Space probes are space missions with robotic spacecraft. Space probes leave the vicinity of the Earth and approach the moon or enters interplanetary space. Space agencies of the Soviet Union, the United States, Europe, Russia, and Japan have all launched space probes to other planets in the Solar System, and to several asteroids and comets.
Types of space probes.
A space probe destined for a planet or other astronomical body can be classified as a "flyby," "impactor," "orbiter," or "lander" mission. Historically, flyby missions proved easiest to accomplish, as they did not require the precise navigation needed for an impact, nor the need for additional propulsion to conduct a maneuver to enter orbit. Upon landing some landers have released "rovers" which travel across the surface of the astronomical body upon which they have landed.
Interplanetary trajectories of space probes.
Once a probe has left the vicinity of Earth, its trajectory will likely take it along an orbit around the Sun similar to the Earth's orbit. To reach another planet, the conceptually simplest means is to execute a Hohmann transfer orbit maneuver. More complex techniques, such as gravitational slingshots, can be more efficient, though the may require the probe to spend more time in transit. A technique using very little propulsion, but possibly requiring a considerable amount of time, is to follow a trajectory on the Interplanetary Transport Network.
Some notable space probes.
The first successful space probe was the Soviet Luna 1 flyby of the Moon in 1959. Luna 1 reached the escape velocity of the Earth, and passed within 5,995 km (3,725 mi) of the Moon's surface after 34 hours of flight. It then went into orbit around the Sun, between the orbits of Earth and Mars.
Huygens space probe:
The Huygens probe was a lander constructed by the European Space Agency (ESA) and launched as part of the Cassini-Huygens mission to Saturn's moon Titan. Huygens separated from the Cassini orbiter on December 25, 2004, and landed on Titan on January 14, 2005. It returned 350 pictures from the surface.
Space probe Spirit and Opportunity:
The Mars Exploration Rovers, Spirit and Opportunity landed on Mars to explore the Martian surface and geology, and search for and clues to past water activity on Mars. They were each launched in 2003 and landed in 2004. As of January 24, 2007, both Spirit and Opportunity have lasted for more than three years on Mars--when they were intended to last only three months. On February 6, 2007, Opportunity had traversed more than 10 km (6.2 mi) on the surface of Mars.
Space probe Voyager 1:
Voyager 1 is an 815-kilogram probe launched September 5, 1977. It is Currently still operational, making it the longest-lasting mission of the U.S. National Aeronautics and Space Administration (NASA). It visited Jupiter and Saturn and was the first probe to provide detailed images of the moons of these planets.
Voyager 1 is the farthest human-made object from Earth, travelling away from both the Earth and the Sun at a relatively faster speed than any other probe. As of August 12, 2006, Voyager 1 is over 14.96 terameters (14.96×1012 meters, or 14.96×109 km, 100 AU, or 9.3 billion miles) from the Sun. At this distance, signals from Voyager 1 take more than thirteen hours to reach its control center at the Jet Propulsion Laboratory. Voyager 1 has achieved solar escape velocity, meaning that its trajectory will not return it to the solar system.
Along with Pioneer 10, Pioneer 11, and its sister ship Voyager 2, Voyager 1 is an interstellar probe.
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