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.
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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)
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$\begingroup$ Problem solved! Therefore it's perfectly OK to accept your own answer. $\endgroup$ – uhoh Mar 12 '18 at 19:12
