# Calculate the state vector of planets and moons

What is the efficient way to calculate the state vector of planets and moons?

The coordinate system for planets would be with center in Solar System Baricenter, for Moon- with center in Earth and in Solar System Baricenter.

## 1 Answer

The use of JPL kernels (de430.bsp) and python jplephem package worked for me.

Compared with the JPL Horizons, results are the same.

from jplephem.spk import SPK
kernel = SPK.open('de430.bsp')

position = kernel[0,3].compute(2457061.666666667)

print(position)

• Problem solved! Therefore it's perfectly OK to accept your own answer. – uhoh Mar 12 '18 at 19:12