Near-Earth asteroids

Chart of near-Earth asteroids

Since February 2011, the mission of NASA NEOWISE, dedicated to research in the infrared small body, has completed its investigation of asteroids and comets in our solar system.
NEOWISE discovered 20 comets, more than 33 000 asteroids in the main belt between Mars and Jupiter, and 134 near-Earth objects (NEO).
The NEO are asteroids or comets with orbits of less than 1.3 AU, ie, they can approach within 45 million miles from the path of the Earth.
The new model representing the cover of NEOs is presented to the left of the image.
We can thus compare it with the old model, which estimates in the visible, were higher (right image).
NEOWISE observations can be reduced by 40%, the actual number of near-Earth asteroids that exceed 100 meters. The observations in the infrared NEOWISE are more accurate than those obtained previously in visible light because asteroids of similar size emit roughly the same amount of infrared radiation, as they reflect a highly variable quantity of visible light depending on their albedos.
The results of NEOWISE can redefine the number of asteroids Sizeable, from 35 000 to 19 500, however, the majority of objects still to be discovered.

Image: Representation of the inner solar system where each red dot represents one asteroid. Of course the sizes of objects are not to scale.

WISE

Space Telescope WISE (Widefield Infrared Survey Explorer) is a satellite carrying an infrared telescope designed to photograph sensitive the entire sky. One of its objectives is to detect the infrared asteroids in the solar system and of course the Near Earth Objects.
As the infrared observations are sensitive to temperature, the telescope WISE and its detectors are kept at very cold temperatures (258º C, only 15º Celsius above absolute zero) by a cryostat filled with solid hydrogen at instead of ice.
Solar panels that always point to the Sun, which provide electricity for the satellite needs to function.
WISE is in orbit above the dividing line between night and day on Earth, the telescope is on a right angle to the sun and Earth.
The orbits of WISE, aligned to the North Pole to the South Pole, passing through the equator, can scan a strip of sky. As the Earth moves around the Sun, WISE scans the entire sky, after six months.
WISE capture an image of the sky every 11 seconds. Each image covers an area of the sky, three times larger than the full Moon.

Every six months, WISE is nearly 1,500,000 pictures covering the entire celestial sphere.
Each picture is taken in four different wavelengths. Data taken by WISE are sent by radio transmission, four times a day and downloaded to computers to group images that will produce an atlas covering the entire celestial sphere.

Image: Artist Image Space Telescope WISE (Widefield Infrared Survey Explorer)