Introduction to Space Exploration - Robotic Space Explorers
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Space programs centered on human explorers are very expensive. It is far cheaper to build and send mechanized (robotic) spacecraft to do the exploring. During the 1960s the Apollo program dominated the spotlight, but it was not the only space exploration project in operation.
Beginning in 1962 NASA launched robotic probes that flew by Mercury, Venus, or Mars and beamed back photographs of them. During the 1970s more sophisticated robotic spacecraft landed on Mars or were sent to fly by the outer planets (Jupiter, Saturn, Uranus, Neptune, and Pluto). These missions were given heroic names, including Mariner, Viking, and Voyager.
In 1990 a robotic spacecraft called Magellan set down on the surface of Venus. It was named after Ferdinand Magellan (c. 1480–1521), the Portuguese explorer who led the first sailing expedition to circle the world. In 1995 a spacecraft named after Galileo Galilei began orbiting Jupiter.
Interplanetary exploration is tough, even for machines. During the 1990s NASA lost three robotic spacecraft on their way to Mars. Another one safely made it to the Martian surface. In the early 2000s NASA sent two more missions to Mars. The first was called Mars Odyssey and included a probe that went into orbit around the planet in 2001. It was joined two years later by a European Space Agency (ESA) probe called the Mars Express. Unfortunately, a lander from this mission was lost on its way to the surface. In 2004 NASA's Mars Exploration spacecraft successfully put down two rovers on Mars named Spirit and Opportunity. As of February 2006 these two rovers continued to explore the surface of Mars while the three surviving orbiters circled overhead.
In 2004 NASA's Cassini spacecraft went into orbit around Saturn after a seven-year journey from Earth. The orbiter released the ESA-provided Huygens probe, which provided the first-ever close-up photographs of Titan, Saturn's largest moon. In 2005 two new robotic missions were launched toward other planets: NASA's Mars Reconnaissance Orbiter and the ESA's Venus Express. They were expected to reach their destinations in 2006.
Not all space exploration requires long-distance travel. Advances in computers and telescopes have allowed scientists to do a lot of exploring with robotic spacecraft stationed nearby Earth. Dozens of these high-technology machines take photographs, measure radiation waves, and collect data on galactic and solar phenomena.
The latest generation of robotic explorers are designed to snatch samples in outer space and return them to Earth. The first such mission to return was conducted by a NASA spacecraft named Genesis. In 2004 it crash-landed in the Utah desert following an equipment malfunction during reentry. Fortunately, some of its valuable cargo was saved—samples of the solar wind (charged particles emitted from the sun) collected a million miles from Earth. Also in 2004 the NASA spacecraft Stardust sailed nearby the comet Wild 2 as it journeyed around the sun. Stardust collected dust particles believed to be 4.5 billion years old and returned them safely to Earth in January 2006.
In November 2005 Japan's Hayabusa spacecraft landed on the asteroid Itokawa between Earth and Mars to collect dust samples. Equipment and communication problems have plagued the mission, and scientists are hopeful, but not certain, that the samples were collected and will return to Earth in 2010.