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NarrowWorksheet2
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[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
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In general the user should calibrate EIS data before he/she attempts to look it. This is because EIS data are affected by warm pixels on the CCD which make it difficult to study the images. The EIS calibration routine is called 'eis_prep'.
Generally it is recommended that you calibrate your data file before you begin taking a look at it. This is because EIS data are affected by warm pixels on the CCD which make it difficult to study the images.
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For the present worksheets we will analyze a data-set taken on 2006 December 9 at 11:30. Worksheet 1 described how to download this file. If it's still in your working directory, then do:
To calibrate your data, the standard call to eis_prep is
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{{{
IDL> filename=’eis_l0_20061209_113031.fits’
}}}
IDL> eis_prep,filename,/default,/save,/retain,/quiet
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If you defined the $HINODE_DATA directory and moved the file there, then you can do:
To see what these keywords do (and see other options), go to the wiki section on [eis_prep keywords|eis_prep_call]. The individual steps performed by eis_prep are described in detail in the wiki section on [eis_prep|eis_prep].
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{{{
IDL> filename=eis_find_file('9-dec-2006 11:30')
}}}
The keyword /default makes the routine use the default processing options, and the keyword /save makes eis_prep create two files in your current working directory. These are the level-1 FITS file, and the error FITS file.
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The standard call to eis_prep is:
TIP: it is a good idea to compress these files with gzip and move them to a directory called /level1.
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{{{
IDL> eis_prep, filename, /default, /save, /retain, /quiet
}}}
NOTE: “bad” data (referred to as missing) are flagged with a value of -100 in the error FITS file arrays (not the level-1 arrays). The missing data in the level-1 arrays are replaced with the median value of the surrounding pixels. This is useful for display purposes, but for scientific analysis you should not use any pixels flagged as missing.
With the /default option, eis_prep does the following things:
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The /save keyword results in two files being created in the user's directory which have the names:
* Flag any saturated data as missing (saturated data have a DN value of 16383)
* Remove the CCD pedestal and dark current
* Flag hot pixels as missing
* Flag warm pixels as missing (not implemented at present)
* Flag cosmic rays as missing
* Calibrate data, and create error arrays
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{{{
eis_l1_20061209_113031.fits
eis_er_20061209_113031.fits
}}}
!Exercise
#Using commands from Worksheet 2, how many pixels in the Fe XII 195 data array have been flagged as missing by eis_prep?
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TIP: it is a good idea to compress these files with gzip.
(If you defined the $HINODE_DATA environment variable in Worksheet 1, then use the eis_ingest.pro routine to transfer the files into your data directory.)
The first file is the level-1 EIS FITS file containing calibrated intensity arrays. The second file is the error file which contains the corresponding 1-sigma intensity errors for the arrays stored in the level-1 file.
Full details of the various keyword inputs to eis_prep are given in [EIS Software Note #1|ftp://sohoftp.nascom.nasa.gov/solarsoft/hinode/eis/doc/eis_notes/01_EIS_PREP/eis_swnote_01.pdf], where detailed descriptions of the various steps performed by eis_prep are given.
One feature of eis_prep is that bad pixels in the data are flagged as 'missing'. These bad pixels can be due to cosmic ray hits, saturated pixels, dust particles on the detector, hot pixels and warm pixels. The latter are by far the most numerous, and are described in more detail in [EIS Software Note #6|ftp://sohoftp.nascom.nasa.gov/solarsoft/hinode/eis/doc/eis_notes/06_HOT_WARM_PIXELS/eis_swnote_06.pdf]. Bad pixels are flagged only in the error file and are assigned a value of -100. The bad pixels in the level-1 file are replaced by a value interpolated from neighbouring pixels. More details about the effect of missing data on EIS data analysis and interpolation methods are given in [EIS Software Note #13|ftp://sohoftp.nascom.nasa.gov/solarsoft/hinode/eis/doc/eis_notes/13_INTERPOLATION/eis_swnote_13.pdf].
This page (revision-13) was last changed on 07-Dec-2016 14:14 by Peter YoungTop