OpenOrb (or OOrb) is an open-source orbit-computation package.

OOrb contains, e.g., the statistical orbital ranging method (hereafter referred to as Ranging). Ranging is used to solve the orbital inverse problem of computing non-Gaussian orbital-element probability density functions (p.d.f.s) based on input astrometry.

Ranging is optimized for cases where the amount of astrometry is scarce or spans a relatively short time span. Ranging-based methods have successfully been applied to a variety of different topics such as rigorous ephemeris prediction, orbital-element-distribution studies for trans-neptunian objects, the computation of invariant collision probabilities between NEOs and the Earth, detecting linkages between astrometric asteroid observations within an apparition as well as between apparitions, and in the rigorous analysis of the impact of orbital arc-length and/or astrometric uncertainty on the uncertainty of the resulting orbits.

In OOrb, tools for making ephemeris predictions and classification of objects (i.e., NEO-MBO-TNO) are also available.

Some additional documentation is available by doing

cd doc

make pdf which should produce a PDF document 'OpenOrb_Tutorial_vN.N.pdf'.

When using this software please cite

Granvik, M., Virtanen, J., Oszkiewicz, D., Muinonen, K. (2009). 
OpenOrb: Open-source asteroid orbit computation software including statistical ranging. 
Meteoritics & Planetary Science 44(12), 1853-1861.