Data Provider Groups | Data Provider Elements

Rel Position Velocity

Reports the apparent relative position and velocity, as viewed from the base object, expressed with respect to the base object's central body.

Planets report position and velocity with respect to the Sun.

Available for these objects: Access

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
TrueOfDateRotating	A variation of the Fixed system where pole wander is ignored. The equator is the same as the TrueOfDate equator and the frame spins about the TrueOfDate z-axis.
Fixed	A coordinate system attached to the central body and rotating with it. The z-axis is nominally along the rotation axis.
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).
Body	The body fixed axes of the base object.

Data Provider Elements

Name	Dimension	Type	Description
Time	Date	Real Number or Text	Time.
x	Distance	Real Number	The X component of the apparent relative position vector.
y	Distance	Real Number	The Y component of the apparent relative position vector.
z	Distance	Real Number	The Z component of the apparent relative position vector.
Range	Distance	Real Number	The magnitude of the apparent relative position vector.
x/Range	Unitless	Real Number	The direction cosine of the apparent relative position vector along the X-axis.
y/Range	Unitless	Real Number	The direction cosine of the apparent relative position vector along the Y-axis.
z/Range	Unitless	Real Number	The direction cosine of the apparent relative position vector along the Z axis.
xVel	Rate	Real Number	The X-component of the apparent relative velocity.
yVel	Rate	Real Number	The Y-component of the apparent relative velocity.
zVel	Rate	Real Number	The Z component of the apparent relative velocity.
RelSpeed	Rate	Real Number	The magnitude of the apparent relative velocity vector.
Right Ascen	Longitude	Real Number or Text	The signed angle measured from the X axis to the projection of the apparent relative position vector into the XY plane. The angle increases in the direction found by the right hand rule about the Z axis.
Declination	Latitude	Real Number or Text	The angle between the apparent relative position vector and the XY-plane. The angle is positive when the Z component is positive.
LightTimeDelay	Time	Real Number	The light time delay used in computing the base and target object's location.