1 Introduction

In this paper we address two fundamental aspects which influence, to different extent, the photometric quality of IUE high resolution spectra, i.e. the correction for the echelle blaze function (ripple correction), and the absolute calibration. The results of this study, which are based on about one thousand spectra, mainly of IUE standard stars, have been implemented in the IUE Newly Extracted Spectra system (INES), a data archive and distribution facility developed by the IUE ESA project (see Wamsteker et al. 1999), as well as in the NEWSIPS data reduction package (Nichols & Linsky 1996; Garhart et al. 1997). Full details on the INES system are provided by Rodríguez-Pascual et al. (1999, Paper I) for low resolution data, and by González-Riestra et al. (1999a, Paper III) for high resolution data.