On 30.Jan.96, SUMER performed a raster of the Sun center in the emission line of Oxygen VI (1031.9 Å, transition region, 300 000 K) on Detector A. Slit 2 (1.0 x 300 arcsec²) was used, the exposure time was 3 seconds, the raster step was 0.76 arcsec (oversampling), 360 raster steps were performed, thus an area of 273 arcsec (east-west) x 300 arcsec (north-south) was covered in 18 minutes.
Some flatfield-type image corrections were applied to the intensity pictures. There were no data faults. Line shift and line width were determined with a simple Gaussian fitting, but only pixels containing significant intensity (in this case more than 33 counts/s/arcsec²/line) were considered, leading to some white and dark regions, respectively. The "theoretical" line center was assumed to be the line's centers-of-gravity averaged over all raster steps for each spatial pixel.
The figures below show
The pictures above give some information about the spectral window.
On the left, the average detector image of the first 90 raster steps is shown. The 300 arcsec north-south extension of the slit covers 289 pixels on the detector; 50 (spectral) pixels x 360 (spatial) pixels, a portion of the detector covering the emission line of interest, was transmitted per raster step. One spectral pixel corresponds to 0.044 Å, the whole spectral window is 2.2 Å wide. The north-south extension of a pixel is 1.038 arcsec.
On the right, the line profile is shown as intensity vs. spectral pixel. Since the wide 50-pixel-window was used, there was enough information to get a continuum picture, too. The spectral pixels regarded as continuum are marked (*). The continuum intensity is two orders of magnitude smaller than the line intensity, but the underlying structure is still visible in the continuum intensity image.
IED, 21.Jul.97