Given a counts light curve prepared using gtbin for a specific location on the sky, this tool computes the exposure (cm2-s) associated with each time bin, allowing a light curve in photons/s to be computed.
If the light curve file contains DSS keywords from gtselect that describe an acceptance cone on the sky from which the events are extracted, this tool will perform an aperture correction, i.e., it will adjust the exposure as a function of energy to account for the tails of the psf that lie outside the acceptance cone.
In order to provide reasonably accurate flux estimates for broad energy bands, the exposure must be weighted by a function that approximates the spectral shape of the target source. This function may either be specified using an XML model definition such as those used with gtlike, or it can be given as a simple spectral index.
Usage: gtexposure infile scfile irfs srcmdl target specin ra dec rad apcorr emin emax enumbins