Parameters - Longitude Of The Periapsis

Longitude of the periapsis

This article may be confusing or unclear to readers. Please help us clarify the article; suggestions may be found on the talk page. (July 2009)

In celestial mechanics, the longitude of the periapsis (symbolized ϖ) of an orbiting body is the longitude (measured from the point of the vernal equinox) at which the periapsis (closest approach to the central body) would occur if the body's inclination were zero. For motion of a planet around the Sun, this position could be called longitude of perihelion. The longitude of periapsis is a compound angle, with part of it being measured in the plane of reference and the rest being measured in the plane of the orbit. Likewise, any angle derived from the longitude of periapsis (e.g. mean longitude and true longitude) will also be compound.
Sometimes, the term longitude of periapsis is used to refer to ω, the angle between the ascending node and the periapsis. That usage of the term is especially common in discussions of binary stars and exoplanets.^[1] However, the angle ω is less ambiguously known as the argument of periapsis.

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Parameters - Argument Of Periapsis

Argument of periapsis

The argument of periapsis (also called argument of perifocus or argument of pericenter), symbolized as ω, is one of the orbital elements of an orbiting body. Specifically, ω is the angle between the orbit's periapsis (the point of closest approach to the central point) and the orbit's ascending node (the point where the body crosses the plane of reference from South to North). The angle is measured in the orbital plane and in the direction of motion. For specific types of orbits, words such as "perihelion" (for Sun-centered orbits), "perigee" (for Earth-centered orbits), "periastron" (for orbits around stars) and so on may replace the word "periapsis". See apsis for more information.

This section may be confusing or unclear to readers. (January 2012)

An argument of periapsis of 0° means that the orbiting body will be at its closest approach to the central body at the same moment that it crosses the plane of reference from South to North. An argument of periapsis of 90° means that the orbiting body will reach periapsis at its northmost distance from the plane of reference.
Adding the argument of periapsis to the longitude of the ascending node gives the longitude of the periapsis. However, especially in discussions of binary stars and exoplanets, the terms "longitude of periapsis" or "longitude of periastron" are often used synonymously with "argument of periapsis".

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Parameters - Longitude Of The Asending Node

Longitude of the ascending node

This article may be confusing or unclear to readers. Please help us clarify the article; suggestions may be found on the talk page. (July 2009)

The longitude of the ascending node.

The longitude of the ascending node (☊ or Ω) is one of the orbital elements used to specify the orbit of an object in space. It is the angle from a reference direction, called the origin of longitude, to the direction of the ascending node, measured in a reference plane.^[1] Commonly used reference planes and origins of longitude include:

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Paramaters - Azimuth

Azimuth

The azimuth is the angle formed between a reference direction (North) and a line from the observer to a point of interest projected on the same plane as the reference direction

An azimuth (ⁱ/ˈæzɪməθ/) is an angular measurement in a spherical coordinate system. The vector from an observer (origin) to a point of interest is projected perpendicularly onto a reference plane; the angle between the projected vector and a reference vector on the reference plane is called the azimuth.
An example is the position of a star in the sky. The star is the point of interest, the reference plane is the horizon or the surface of the sea, and the reference vector points north. The azimuth is the angle between the north vector and the perpendicular projection of the star down onto the horizon.^[1]
Azimuth is usually measured in degrees (°). The concept is used in navigation, astronomy, engineering, mapping, mining and artillery.

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Parameters - Horizontal Coordinate System

Horizontal coordinate system

Azimuth is measured from the north point (sometimes from the south point) of the horizon around to the east; altitude is the angle above the horizon.

The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane. This coordinate system divides the sky into the upper hemisphere where objects are visible, and the lower hemisphere where objects cannot be seen since the earth is in the way. The great circle separating hemispheres is called celestial horizon or rational horizon. The pole of the upper hemisphere is called the zenith. The pole of the lower hemisphere is called the nadir. ^[1]
The horizontal coordinates are:

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Parameters - Orbital inclination Change

Orbital inclination change

Orbital inclination change is an orbital maneuver aimed at changing the inclination of an orbiting body's orbit. This maneuver is also known as an orbital plane change as the plane of the orbit is tipped. This maneuver requires a change in the orbital velocity vector (delta v) at the orbital nodes (i.e. the point where the initial and desired orbits intersect, the line of orbital nodes is defined by the intersection of the two orbital planes).
In general, inclination changes can take a very large amount of delta v to perform, and most mission planners try to avoid them whenever possible to conserve fuel. This is typically achieved by launching a spacecraft directly into the desired inclination, or as close to it as possible so as to minimize any inclination change required over the duration of the spacecraft life. Planetary flybys are the most efficient way to achieve large inclination changes, but they are only effective for interplanetary missions.

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Parameters - Orbital Inclination

Orbital inclination

Fig. 1: One view of inclination i (green) and other orbital parameters

Inclination in general is the angle between a reference plane and another plane or axis of direction.

 

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Parameters - Eccentricity

Orbital eccentricity

An elliptic Kepler orbit with an eccentricity of 0.7 (red ellipse), a parabolic Kepler orbit (green) and a hyperbolic Kepler orbit with an eccentricity of 1.3 (blue outer line)

The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values between 0 and 1 form an elliptical orbit, 1 is a parabolic escape orbit, and greater than 1 is a hyperbola. The term derives its name from the parameters of conic sections, as every Kepler orbit is a conic section. It is normally used for the isolated two-body problem, but extensions exist for objects following a rosette orbit through the galaxy.

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Parameters - Apsis

Apsis

"Apogee", "Aphelion", "Perigee" and "Perihelion" redirect here. For the literary journal, see Perigee: Publication for the Arts. For Edenbridge's Album, see Aphelion (album). For the architectural term, see Apse. For other uses, see Apogee (disambiguation) and Perihelion (disambiguation).

Apsides 1) Apoapsis; 2) Periapsis; 3)
Focus

An apsis (Greek ἁψίς, gen. ἁψίδος), plural apsides (/ˈæpsɨdiːz/; Greek: ἁψίδες), is a point of greatest or least distance of a body in an elliptic orbit about a larger body. For a body orbiting the Sun the greatest and least distance points are called respectively aphelion and perihelion (/æpˈhiːliən/, /ˌpɛrɨˈhiːliən/), whereas for any satellite of Earth including the Moon the corresponding points are apogee and perigee (/ˈpɛrɨdʒiː/). The generic suffix, independent of the particular central body, can be either apsis or centre, hence apoapsis, apocentre or apapsis (from ἀπ(ό) (ap(ó)), meaning "from"), and periapsis or pericentre (from περί (peri), meaning "around"). During the Apollo program, the terms pericynthion and apocynthion (referencing Cynthia, an alternative name for the Greek Moon goddess Artemis) were used when referring to the Moon.^[1]
A straight line connecting the periapsis and apoapsis is the line of apsides. This is the major axis of the ellipse, its greatest diameter. For a two-body system the center of mass of the system lies on this line at one of the two foci of the ellipse. When one body is sufficiently larger than the other it may be taken to be at this focus. However whether or not this is the case, both bodies are in similar elliptical orbits each having one focus at the system's center of mass, with their respective lines of apsides being of length inversely proportional to their masses. Historically, in geocentric systems, apsides were measured from the center of the Earth. However in the case of the Moon, the center of mass of the Earth-Moon system or Earth-Moon barycenter, as the common focus of both the Moon's and Earth's orbits about each other, is about 75% of the way from Earth's center to its surface.
In orbital mechanics, the apsis technically refers to the distance measured between the centers of mass of the central and orbiting body. However, in the case of spacecraft, the family of terms are commonly used to describe the orbital altitude of the spacecraft from the surface of the central body (assuming a constant, standard reference radius)

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Parameters - Semi-minor Axis

Semi-minor axis

The semi-major (in red*) and semi-minor axis (in blue*) of an ellipse.
(* on some browsers)

In geometry, the semi-minor axis (also semiminor axis) is a line segment associated with most conic sections (that is, with ellipses and hyperbolas) that is at right angles with the semi-major axis and has one end at the center of the conic section. It is one of the axes of symmetry for the curve: in an ellipse, the shorter one; in a hyperbola, the one that does not intersect the hyperbola.

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Parameters - Semi-major Axis

Semi-major axis

The semi-major and semi-minor axis of an ellipse

In geometry, the major axis of an ellipse is the longest diameter: a line (line segment) that runs through the center and both foci, with ends at the widest points of the shape. The semi-major axis is one half of the major axis, and thus runs from the centre, through a focus, and to the edge of the ellipse; essentially, it is the radius of an orbit at the orbit's two most distant points. For the special case of a circle, the semi-major axis is the radius. One can think of the semi-major axis as an ellipse's long radius.
The length of the semi-major axis a of an ellipse is related to the semi-minor axis' length b through the eccentricity e and the semi-latus rectum ℓ, as follows:

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Orbit - Aerosynchronous Orbit

Areosynchronous orbit

Areosynchronous orbits are class of synchronous orbits for artificial satellites around the planet Mars. As with all synchronous orbits, an areosynchronous orbit has an orbital period equal in length to Mars's sidereal day. A satellite in areosynchronous orbit does not necessarily maintain a fixed position in the sky as seen by an observer on the surface of Mars, however such a satellite will return to the same apparent position every Martian day.
The orbital altitude required to maintain an areosynchonous orbit is approximately 17,000 kilometres (11,000 mi). If a satellite in areosynchonous orbit were to be used as a communication relay link, it "would experience communications ranges of 17,000 to 20,000 kilometres (11,000 to 12,000 mi)" to various points on the visible Martian surface.^[1]
An areosynchronous orbit that is equatorial (in the same plane as the equator of Mars), circular, and prograde (rotating about Mars's axis in the same direction as the planet's surface) is known as an areostationary orbit (ASO). To an observer on the surface of Mars, the position of a satellite in ASO would appear to be fixed in a constant position in the sky. The ASO is analogous to a geostationary orbit (GSO) about Earth.^{[citation needed]}
Although no satellites currently occupy areosynchronous or areostationary orbits, some scientists^[who?] foresee a future telecommunications network for the exploration of Mars.^{[citation needed]}

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