iOrbit contains two demo packages: ground and helio demos for respectively Geocentric and Heliocentric objects. Each demo provides three analytic Astrodynamics algorithms (Kepler, Lambert and Gauss-Angles-only) for fast and reasonably accurate orbit computations.
The DerAstrodynamics Kepler algorithm computes analytically the position and velocity vectors at a user specified past or future time given the current position and velocity vectors, and the two times. The analytic Post Keplerian (Kepler+) solution, which is more accurate and closer to the solution of numerical integration, is much more suitable for realistic simulations and graphical displays.
The DerAstrodynamics Lambert algorithm computes two velocity vectors given two position vectors, the two times and the inclination indication of the transfer orbit (not the same as the transfer motion direction). This Lambert algorithm has multi-revolution capability, Post Keplerian (Kepler+) accuracy and is almost unbreakable over millions of arbitrary test cases. The solution of the Lambert algorithm can be used for initial orbit determination, orbital transfer (rendezvous, intercept), mission planning, space debris collision and many other applications.
The DerAstrodynamics Gauss algorithm computes the Post Keplerian (Kepler+) orbit of an observed object based on three time-elapsed sighting of the (known or unknown) object and the location of the observer. This new angles-only Initial Orbit Determination algorithm for optical sensors and optical telescopes utilizes an innovative range solving technique to solve for range without guesswork or brute-force searching. The output includes not just the position and velocity vectors, but also the TLE mean orbital elements at the second time point.