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At line 1 changed one line
!!!Worksheet 2 - Reading and browsing data
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
!!!Worksheet 2 - Calibrating EIS data (eis_prep)
At line 3 changed one line
The EIS FITS file to be used in all the worksheets is from 9-Dec-2007, 11:30 UT:
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'.
At line 5 changed one line
filename=’eis_l0_20061209_113031.fits’
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:
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(NOTE: you may need to add the path name, depending on where the file is located.)
{{{
IDL> filename=’eis_l0_20061209_113031.fits’
}}}
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To read an EIS FITS file from the command line, type:
If you defined the $HINODE_DATA directory and moved the file there, then you can do:
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IDL> data=obj_new(‘eis_data’,filename)
{{{
IDL> filename=eis_find_file('9-dec-2006 11:30')
}}}
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data is an IDL object. You can extract information from the object using various methods. E.g.,
The standard call to eis_prep is:
At line 15 changed 3 lines
IDL> exp=data->getexp()\\
IDL> xpos=data->getxpos()\\
IDL> wd0=data->getvar(0)\\
{{{
IDL> eis_prep, filename, /default, /save, /retain, /quiet
}}}
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wd0 is a 3D array containing the window data for the specified window (0 in this case). You can get a list of all methods by doing:
The /save keyword results in two files being created in the user's directory which have the names:
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IDL> data->display_methods
{{{
eis_l1_20061209_113031.fits
eis_er_20061209_113031.fits
}}}
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To extract the header into a string array, do:
TIP: it is a good idea to compress these files with gzip.
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IDL> hdr_obj=data->gethdr()\\
IDL> text=hdr_obj->getbte_hdr()
(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.)
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A number of useful header tags can be sent to a structure by doing:
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.
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IDL> eis_get_hdr_struc,data,hdrstr
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.
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To find which wavelength windows are contained in data, do:
IDL> wininfo=eis_get_wininfo(filename,/list)
!Exercise
#Using eis_get_wininfo and the getvar() object method, extract an image in Fe XII 195 by summing all wavelength pixels in the window. Plot the image. What do you have to do to the image to orient it correctly? (You may need to refer to XRT images from Day 1 of the workshop.)
#Using the following commands:
IDL> aux_data=data->getaux_data()\\
IDL> exptimes=data->sec_from_obs_start(*(aux_data.ti_1))\\
IDL> xpos=data->getxpos()\\
work out in which direction EIS rasters (east-west, or west-east).
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