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Astron. Astrophys. 346, 626-632 (1999)

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Appendix A: polarization study of the GOLF experiment

The GOLF instrument is an optical system that allows us to combine the Stokes parameters of the incident solar light to measure different physical solar magnitudes such as the radial velocity or the SMMF. In this appendix an optical description of the experiment is given in terms of the Stokes parameters and the Mueller matrix of each optical component (for a detailed study of the polarized light see e.g. Casas 1980).

The GOLF instrument has 3 optically active elements: a movable linear polarizer (P), a fixed quarter wave plate ([FORMULA]) and another rotating quarter wave plate ([FORMULA]) (for a deeper description of these components see Gabriel et al. 1995). Denoting by I, Q, U and V the four components of the Stokes vector, the properties of the light at the exit of the system can be described by:

[EQUATION]

where the subscript o stands for the solar light parameters at the entrance of the instrument.

If we suppose that the first quarter wave plate ([FORMULA]) is making an angle [FORMULA], with the optical axis, we can substitute the matrices of each element and perform the matrix product. The result is a function of two parameters, the angle [FORMULA] between the polarizer P and the optical axis; and [FORMULA] between the second quarter wave plate ([FORMULA]) and the optical axis:

[EQUATION]

In Fig. A1 we can see the nominal working cycle of GOLF and the Stokes parameters of each measurement.

[FIGURE] Fig. A1a and b. Nominal GOLF 80 second working cycle a including Stokes parameters associated with each measurement and the related sampling points over the solar profiles b corresponding to the first 8 (40 s). Here, [FORMULA] and [FORMULA]

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© European Southern Observatory (ESO) 1999

Online publication: May 21, 1999
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