University of Utah

What is FROGS?
FROGS stands for Fancy Reconstruction by Optimization over Gamma ray Simulations. It is an implementation of the image template analysis for arrays of Cherenkof telescopes. Relevant references are Le Bohec et al., 1998 and de Naurois and Rolland, 2011. The likelihood is calculated as by de Naurois and Rolland but the model is tabulated and obtained from simulations of a large number of gamma ray showers instead of being obtained from a semi analytical model. FROGS was developped in the context of the GrISU(tah) simulation and analysis programs and of VERITAS but it is specific to neither. It is written in plain c but requires a c++ compiler and the GSL libraries and the Cherenkov telescope data to be stored in some specific structures in a function to be written by the user. There is no actual documentation but the comments and example provided in the program files should be sufficient. The FROGS functions are currently maintained by Stephane Vincent ( and Stephan LeBohec (

Anyone is welcome to download the FROGS files to use them for any chosen purpose under the terms specified in the GNU General Public License. An explicit reference to the package and this distribution page should be given in publication of studies using the FROGS functions. Comments and suggestions can be made by writing directly to the authors Stephane Vincent ( and Stephan LeBohec (


Comments regarding the web page itself should be sent to Stephan LeBohec (