After nearly a four-month delay, the space shuttle Discovery successfully launched from Florida's Kennedy Space Center this afternoon and is now headed to the International Space Station.
The shuttle took off at 4:53pm Eastern after a slight delay due to a central command system display that was not operating properly.
"Discovery is now making one last reach for the stars," NASA officials said during a live webcast of the launch.
By 5:03pm space shuttle Discovery reached orbit and was on its way to the ISS. "Good to be here," Discovery Commander Lindsey radioed soon after the three main engines shut off and the external fuel tank was jettisoned.
In a post-launch press conference, Bill Gerstenmaier, associate administrator for Space Operations at NASA, said Thursday was "a pretty tremendous day in space flght for us."
Discovery's "performance was perfectly nominal during ascent," he continued, though he cautioned that much work remains to be done. "When we get Discovery back [on Earth], we can talk about how things really went."
It was a "great way to go out," said shuttle launch director Mike Leinbach, referring to Discovery's impending retirement. "She gave us a little bit of a fit today, but it was a great way to get [the] crew on their way," he said, referring to the slight delay.
When asked about the emotion involved in seeing Discovery launch for the last time, Leinbach said that while "counting down, we were busy doing our jobs, so the emotion didn't have time to kick in." After it left, however, "there were a lot of pats on the back," he said. The crew also presented Leinbach with a signed banner from the hatch cover that he said will be a special reminder of Discovery.
This mission, known as STS-133, will be the 35th shuttle mission to the ISS. It will last for 11 days, and will deliver and install the Permanent Multipurpose Module, the Express Logistics Carrier 4, and provide critical spare components to the ISS.
One of passengers aboard Discovery will be Robonaut 2, which will be the first humanoid robot in space. Its primary mission is to teach engineers how dexterous robots behave in space, but NASA said the hope is that it can one day be used outside the station to help spacewalkers make repairs or perform scientific work.
The robot, known as R2, has a long trip. R2 will be packed amongst supplies and equipment before being installed on the Unity module, a U.S.-built section of the ISS. R2 probably won't be unpacked until several months after it arrives, NASA said, after which it will be operated inside the Destiny lab for operational testing. "There are no plans to return R2 to Earth," NASA said.
The launch was originally scheduled for November 1, but it was delayed multiple times thanks to weather, leaks, and cracks. By early January, however, NASA technicians were confident they had resolved all issues, and set the launch date for February 24.
A biking accident, however, later prompted NASA to replace astronaut Tim Kopra with astronaut Steve Bowen on the STS-133 Discovery mission. Kopra will recover, but not quickly enough for today's launch. Other Discovery crew members include Commander Steven Lindsey, Pilot Eric Boe and Mission Specialists Alvin Drew, Michael Barratt, Nicole Stott.
On February 1, Discovery completed its slow crawl to the launch pad. It reached its destination at 2:55am Eastern time after a seven-hour, 3.4-mile trek. Earlier this week, the shuttle was cleared for takeoff.
After Discovery, NASA has two additional shuttle launches on the schedule before retiring the fleet. The Shuttle Endeavour is scheduled for April 19; the crew for that flight includes astronaut Mark Kelly - husband of Rep. Gabrielle Giffords. The final flight, Shuttle Atlantis, is scheduled for June 28.
Also this week, NASA delayed the planned launch of the Glory spacecraft due to a technical issue; it is now rescheduled for 5:09am Friday. Glory was scheduled to launch aboard an Orbital Sciences Taurus XL rocket from Vandenberg Air Force Base in California in order to gather more data about sun- and climate-influencing particles called aerosols.
For more on the history of Discovery, check out the slideshow above.
Editor's Note: This story was updated at 6:30pm with comment from the post-launch press conference.