Polarization Calibration of HMI
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Polarization Calibration of HMI A. Norton, J. Schou, D. Elmore, J. Borrero, S. Tomczyk, G. Card + High Altitude Observatory National Center for Atmospheric Research
description
Polarization Calibration of HMI. A. Norton, J. Schou, D. Elmore, J. Borrero, S. Tomczyk, G. Card + High Altitude Observatory National Center for Atmospheric Research. Polarization Modulation Schemes. Mod A - 4 observations mix linear & circular (80 sec) I Q U V - PowerPoint PPT Presentation
Transcript of Polarization Calibration of HMI
Polarization Calibration of HMI
A. Norton, J. Schou, D. Elmore,
J. Borrero, S. Tomczyk, G. Card +High Altitude Observatory
National Center for Atmospheric Research
Polarization Modulation Schemes
Mod A - 4 observations mix linear & circular (80 sec) I Q U V
I Q U VMod C - 6 obs separate linear & circular I±Q, I±U, I±V (120 sec)
Can correct for velocity during Mod C.
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ModA =
1 0.809 0 0.588
1 −0.809 0 0.588
1 0 0.809 −0.588
1 0 −0.809 −0.588
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ModC =
1 1 0 0
1 −1 0 0
1 0 1 0
1 0 −1 0
1 0 0 1
1 0 0 −1
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Polarization Calibration Unit (PCU) G. Card, D. Elmore, S. Tomczyk, K. Streander +
Linear Polarizer & a 1/4 Waveplate:
*Moved in/out of beam (1.25 resolution)
*Rotate optics (0.001° resolution)
Inputs fixed states of polarization into HMI for calibration purposes
PCU HMI Tel HMI Polarizer
1/4 1/2 LinWP WP WP Pol
HMI TelRet (,)
Lin 1/4Pol WP
17 Unknowns in optical path:3 - Input light - Slamp= ([1.0], [q], [u], [v])4 - PCU - transmissions, retardation error and mount error of WP2 - HMI tel - retardation and angle6 - HMI Polarizer - mount errors and retardation errors for WPs, 2 - CCD - gain, bias
Sin Sout
Calculating theT-Matrix & Polarimeter Response Matrix
1. Calibration sequences selected to constrain unknowns: With PCU elements in/out of beam and at various angles, step through a variety of HMI waveplate orientations. Short sequence - 69 exposures, includes Mod A Long sequence - 140 exposures, includes Mod C.
2. Forward model light path.
3. Use least squares fitting routine to solve for unknowns.
4. Combine for Telescope matrix & Polarimeter Response Matrix. [ ]measured Suns s= XT
Monte Carlo Simulations - Photon Noise
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T =
1 0 0 0
0 0.98 0.04 −0.20
0 0.04 0.94 0.35
0 0.20 −0.35 0.91
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Terrors =
0 0 0 0
0 0.97 0.87 4.52
0 0.87 1.33 3.50
0 4.52 3.50 1.53
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×10−5
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X =
1 1.81 0.65 1.62
1.03 −1.60 0.15 1.71
0.67 −0.09 1.60 −1.92
0.47 −0.12 −2.4 −1.41
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Xerrors =
5.2 8.8 12.9 12.6
5.9 5.7 22.8 10.4
4.1 16.8 10.8 14.4
5.0 28.4 9.3 4.8
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×10−5
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OIPD =
0.01 0.1 0.1 0.1
0.001 0.01 0.01 0.01
0.001 0.01 0.01 0.01
0.001 0.01 0.01 0.01
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≈ 0.1%Calibration requirement are that uncertainties in [XT] < 0.1%
Calibration in Progress
1st magnetogram 2/7/06 courtesy of J. Schou
Polarization data taken Feb 9-10
With PCU in beam. Work in progress.
Please check HAO website for updates
http://web.hao.ucar.edu/hmi
