M. Collados Instituto de Astrofísica de Canarias CASSDA School 20-25 Apr 2015 - Tenerife M....

M. ColladosInstituto de Astrofísica de Canarias

CASSDA School 20-25 Apr 2015 - Tenerife



TIP@GRIS DATA REDUCTION AND

CALIBRATION

M. Collados





TIP@GRIS DATA REDUCTION AND

CALIBRATION+

Some notions on theRadiative Transfer Equation

and Inversion Techniques



2 ferroelectric liquid crystals (TIP)

δ1 = 155º δ2 = 75º θ1 = 70º θ2 = 155º Δθ = 50º

Polarimetric techniques

4 independent modulation states

Fixed retardances

θ 2= θ 2(Voltage)

θ 1= θ 1(Voltage)Polarizer

Polarizing beamsplitter




Why a polarizing beamsplitter instead of a polarizer?

Spatial modulation (Dual beam)

Temporal modulation (Single beam)




Spatial modulation (Dual beam)

Temporal modulation (Single beam)

Seeing-induced crosstalk

Flatfield-induced crosstalk




Temporal and Spatial modulation

Beam exchange



Reduction steps

• Bad pixel correction

• Dark current subtraction

• Flatfield correction

• Telescope + polarimeter calibration

• Demodulation + Beam merging

• Residual fringes correction



1.- Bad pixel correction

raw image Corrected for bad pixels



2.- Dark current subtraction

Important

• Same exposure time

as observations



3.- Flatfield correction

CORRECTION FOR

• Line inclination

• Beam misalignment

λ 1565 nm

Important

• One flat per

modulation state




λ 1565 nm

CORRECTION FOR

• Line inclination

• Beam misalignment

Important

• One flat per

modulation state




λ 1565 nmModulation state 1



4.- Telescope + polarimeter calibration



{




Unknowns:




Residual crosstalk Q, U, V ↔ Q, U, V ≈ 1%

4.- Telescope + polarimeter calibration (IV)



5.- Demodulation + Beam merging

N = T(t) I I = D(t) N // D(t) T(t) = 1→ → → →



On-line Stokes images visualization




Single beam Dual beam

I

V




Single beam Dual beam

Q

U




UQ

I V



Routines

pro cal15650lambda=15650. ; polarimetric calibrationfilecal=['27apr14.005','27apr14.009','27apr14.012','27apr14.019', $ '28apr14.001','28apr14.005','28apr14.007', $ '29apr14.002','29apr14.005','29apr14.008','29apr14.011', $ '30apr14.000','30apr14.005','30apr14.008', $ '30apr14.013','30apr14.016', $ '01may14.002','01may14.005','01may14.007', $ '02may14.002','02may14.005','02may14.012', $ '02may14.016','02may14.019', $ '03may14.001','03may14.006','03may14.010','03may14.014', $ '03may14.017','03may14.025','03may14.029', $ '05may14.001','05may14.006'] get_teles,filecal,lambda=lambda,xtau=xtau,/verbose,/displayreturnend



Routines

pro cal27apr14 ; data calibration xtau=[0.9917,174.02,1.0014,536.71] ; using all calib files ; 27 Apr - 5 Mayfileff=['27apr14.006']filecal=['27apr14.005']map='27apr14.000'gris,map,fileff,filecal,lambda=15650.,xtau=xtau,/xtalkreturnend



Data handling and preparation prior to analysis

(not included yet in standard routines)

- Continuum rectification

- Wavelength calibration

- Stray light (and PSF) evaluation

COMPARISON WITH FTS



Line Identification



Calculate dispersion



Wavelength calibrated spectrum



Continuum rectification

15th order polynomial FTS in redOBS in white



Continuum rectification

OBS in white FTS in red



2. Spectral Resolution + Stray Light

σteor= 56 mA



2. Spectral Resolution + Stray Light

FTS in redOBS in white



All steps



3. The radiative transfer equation

Synthesis

Inversion




In Intensity

t Optical depth

Sn Source function

K Absorption matrix

RTE (stationary and plane-parallel)




Unno-Rachkovsky equations

observer

LTE




Zeeman splitting




In Intensity

t Optical depth

Sn Source function

K Absorption matrix

O Evolution or extintion

operator

RTE (stationary and plane-parallel)




Free parameters: B, θ, χ, B0, B1, η, Δλd , a, v

Mag. field Source

function Line

shape Line

position

with



Profiles for different field strength



Profiles for different field inclination



Profiles for different field azimuth



RX Response function


Parameter perturbation

RTE perturbation

Perturbation solution

𝑅𝑥 (𝜏5 )=𝛿𝐼 ν

𝛿𝑥



Initial model

T

Synthesis Isyn

Observation

Iobs

Perturbed profile

δI = Isyn - Iobs

Perturbed model

δT

4. The RTE inversion



• Existence of solution?

• Unicity of solution?




Least squares




5. The RTE inversion (SIR)



6. Information obtained from spectral lines

1.- Temperature stratification

2.- LOS velocity stratification

3.- Magnetic field vector stratification

4.- Atomic parameters

5.- Element abundance



Magnetic field

Westendorp Plaza et al. (2001)

6. Information obtained from spectral lines

M. Collados Instituto de Astrofísica de Canarias CASSDA School 20-25 Apr 2015 - Tenerife M....

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