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  • The Blue Marble


    rightThe Blue Marble is an image of planet Earth taken on December 7, 1972, by the crew of the Apollo 17 spacecraft at a distance of about from the surface. It is one of the most reproduced images in history. The image has the official NASA designation AS17-148-22727 and shows the Earth from the point of view of the Apollo crew travelling towards the Moon. The translunar coast photograph extends from the Mediterranean Sea to Antarctica. This was the first time the Apollo trajectory made it possible to photograph the south polar ice cap, despite the Southern Hemisphere being heavily covered in clouds. In addition to the Arabian Peninsula and Madagascar, almost the entire coastline of Africa is clearly visible. The Asian mainland is on the horizon. The name has also been applied by NASA to a 2012 series of image data sets covering the entire globe at relatively high resolution, created by carefully sifting through satellite-captured sequences taken over time, to eliminate as much cloud cover as possible from the collated set of images.

  • Satellite


    NASA's Earth-observing fleet as of June 2012. A full-size model of the Earth observation satellite ERS 2 In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as Earth's Moon. In 1957 the Soviet Union launched the world's first artificial satellite, Sputnik 1. Since then, about 8,100 satellites from more than 40 countries have been launched. According to a 2018 estimate, some 4,900 remain in orbit, of those about 1,900 were operational; while the rest have lived out their useful lives and become space debris. Approximately 500 operational satellites are in low-Earth orbit, 50 are in medium-Earth orbit (at 20,000 km), and the rest are in geostationary orbit (at 36,000 km). A few large satellites have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few asteroids, a comet and the Sun. Satellites are used for many purposes. Among several other applications, they can be used to make star maps and maps of planetary surfaces, and also take pictures of planets they are launched into. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and space telescopes. Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways. Well-known (overlapping) classes include low Earth orbit, polar orbit, and geostationary orbit. A launch vehicle is a rocket that places a satellite into orbit. Usually, it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, or aboard a plane (see air launch to orbit). Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control and orbit control.

  • Satellite imagery


    The first images from space were taken on the sub-orbital V-2 rocket flight launched by the U.S. on October 24, 1946.Satellite imagery (also Earth observation imagery or spaceborne photography) are images of Earth or other planets collected by imaging satellites operated by governments and businesses around the world. Satellite imaging companies sell images by licensing them to governments and businesses such as Apple Maps and Google Maps.

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