The path of an object that is moving around a second
object or point under the influence of gravity. This field provides information
about orbital parameters of a platform from which the data were taken. It
- <Orbit_Altitude>: altitude of platform above
the Earth’s surface.
- <Orbit_Inclination>: angular distance of the
orbital plane from the
plane of the planet’s equator, stated in degrees. [Angle between
orbit and equator].
- <Equator_Crossing>: time at which the platform
crosses the equator.
- <Period>: time it takes a platform to make one
full orbit.
- <Repeat_Cycle>: time that the satellite passes
vertically over the same location.
- <Perigee>: point in the orbit where an Earth
satellite is closest to the Earth. Opposite of apogee.
- <Apogee>: point in the orbit where an Earth satellite
is farthest from the Earth. Opposite of perigee.
- <Orbit_Type>: Orbital types may include Low Earth
Orbit (LEO), Medium Earth Orbit (MEO), Geosynchronous Orbit (GEO), or
Highly Elliptical Orbit (HEO).
With the information requested previously related to altitude, inclination,
etc., one has more information than one can deduce from any one of several
classification schemes. The most useful addition might be to allow the
user to immediately gain information on areas of observation and overpass
times. Therefore, indicating a choice within the following categories
might prove to be immediately helpful to the data user:
- LEO: Low Earth Orbits
Definition: Platforms that orbit between 80 km and 2000 km.
Choices include:
- LEO > Low Earth Orbit > Inclined Non-Polar
- LEO > Low Earth Orbit > Polar Sun-Synchronous
- LEO > Low Earth Orbit > Polar Non-Sun-Synchronous
- LEO > Inclined Non-Polar
Definition: A LEO orbit that has an inclination of less than 70 degrees.
Platforms in “Inclined Non-Polar” orbits are not sun-synchronous.
Exanples:
LEO > Inclined Non-Polar > International Space
Station (360 km) [inclination 51.6 deg]
LEO > Inclined Non-Polar > Space Shuttle (300-400
km) [inclination usually about 57 deg]
LEO > Inclined Non-Polar > TOPEX/PoSEIDON [inclination 66.5
deg]
LEO > Inclined Non-Polar > TRMM [inclination
35 deg]
LEO > Inclined Non-Polar > UARS [inclination
57 deg]
- LEO > Polar Sun-Synchronous
Definition: Platform (satellite) that passes all latitudes at the
same local solar time each day [through a combination of proper altitude
and inclination]. Orbits lie within 20 degrees of a 90 degree inclination
from the equator. To maintain this synchronicity, the orbital plane
must rotate about 1 degree per day.
Examples:
LEO > Polar Sun-Synchronous > Nimbus-7 [the
first sun synchronous, 99.15 deg inclination]
LEO > Polar Sun-Synchronous > Aqua [98.2 deg
inclination]
LEO > Polar Sun-Synchronous > Terra [98.2 deg
inclination]
LEO > Polar Sun-Synchronous > Aura [98.2 deg
inclination]
LEO > Polar Sun-Synchronous > Meteor-3M [1000
km orbit; 100 deg inclination]
LEO > Polar Sun-Synchronous > CALIPSO (98.2
deg inclination]
- LEO > Polar Non-Sun-Synchronous
Definition: Platform (satellite) maintains a polar orbit that does
not synchronize latitude passes with solar time.
Examples:
LEO > Polar Non-Sun-Synchronous > Meteor2 [altitude:
850-950 km;
inclination 81-82 deg]
LEO > Polar Non-Sun-Synchronous > CHAMP [inclination:
87.4 deg]
LEO > Polar Non-Sun-Synchronous > ICESat [inclination:
94 deg]
LEO > Polar Non-Sun-Synchronous > GRACE [inclination:
89 deg]
- MEO> Medium Earth Orbit [aka Intermediate
Circular Orbits]
Definition: Platform orbits lie between 2000 km to 35,786 km,
but most commonly at 20,200 km or 20,650, with an orbital period of
12 hours). Note that the Van Allen Belts of high energy protons lie
within the MEO orbital range ands.
Choices include:
- MEO > Semi-Synchronous > Navigation
- MEO > Semi-Synchronous > Communications
- MEO > Semi-Synchronous > Geodetic/Space Environment
- MEO > Semi-Synchronous > Navigation
Definition:
Satellites in Medium Earth Orbits (MEO) that perform navigation processes,
using techniques to establish position and velocity of an object (or
platform).
Examples:
MEO > Semi-Synchronous > Navigation > NAVSTAR (NAVigation System using Timing And Ranging)
MEO > Semi-Synchronous > Navigation > GLONASS (GLObal NAvigation Satellite System)
- MEO > Semi-Synchronous > Communications
Definition:
Satellites that are used for telecommunications such as telephony,
television, mobile communications, amateur and commercial radio, and
broadband internet.
Example:
- MEO > Semi-Synchronous > Geodetic/Space Environment
Definition: These are MEO platforms that perform geodetic observations
(for example, LAGEOS) or space physics observations (for example,
FAST). They are neither Navigation nor Communications satellites.
Examples:
MEO > Semi-Synchronous > Geodetic/Space Environment
> LAGEOS
MEO > Semi-Synchronous > Geodetic/Space Environment > FAST
MEO > Semi-Synchronous > Geodetic/Space Environment > Explorer-31
- GEO: Geosynchronous Orbits (aka Clarke
Orbit)s
Definition: Platform orbits with a revolution of exactly one day
at an altitude of 35,786 km. Any orbit, which has a period equal to
the Earth’s rotational period. The orbit’s eccentricity
and inclination may not necessarily be zero. When the orbit is circular
and the rotational period has zero inclination, the platform is considered
to also be “geostationary”.
- HEO: High Earth Orbits/Highly Elliptical Orbits
Definition: A High Earth Orbit is any orbit above geosynchronous
(above 35,786 km). A Highly Elliptical Orbit is an orbit of low perigee
(about 1000 km) and a high apogee over 35,786 km). These orbits have
an inclination between 50 and 70 degrees. Highly elliptical orbits
are mainly perturbed by the Earth’s oblateness and by gravitational
attraction of the Sun and Moon. HEOs are popular orbits for Earth
magentospheric measurements and astronomical observatories.
Choices include:
- HEO > Highly Elliptical Orbit
- HEO > Highly Elliptical Orbit > Molniya
- HEO > Highly Elliptical Orbit > Tundra
Examples:
HEO > Highly Elliptical Orbit > Cluster II [Perigee:17,200km Apogee: 120,500 km, Period=620 m]
HEO > Highly Elliptical Orbit > Orbiting Geophysical
Observatory 1 (OGO)
[Perigee: 281 km Apogee: 149,385 km, Period=3839 m]
HEO > Highly Elliptical Orbit > Advanced Composition
Explorer (ACE) [Perigee: 179 km Apogee: 1,256,758 km,
Period=1398 h]
HEO > Highly Elliptical Orbit > IMP-8 [Perigee:
22.11RE Apogee: 45.26RE, Period=11.99 d]]
HEO > Highly Elliptical Orbit > Molniya >
[Perigee: 495 km Apogee 39.587 km]
HEO > Highly Elliptical Orbit > Tundra (inclination 33.4 degrees; orbital period about 12 hours
- LPO: Lagrangian Point Orbits
Definition: A location in space around a rotating two-body system
(such as the Earth-Moon or Earth-Sun) where the pulls of the gravitating
bodies combine to form a point at which a third body of negligible
mass would be stationary relative to the two bodies. Lagrangian points
are named after the Italian-born French mathematician and astronomer
Joseph Louis de Lagrange who first showed their existence There are
five Lagrangian points in all, three of which are unstable because
the slightest disturbance to any object located at one of them causes
the object to drift away permanently. Until recently, this meant that
the unstable Lagrangian points seemed to have no practical application
for spaceflight. Now, however, they are known to have immense significance
and have become the basis for chaotic control. In addition, growing
numbers of spacecraft are being placed in halo orbits around the L1
and L2 points; station-keeping, in the form of regular thruster firings,
are needed to maintain these orbits. (Source: The Encyclopedia of
Astrobiology, Astronomy and Spaceflight: http://www.daviddarling.info/encyclopedia/L/Lagpoint.html
Choices include:
- LPO > L1 > Lissajous Orbit > Halo Orbit
- LPO > L1 > Lissajous Orbit > Lyapunov Orbit
- LPO > L2
Examples:
LPO > L1 > Lissajous Orbit > Halo Orbit > SOHO
LPO > L1 > Lissajous Orbit > Halo Orbit > ACE
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<Orbit>
<Orbit_Altitude>real number or text expressed in km</ Orbit_Altitude>
<Orbit_Inclination>real number or text expressed in degrees (°)
</Orbit_Inclination>
<Equator_Crossing> real number or text expressed as a usually a local
time in hh:mm format followed by “am” or “pm”.</Equator_Crossing>
<Period> real number or text expressed in minutes</Period>
<Repeat_Cycle> real number or text expressed in days and/or revolutions
</Repeat_Cycle
<Perigee> real number or text expressed in km</Perigee>
<Apogee> real number or text expressed in km </Apogee>
<Orbit_Type>type of orbit keyword </Orbit_Type>
</Orbit>
* All fields may contain 1 to 80 characters of the printable
UTF-8 character set.
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- <Orbit>
<Orbit_Altitude>705 km</Orbit_Altitude>
<Orbit_Inclination>98.2°</Orbit_Inclination>
<Equator_Crossing>1:30 pm (south to north) and 1:30 am (north to south)
</Equator_Crossing>
<Period> 98.8 minutes</Period>
<Repeat_Cycle>16 days (233 revolutions)</Repeat_Cycle>
<Perigee>673 km (Periapsis)</Perigee>
<Apogee>686 km (Apoapsis)</Apogee>
<Orbit_Type>LEO > Polar Sun-Synchronous</Orbit_Type>
</Orbit>
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