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Topic: Earth orbit

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High Earth Orbit

Intermediate circular orbit

Low Earth orbit

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Geostationary transfer orbit

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	Low Earth orbit - Wikipedia, the free encyclopedia
		A low Earth orbit (LEO) is an orbit around Earth between the atmosphere and the Van Allen radiation belt, with a low angle of inclination.
		Orbits higher than this are subject to early electronic failure because of intense radiation and charge accumulation.
		Orbits with a higher inclination angle are usually called polar orbits.
	en.wikipedia.org /wiki/Low_Earth_orbit (472 words)

	Earth orbit - Wikipedia, the free encyclopedia
		Earth orbit is an orbit around the planet Earth.
		Artificial satellites are launched into Earth orbit, and spacecraft bound for other locations in the solar system usually begin their missions by first attaining Earth orbit, before altering course to another planet, moon, or heliocentric (solar) orbit.
		Of special interest are LEO (Low Earth Orbit), HEO (High Earth Orbit) and geosynchronous orbit.
	en.wikipedia.org /wiki/Earth_orbit (97 words)

	Footprints by Dish Size - Definition of Geostationary (Geosynchronous), Polar, LEO, HEO, MEO, Sun Synchronous Orbits, ... (Site not responding. Last check: 2007-10-06)
		While there are special orbits that are designed for specific purposes, three general classes of orbits have come into wide spread use for observations of the earth and for microwave communication with the earth: Geostationary orbits, low earth orbits, (LEOs) and polar orbits.
		More technically, a geostationary orbit is a circular prograde orbit in the equatorial plane with an orbital period equal to that of the earth; this is achieved with an orbital radius of 6.6107 (equatorial) earth radii, or an orbital height of 35786 km.
		Radarsat is in orbit 798 kilometres above the Earth, at an angle of inclination of 98.6 degrees to the equator as it circles the globe from north pole to south pole.
	www.geo-orbit.org /sizepgs/geodef.html (6827 words)

	Earth
		In Roman Mythology, the goddess of the Earth was
		The Earth is 4.5 to 4.6 billion years old, but the oldest known rocks are about 4 billion years old and rocks older than 3 billion years are rare.
		Earth is the only planet on which water can exist in liquid form on the surface (though there may be liquid ethane or methane on Titan's surface and liquid water beneath the surface of Europa).
	seds.lpl.arizona.edu /nineplanets/nineplanets/earth.html (1605 words)

	NOAA Paleoclimatology Program - Orbital Variations and Milankovitch Theory
		If the earth's axis were "straight up and down" relative to the orbital plane, as in the right-hand image, there would be no seasons, since every point on the earth would receive the same amount of sun each day of the year.
		The earth's orbit around the sun is not quite circular, which means that the earth is slightly closer to the sun at some times of the year than others.
		The "roundness", or eccentricity, of the earth's orbit varies on cycles of 100,000 and 400,000 years, and this affects how important the timing of perihelion is to the strength of the seasons.
	www.ncdc.noaa.gov /paleo/milankovitch.html (862 words)

	Tutorial on Earth/Sun Relations and Seasons
		The inclination of the Earth's axis means that at different locations on its orbit around the sun, different parts of the earth are tilted toward the sun, and the part that is tilted toward the sun is the part that is having summer.
		Since the earth's axis is tilted 23 ½ degrees, then on this particular day, the sun's rays are striking the earth directly at a latitude approximately 23 ½ degrees north of the equator (that is, the sun's rays are coming in at an angle of 90 degrees here; this is the subsolar point).
		The southern hemisphere of the earth is tilted toward the sun, and the sun's rays are perpendicular to the earth's surface at 23 ½ degrees south.
	daphne.palomar.edu /jthorngren/tutorial.htm (2228 words)

	About Spitzer: Innovative Orbit
		An important breakthrough in the redesign of Spitzer was to abandon the idea of placing the observatory into Earth orbit and instead to insert it into an Earth-trailing heliocentric orbit.
		The drifting heliocentric orbit places Spitzer in "deep space," where the ambient temperatures are about 30 to 40 K. By using Nature to assist in cooling the Observatory, Spitzer can carry much less liquid helium cryogen than it would need in an Earth orbit.
		A consequential benefit of the solar orbit is that Spitzer will have a large instantaneous view of the celestial sky.
	www.spitzer.caltech.edu /about/orbit.shtml (483 words)

	The Seasons and the Earth's Orbit - Milankovitch Cycles (Site not responding. Last check: 2007-10-06)
		We have all been taught that the seasons are caused by the tilt of the Earth's axis of rotation - the 23.4° offset of the axis from a direction perpendicular to the Earth's orbital plane.
		The Earth's orbit is an ellipse, and there is a slow change in its orientation, which gradually shifts the point of perihelion in space.
		The mechanism by which the Earth's orbital eccentricity could affect the climate in such a direct and important way is not known, although recent evidence (published in 2000) indicates that atmospheric carbon dioxide may play a leading role in amplifying the orbital effect.
	aa.usno.navy.mil /faq/docs/seasons_orbit.html (1561 words)

	6(h). Earth-Sun Geometry
		The Earth's axis is not perpendicular to the plane of the ecliptic, but inclined at a fixed angle of 23.5°.
		During the summer solstice the Earth's North Pole is tilted 23.5° towards the sun relative to the circle of illumination.
		During the equinoxes, the axis of the Earth is not tilted toward or away from the sun and the circle of illumination cuts through the poles.
	www.physicalgeography.net /fundamentals/6h.html (1627 words)

	Definition of Low Earth orbit
		A low Earth orbit (LEO) is an orbit in which objects such as satellites are below intermediate circular orbit (ICO) and far below geostationary orbit, but typically around 350 - 1400 km above the Earth's surface.
		A low earth orbit is a stepping-stone to travel beyond orbit but it is also very useful for communication satellites because of its proximity to Earth.
		Although gravity at the height concerned is by itself not much less than on the surface of the Earth (it reduces 1% every 30 km), people and objects in orbit are weightless (see article).
	www.wordiq.com /definition/Low_Earth_orbit (375 words)

	THE EARTH - ENCHANTED LEARNING SOFTWARE
		The Earth is closest to the Sun (this is called perihelion) around January 2 each year (91.4 million miles = 147.1 million km); it is farthest away from the Sun (this is called aphelion) around July 2 each year (94.8 million miles = 152.6 million km).
		The Earth's axis is tilted from perpendicular to the plane of the ecliptic by 23.45°.
		The Earth's atmosphere is a thin layer of gases that surrounds the Earth.
	www.enchantedlearning.com /subjects/astronomy/planets/earth (929 words)

	Near Earth Object Map (Site not responding. Last check: 2007-10-06)
		The terrestrial planets (Mercury, Venus, Earth and Mars) are shown on the diagram by Cyan or White squares, and their orbits are represented by the blue ellipses around the Sun (the yellow dot at the centre).
		However, their orbits are close enough to the Earth that they could potentially be perturbed by the influence of the planets and begin to cross the Earth's orbit in a short time.
		These cross the Earth's orbit and are the most directly identifiable astronomical threat for the near future.
	szyzyg.arm.ac.uk /~spm/neo_map.html (568 words)

	Earth's Orbit (Site not responding. Last check: 2007-10-06)
		This orbit is highly regular, but there do exist tiny variations in it that affect the amount of heat received from the Earth by the Sun, and therefore the Earth's climate.
		These variations occur over tens and hundreds of thousands of years, and are believed to explain the switching of the Earth's climate between Ice Ages and warmer periods.
		Currently the Earth's climate lies in a warm period, but some scientists believe that the next Ice Ages is not too far away.
	www.ace.mmu.ac.uk /eae/Climate_Change/Younger/Earths_Orbit.html (99 words)

	Near-Earth Asteroid 3753 Cruithne
		The near-Earth asteroid 3753 Cruithne is in an unusual orbit about that of the Earth, one which is known in the lingo of celestial mechanics as being co-orbital with the Earth (meaning it shares the Earth's orbit with it) and, more particularly, as being of the "horseshoe" type.
		Though the asteroid thus appears to orbit the Earth, this is a result of the frame of reference we are using.
		Also note that the presence of the Earth at the centre of the kidney is simply a result of their mutual synchronization: the Earth is lined up with the asteroid and Sun when the asteroid is at perihelion (its closest approach to the Sun).
	www.astro.uwo.ca /~wiegert/3753/3753.html (2229 words)

	Earth Orbit
		All geostationary satellites orbit the Earth equatorially (in an east-west circle) at a height of approximately 22,237 miles.
		Other satellite orbits are equatorial (east-west circle), polar (north-south circle) and elliptical, the latter having an orbit that changes drastically in altitude during a single orbit.
		Many polar orbits are calculated to be solar synchronous, meaning that the plane of the orbit remains at a constant angle to the light of the sun.
	dolio.lh.net /~apw/astro/orbit.html (1224 words)

	Earth's Orbit (Site not responding. Last check: 2007-10-06)
		The most important thing, first of all, is the fact that Earth is Earth, not Mercury--meaning our planet is at just the right distance from our sun to support life.
		Well, even with 4.6 billion years to move, the earth's orbit is remarkably stable, meaning it would not move a much as the sun's diameter would change.
		This brief study of Earth's solar orbit and our sun's lifespan is evidence enough of why we must question evolution, rather than accept it religiously, along with all supposed "proof" that supports it.
	www.feltd.com /orbit.html (844 words)

	Eyes on the Sky, Feet on the Ground: Chapter Two
		As the Earth orbits the Sun, the orientation of its rotational axis is held fixed, so that if we imagine it extended into space, it is always pointing towards Polaris, the pole star.
		As the Earth orbits around the Sun, for a portion of the year the Sun is in the same direction as the tilt happens to be.
		Because the Earth's orbit around the Sun is not perfectly circular, the Sun's position at a specific time (as given by the clock) changes Eastwardly and Westerwardly as well.
	hea-www.harvard.edu /ECT/the_book/Chap2/Chapter2.html (4287 words)

	SPACE.com -- More Moons Around Earth? Its Not So Loony (Site not responding. Last check: 2007-10-06)
		Earth has a second moon, of sorts, and could have many others, according to three astronomers who did calculations to describe orbital motions at gravitational balance points in space that temporarily pull asteroids into bizarre orbits near our planet.
		Cruithne, discovered in 1986, and then found in 1997 to have a highly eccentric orbit, cannot be seen by the naked eye, but scientists working at Queen Mary and Westfield College in London were intrigued enough with its peregrinations to come up with mathematical models to describe its path.
		A moon typically is defined as an object whose orbit encompasses a planet, say, the Earth, rather than the sun, said Carl Murray, who worked with Namouni and Christou on the research.
	www.space.com /scienceastronomy/solarsystem/second_moon_991029.html (1148 words)

	Low Earth Orbit
		As the celebration of the Earth’s orbit around the Sun is a major part of my own spiritual life, it seemed only appropriate that something special accompany the Solstice, particularly as it marked the "flipping of the calendar" in the grand countdown to the Eschaton, from fourteen years and a bit, to thirteen and change.
		By this, I mean to say that I study the way the Earth is coming to an end, a final culmination and consummation of the grand experiment of life.
		The End of History is not the End of Earth, for this vision did not end as a view of Earth in space, at long last united with its human component; that vision I had had before, and have had repeatedly over the last decade.
	www.hyperreal.org /~mpesce/lowearth.html (6454 words)

	BBC News \| SCI/TECH \| Planet Earth on the move
		To expand the Earth's orbit around the Sun at a rate that compensates for the increasing brightness of the star would require an asteroid encounter every 6,000 years, or about every 240 generations.
		Earth's gradual outward migration may require adjustments to be made to the orbits of other planets as well.
		However, "as a way of preserving the entire biosphere of the Earth, this method is promising and efficient," they say.
	news.bbc.co.uk /hi/english/sci/tech/newsid_1154000/1154784.stm (640 words)

	CNN.com - Sci-Tech - Space - Astronomers hatch plan to move Earth's orbit from warming sun - February 5, 2001
		One million encounters would move the Earth out 41 million miles, or about 50 percent farther from the sun than it is today.
		But the researchers say that if the technique is repeated an average of every 6,000 years, the orbit could be increased to keep pace with the Sun's increasing brightness.
		Another possible side effect of shooting such a large object past Earth, the scientists say, would be to increase the planet's rotation.
	archives.cnn.com /2001/TECH/space/02/05/earth.move (503 words)

	Milankovitch Cycles
		The episodic nature of the Earth's glacial and interglacial periods within the present Ice Age (the last couple of million years) have been caused primarily by cyclical changes in the Earth's circumnavigation of the Sun.
		When the Earth's orbit is most elliptical the amount of solar energy received at the perihelion would be in the range of 20 to 30 percent more than at aphelion.
		Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth's axis in relation to its plane of orbit around the Sun.
	www.homepage.montana.edu /~geol445/hyperglac/time1/milankov.htm (849 words)

	BBC NEWS \| Science/Nature \| Earth's little brother found
		But it shares the Earth's orbit around the Sun, at first on one side of the Earth and then escaping to travel along our planet's path around the Sun until it encounters the Earth from the other side.
		It is clear that 2002 AA29 was discovered by accident at a time when it was at one end of its horseshoe orbit and, being at its closest to the Earth, was bright enough to be detected in an automated sky survey.
		Some have speculated that it could be nudged into a permanent Earth orbit where it could be studied at greater length.
	news.bbc.co.uk /1/hi/sci/tech/2347663.stm (645 words)

	Earth and Moon Viewer
		In addition to the Earth, you can also view the Moon from the Earth, Sun, night side, above named formations on the lunar surface.
		The Earth and Moon Viewer would have been enormously more difficult to implement without the help of the software and imagery mentioned in the credits.
		Home Planet, Earth screen saver, Sky screen saver, Moontool, Craters screen saver, and an Excel catalogue of the Palomar Observatory Sky Survey.
	www.fourmilab.ch /earthview/vplanet.html (335 words)

	Aphelion Away!
		In fact, if you drew Earth's orbit on a sheet of paper it would be difficult to distinguish from a perfect circle.
		"Earth's temperature (averaged over the entire globe) is slightly higher in July because the Sun is shining down on all that land, which heats up rather easily," says Spencer.
		Daily Earth Temperatures from Satellites -View global atmospheric temperature trends at different layers of the atmosphere, courtesy of the Global Hydrology and Climate Center.
	science.nasa.gov /headlines/y2001/ast03jul_1.htm (1115 words)

	SORCE
		Solar radiation is the dominant, direct energy input into the terrestrial ecosystem; and it affects all physical, chemical, and biological processes.
		Data obtained by the SORCE experiment will be used to model the Sun's output and to explain and predict the effect of the Sun's radiation on the Earth's atmosphere and climate.
		It launched into a 645 km, 40 degree orbit and is operated by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado (CU) in Boulder, Colorado, USA.
	lasp.colorado.edu /sorce (475 words)

	USATODAY.com - Sun too close? We'll just change Earth's orbit (Site not responding. Last check: 2007-10-06)
		Anyone worried about the sun frying Earth sometime in the next billion years can rest easy: Astronomers have devised a way to move our planet to a safer orbit.
		The researchers say mankind will need a scheme like this to save Earth's atmosphere from the heat of the sun, predicted to grow 11% hotter over the next 1.1 billion years.
		A miscalculation might send the 62-mile-wide asteroid slamming into Earth, which "would sterilize the biosphere most effectively, at least to the level of bacteria," the astronomers warn.
	www.usatoday.com /news/science/astro/2001-02-15-orbit.htm (474 words)

	Low Earth orbit microsatellites for data communications using small terminals
		The orbital inclination, the angle between the orbital and the equatorial plane, determines the extent of coverage of the earth's surface and also the frequency of visibility for a given latitude.
		The polar sun-synchronous circular orbit which is a common low Earth orbit choice for remote sensing satellites has a number of advantages for simple communications services.
		Each of the microsatellites currently in-orbit is routinely used to evaluate the interference profile in the uplink channels.
	www.ee.surrey.ac.uk /SSC/CSER/UOSAT/papers/icdsc10/icdsc10.html (3294 words)

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