NovasTerra Method

public static void Terra(
	OnSurface Location,
	double St,
	ref double[] Pos,
	ref double[] Vel
)

Public Shared Sub Terra ( 
	Location As OnSurface,
	St As Double,
	ByRef Pos As Double(),
	ByRef Vel As Double()
)

Parameters

Location  OnSurface

Structure containing observer's location

St  Double

Local apparent sidereal time at reference meridian in hours.

Pos  Double

Position vector of observer with respect to center of Earth, equatorial rectangular coordinates, referred to true equator and equinox of date, components in AU.

Vel  Double

Velocity vector of observer with respect to center of Earth, equatorial rectangular coordinates, referred to true equator and equinox of date, components in AU/day.

This function ignores polar motion, unless the observer's longitude and latitude have been corrected for it, and variation in the length of day (angular velocity of earth).

The true equator and equinox of date do not form an inertial system. Therefore, with respect to an inertial system, the very small velocity component (several meters/day) due to the precession and nutation of the Earth's axis is not accounted for here.

Reference