Tuesday was a day of anniversaries for space exploration. It was 50 years since the first human ventured into space and 30 years since the first test flight of the U.S. space shuttle. Scientific advances that began in a time of competition between the United States and the Soviet Union resulted in an international orbiting outpost.
It was 30 years ago - April 12, 1981 - that two U.S. Navy pilots took the space shuttle Columbia on the first test flight of a reusable spacecraft.
Since then, NASA's five space shuttles have flown more than 130 times, carrying more than 350 people into orbit and traveling more than 800 million kilometers.
NASA Administrator Charles Bolden praised the advances during a ceremony at the Kennedy Space Center in Florida. Bolden, himself a retired astronaut, was overcome with emotion as he spoke of his flights on the shuttles Columbia, Discovery and Atlantis.
"There is no more awe-inspiring or humbling experience than flying to space. With seven million pounds [i.e., three million kilograms] of thrust beneath you, you are aware of your frailty as a human being and also the great things of which we are capable. My experience as commander of [1994's Discovery mission] STS-60 - the first flight of a Russian cosmonaut on the shuttle - taught me that there is no limit to what we - what we - can accomplish," he said.
That sense of international cooperation did not exist half-a-century ago, when the United States and the Soviet Union were competing in what became known as "the space race."
On April 12, 1961, Soviet cosmonaut Yuri Gagarin became the first person to orbit the Earth. His flight lasted 108 minutes.
Now, leaps and bounds and decades later, people live in an international orbiting space station some 350 kilometers above the planet. In the space station today there are three Russian cosmonauts, one Italian astronaut and U.S. astronauts Ron Garan and Cady Coleman.
Speaking from the station on Tuesday, Coleman reflected on the advances in space exploration.
"Fifty years ago, the first human left the planet and orbited our Earth. Now, just 50 years later, living in space is considered to be practically normal. The fact that my fourth grade son's classmates think it's perfectly normal that his mother calls from space and helps with homework [shows] we've really come a very, very long way," she said.
Astronaut Ron Garan said the goal is to make space travel as routine as air travel.
"I think the more people that can get the experience of looking back on Earth and seeing how beautiful it is and seeing that we're all just riding on this fragile oasis through the solar system together, and that we're all in this together, I think the more people that can see that, I think the better off everybody is going to be," he said.
Garan said greater international cooperation is one of the enduring legacies of the past 50 years of human spaceflight.
"You look at us today, you know the six of us on board representing the 15 nations of the International Space Station partnership - and representing all the nation's of the world, really - and you see where we've come," he said.
Near Moscow, Russian President Dmitry Medvedev marked the 50th anniversary of Gagarin's flight with a call to the space station's crew. Mr. Medvedev called space exploration a Russian priority, and said his country will continue to invest its resources there. He said he is confident that space exploration has, what he called, "a gigantic future."
NASA is preparing for the future of its soon-to-be-retired shuttle fleet. The U.S. space agency plans to focus on developing the next generation of spacecraft that can venture to asteroids or Mars.
During Tuesday's ceremony at the Kennedy Space Center, NASA Administrator Bolden announced the institutions that will receive the retired space shuttles. The Kennedy Space Center in Florida will get Atlantis. Endeavour will be displayed near Los Angeles at the California Science Center. Discovery's new home will be at the Smithsonian Air and Space Museum's annex just outside of Washington. The Intrepid Sea, Air and Space Museum in New York City will get Enterprise, which was the first full-scale test vehicle of the shuttle program.
The shuttles Challenger and Columbia were lost in accidents in 1986 and 2003, respectively.