Redstone rocket to propel a satellite -- Explorer 1 -- into Earth's orbit. Explorer 1 carried instrumentation to detect cosmic rays and revealed, in an experiment led by James Van Allen of the University of Iowa, a much lower cosmic ray count than expected.
This led to the discovery of two doughnut-shaped zones eventually named for Van Allen filled with charged particles trapped by Earth's magnetic field. Bolstered by these successes, several companies raced to develop and deploy satellites in the s. One of these was Hughes Aircraft and its star engineer Harold Rosen. Rosen led a team that turned Arthur C. Clarke's concept -- a communications satellite positioned in Earth's orbit so it could bounce radio waves from one location to another -- into a feasible design.
In July , Rosen and his colleagues watched as Syncom 2 soared into space and navigated into a roughly geosynchronous orbit.
President Kennedy used the new system to have a conversation with the Nigerian prime minister in Africa you can listen here. This was followed by Syncom 3, which could actually broadcast television. Sputnik's transmissions died along with its battery after only three weeks, but its effects have been felt for decades.
We can see fires around the world and determine the altimetry of water and waves from space. Site Map Contact Us. March 31, Credit: NASA. Recent News. While some satellites are best used around the equator, others are better suited to more polar orbits — those that circle the Earth from pole to pole so that their coverage zones include the north and south poles. Examples of polar-orbiting satellites include weather satellites and reconnaissance satellites. There are an estimated half-million artificial objects in Earth orbit today , ranging in size from paint flecks up to full-fledged satellites — each traveling at speeds of thousands of miles an hour.
Only a fraction of these satellites are useable, meaning that there is a lot of "space junk" floating around out there. With everything that is lobbed into orbit, the chance of a collision increases. Space agencies have to consider orbital trajectories carefully when launching something into space. Agencies such as the United States Space Surveillance Network keep an eye on orbital debris from the ground, and alert NASA and other entities if an errant piece is in danger of hitting something vital.
This means that from time to time, the ISS needs to perform evasive maneuvers to get out of the way. Collisions still occur, however. One of the biggest culprits of space debris was the leftovers of a anti-satellite test performed by the Chinese, which generated debris that destroyed a Russian satellite in Also that year, the Iridium 33 and Cosmos satellites smashed into each other, generating a cloud of debris.
NASA, the European Space Agency and many other entities are considering measures to reduce the amount of orbital debris. Some suggest bringing down dead satellites in some way , perhaps using a net or air bursts to disturb the debris from its orbit and bring it closer to Earth.
Others are thinking about refueling dead satellites for reuse, a technology that has been demonstrated robotically on the ISS. Most planets in our solar system have natural satellites, which we also call moons. For the inner planets: Mercury and Venus each have no moons.
Earth has one relatively large moon, while Mars has two asteroid-sized small moons called Phobos and Deimos. Phobos is slowly spiralling into Mars and will likely break apart or fall into the surface in a few thousand years. Beyond the asteroid belt, are four gas giant planets that each have a pantheon of moons. As of late , Jupiter has 69 known moons, Saturn has 53, Uranus has 27 and Neptune has 13 or New moons are occasionally discovered — mainly by missions either past or present, as we can analyze old pictures or by performing fresh observations by telescope.
Saturn is a special example because it is surrounded by thousands of small objects that form a ring visible even in small telescopes from Earth. Scientists watching the rings close-up over 13 years, during the Cassini mission , saw conditions in which new moons might be born.
Scientists were particularly interested in propellers, which are wakes in the rings created by fragments in the rings.
Islamic astronomer Ibn al-Shatir — of the Maragha school accepts the geocentric model but produces configurations that challenge the Ptolemaic model. His calculations are similar to the later calculations of Copernicus. Polish astronomer Copernicus — proposes that the Sun is stationary in the centre of the Universe and the Earth and other planets revolve around it. The church suppresses this controversial idea but it revolutionises astronomy.
Danish astronomer Tycho Tyge Brahe — designs and builds instruments that allow him to accurately observe stellar and planetary positions. His records of the motion of Mars are later used by Kepler. His discoveries prove the Copernican heliocentric system. The Roman Inquisition finds him guilty of heresy. He develops the three laws of planetary motion, and his accurate astronomical tables provide evidence for the Copernican heliocentric model. Sir Isaac Newton — publishes Principia in which he states the three laws of motion and describes universal gravity.
This lays the foundation for our understanding of rockets, satellites and orbits. Russian Konstantin Tsiolkovsky — proposes using rocketry to launch spacecraft.
He also describes a space station in detail and the use of orbiting spacecraft for detailed observation of the Earth and scientific experiments. British science fiction writer and inventor Arthur C Clarke — publishes an article that shows how geostationary satellites could be used for worldwide radio and television broadcasts and communication.
The Soviet Union launches Sputnik, the first artificial satellite to orbit around the Earth.
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