In search of random noise
In order to make the best high resolution images of IRAS data it is necessary to incorporate any knowledge about the instrument into a model: the IRAS model. This is necessary since every remaining systematic effect will be amplified by any high resolution technique into spurious artifacts in the images. The search for random noise is in fact the never-ending quest for better quality results, and can only be obtained by better models. The Dutch high-resolution effort has resulted in HIRAS which drives the MEMSYS5 algorithm. It is specifically designed for IRAS image construction. A detailed description of HIRAS with many results is in preparation. In this paper we emphasize many of the instrumental effects incorporated in the IRAS model, including our improved 100 micron IRAS response functions.