...model

The PSF functions for the three cameras are given in the Web-version of the NEWSIPS manual at http://archive.stsci.edu/iue/manual/newsips/add4/spatpsf.html.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...Aperture.

Checks of both background solutions and continuum fluxes from the ``MXHI"-file data products obtained for Large- and Small-Aperture images taken at nearly the same time show no indication of a dependence of background solutions on aperture type.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...NEWSIPS.

Background fluxes in the prototype software are in IUE Flux Numbers (FN) per pixel. All NEWSIPS Flux Numbers are divided by 32. Extracted fluxes (MXHI/MXLO files) are left in these divided units but are summed over the extraction slit length. Except for Figs. 3 and 4, we will depict results in FN Units corresponding to the units for net fluxes in the final archive data product.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...flux.

In general, an ITF may be epoch-dependent. The IUE Project took a full set of calibration images in 1992 for the determination of a second ITF, but insufficient funds prevented the construction of a second ITF and concomitant calibration files.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.

...illuminations.

We note that a similar but milder tendency was found in the LWP camera. No tendency was found in the LWR camera. These findings are consistent with our nondetection of changes in the background levels across the long-wavelength cameras for $\tau$ Sco.

.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.