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Topic: Lunar orbit

	Orbit and Phases of the Moon
		The orbit of the Moon is very nearly circular (eccentricity ~ 0.05) with a mean separation from the Earth of about 384,000 km, which is about 60 Earth radii.
		In this figure, the various positions of the Moon on its orbit are shown (the motion of the Moon on its orbit is assumed to be counter-clockwise).
		Java applet illustrating the orbit of the moon around the Earth and the corresponding phases of the Moon as viewed from Earth.
	csep10.phys.utk.edu /astr161/lect/time/moonorbit.html (482 words)

	Moon - Wikipedia, the free encyclopedia
		In terms of elements, the lunar crust is composed primarily of oxygen, silicon, magnesium, iron, calcium, and aluminium, but important minor and trace elements such as titanium, uranium, thorium, potassium, and hydrogen are present as well.
		Topography of the Moon, referenced to the lunar geoid.
		The neutron spectrometer on Lunar Prospector indicated the presence of excess hydrogen at the lunar poles, which is likely due to the presence of water ice in the upper few meters of the regolith within permanently shadowed craters.
	en.wikipedia.org /wiki/Moon (7090 words)

	Apollo Flight Journal - Lunar Orbit Insertion
		Lunar Orbit Insertion, on the surface, appears to be a standard orbital mechanics problem, solvable using straightforward, albeit sophisticated tools to calculate a solution.
		A second set, the lunar orbit shape solutions, ensure that the apocynthion and pericynthion constraints are met, at the possible expense of the other constraints.
		Planning and executing the Lunar Orbit Insertion maneuver is an example of the teamwork between the flight controllers and the crew.
	history.nasa.gov /afj/loiessay.htm (1177 words)

	Lunar Republic : Lunar Glossary and Dictionary
		An extensive segment of the lunar surface, specifically in the mare regions, is comprised primarily of basalt resulting from lava flows.
		Lunar eclipse, Period in which the Earth is positioned so as to obscure the Moon from sunlight.
		The mare material is comprised primarily of basaltic lava flows, in contrast to the anorthosites in the highlands.
	www.lunarrepublic.com /info/glossary.shtml (1802 words)

	NASA - A New Paradigm for Lunar Orbits
		Bizarre Lunar Orbits (Science@NASA) -- Mysterious concentrations of mass in the Moon's ancient lava seas disturb the orbits of Moon-circling spacecraft.
		The stability of high lunar orbits (as well as of stars and fl holes) is all about angular momentum—the force that keeps a top or gyroscope or ice skater spinning upright, even if perturbed slightly from the side.
		One last brief primer before turning to orbits: The magnitude of the angular momentum vector depends on three quantities: the rate of spin, the mass of the spinning object, and the distance of the mass from the axis (the lever arm distance).
	science.nasa.gov /headlines/y2006/30nov_highorbit.htm (1543 words)

	Artemis Project: On-orbit rendezvous is expensive and dangerous.
		On-orbit rendezvous was a big worry for NASA, when the agency first got its commission to land a man on the moon.
		On-orbit rendezvous has a long and proven history; NASA and the Russian Space Agency have honed the techniques and all the supporting data (such as models of Earth's gravitational field) to near perfection.
		Then, after their explorations on the lunar surface were complete, the Apollo astronauts flew the Lunar Module Ascent Stage back to lunar orbit, where they made their rendezvous with the orbiting command module.
	www.asi.org /adb/j/02/on-orbit-rndz.html (1096 words)

	Low Cost Lunar Mission for the Year 2000
		The Earth's orbital plane is inclined at 23.45° to the ecliptic, and the lunar orbital plane is inclined at 5.15°.
		This orbit is particularly suited to high resolution mapping as may be required by future missions, but is strongly affected by the non-uniformness of the lunar gravitational field.
		Once in lunar orbit, the cold gas reaction control system will be used in combination with three orthogonal reaction wheels in order to provide three main control modes; Earth pointing for high speed data dumping, lunar surface pointing for specific scientific instruments, and sun pointing.
	www.ee.surrey.ac.uk /CSER/UOSAT/papers/iaf96/lunar/earthrise.html (3635 words)

	Frequently Asked Questions (Site not responding. Last check: 2007-10-19)
		If Lunar Prospector discovers water ice on the Moon, a very important local resource will be available to astronauts because we use water to drink, to bathe and to fuel spacecraft (after splitting water molecules into their individual elemental components, hydrogen and oxygen).
		Lunar Prospector will be in a polar orbit because we want to map the entire surface of the Moon.
		Outgassing is the venting of gases from the lunar interior.
	lunar.arc.nasa.gov /printerready/project/faq.html (2951 words)

	Lunar orbit - Wikipedia, the free encyclopedia
		The first spacecraft the enter a true lunar orbit, in the sense that it was a satellite continuously going around the Moon, was the USA's Lunar Orbiter 1 in 1965.
		Selection of an orbit was constrained on the low side by lunar mountains reaching heights of 20,000 feet (nearly seven kilometers), and on the high side by the need to obtain suitable imagery.
		Gravitational anomalies slightly distorting the orbits of the Lunar Orbiters led to the discovery of mascons, concentrations of mass beneath the lunar surface caused by large impacting bodies at some remote time in the past.
	en.wikipedia.org /wiki/Lunar_orbit (294 words)

	Lunar Orbit Rendezvous and the Apollo Program
		Pictured is the Apollo lunar module during rendezvous in lunar orbit with the command module.
		John C. Houbolt explains the lunar orbit rendezvous concept that, in the opinion of many historians, was chief among the reasons why the U.S., in less than a decade, managed humankind's first extraterrestrial excursions.
		Once in lunar orbit, two of the crew members donned spacesuits and climbed into the lunar excursion module, detached it from the mother ship and "flew" it down to the lunar surface.
	oea.larc.nasa.gov /PAIS/Rendezvous.html (2756 words)

	Space Propulsion and Mission Analysis Office
		Lunar Communication is an important aspect of manned and unmanned missions to the moon.
		Depending on the communication requirements that are needed to support a human lunar base, communication links may be needed between the lunar base, the lunar surface, moving assets such as rovers, the spacecraft in transport, the lunar near side, the lunar far side, and the Earth.
		Additionally, depending on the communication and navigation coverage requirements in the Lunar mission architecture of the lunar surface, a lunar orbiting relay satellite constellation might be considered as a relay link.
	trajectory.grc.nasa.gov /projects/lunar.shtml (715 words)

	NASA - Bizarre Lunar Orbits
		The low orbits of both subsatellites were to be similar ellipses, ranging from 55 to 76 miles (89 to 122 km) above the lunar surface.
		The orbit of the relatively long-lived Apollo 15 subsatellite PFS-1 had an inclination of 28º, which turned out to be close to the inclination of one of the frozen orbits—but poor PFS-2 was cursed with an inclination of only 11º.
		Lunar Prospector had to do a maneuver every two months to keep itself in its initial circular orbit of 60 miles (100 km)—and more often than once a month when it was orbiting at only 20 miles (30 km) altitude.
	science.nasa.gov /headlines/y2006/06nov_loworbit.htm (1085 words)

	Russia's unmanned missions toward the Moon
		The missions which did not reach the orbit would not be acknowledged at all at the time.
		Although the USSR virtually abandoned lunar exploration with the end of the Moon race in mid-1970s, Russian scientists still saw the Moon as potential target for research.
		Speaking to journalists, the head of Roskosmos Anatoly Perminov said that lunar exploration was a priority during the meeting and several contracts involving Russian and Chinese organizations were signed.
	www.russianspaceweb.com /spacecraft_planetary_lunar.html (599 words)

	Lunar orbit (Henry Spencer) (Site not responding. Last check: 2007-10-19)
		The choice of lunar orbit is determined by exactly where the spacecraft is when the Moon arrives.
		To a crude first approximation, an economy trajectory to the Moon is an elliptical orbit with its perigee as low as possible and its apogee at roughly lunar distance.
		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)

	lunar-orbit rendezvous (LOR)
		The concept of lunar-orbit rendezvous was first discussed by the Russian rocket theoretician Yuri Kondratyuk in 1916 and later by the British scientist H. Ross.
		As a means of reaching the Moon’s surface, it has the advantage that the lunar landing vehicle can be designed specifically for this task and be of low mass since all the equipment and supplies for the return to Earth can be left in lunar orbit.
		Against this, however, must be set the difficulty and danger of having to maneuver and dock two vehicles in lunar orbit.
	www.daviddarling.info /encyclopedia/L/lunar-orbit_rendezvous.html (210 words)

	Lunar Base Studies - 1994: LANTR and LUNOX
		This NTR is reusable, transporting 8,800kg of cargo from Earth orbit to lunar orbit, where it rendezvous with the LLV.
		The mass of the entire spacecraft in low Earth orbit is reduced from 132t to 98t since no new LLV must be transported to lunar orbit on each flight.
		To the north, a Lunar Landing Vehicle lifts off from from the Moon carrying a mobile LUNOX tanker vehicle to an orbiting propellant depot in low lunar orbit.
	www.nss.org /settlement/moon/LANTR.html (1607 words)

	Space Today Online -- Solar System Moons
		Telemetry data from Lunar Prospector was used to produce a gravity map of both the near and far sides of the Moon.
		Lunar Prospector is scheduled to continue gathering data at an altitude of 62 miles above the Moon throughout 1998.
		Lunar Prospector's science instruments were provided by the Los Alamos National Laboratory, the University of California Berkeley Space Science Laboratory, the University of Arizona at Tucson, NASA's Goddard Space Flight Center at Greenbelt, Maryland, and NASA's Jet Propulsion Laboratory at the California Institute of technology at Pasadena, California.
	www.spacetoday.org /SolSys/Moons/LunarProspector.html (2092 words)

	Lunar Orbiter
		A faultless deboost maneuver on August 14 achieved the desired initial elliptic orbit around the moon, and one week later the spacecraft was commanded to make a transfer maneuver to place it in a final close-in elliptic orbit of the moon.
		During the spacecraft's stay in the final close-in orbit, the gravitational fields of the earth and the moon were expected to influence the orbital elements.
		Lunar Orbiter II mission as of November 28 indicated that the first phase of the photographic mission was completed when the final photo was taken on the afternoon of November 25.
	www.astronautix.com /craft/lunbiter.htm (2042 words)

	A Rotovator for Lunar Tourism
		It utilizes a rotating tether in Lunar orbit, which can capture a payload from a trans-Earth trajectory, soft-land it on the Lunar surface, then lift an equal mass payload off the Moon and release it on a trans-Earth trajectory, all with nominally zero propellant consumption and no momentum loss.
		With a one orbit delay between a release and the next capture (and again a 45:1 mass ratio), about 1.3 miles of the altitude loss is not cancelled out.
		For lunar tourism, the Moon's limbs (the eastern-most and western-most points visible from Earth) are desirable locations due to their favorable view of Earth (it will be easier to see Earth through a window if it appears near the horizon rather than high in the sky).
	members.aol.com /Nathan2go/lunavat.htm (2175 words)

	CNN - U.S. space probe moving into lunar orbit - January 11, 1998
		Lunar Prospector was launched Tuesday on a one-year mission to scan the moon for minerals and possible water ice, which could one day be used by human settlers.
		Lunar Prospector does not carry a camera, but is equipped with five instruments designed to map the composition of the entire lunar surface.
		With a price tag of $63 million, the Lunar Prospector is a modest successor to the multibillion-dollar Apollo project, which put 12 men on the surface of the moon from 1969 to 1972.
	www.cnn.com /TECH/9801/11/space.probe (539 words)

	Apollo Lunar Module
		At the end of a lunar visit, the interstage fittings were severed by an explosive device.
		The LM was then jettisoned into the moon's orbit and set to crash into the moon's surface at a predetermined time.
		Apollo 9 - simulated in Earth orbit the operation of lunar module to landing and takeoff from lunar surface and rejoining with command module.
	www.sln.org /pieces/schutte/LMintro2.html (635 words)

	Why Don't we have a Lunar Eclipse Every Month?
		Lunar eclipses can only happen when the Moon is full and it passes behind the Earth and into its' shadow.
		If the Moon's orbit around the Earth were in the same plane as the Earth's around the Sun (the ecliptic,) we would indeed have a monthly eclipse.
		The farthest north of the celestial equator that the moon can be is 23 1/2 degrees plus the 5 degree inclination of the lunar orbit or 28 1/2 degrees.
	starryskies.com /The_sky/events/lunar-2003/eclipse2.html (608 words)

	Lunar Excerssion Module \| Scholastic.com
		Because little was known about the lunar surface when construction began in 1962, engineers designed the cantilever landing gear — consisting of four sets of legs, each ending in a dish-shaped pod — so that the vehicle could land safely and remain upright on a variety of surfaces.
		In lunar orbit, two crew members transferred from the Apollo Command Module to the LM ascent stage through a docking tunnel, undocked the LM, and landed on the Moon.
		The descent stage was left on the Moon and the ascent stage was jettisoned in lunar orbit.
	content.scholastic.com /browse/article.jsp?id=5158 (535 words)

	Lunar Prospector
		The Lunar Prospector is designed for a low polar orbit investigation of the Moon, including mapping of surface composition and possible deposits of polar ice, measurements of magnetic and gravity fields, and study of lunar outgassing events.
		Lunar calibration data was collected during the 11.6- and 3.5-hour orbits.
		Lunar Prospector, built for the NASA Ames Research Center by Lockheed Martin, is a spin-stabilized spacecraft designed to provide NASA with the first global maps of the moons surface and its gravitational magnetic fields, as well as look for the possible presence of ice near the lunar poles.
	www.solarviews.com /eng/lunpros.htm (1101 words)

	A New Paradigm for Lunar Orbits
		For a lunar orbit higher than 430 miles, Earth's pull is actually strong enough to whisk a spacecraft out of the game.
		Ely and his colleagues calculate that certain elliptical, high-inclination, high-altitude lunar orbits may remain stable for periods of at least a century.
		For lunar communications and navigation, Ely recommends spacing three satellites 120º apart in the same elliptical orbit at an inclination of 51º.
	www.physorg.com /news84202564.html (875 words)

	Lunar Orbiter 1
		The Lunar Orbiter 1 spacecraft was designed primarily to photograph smooth areas of the lunar surface for selection and verification of safe landing sites for the Surveyor and Apollo missions.
		The spacecraft was tracked until it impacted the lunar surface on command at 7 degrees N latitude, 161 degrees E longitude (selenographic coordinates) on October 29, 1966.
		The Lunar Orbiter 1 spacecraft carried 20 micrometeoroid detectors, located on the tank deck periphery, for the detection of micrometeoroids in the lunar environment.
	www.solarviews.com /eng/orbiter1.htm (972 words)

	2001 TrailBlazer Commercial Moonshot to Return Lunar Video
		During its two-fold mission TrailBlazer will return images of Earthrise as seen from lunar orbit, before turning its gaze to the lunar surface where it will return closeup images of the moon from low altitude, for aerial photography customers and sponsors seeking publicity.
		For further information, please contact TransOrbital plans for the Lunar TrailBlazer Project to be the beginning of a series of commercial spacecraft "firsts" in lunar orbit and on the lunar surface.
		TransOrbital plans for the Lunar TrailBlazer Project to be the beginning of a series of their commercial spacecraft "firsts" in lunar orbit and on the lunar surface.
	www.spacedaily.com /news/transorbital-99a.html (511 words)

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