This page (revision-14) was last changed on 27-Nov-2017 16:38 by Peter Young

This page was created on 08-Oct-2013 20:24 by Peter Young

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EISCalibration
EISCalibration

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At line 1 removed 3 lines
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
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This method is described in [Del Zanna (2013)|http://adsabs.harvard.edu/abs/2013A%26A...555A..47D]. If you derived a line intensity with the original lab calibration, then the corrected intensity is derived by multiplying by the factor
!!H. Warren method
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{{IDL> cal_factor=eis_ltds(date,wvl)}}
I have attempted to extend Giulio's method of using the atomic data to infer the shape of the effective areas by including information from the SDO/EVE instrument. EIS routinely makes full-disk mosaics (HOP130), which can be used to compute irradiances that be compared with those from EVE.
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where 'date' is the observation date and 'wvl' is the wavelength.
If you had previously used the /correct_sensitivity option in eis_prep, then the correction factor is given by:
{{IDL> cal_factor=eis_ltds(date,wvl,/undecay)}}
!!Warren, Ugarte-Urra, and Landi method
We have attempted to extend Giulio's method of using the atomic data to infer the shape of the effective areas by including information from the SDO/EVE instrument. EIS routinely makes full-disk mosaics (HOP130), which can be used to compute irradiances that be compared with those from EVE. Below is a comparison of the EIS and EVE irradiances for 195.
[{Image src = 'eis_eve_ratio.fe_12_195_119.jpg' width='600'}]
We then use very deep observations taken above the limb to fit a model that includes both an emission measure distribution and potential modifications to the effective areas. The effective area near 195 is fixed to lie on the EIS-EVE curve shown above. Here is an example of this applied to some off-limb spectra taken in 2007.
[{Image src = 'eis_spec_20071104_202810_256_129.dem.jpg' width='600'}]
By repeating this analysis for several periods during the mission we are able to infer the effective areas as a function of wavelength and time. Details are given in a paper recently submitted to [astro-ph|http://arxiv.org/pdf/1310.5324v2.pdf].
There is software distributed in SSW that computes the new effective areas. Perhaps the most useful routine is [eis_recalibrate_intensity.pro|http://sohowww.nascom.nasa.gov/solarsoft/hinode/eis/idl/atest/hwarren/calibration/eis_recalibrate_intensity.pro] which takes an intensity computed with the pre-flight calibration and computes the corresponding intensity for the modified effective areas. One can also use [eis_ea_nrl|http://sohowww.nascom.nasa.gov/solarsoft/hinode/eis/idl/atest/hwarren/calibration/eis_ea_nrl.pro] to compute the new effective areas as a function of wavelength and time.
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!!Applying the new calibrations to the output from EIS_AUTO_FIT
If you use the Gaussian fitting routine EIS_AUTO_FIT, then the recommendation is to apply the new calibrations at the EIS_GET_FITDATA stage. For example,
{{IDL> int=eis_get_fitdata(fitdata,/int,calib=1}}
will apply the Del Zanna (2013) calibration to the output intensity. The options are:
0 - the calibration is not changed\\
1 - the Del Zanna (2013) calibration is applied\\
2 - /correct_sensitivity is "undone" and the Del Zanna (2013) calibration is applied\\
3 - the Warren et al. (2014) calibration is applied\\
4 - /correct_sensitivity is "undone" and the Warren et al. (2014) calibration is applied
To summarize, the steps to be done are:
* Use EIS_PREP to calibrate the level-0 file with standard options (no /correct_sensitivity).
* Extract the windata structure using EIS_GETWINDATA with the /refill option.
* Perform the Gaussian fit with EIS_AUTO_FIT.
* Extract the intensity array with EIS_GET_FITDATA using the calib option set to 1 or 3 (Del Zanna or Warren).
This page (revision-14) was last changed on 27-Nov-2017 16:38 by Peter YoungTop