hubble to keep functioning until 2014, when it is due to be replaced by the James Webb Space Telescope, a highly sophisticated device with an eagle-eye camera.
"If successful we will be entering our second quarter century. That's not bad for a mission that we hoped will last for 10 to 15 years," said Ed Weiler, associate administrator of NASA's science missions directorate.
Hubble "will be more powerful and robust than ever before and will continue to enable world class science for at least another five years and overlap with the James Webb Space Telescope," he added.
The crew will carry out a variety of tasks including replacing electronic circuit boards and installing a new imaging camera and a Cosmic Origins Spectrograph -- an especially sensitive instrument designed to split light it captures into individual wavelengths.
NASA says the spectrograph will not only be able to study stars, planets and galaxies but also basic elements found throughout the cosmos, such as carbon and iron.
And the new instruments will allow Hubble to peer even further back into time, perhaps as far back as some 600 million years after the Big Bang birth of the universe.
The maintenance is overdue after the years-long delay for US space flights since the 2003 Columbia disaster that saw the shuttle disintegrate as it re-entered Earth's atmosphere, killing all seven crew members.
Source: AFP American Edition