Data Provider Groups | Data Provider Elements

Delaunay Elements

A set of canonical angle-action variables commonly used in general perturbation theories. An orbit is defined by a set of conjugate angle-action pairs. The elements are computed using ephemeris with respect to the object's central body, as observed from the requested coordinate system, as a function of time.

Available for these objects: Satellite

Type: Time-varying data.

Availability: Reports | Graphs | Dynamic Displays | Strip Charts

Data Provider Groups

Data can be requested in a variety of coordinate systems, where the origin of the coordinate system is the object's central body. The available coordinate systems depend on the object's central body. Nominally, the systems Fixed, Inertial, J2000, TrueOfDate, and MeanOfDate are supported, although some central bodies (notably the Earth and Sun) have more.

The following lists the 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 nonrotating 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 TDB = JD 2451545.0 TDB).

Data Provider Elements

Name	Dimension	Type	Description
Time	Date	Real Number or Text	Time.
Z Comp of Ang Mom	Unitless	Real Number	The Z component of the orbit angular momentum vector. This action variable, classically designated as H, is paired with the right ascension of the ascending node angle variable.
Ang Momentum	Unitless	Real Number	The magnitude of the orbit angular momentum vector. This action variable, classically designated as G, is paired with the argument of perigee angle variable.
sqrt(mu * a)	Unitless	Real Number	The sqrt of the product of the gravitational parameter and the semi-major axis. This action variable, classically designated as L, is paired with the mean anomaly angle variable.
RAAN	Longitude	Real Number or Text	The angle in the XY plane from the X axis to the ascending node, measured in a right-handed sense about the Z axis. in the equatorial plane. For equatorial orbits, the ascending node is defined to be directed along the positive X axis, and thus the value is 0.0.
Arg of Perigee	Angle	Real Number or Text	The angle from the ascending node to the periapsis vector measured in the orbit plane in the direction of the object's motion. The periapsis vector locates the closest point of the orbit. For a circular orbit, the value is defined to be zero (i.e., periapsis at the ascending node).
Mean Anomaly	Angle	Real Number or Text	A measure of the time past periapsis passing, expressed as an angle.