The CATS project started in 1992 as a lightweight alternative to the MASS simulator. The MASS simulator was designed by the former Centre d'Etudes de la Navigation Aérienne in ADA, and used a mass-energy model (MASS is still alive and still in use for real time simulations at DSNA/DTI, but also at the Eurocontrol Experimental Centre). This model is accurate, but also quite slow, and MASS was not easy to use for fast-time simulations.

The CATS simulator uses a tabulated model based on the BADA Eurocontrol performance model. This model is public domain and available on the Eurocontrol Experimental Centre web site. Tabulated models are less precise than mass-energy models, but are very well suited for fast-time simulations.

CATS became the de facto standard for fast time simulation at DSNA/DTI, under the name OPAS. CATS and OPAS have slightly diverged. CATS remains a research product, with lot of different modules, including highly efficient conflict detection and resolution modules (see projects SAGES, ERCOS and FACES homepage). It is still maintained internaly by the POM team. OPAS is now maintained by the PER team of DSNA/DTI.

CATS can handle French, European, and even US traffic; it can use data from the french CAUTRA system, the CFMU european databases or the data of the NASA fast-time simulator FACET. Simulating one day of european traffic (including conlict detection) takes around 15 to 30 minutes, depending on the machine CATS is running on.

CATS has been used for many different purposes, including comparison of European/US traffic, european airspace complexity reports, etc...


The CATS simulator is not public domain. A reduced version, called DOGS was distributed on the open ATC website. Unfortunately this web site is now dead, and DOGS has apparently disappeared from the surface of earth... Enquiries about the availability of OPAS must be directed to the head of the PER team of DSNA/DTI.

CATS, DOGS and OPAS are written in Ocaml.

Usefull links

Main publications

There are very few publications describing specifically CATS, as it is mainly a support tool.

A traffic complexity approach through cluster analysis} Nicolas Durand, Geraud Granger ATM2003 (2003/05/15)

Arithmetic simulation and performance metrics Jean-Marc Alliot, Geraud Granger, Jean-Marc Pomeret Digital Avionics System conference 2002 and Technical Interchange Meeting on Performance 2002 (2002/05/15)

A statistical analysis of the influence of vertical and ground speed errors on conflict probe Jean-Marc Alliot and Nicolas Durand and Geraud Granger ATM 2001 (2001/07/01)

CATS: A complete Air Traffic Simulator JM Alliot, JF Bosc, N Durand, L Maugis 16th DASC. Also available in HTML format (1997/10/26)

Statistical Study of the French Airspace Congestion Nicolas Durand, Jean-François Bosc, Jean-Marc Alliot (1994/07/01)

More publications discussing CATS can be found on projects SAGES, ERCOS and FACES homepages.

All publications of the POM team can be found here.

The publications of the former LOG (Global optimization lab) may be found there.

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