The OrbFit Software Package

Warning The OrbFit software system is growing in complexity and scope: to keep up with this growth, this web site also needs to be restructured. Please be patient while work is in progress.

Structure OrbFit has undergone another major upgrade. The version 5.0 results from the merge of the previous operational version 4.2, including the new astrometric error model and various other improvements, with the version 4.3 which has never been distributed because was under test. In practice, the capabilities from 4.3 which have been incorporated include the capability to determine the semiempirical parameters appearing in the non-gravitational perturbations on asteroids, such as the direct radiation pressure, the Yarkovsky effect, and cometary outgassing. Thus covariance matrices can be up to 10x10, rather than just 6x6. Of course solution without non-gravitational parameters are still possible, but please note that the format for the orbits and covariances has been updated to make room for the new dynamical parameters and their uncertainties. OrbFit is divided into two subsets.
  • The distribution, which is free software, available under GPL; it contains the libraries, and the executable programs fitobs, catpro and orbfit. This portion provides the main algorithms for orbit propagation, ephemerides computation, orbit determination, close approach analysis, and impact monitoring. Starting from version 4.0, the OrbFit distribution also includes the software previously distributed as ORBIT9. The ORBIT9 software system used to be a plug-in of the Fortran77 version of OrbFit, and has been maintained as standalone free software. It has now been converted to Fortran95 and has been included in the distribution, thus making maintenance and upgrades easier. ORBIT9 provides long term orbit propagation for asteroids and other solar system bodies, computation of Lyapounov exponents, computation of proper elements, both analytic and synthetic, and a Graphics Interactive Fourier Filtering program for displaying the results.

    Download here: The OrbFit distribution for LINUX

  • a non-distributed part, containing the software specifically used to maintain the online information systems NEODyS and AstDyS and also for our research on different topics.

Requirements The software we are providing has been developed under LINUX and is distributed in a package allowing for automatic compilation on whatever target computer with a LINUX operating system; compilation is possible under the free Fortran95 compiler gfortran, although we mostly use the commercial compilers Intel and Lahey.

The OrbFit Consortium The idea of creating the OrbFit software came from Prof. Andrea Milani Comparetti (University of Pisa, Italy), who developed most of the algorithms and wrote a large part of the code. Other authors of the OrbFit software are scientists working in the field of celestial mechanics, with specific experience of dynamics and orbit determination for both natural celestial bodies (asteroids, comets, satellites, planets) and artificial spacecraft (satellites, interplanetary probes). The OrbFit software has been created, and is currently being maintained and expanded, by a Consortium of researchers working in different institutions.

Currently the OrbFit Consortium has the following Board of Directors:

  • Linda Dimare (SpaceDyS s.r.l.)
  • Giovanni F. Gronchi (University of Pisa, Italy)
  • Zoran Knezevic (Serbian Academy of Sciences and Arts, Serbia)
  • Federica Spoto (Minor Planet Center, United States)
  • Giacomo Tommei (University of Pisa, Italy)
  • Giovanni B. Valsecchi (IAPS-INAF, Italy)
Besides the scientists in the Board, the following researchers have contributed or are currently contributing to the development and mantainance of the software:

  • Oscar Arratia (University of Valladolid, Spain)
  • Sabrina Baccili (former student, University of Pisa, Italy)
  • Fabrizio Bernardi (SpaceDyS s.r.l.)
  • Alessia Bertolucci (SpaceDyS s.r.l.)
  • Mario Carpino (Astronomic Observatory of Brera, Italy)
  • Luisa Cattaneo (former student, University of Pisa, Italy)
  • Steve R. Chesley (JPL-Pasadena, United States)
  • Alessio Del Vigna (SpaceDyS s.r.l. and University of Pisa, Italy)
  • Davide Farnocchia (JPL-Pasadena, United States)
  • Alessandra La Spina (University of Pisa, Italy)
  • Karri Muinonen (University of Helsinki, Finland)
  • Bojan Novakovic (University of Belgrade, Serbia)
  • Maria Eugenia Sansaturio (University of Valladolid, Spain)

Webmaster Questions about this software can be addressed to

orbfit [at]

Last updated November 22, 2020