KOST is the Kepler Orbital Simulation Toolkit. It is a small programming library, intended to make life easier for programmers who have to deal with Keplerian two-Âbody models, which are often useful for describing and predicting the motion of spacecrafts and celestial bodies. KOST is available for the C programming language, and it contains some utility functions for use in C++.
The structs of KOST are deliberately designed to be as compatible as possible with the structs of Orbiter, but it is possible to use KOST in standalone applications without access to the Orbiter API.
Version 0.75 has the same API as version 0.5, but the accuracy of orbital element calculation has improved, especially for some special cases, such as equatorial and radial orbits. It also comes with a program to test the accuracy of KOST.