[perihelions]

Do I understand right, that it's summing ~2 million spherical harmonic terms, and the optimization is that that's accomplished in ~200 ms (per test point?)? Does this force field feed into something like a Runge-Kutta solver for predicting orbits? (I don't know much about orbital mechanics).

[sphw]

Yup, your understanding is correct. When set to full fidelity, it computes and sums 2,331,720 terms. What we optimized is the way the spherical harmonics are generated, which allows for the generation and summation to happen in less than 250 ms. Once that force information is generated, it is passed to a semi-implicit integrator – we also support RK4, but this test was using semi-implicit. That allows you to run orbital dynamics simulations; our primary use case is for testing satellite control systems.