Data Provider Groups | Data Provider Elements
Equinoctial Elements
The position and velocity of the object, as observed from the requested coordinate system, expressed in equinoctial elements as a function of time. 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 derivative of the acceleration; for this reason, these values will not be reported for the J2, J4 and SGP4 propagators.
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 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 TDB = JD 2451545.0 TDB). |
Data Provider Elements
| Name | Dimension | Type | Description |
|---|---|---|---|
| Time | Date | Real Number or Text | Time. |
| Semi-Major Axis | Distance | Real Number | A measure of the size of the orbit. Orbits with eccentricity less than 1 are ellipses, with major and minor axes identifying the symmetry axes of the ellipse, the major axis being the longer one. The value is half the length of the major axis. |
| e * sin(omegaBar) | Unitless | Real Number | h = eccentricity * sin(right_ascension_of_the_ascending_node + argument_of_periapse). Equinoctial elements h and k together describe the shape of the orbit and the location of the periapse. |
| e * cos(omegaBar) | Unitless | Real Number | k = eccentricity * cos(right_ascension_of_the_ascending_node + argument_of_periapse). Equinoctial elements h and k together describe the shape of the orbit and the location of the periapse. |
| tan(i/2) * sin(raan) | Unitless | Real Number | p = tan(inclination/2) * sin(right_ascension_of_the_ascending_node). Equinoctial elements p and q together describe the orientation of the orbit plane. Retrograde orbits have a singularity at zero inclination, and posigrade orbits have a singularity at 180 deg inclination. |
| tan(i/2) * cos(raan) | Unitless | Real Number | q = tan(inclination/2) * cos(right_ascension_of_the_ascending_node). Equinoctial elements p and q together describe the orientation of the orbit plane. Retrograde orbits have a singularity at zero inclination, and posigrade orbits have a singularity at 180 deg inclination. |
| Mean Lon | Longitude | Real Number or Text | mean longitude is the sum: right_ascension_of_the_ascending_node + argument_of_periapse + mean_anomaly. A measure of the location within the orbit. |
| Direction | Unitless | Text | The type of equinoctial elements. Retrograde has its singularity at an inclination of 0 deg. Posigrade has its singularity at an inclination of 180 deg. |
| Semi-Major Axis Rate | Rate | Real Number or Text | Rate of change of semi-major axis. Computed by applying the variation of parameters equations of motion to the perturbative acceleration. |
| e * sin(omegaBar) Rate | Unitless Per Time | Real Number or Text | Rate of change of h. Computed by applying the variation of parameters equations of motion to the perturbative acceleration. |
| e * cos(omegaBar) Rate | Unitless Per Time | Real Number or Text | Rate of change of k. Computed by applying the variation of parameters equations of motion to the perturbative acceleration. |
| tan(i/2) * sin(raan) Rate | Unitless Per Time | Real Number or Text | Rate of change of p. Computed by applying the variation of parameters equations of motion to the perturbative acceleration. |
| tan(i/2) * cos(raan) Rate | Unitless Per Time | Real Number or Text | Rate of change of q. Computed by applying the variation of parameters equations of motion to the perturbative acceleration. |
| Mean Lon Rate | AngleRate | Real Number or Text | Rate of change of mean longitude including the osculating mean motion. Computed by applying the variation of parameters equations of motion to the perturbative acceleration. |
| Mean Lon Perturb Rate | AngleRate | Real Number or Text | Rate of change of mean longitude excluding the osculating mean motion. Computed by applying the variation of parameters equations of motion to the perturbative acceleration. |
| Mean Motion | AngleRate | Real Number | A measure of the osculating period of the orbit, expressed as an angular rate. The value is 2pi rad / orbit_period. |