Hinode / EIS Hinode Data Analysis Workshop, Paris, Nov 2007 Dr Peter Young, Rutherford Appleton...

Dr Peter Young, Rutherford Appleton LaboratoryDr Peter Young, Rutherford Appleton LaboratoryHin

od

e /

EIS

Hin

od

e /

EIS

Hinode Data Analysis Workshop, Paris, Nov 2007Hinode Data Analysis Workshop, Paris, Nov 2007

What does eis_prep do?What does eis_prep do?

Dr Peter YoungDr Peter YoungRutherford Appleton Laboratory, UKRutherford Appleton Laboratory, UK


od

e /

EIS

Hin

od

e /

EIS


eis_prepeis_prep

• eis_prep takes a level-0 EIS FITS file and calibrates iteis_prep takes a level-0 EIS FITS file and calibrates it• The output is a level-1 EIS FITS fileThe output is a level-1 EIS FITS file

• Pixel intensities are stored in Pixel intensities are stored in data numberdata number (DN) units in the level-0 file (DN) units in the level-0 file• In the level-1 FITS file they are stored as erg cmIn the level-1 FITS file they are stored as erg cm-2-2 s s-1-1 sr sr-1-1 ÅÅ-1-1

• In addition to the level-1 file, an additional error file is createdIn addition to the level-1 file, an additional error file is created• The error file contains 1The error file contains 1σσ errors on the intensities errors on the intensities


od

e /

EIS

Hin

od

e /

EIS


‘‘Missing’ dataMissing’ data

• Some pixels in the data should not be used for analysis, e.g.,Some pixels in the data should not be used for analysis, e.g.,– saturated pixelssaturated pixels– defective pixelsdefective pixels– cosmic rayscosmic rays

• These pixels are flagged by eis_prep by giving them the value -100 in These pixels are flagged by eis_prep by giving them the value -100 in the error FITS file (the error FITS file (notnot the level-1 file) the level-1 file)


od

e /

EIS

Hin

od

e /

EIS


eis_prep: Step 1eis_prep: Step 1

• The first thing eis_prep does is flag any saturated pixels as missing The first thing eis_prep does is flag any saturated pixels as missing datadata

• Saturated pixels have a value of 16,383 DN (2Saturated pixels have a value of 16,383 DN (21414-1)-1)


od

e /

EIS

Hin

od

e /

EIS


eis_prep: Step 2eis_prep: Step 2

• The CCD pedestal and dark current are removedThe CCD pedestal and dark current are removed• For most data-sets the method is as follows:For most data-sets the method is as follows:

– take specified 3D window arraytake specified 3D window array– find 2 % of pixels with the lowest DN valuesfind 2 % of pixels with the lowest DN values– find the median value of these 2 % pixelsfind the median value of these 2 % pixels– subtract this value from every pixelsubtract this value from every pixel

• Around 1 % of pixels will end up with a negative DN value after this Around 1 % of pixels will end up with a negative DN value after this processprocess– these pixels will be flagged as missingthese pixels will be flagged as missing


od

e /

EIS

Hin

od

e /

EIS


Warm and hot pixelsWarm and hot pixels

• The EIS detectors exhibit a number of pixels that yield anomalously The EIS detectors exhibit a number of pixels that yield anomalously high DN valueshigh DN values

• The brightest of such pixels are termed “hot pixels”The brightest of such pixels are termed “hot pixels”• All others are referred to as “warm pixels”All others are referred to as “warm pixels”

• These pixels can have different characteristics:These pixels can have different characteristics:– some are permanentsome are permanent– some last for several weeks and then disappearsome last for several weeks and then disappear– some flickersome flicker


od

e /

EIS

Hin

od

e /

EIS


Warm and hot pixels, and cosmic raysWarm and hot pixels, and cosmic rays

• The EIS cosmic ray removal routine (eis_despike) flags most of the The EIS cosmic ray removal routine (eis_despike) flags most of the warm and hot pixelswarm and hot pixels

Cosmic rayCosmic ray Hot pixelHot pixel Warm pixelsWarm pixels

Image cleaned with Image cleaned with eis_despikeeis_despike

Raw data Raw data


od

e /

EIS

Hin

od

e /

EIS


Warm and hot pixels, and cosmic raysWarm and hot pixels, and cosmic rays

• Warm and hot pixels lying within a line profile are often not flagged by Warm and hot pixels lying within a line profile are often not flagged by eis_despikeeis_despike

• For these, it is necessary to flag them by using warm and hot pixel For these, it is necessary to flag them by using warm and hot pixel mapsmaps

• The maps are created using engineering studies and stored in The maps are created using engineering studies and stored in SolarsoftSolarsoft

• Hot pixel maps:Hot pixel maps:– $SSW/$SSW/hinode/eis/data/cal/hphinode/eis/data/cal/hp

• Warm pixel maps:Warm pixel maps:– not implemented yetnot implemented yet


od

e /

EIS

Hin

od

e /

EIS


Step 3: HPs, WPs and CRsStep 3: HPs, WPs and CRs

• Step 3a:Step 3a:– use hot pixel map to flag hot pixelsuse hot pixel map to flag hot pixels

• Step 3b (not implemented yet):Step 3b (not implemented yet):– use warm pixel map to flag warm pixelsuse warm pixel map to flag warm pixels

• Step 3c:Step 3c:– flag cosmic rays using eis_despikeflag cosmic rays using eis_despike– (note: eis_despike calls the CDS routine new_spike)(note: eis_despike calls the CDS routine new_spike)

• All flagged pixels are marked as missingAll flagged pixels are marked as missing


od

e /

EIS

Hin

od

e /

EIS


Warm pixels and hot pixelsWarm pixels and hot pixels

• The numbers of WPs and HPs on the CCDs are increasing with timeThe numbers of WPs and HPs on the CCDs are increasing with time• There are many more WPs then HPsThere are many more WPs then HPs• Currently (Oct 2007) around 4 % of the CCD pixels are WPsCurrently (Oct 2007) around 4 % of the CCD pixels are WPs• In two years time predicted to be 12-15 %In two years time predicted to be 12-15 %

Louise Bradley, Louise Bradley, MSSLMSSL


od

e /

EIS

Hin

od

e /

EIS


Step 4: calibrated intensitiesStep 4: calibrated intensities

• DN values are converted first to photonsDN values are converted first to photons• Photons converted to erg cmPhotons converted to erg cm-2-2 s s-1-1 sr sr-1-1 ÅÅ-1-1 using EIS effective area curves using EIS effective area curves• Curves derived before launch in lab. calibrationCurves derived before launch in lab. calibration• Curves available in:Curves available in:

– $SSW/hinode/eis/response$SSW/hinode/eis/response


od

e /

EIS

Hin

od

e /

EIS


Step 5: errors on intensityStep 5: errors on intensity

• Fractional errors given by:Fractional errors given by:

• 2.5 is an estimate of the CCD read noise2.5 is an estimate of the CCD read noise

[ (Photons) + (2.5)[ (Photons) + (2.5)22 ] ]1/21/2 / Photons / Photons

Hinode / EIS Hinode Data Analysis Workshop, Paris, Nov 2007 Dr Peter Young, Rutherford Appleton...

Documents

Transcript of Hinode / EIS Hinode Data Analysis Workshop, Paris, Nov 2007 Dr Peter Young, Rutherford Appleton...