This page (revision-27) was last changed on 26-Oct-2022 21:57 by Peter Young

This page was created on 07-Jun-2010 19:35 by PeterYoung

Only authorized users are allowed to rename pages.

Only authorized users are allowed to delete pages.

Page revision history

Version Date Modified Size Author Changes ... Change note
27 26-Oct-2022 21:57 7 KB Peter Young to previous
26 07-Dec-2016 14:14 6 KB Peter Young to previous | to last
25 05-Apr-2011 18:14 6 KB PeterYoung to previous | to last
24 08-Jul-2010 15:42 6 KB PeterYoung to previous | to last
23 06-Jul-2010 16:15 7 KB PeterYoung to previous | to last
22 05-Jul-2010 10:39 7 KB ViggoHanst to previous | to last
21 03-Jul-2010 14:22 7 KB ViggoHanst to previous | to last

Page References

Incoming links Outgoing links
EISmethods
EISmethods

Version management

Difference between version and

At line 1 removed 2 lines
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
At line 7 changed 2 lines
{{{IDL> data=obj_new('eis_data',filename)
}}}
IDL> data=obj_new('eis_data',filename)
At line 14 changed 2 lines
{{{IDL> data->display_methods
}}}
IDL> data->display_methods
At line 23 changed 2 lines
{{{IDL> wd=data->getvar(iwin)
}}}
IDL> wd=data->getvar(iwin)
At line 26 changed one line
where iwin is either the index of the window you want (beginning with 0), or the wavelength of the line you are interested in (e.g., 195.12, the correct window will be found as long as the wavelength given lies within the line window that was observed.) It is also possible to use the name of the line window (e.g. 'FE XII 195.120'), but in that case the string entered must be an exact copy of the name the line is known as in the fits file.
where iwin is either the index of the window you want (beginning with 0), or the wavelength of the line you are interested in (e.g., 195.12).
At line 30 removed 9 lines
WARNING: be careful with using WD to generate images in an emission line. The first dimension of WD is always wavelength and the second dimension is Solar-Y. For raster data, the third dimension will be Solar-X but ordered according to the time each exposure was taken. Since EIS rasters west-to-east this ordering is the opposite to how IDL displays images. It is recommended that you use moments to generate images - see the section further down in this document.
To get the 1D wavelength array for the window, do:
{{{IDL> wvl=data->getlam(iwin)
}}}
although bear in mind that the spectra shift in the detector-X direction during an orbit, and in the Y-direction due to the tilt of the EIS slit relative to the detector. These issues are discussed in [EIS Software Note 5|http://solarb.mssl.ucl.ac.uk/SolarB/eis_docs/eis_notes/05_WAVELENGTH_CORRECTION/eis_swnote_05.pdf] and [EIS Software Note 4|http://solarb.mssl.ucl.ac.uk/SolarB/eis_docs/eis_notes/04_SLIT_TILT/eis_swnote_04.pdf], respectively.
At line 41 changed one line
The heliocentric coordinates for the center of a raster at a given wavelength, WVL, are obtained with:
The heliocentric coordinates for the data are given by
At line 43 changed 4 lines
{{{
IDL> xcen=data->getxcen(/raster)
IDL> ycen=data->getycen(wvl,/raster)
}}}
IDL> xpos=data->getxpos()\\
IDL> ypos=data->getypos()
At line 48 changed one line
More details about EIS pointing information are given on the wiki page [Obtaining pointing information from EIS data|EISPointing].
XPOS gives the X-coordinate for each slit position and YPOS gives the position for each pixel in the Y direction.
At line 34 added one line
In addition if you want the coordinates of the center of the raster do:
At line 51 changed one line
!!Time routines
IDL> xcen=data->getxcen()\\
IDL> ycen=data->getycen()
At line 53 changed one line
!Exposure time
Note that each of these is an array of same size as the number of exposures. This is because the center of the raster moves with time due to the spacecraft jitter.
At line 55 changed one line
The exposure time (in seconds) for each exposure of the raster is given by
!!Exposure times
At line 57 changed 2 lines
{{{IDL> exp_time=data->getexp()
}}}
The exposure time for each exposure of the raster is given by
At line 60 changed one line
Note that the exposure times generally vary between exposures, and will not be exactly equal to the requested exposure time.
IDL> exp_time=data->getexp()
At line 62 removed 31 lines
!The start and end times of an exposure
The start and end times of an exposure can be obtained through the shutter open and close times (ti1 and ti2):
{{{IDL> ti1=data->getti_1()
IDL> ti2=data->getti_2()
}}}
The units are given in TI format, which is the Hinode spacecraft time. The TI format can be converted to standard time formats using:
{{{IDL> tai=data->ti2tai(ti)
IDL> utc=data->ti2utc(ti)
IDL> sec=data->sec_from_obs_start(ti)
}}}
The last method gives the time in second since the start of the first exposure in the sequence.
NOTE: the difference between the shutter open and close times, and the exposure time returned by the getexp() method generally do not agree. The former being larger by a fraction of a second. There are various technical reasons for this including a latency between the Instrument Control Unit (ICU) communicating with the Mechanism & Heater Controller (MHC), and a delayed response time of the MHC. __Users are recommended to always use the exposure time returned by getexp().__
!Other time routines
The date of an observation can be obtained with various methods:
{{{IDL> date_obs=data->getdate_obs()
IDL> date=data->getdate()
IDL> date=data->date_obs2date(date_obs)
IDL> days=data->days_since_launch(date)
}}}
getdate_obs() gives the date in 'yyyy-mm-ddThh:mm:ss.sss' format, and getdate() in 'yyyymmdd' format. The date_obs2date converts the former to the latter format, if no date_obs is given the data object's date_obs is converted. days_since_launch() gives the number of days since launch, if no date is given then the data object's date is used.
At line 97 changed one line
{{{IDL> hdr_obj=data->gethdr()}}}
IDL> hdr_obj=data->gethdr()
At line 101 changed one line
{{{IDL> hdr_obj->display_methods}}}
IDL> hdr_obj->display_methods
At line 105 changed one line
{{{IDL> text=hdr_obj->getbte_hdr() }}}
IDL> text=hdr_obj->getbte_hdr()
At line 109 changed 2 lines
{{{IDL> date_obs=fxpar(text,'DATE_OBS')
}}}
IDL> date_obs=fxpar(text,'DATE_OBS')
At line 112 removed 20 lines
Any field in the fits header can also be accessed easily by using, i.e. the above can be performed by typing
{{{IDL> date_obs=hdr_obj->getinfo('DATE_OBS')
}}}
The 'GETINFO' method can also be called by the eis data object to access the fits header fields, in which case there is no need to open the eis header object, just simply write
{{{IDL> date_obs=data->getinfo('DATE_OBS')
}}}
(The data object accesses the header object associated with it and returns the header information required)
!!Intensity units
To find the units for the intensity arrays in the data object, do
{{{IDL> units=data->getunit()}}}
which returns a 3-element string array, with the first element containing the intensity units. (The other elements are empty.)
At line 138 changed one line
{{{IDL> cal=data->getcal()}}}
IDL> cal=data->getcal()
At line 142 changed 2 lines
{{{IDL> iwin=data->getwindx(195.12)
IDL> wp=cal->warm_pixels(data,iwin[0])}}}
IDL> iwin=data->getwindx(195.12)\\
IDL> wp=cal->warm_pixels(data,iwin)
At line 153 changed one line
{{{IDL> m=obj_new(‘eis_moment’,data,iwin=195.12)}}}
IDL> m=obj_new(‘eis_moment’,data,iwin=195.12)
At line 159 changed one line
{{{IDL> m->help}}}
IDL> m->help
At line 165 changed one line
{{{IDL> m=obj_new(‘eis_moment’,data,iwin=195.12,/gauss)}}}
IDL> m=obj_new(‘eis_moment’,data,iwin=195.12,/gauss)
At line 171 removed 15 lines
To view the moments or Gauss fitting parameters you first need to create an IDL map from the moment object, e.g.,
{{{IDL> mmap=m->mk_eis_map(195.12,/vel)}}}
You can also view a 'quick and dirty' map from the data object 'd' directly via,
{{{IDL> mmap=d->mk_eis_map(195.12)}}}
This will give an intensity map computed by summing in wavelength the pixels in the spectral window.
[IDL maps|http://hesperia.gsfc.nasa.gov/~zarro/idl/maps/maps.html] are a widely used means of storing solar image data and to plot the velocity map just created, do:
{{{IDL> plot_map, mmap}}}
To view intensity or line width maps simply use the /int and /wid keywords for mk_eis_map.
This page (revision-27) was last changed on 26-Oct-2022 21:57 by Peter YoungTop