MHO_ManualPolPhaseCorrection

Purpose

MHO_ManualPolPhaseCorrection applies a user-specified polarization-specific phase offset to visibility data. The operator computes a constant phase correction phasor from the offset (in degrees) and multiplies all matching visibility elements per channel. The correction accounts for sideband inversion (LSB vs USB) and distinguishes between reference and remote stations.

Control File Trigger

  • Keywords: pc_phase_offset_x, pc_phase_offset_y, pc_phase_offset_r, pc_phase_offset_l

  • Category: calibration

  • Priority: 3.5

Each keyword selects one of the four polarization states (X, Y, R, L). The keyword name determines the polarization via the suffix (_x, _y, _r, _l).

Parameters for pc_phase_offset_<pol> keywords

Parameter

Type

Description

value

real

Phase offset in degrees applied to the specified polarization.

Input Data

This operator acts on the visibility_type container.

Algorithm

MHO_ManualPolPhaseCorrection has no Initialize method; all work occurs in ExecuteInPlace.

The builder (MHO_ManualPolPhaseCorrectionBuilder) parses the polarization from the keyword name and resolves station identifiers.

Execution (``ExecuteInPlace``):

  1. Iterate over the reference (index 0) and remote (index 1) stations.

  2. For each station, check applicability via IsApplicable: the operator matches if any configured station identity equals the station’s Mark4 ID (1-character match) or 2-character station code (2-character match). Wildcard ? matches any Mark4 ID, and ?? matches any station code.

  3. If applicable, retrieve the polarization-product axis and channel axis.

  4. For each polarization product:

    1. Check polarization match via PolMatch: the character at the station’s index in the pol-product label must equal the configured polarization (case-insensitive).

    2. Store the phase offset (converted to radians) as metadata on the pol-product axis under the key ref_pcphase_offset_<pol> or rem_pcphase_offset_<pol> (depending on station index).

    3. For each channel ch:

      1. Convert the phase offset from degrees to radians: theta = phase_offset * pi / 180.

      2. Construct the correction phasor: Phi = exp(i * theta).

      3. Apply sideband conjugation: if the channel’s net_sideband tag equals L (lower sideband), conjugate the phasor: Phi = conj(Phi).

      4. Apply station conjugation: if the station index is 0 (reference station), conjugate the phasor: Phi = conj(Phi).

      5. Multiply the visibility sub-view at (pol-product, channel) by Phi.

Effect on Data

For each matching station and polarization, the operator applies a constant phase rotation to every channel in the visibility data. The phase rotation is determined by the user-specified offset in degrees. The correction phasor is conjugated for both lower-sideband data and reference-station data (so the net sign depends on which combination applies). The phase offset value (in radians) is stored as metadata on the polarization-product axis for later inspection.