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Topic: Polar orbit

	Polar orbit (Site not responding. Last check: 2007-10-16)
		A polar orbit is a satellite orbit that passes over, or very close to, both poles of the Earth.
		Polar orbits are 90-degree inclination orbits, meaning that the orbit is at 90-degrees to the plane of the equator.
		This type of orbit is useful for spacecraft that perform mapping or surveillance operations, such as the NOAA Tiros satellites and the Landsat satellites.
	www.centennialofflight.gov /essay/Dictionary/POLAR_ORBIT/DI154.htm (155 words)

	Satellite Orbits
		The satellite orbits at an elevation of approximately 35,790 km because that produces an orbital period (time for one orbit) equal to the period of rotation of the Earth (23 hrs, 56 mins, 4.09 secs).
		Because a geostationary orbit must be in the same plane as the Earth's rotation, that is the equatorial plane, it provides distorted images of the polar regions with poor spatial resolution.
		These orbits may be determined by the region on Earth that is of most interest (i.e., an instrument to study the tropics may be best put on a low inclination satellite), or by the latitude of the launch site.
	asd-www.larc.nasa.gov /SCOOL/orbits.html (496 words)

	RS:Principles: Sensors
		An orbit with an inclination angle of 90º would orbit the Earth crossing the North and South Poles in a plane that is perpendicular to the equatorial plane.
		Polar orbits are usually nearly circular and the satellites have a constant height above the planet.
		The lower altitude of the polar orbits can allow the sensors to study the Earth in greater detail than a higher altitude craft, and it is far less expensive to build, launch, and maintain than a higher altitude satellite.
	chesapeake.towson.edu /data/orbits3.asp (616 words)

	Footprints by Dish Size - Definition of Geostationary (Geosynchronous), Polar, LEO, HEO, MEO, Sun Synchronous Orbits, ...
		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)

	Polar Orbiting Satellites
		Due to the rotation of the Earth, it is possible to combine the advantages of low-altitude orbits with global coverage, using near-polar orbiting satellites, which have an orbital plane crossing the poles.
		A dawn-dusk orbit is a special case of a sun-synchronous orbit in which a satellite perpetually trails the shadow of the Earth cast by the Sun.
		It passes over polar regions on every orbital period (remember, the pole is a point), but much more rarely over the same equatorial regions (2 times a day for most current meteorological satellites; more generally it depends on the drift and the ground swath).
	tornado.sfsu.edu /Geosciences/classes/m490_790/Monteverdi/Satellite/PolarOrbiter/Polar_Orbits.html (1172 words)

	ESA - Launchers Home - Types of orbits
		A geostationary orbit, often referred to as a GEO orbit, circles the Earth above the equator from west to east at a height of 36 000 km.
		The orbital track of the satellite does not have to cross the poles exactly for an orbit to be called polar, an orbit which passes within 20 to 30 degrees of the poles is still classed as a polar orbit.
		Generally these orbits are used for Earth observation, solar study, weather forecasting and reconnaissance, as ground observation is improved if the surface is always illuminated by the Sun at the same angle when viewed from the satellite.
	www.esa.int /SPECIALS/Launchers_Home/ASEHQOI4HNC_0.html (509 words)

	Basics of Space Flight Section I. The Environment of Space
		Polar orbits are 90 degree inclination orbits, useful for spacecraft that carry out mapping or surveillance operations.
		A polar orbit will not be able to take advantage of the "free ride" provided by Earth's rotation, and thus the launch vehicle must provide all of the energy for attaining orbital speed.
		A walking orbit whose parameters are chosen such that the orbital plane precesses with nearly the same period as the planet's solar orbit period is called a sun synchronous orbit.
	www2.jpl.nasa.gov /basics/bsf5-1.html (1166 words)

	SatMet - Polar Orbit
		Polar orbiting satellites travel in a circular orbit moving from pole to pole.
		The basic operational mode deploys two polar orbiting satellites continuously, one passing north to south (descending) and the other passing south to north (ascending), circling the earth every 12 hours.
		Polar Orbiting Satellites are inserted into sun-synchronous orbits which place the spacecraft in a relatively constant relationship to the sun so that the ascending node will remain at a constant solar time, permitting images and data to be received by direct broadcast at the same time each day.
	cimss.ssec.wisc.edu /satmet/modules/sat_basics/polar_orbit.html (208 words)

	Coverage and Orbits
		Geostationary orbits are circular orbits that are orientated in the plane of the Earth's equator.
		The "ascending" portion of the orbit corresponds to that portion of the orbit when the satellite is moving from south to north, while the "descending" part of the orbit corresponds to north to south movement.
		Since polar orbiting satellites are naturally of particular importance in polar regions (due to a combination of poor coverage by geostationary satellites and the frequent overflights of the satellites) it is useful to look at the orbits in a polar stereographic point of view.
	www.rap.ucar.edu /~djohnson/satellite/coverage.html (2095 words)

	RS:Principles: Intro to Satellites and Orbits
		The amount of solar radiation present at polar latitudes is often insufficient for visible light sensors, limiting the use of passive detectors to lower latitudes.
		A satellite's orbit around the Earth is in the shape of an ellipse, and the Earth's center of mass is at one of the focal points of the ellipse.
		A geostationary satellite orbits the Earth in an equatorial orbit at an altitude where its period is equal to that of the Earth's rotation (24 hours).
	chesapeake.towson.edu /data/all_orbits.asp (2291 words)

	Polar orbit - Wikipedia, the free encyclopedia
		A satellite in a polar orbit passes above or nearly above both poles of the planet (or other celestial body) on each revolution.
		The disadvantage to this orbit is that no one spot on the Earth's surface can be sensed continuously using this orbiting method.
		To face one polar area a large part of the time, albeit at a large distance, an elliptic orbit with a high eccentricity with apogee above that area, is applied: a Molniya orbit.
	en.wikipedia.org /wiki/Polar_orbit (181 words)

	Polar Orbiting Satellites
		Different types of satellite orbits have different uses: while the synchronous orbit is best for communication satellites, Lagrangian point orbits help monitor the solar wind before it reaches Earth.
		Magnetic fields from the magnetosphere are a disturbing factor in such a mission, a factor that strongly depends on the orientation of the orbit relative to the Sun's direction.
		By placing the satellite in a sun-synchronous orbit near the dawn-dusk plane (90 degrees to the noon-midnight plane described earlier), not only was the interference kept small, but because the orbit's orientation relative to the Sun did not change, the disturbance also stayed more or less the same throughout the mission.
	www-istp.gsfc.nasa.gov /Education/wlopolar.html (917 words)

	Tech Museum \| Satellites \| Polar Orbits
		The only difference is that a satellite in polar orbit travels a north-south direction, rather than the more common east-west direction.
		Polar orbits are useful for viewing the planet's surface.
		We say that a polar orbit has an inclination, or angle, of 90 degrees.
	www.thetech.org /exhibits/online/satellite/4/4b/4b.1.html (138 words)

	The Polar Orbit (Site not responding. Last check: 2007-10-16)
		If a satellite were in a truly polar orbit, circling the globe at 90 degrees relative to the equator, it would move with the planet, experiencing different conditions throughout the year.
		However, if the orbit is tilted or inclined slightly away from a true north-south orbit, the asymmetric gravitational pull of the planet will cause a slow precession in the orbital plane.
		A further refinement of the sun-synchronous orbit is the dusk-to-dawn orbit.
	www.aero.org /publications/crosslink/winter2005/01_sidebar1.html (422 words)

	polar orbit
		An orbit at another inclination covers a smaller portion of the Earth, omitting areas around the poles.
		Placing a satellite into terrestrial polar orbit demands more energy, and therefore more propellant, than does achieving a direct orbit of low inclination.
		Since a polar orbit is not able to take advantage of the free ride provided by Earth’s rotation, the launch vehicle must provide all of the energy for attaining orbital speed.
	www.daviddarling.info /encyclopedia/P/polar_orbit.html (217 words)

	[No title] (Site not responding. Last check: 2007-10-16)
		A geostationary orbit is an orbit where the satellite appears to be stationary (hence the name) over one spot on the Earth.
		No, a geosync orbit with an inclination (relative to the equator) creates an eight-like groundtrack, with the top and th bottom of the eight being at a latitude with the same angle as the inclination.
		The lower the inclination, the greater the effect is, and at a true polar orbit it is zero.
	www.orbitersim.com /v2/read.asp?id=20195 (1246 words)

	Ulysses
		Ulysses has twice before orbited the Sun’s polar caps, first during a minimum in the number of sunspots and then when the sunspot number was at its maximum.
		During the first Ulysses orbit, the Sun’s magnetic poles were positive with outward fields in the north and negative or inward fields in the south.
		During Ulysses second orbit at sunspot maximum, the Sun’s polar fields disappeared and then reappeared with the opposite sense, negative or inward in the north and positive or outward in the south.
	ulysses.jpl.nasa.gov (351 words)

	Lunar orbit (Henry Spencer)
		Newsgroups: sci.space.history From: Henry Spencer Subject: Re: Apollo polar orbit question Date: Mon, 1 Dec 1997 00:51:08 GMT In article <65sru2$fgt@omnifest.uwm.edu>, Chris Roth wrote: >Suppose one of the final Apollo flights was a nonlanding >mission.
		That only happens twice a month in a lunar polar orbit, because the orbit is roughly fixed in space (lunar orbital precession is negligible) as the Moon goes around in its orbit.
		It is marginally possible that a carefully-chosen and quite low orbit could exploit lunar mascons to do the same trick, given a complete and detailed understanding of the lunar gravitational field (which we don't have yet), but I wouldn't bet money on it.
	yarchive.net /space/orbits/lunar_orbit.html (1805 words)

	Polar Orbits (Site not responding. Last check: 2007-10-16)
		CAPTION: This is a polar stereographic presentation of the north polar region, showing a single pass by a polar orbiting satellite (NOAA-11 in this example).
		CAPTION: This is a polar stereographic presentation of the north polar region, showing the tracks of seven consecutive overpasses by a polar orbiting satellite.
		CAPTION: This is a polar stereographic presentation of the south polar region, showing a single pass by a polar orbiting satellite (NOAA-11 in this example).
	www.rap.ucar.edu /~djohnson/satellite/polar.html (375 words)

	ESA Science & Technology: Orbit/Navigation
		Direct injection into a solar polar orbit from the Earth is not feasible, because the energy required cannot be provided even by the most powerful launch vehicles available today.
		A polar orbit around the Sun can be achieved, however, by taking advantage of a gravity assist by another planet.
		The orientation of the orbit is such that Ulysses passes first over the south pole of the Sun, followed by the Sun's north pole roughly one year later.
	sci.esa.int /science-e/www/object/index.cfm?fobjectid=31043 (615 words)

	Space Weather: Important Satellite Orbits
		At an altitude of 22,300 miles (35,890 kilometers), a satellite in a circular orbit in the equatorial plane moves around the Earth at the same speed that the Earth rotates.
		If the orbit plane is inclined away from the true north-south direction, the asymmetric pull of the Earth's gravitational field causes the orbit to precess (move around the Earth in local time).
		The sun-synchronous orbit is a special case of near-Polar orbit with inclination of 98.7 degrees, that precesses at exactly the required rate (~ 1 degree per day) to remain in the same local time plane as the Earth rotates around the sun.
	www.windows.ucar.edu /spaceweather/types_orbits.html (437 words)

	saturn V booster in polar orbit?? - Forums powered by UBBThreads™ (Site not responding. Last check: 2007-10-16)
		The normal solar orbit if the Saturn third stage escaped Earths gravity long enough to achieve it, should be an orbit not unlike the Earths orbit but with a slightly different period.
		It was observed a number of times, enough to determine its orbit, and learn that it had only been in Earth orbit a short while; it had passed through the Sun-Earth-L1 point to be recaptured by Earth's gravity.
		Even in Earth orbit it would not probably be visible at all times which was what I was referring to by passing.
	uplink.space.com /showflat.php?Board=sciastro&Number=501644 (1185 words)

	Landsat 7 Orbit & Coverage
		The orbit of Landsat 7 is repetitive, circular, Sun-synchronous, and near polar at a nominal altitude of 705 km (438 miles) at the Equator.
		The Landsat satellites are not placed in a true polar orbit but rather a near polar orbit which means the path/row numbers do not coincide with latitudes 90° north and south.
		Successive orbits and spacecraft attitude are controlled to assure minimal variation to either side from the intended ground track and framing of scene centers is controlled through LPS processing so that successive images of a specific scene or scenes can be registered for comparison purposes.
	ltpwww.gsfc.nasa.gov /IAS/handbook/handbook_htmls/chapter5/chapter5.html (2131 words)

	Space Today Online - Answers To Your Questions
		Back in 1945, science-fiction author Arthur C. Clarke imagined communications satellites in stationary orbits where they would travel around the world at the same speed the globe is spinning, making them hang stationary over one spot on Earth's surface.
		A satellite on its way to stationary orbit is fired to a special equatorial orbit known as a geostationary transfer orbit (GTO).
		Russia's orbiting space station Mir is another example of a manned satellite.
	www.spacetoday.org /Questions/PolarSats.html (1115 words)

	Aerospaceweb.org \| Ask Us - Launching into Polar Orbit
		In the previous question that you reference, we explained that most rocket launches are done to the east since this direction maximizes the beneficial speed bonus realized by launching in the direction of Earth's rotation.
		But if you want to launch into a polar orbit, which is rotating along a path that crosses the North and South Poles, you need to cancel out that speed bonus.
		Why is the path of an orbiting space vehicle, like the Space Shuttle, in the shape of a sine wave crossing north and south ot the equator when superimposed on a map of the Earth?
	www.aerospaceweb.org /question/spacecraft/q0089.shtml (262 words)

	ESA - Living Planet Programme - MetOp - Orbit (Site not responding. Last check: 2007-10-16)
		With the sun being at a constant angle to the plane of MetOp-A’s orbit, the satellite is in a so-called sun-synchronous orbit.
		Within the Joint Polar System, the international system to which MetOp forms a part, MetOp-A will be responsible for the morning orbit which passes over the Equator at 09.30 local time, whilst the NOAA satellite occupies the afternoon orbit which passes over the Equator at 14.30 local time.
		Together, these two orbits will maximise the coverage over which the observations are made and provide inputs needed for the computer numerical models on which our weather forecasts depend.
	www.esa.int /esaLP/ESAGJ1094UC_LPmetop_0.html (451 words)

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