The date and time for which to calculate the observer's position and velocity vectors.
The geographic location of a point on or near the surface of the Earth.
Selects the date of the Earth's equator in which to express the equatorial coordinates.
The caller may pass false to use the orientation of the Earth's equator
at noon UTC on January 1, 2000, in which case this function corrects for precession
and nutation of the Earth as it was at the moment specified by the time parameter.
Or the caller may pass true to use the Earth's equator at time
as the orientation.
Calculates geocentric equatorial position and velocity of an observer on the surface of the Earth.
This function calculates position and velocity vectors of an observer on or near the surface of the Earth, expressed in equatorial coordinates. It takes into account the rotation of the Earth at the given time, along with the given latitude, longitude, and elevation of the observer.
The caller may pass
ofdateastrueto return coordinates relative to the Earth's equator at the specified time, orfalseto use the J2000 equator.The returned position vector has components expressed in astronomical units (AU). To convert to kilometers, multiply the
x,y, andzvalues by the constant value KM_PER_AU. The returned velocity vector has components expressed in AU/day.