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.
- <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
- <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), Highly Elliptical Orbit (HEO), or Lagrangian Point Orbit (LPO).
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.
- 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.
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
LEO > Inclined Non-Polar > TRMM [inclination
LEO > Inclined Non-Polar > UARS [inclination
- 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.
LEO > Polar Sun-Synchronous > Nimbus-7 [the
first sun synchronous, 99.15 deg inclination]
LEO > Polar Sun-Synchronous > Aqua [98.2 deg
LEO > Polar Sun-Synchronous > Terra [98.2 deg
LEO > Polar Sun-Synchronous > Aura [98.2 deg
LEO > Polar Sun-Synchronous > Meteor-3M [1000
km orbit; 100 deg inclination]
LEO > Polar Sun-Synchronous > CALIPSO [98.2
- LEO > Polar Non-Sun-Synchronous
Definition: Platform (satellite) maintains a polar orbit that does
not synchronize latitude passes with solar time.
LEO > Polar Non-Sun-Synchronous > Meteor2 [altitude:
inclination 81-82 deg]
LEO > Polar Non-Sun-Synchronous > CHAMP [inclination:
LEO > Polar Non-Sun-Synchronous > ICESat [inclination:
LEO > Polar Non-Sun-Synchronous > GRACE [inclination:
- MEO > Semi-Synchronous > Communications
Satellites that are used for telecommunications such as telephony,
television, mobile communications, amateur and commercial radio, and
- 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.
MEO > Semi-Synchronous > Geodetic/Space Environment
MEO > Semi-Synchronous > Geodetic/Space Environment > FAST
MEO > Semi-Synchronous > Geodetic/Space Environment > Explorer-31
- GEO: Geosynchronous Orbits (aka Clarke
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”.