Sun Position (VSOP87)

VSOP87 defines the analytical solutions to the motions of the solar system planets

The main version of VSOP87 defines elliptic variables for the planets as a function of time. The VSOP data provides the following elliptic variables:

A the semi-major axis in Astronomic Units (AU where 1AU = 149597870.7km)

L the mean longitude

k = e cos π where e is the eccentricity and π is the longitude of the perihelion

h = e sin π

q = sin i/2 cos Ω where i is inclination and Ω is the longitude of the ascending node

p = sin i/2 sin Ω

The calculations are based on the time in Julian centuries after the J2000 epoch 2000-01-01 12:00:00.

T = (JDE - 2451545)/365250

References:

https://www.caglow.com/info/compute/vsop87

https://celestrak.org/SpaceData/EOP-All.txt