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The B612 Foundation is a private nonprofit foundation with headquarters in the United States, dedicated to planetary defense against asteroids and other near-Earth object (NEO) impacts. It is led mainly by scientists, former astronauts and engineers from the Institute for Advanced Study, Southwest Research Institute, Stanford University, NASA and the space industry. As a non-governmental organization it has conducted two lines of related research to help detect NEOs that could one day strike the Earth, and find the technological means to divert their path to avoid such collisions. The organization has publicized the true rate of "city-killer" type impacts of the same magnitude as the explosive 1908 Tunguska event, a rate which is from three to ten times greater than previously believed, or about every century on average. It also assisted the Association of Space Explorers in helping the United Nations establish the International Asteroid Warning Network, as well as a Space Missions Planning Advisory Group to provide oversight on proposed asteroid deflection missions. In 2012, the foundation announced it would design and build a privately financed asteroid-finding space observatory, the Sentinel Space Telescope, to be launched in 2017–2018. Once stationed in a heliocentric orbit around the Sun similar to that of Venus, Sentinel's supercooled infrared detector will help identify dangerous asteroids and other NEOs that pose a risk of collision with Earth. In the absence of substantive planetary defense provided by governments worldwide, B612 is conducting a fundraising campaign to cover the Sentinel Mission, estimated at $450 million for 10 years of operation. Fund raising has been very slow—raising only in 2012 and 2013—and, as of June 2015, NASA is re-examining its reliance on private sector approach to space-based NEO survey missions.〔 The B612 Foundation is named for the asteroid home of the eponymous hero of Antoine de Saint-Exupéry's ''The Little Prince''. == Background == When an asteroid enters the planet's atmosphere it becomes known as a 'meteor'; those that survive and fall to the Earth's surface are then called 'meteorites'. While basketball-sized meteors occur almost daily, and compact car-sized ones about yearly, they usually burn up or explode high above the Earth as bolides, (fireballs), often with little notice. During an average 24-hour period, the Earth sweeps through some 100 million particles of interplanetary dust and pieces of cosmic debris, only a very minor amount of which arrives on the ground as meteorites.〔 The larger in size an asteroid or other near-Earth object (NEO), the less frequently it impacts the planet's atmosphere — large meteors seen in the skies are extremely rare, while medium-sized ones are less so, and much smaller ones are more commonplace. Although stony asteroids often explode high in the atmosphere, some objects, especially iron-nickel meteors and other types descending at a steep angle,〔 can explode close to ground level or even directly impact onto land or sea. In the U.S. State of Arizona, the -wide Meteor Crater (officially named Barringer Crater) formed in a fraction of a second as nearly 160 million tonnes of limestone and bedrock were uplifted, creating its crater rim on formerly flat terrain. The asteroid that produced the Barringer Crater was only about 46 meters (150 ft.) in size; however it impacted the ground at a velocity of 12.8 kilometers per second (28,600 mph) and struck with an impact energy equivalent to a 10 megaton (TNT equivalent) nuclear bomb — about 625 times greater than the bomb that destroyed the city of Hiroshima during the Second World War.〔〔 Tsunamis can also occur after a medium-sized or larger asteroid impacts an ocean surface or other large body of water.〔 The probability of a mid-sized asteroid (similar to the one that destroyed the Tunguska River area of Russia in 1908) hitting Earth during the 21st century is now estimated at about 30%. Since the Earth is currently more populated than in previous eras, there is a greater risk of large casualties arising from a mid-sized asteroid impact.〔 However, as of the early 2010s, only about a half of one per cent of Tunguska-type NEOs had been located by astronomers using ground-based telescope surveys.〔 The need for an asteroid detection program has been compared to the need for monsoon, typhoon, and hurricane preparedness.〔〔 As the B612 Foundation and other organizations have publicly noted, of the different types of natural catastrophes that can occur on our planet, asteroid strikes are the only one that the world now has the technical capability to prevent. B612 is one of several organizations to propose detailed dynamic surveys of NEOs and preventative measures such as asteroid deflection.〔〔 Other groups include Chinese researchers, NASA in the United States, NEOShield in Europe, as well as the international Spaceguard Foundation. In December 2009 Roscosmos Russian Federal Space Agency director Anatoly Perminov proposed a deflection mission to the 325 metres (1,066 ft) wide asteroid 99942 Apophis, which at the time had been thought to pose a risk of collision with Earth.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「B612 Foundation」の詳細全文を読む スポンサード リンク
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