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 completely restructured. Please be patient while work is in progress.


Structure OrbFit has undergone two major upgrades. Starting from version 3.0 it has been written in a different language, namely Fortran90/95. The change does not only involve the free format of the source code: the new versions deeply exploit the main features of Fortran90, especially user defined data types and modules.

OrbFit has recently exceeded the 180,000 lines of Fortran95. Also for this reason, it has been necessary to split the global system into three subsets.

  • The Distribution 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. The OrbFit distribution for UNIX, including ORBIT9, amounts to about 97,000 lines of source code.
  • The OrbFit Server Suite is a set of programs combining the OrbFit basic algorithms, as well as new and experimental ones, to provide the functionalities needed by a solar system survey to compile a catalog of orbits for the discovered objects. It is not free software, although it is not commercial either: it is distributed under a special Scienceware License , by which the user are obliged to credit the use of the software in whatever publication using its results. One main feature is the use of the Data Exchange Standard , developed originally for the projects Pan-STARRS and LSST, but now more widely used, to exchange data relevant for population orbit determination. This portion is about 18,500 lines of source code.
  • There is a non-distribution part of OrbFit, containing the software specifically used to maintain the online information systems NEODyS and AstDyS and also for our research on different topics, such as asteroid identification, proper elements for NEA, MOID computation, space debris orbit determination, and so on. Some of this software is transferred to the distribution, as the corresponding part the research is concluded and published. Other parts are specifically connected to some of our long term research programs and thus will not be distributed for now.

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. Installation under some other dialect of UNIX (e.g., BSD, HPUX, Mac OS 10 and later) should be straightforward for an expert user. We are sorry, but we are currently not equipped for distributing OrbFit in a Windows version; more exactly, we do not want to be equipped, by paying a tax to Microsoft to be allowed to provide free software.

Where can I learn more? You can use the online help here, but this document needs to be updated. You may also go directly to our online OrbFit distribution directory. After compiling the code, you can access the OrbFit main programs through the OrbFitSoft graphical interface, available in the ./doc directory.

We have abandoned the original idea of writing a mathematical specification document for OrbFit, because it would be huge and hard to maintain, even assuming we had the time of writing it, which has not been the case so far. However, we have written a textbook Theory of Orbit Determination , by A. Milani and G.F. Gronchi, Cambridge University Press, 2010 (index of this book). The content of this book covers most of the subjects which are needed to understand the working of OrbFit. The copyright for this book has been given to the publisher, thus we cannot make the full text available on the web: we are progressively making available appendixes, comments, errata corrige, and other related material on this site here.

Where can I get OrbFit in Fortran 90/95? You can download the OrbFit distribution for UNIX . However, please note this is the latest version 4.2, which has an important new feature, the use of star catalog debiasing. For this purpose we had to change the format of the observations, adding a column with the star catalog code. The data from AstDyS-2 and NEODyS-2 already have this new feature; to use the .rwo files from these sources, it is necessary to use version 4.2 and later.

Who maintains OrbFit? The OrbFit Consortium.

Last updated February 18, 2012