Polarization Handling

The polarization handling components provide builders for operators that process polarization-specific corrections and transformations in VLBI fringe fitting, including field rotation, parallactic angle corrections, and polarization product summation.

MHO_CircularFieldRotationBuilder

Class	MHO_CircularFieldRotationBuilder
Primary Functionality	Builds a MHO_CircularFieldRotationCorrection operator
Key Features	Constructs and adds CircularFieldRotationBuilder to toolbox Inherits from MHO_OperatorBuilder Requires station mount type information Handles field rotation corrections for circular polarizations

The MHO_CircularFieldRotationBuilder class builds a circular field rotation correction operator that compensates for field rotation effects in circular polarization observations. This correction is essential for maintaining proper polarization alignment as the Earth rotates relative to the observed source. This builder requires station mount type information to properly calculate the field rotation corrections for each station in the VLBI array.

MHO_LinearDParCorrectionBuilder

Class	MHO_LinearDParCorrectionBuilder
Primary Functionality	Builds a delta-parallactic angle correction operator
Key Features	Constructs linear-pol DPar correction operator Handles parallactic angle corrections for linear polarization Returns bool indicating construction success Essential for linear polarization observations

The MHO_LinearDParCorrectionBuilder class builds a delta-parallactic angle correction operator for linear polarization observations. This correction compensates for the effect of the parallactic angle difference in the magnitude of the power distributed between the parallel and cross-handed polarization products. It is only applied when a Pseudo-Stoke-I summation of all four pol-products (XX, XY, YY, YX) is requested.

MHO_MixedPolYShiftBuilder

Class	MHO_MixedPolYShiftBuilder
Primary Functionality	Builds operator for 90-degree phase shift to Y pol in mixed fringes
Key Features	Constructs MHO_MixedPolYShift operator Handles mixed linear-circular fringe polarization corrections Applies 90-degree phase shift to Y polarization

The MHO_MixedPolYShiftBuilder class builds an operator that applies a 90-degree phase shift to the Y polarization in mixed linear-circular fringe observations. This correction is a useful approximation when processing data that combines linear and circular polarization systems.

MHO_PolProductSummationBuilder

Class	MHO_PolProductSummationBuilder
Primary Functionality	Builds operator for polarization product summation
Key Features	Constructs PolProductSummation operator Handles polarization product summation Supports pseudo-Stokes-I calculations Returns bool indicating construction success

The MHO_PolProductSummationBuilder class builds an operator that performs summation over specified polarization products. This is necessary for creating composite polarization measurements such as pseudo-Stokes-I parameters, but also sums of the form RR+LL. This functionality is useful for total intensity measurements from polarized VLBI observations.