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At line 1 added 2 lines
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
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Whereas the width of each spectral window can vary (see Line Lists below), the height of the image ''y%%sub size%%'' read out from the CCDs is necessarily fixed for each window. So each raster has the same height in all spectral windows. This height is expressed in arcseconds.
Whereas the width of each spectral window can vary (see Line Lists below), the height of the image ''y%%sub size%%'' read out from the CCDs is necessarily fixed for each window. So each raster has the same height in all spectral windows. This height is expressed in arcseconds. In EIS's design, it was decided that a 512" image height would be sufficient (1 pixel = 1"), so this is the maximum image height that can be made at any one time.
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The most critical part of the raster description that __isn't__ summarised in the ''Raster Title'' is the Line List. This is because the line list is too variable to easily summarised. So, it gets its own panel in the raster description.
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The most critical part of the raster description ''not'' summarised in the ''Raster Title'' is the Line List. This is because the line list is too variable to easily summarised. So, it gets its own panel in the raster description.
Note that, like studies and rasters, line lists have and ID and acronym.
\\
__Rationale of a Line List__\\
When EIS makes a spectral image of a slit- or slot-sized portion of the Sun, it exposes the whole of both detectors, which amounts to some 2 × 2048 × 1024 pixels. At 16 bits per pixel (2 reserved for marking which half of which detector a pixel belongs to), this would create a massive 8 MB for all data from the detector, __at each position on the Sun!__
So, in order to limit telemetry need — even before the transition to the S-band antenna — EIS was designed so that only the spectral portions of interest on the detector would be telemetered to the ground for a given observation.
Line lists are described in terms of absolute wavelength, according to the standard wavelength calibration, so you don't need to work things out in terms of pixel co-ordinates.
__Title__\\
You'll see that, like the raster, a Line List has a one-line so-called ''Title'' string associated with it. Since this is truncated, it doesn't serve much purpose, and we'll skip it here.
__Author__\\
Again, fairly self-explanatory\\
:-)
One point to perhaps reiterate, though, is that you can use a line list created by anyone else in your study. All line lists, rasters, and studies in the OSDB are there to be re-used and cannibalised by anyone wanting to propose an observation.
__Number of lines__\\
There can be up to 25 spectral windows in a line list, but the minimum is normally three: the core lines. The core lines are
||Ion||Wavelength (Å)
|Fe XII |195.12
|Ca XVII|192.82
|He II |256.32
__Line List Detail__\\
Each spectral window can have a width that is an integer multiple of 8, from 8 to 1024 (half a CCD width), and there can be up to 25 windows, each with independent widths. In the example image above, you can see that most windows have a width of 24 pixels (a little over 0.5 Å), which is usually adequate. But a few windows are wider (32, 40 or 48 pixels). Wider windows often (but don't necessarily) indicate that the line list author was trying to capture other lines by using a wider spectral window.
This also helps to explain why the core lines of {{Fe XII}} (195.12 Å) and {{Ca XVII}} (192.82 Å) aren't explicitly included in this line list: they are already covered by the {{Fe XII}} window at 194.91 Å and the {{O V}} window at 192.84 Å, respectively.
This page (revision-57) was last changed on 07-Dec-2016 14:14 by David R WilliamsTop