Purpose and Description
The IRSFRINGE tool is an IDL-based GUI package that allows observers to interactively remove fringes from IRS spectra. Fringes that originate from the detector subtrates are observed in the IRS Short-High (SH) and Long-High (LH) modules. In the Long-Low (LL) module, another fringe component is seen as a result of the pre-launch change in one of the LL filters. The fringes in the Short-Low (SL) module are not spectrally resolved. Usually the fringes are already largely removed in the pipeline processing when the flat field is applied. However, this correction is not perfect and remaining fringes can be removed with IRSFRINGE from data in each module.
IRSFRINGE is available as a stand-alone package and is also part of the Spectroscopic Modeling, Analysis and Reduction Tool (SMART). Two defringing methods can be used. The first method makes use of a robust sine function fitting method. This method uses a first order approximation to the full optical interference model by assuming the the physical and optical parameters are constant within one order range. The second method (under development) makes use of the flat-field and tries to minimize the fringe residuals by matching the flat-field with the data before applying it.
IRSFRINGE operates in two modes: automatic and manual. In the manual mode, tolerance or a number of fringes to be removed can be set.