MAST:IUE:Gallery:Public Relations Images

IUE Public Relations Images

These are public relations images obtained by IUE during its continuing mission, and are identical in format to those used by the IUE staff and guest observers. False color has been added to most images. This page is also available in a text-only format. Much of the information for these images was made available by Scott Snell, Computer Sciences Corp. while working on the IUE Project.

There are two image types: acquisition and spectrum. Acquisition images are taken by the Fine Error Sensor (FES) in a scanning mode: it is commanded to step its aperture across the field if view in a raster pattern to generate a field image. The pixel size is limited by the size of the FES aperture, eight arc seconds. The maximum image size is 16 arc minutes. To the left of the image, North and East are indicated, as well as the spacecraft orientations for Pitch and Yaw. The first set of axes changes from image to image because IUE is required to maintain a fixed orientation with respect to the Sun, not the stars. The second set remains constant since it is fixed within the spacecraft body. Dark patches which appear near the center of the field of view are apertures in the science instrument that admit light to the spectrographs.

Raw spectrum images are obtained by projecting the target spectrum onto an SEC vidicon, which is then "read down" to the ground station at the end of the exposure. The low dispersion images contain a single spectrum on the faceplate, except for the Supernova 1987A images, which contain two spectra - one each for the large and small apertures. The short wavelengths are at the top of the images, with the longer wavelengths at the bottom. In many of the SWP images, a broad emission line is present near the top arising from the cloud of hydrogen that surrounds the Earth, and is not intrinsic to the target.

The high dispersion images (Neptune and Spica) appear to consist of numerous spectra. Each part, or order, covers only a small part of the total range of the detector. These orders are combined to create a single spectrum covering essentially the same range as a low dispersion spectrum, but with greater resolution. For both types of spectra, plots are presented that show the spectrum after it has been processed. The low dispersion plots cover the complete spectrum, while the high dispersion plots only include a portion of the spectrum.