1.2 Philosophy of the IUE Final Archive Image Processing

The philosophy that governed the development of the NEWSIPS system was intended to address four fundamental requirements:

1.

Create a uniformly processed and calibrated archive as the final product of the IUE mission IUE data have been processed using the IUESIPS system since launch in 1978. However, the IUESIPS system has undergone a number of modifications and enhancements since that time, rendering the IUESIPS archived data inhomogeneous and not fully intercomparable. The original IUESIPS system was documented in the IUE Image Processing Information Manual Versions 1.0 and 1.1. A major change to the IUESIPS system occurred in 1981 and this newer version of the software is documented in the IUE Image Processing Information Manual Version 2.0. A modification to the resampling algorithm used to create the spatially resolved (ELBL) file for low dispersion was implemented in 1985. A new photometric calibration was implemented for the LWP camera data in 1988. Later changes have customarily been documented in IUE Newsletters.

2.

Exploit new image processing techniques to improve the photometric accuracy and signal-to-noise ratio of the data

A number of new image processing techniques had been identified since the design of IUESIPS that were demonstrated to produce a more accurate photometric correction and increased signal-to-noise ratio of the extracted IUE data. Implementation of these techniques significantly improves the quality of the Final Archive.

3.

Verify and correct fundamental information for each image

In addition to providing a uniformly processed archive with improved photometric and signal-to-noise properties, the IUE Project has expended considerable effort in verifying the information available for each image.

4.

Base the contents of the Final Archive on requirements from the research community

In defining the specifications for the IUE Final Archive, and in developing the new processing algorithms and calibrations, the IUE Project was guided by the recommendations of the Final Archive Definition Committee, chaired by Dr. Jeffrey Linsky. This very active committee represented a unique grassroots effort by the astronomical community to assist in defining the scientific content of a NASA space mission, optimizing its utility for future researchers.

It is important to note that the data processed with NEWSIPS differ in fundamental ways from the data processed with IUESIPS. Images processed with these two systems are not directly intercomparable.