Data Providers: Satellite: Equinoctial Elements

The position and velocity of the object, expressed in equinoctial elements, as a function of time in the requested coordinate system. Equinoctial elements are a set of orbital elements that are not singular when the eccentricity becomes zero or the orbit is equatorial. Rates of the elements may also be reported. Rates are computed using variation of parameters expressions with the perturbative acceleration which is computed as the total acceleration minus the two body acceleration, expressed in the requested coordinate system. Due to the method of computation, element rates will not be consistent with finite differencing of the element values for cases where the velocity is not the true time derivitive of the acceleration; for this reason, these values will not be reported for the J2, J4 and SGP4 propagators. The elements can be requested in a variety of coordinate systems. The available coordinate systems depend on the object's central body. Nominally, the systems Inertial, J2000, TrueOfDate, and MeanOfDate are supported, although some central bodies (notably the Earth and Sun) have more. The following lists the inertial systems available for Earth.

Name	Description
ICRF	International Celestial Reference Frame. The ICRF axes are defined as the inertial (i.e., kinematically non-rotating) axes associated with a general relativity frame centered at the solar system barycenter (often called the BCRF).
MeanOfDate	The mean equator mean equinox coordinate system evaluated at the requested time.
MeanOfEpoch	The mean equator mean equinox coordinate system evaluated at the epoch of the object.
TrueOfDate	The true equator true equinox coordinate system evaluated at the requested time.
TrueOfEpoch	The true equator true equinox coordinate system evaluated at the epoch of the object.
B1950	The mean equator mean equinox coordinate system evaluated at the beginning of the Besselian year 1950 (31 December 1949 22:09:46.866 = JD 2433282.4234591).
TEMEOfEpoch	The true equator mean equinox coordinate system evaluated at the epoch of the object.
TEMEOfDate	The true equator mean equinox coordinate system evaluated at the requested time.
AlignmentAtEpoch	The non-rotating coordinate system coincident with the Fixed system evaluated at the object's coordinate reference epoch.
J2000	The mean equator mean equinox coordinate system evaluated at the J2000.0 epoch (2000 January 1.5 = JD 2451545.0 TDB).

Name

Description

ICRF

International Celestial Reference Frame. The ICRF axes are defined as the inertial (i.e., kinematically non-rotating) axes associated with a general relativity frame centered at the solar system barycenter (often called the BCRF).

MeanOfDate

The mean equator mean equinox coordinate system evaluated at the requested time.

MeanOfEpoch

The mean equator mean equinox coordinate system evaluated at the epoch of the object.

TrueOfDate

The true equator true equinox coordinate system evaluated at the requested time.

TrueOfEpoch

The true equator true equinox coordinate system evaluated at the epoch of the object.

B1950

The mean equator mean equinox coordinate system evaluated at the beginning of the Besselian year 1950 (31 December 1949 22:09:46.866 = JD 2433282.4234591).

TEMEOfEpoch

The true equator mean equinox coordinate system evaluated at the epoch of the object.

TEMEOfDate

The true equator mean equinox coordinate system evaluated at the requested time.

AlignmentAtEpoch

The non-rotating coordinate system coincident with the Fixed system evaluated at the object's coordinate reference epoch.

J2000

The mean equator mean equinox coordinate system evaluated at the J2000.0 epoch (2000 January 1.5 = JD 2451545.0 TDB).