MHO_ManualChannelPhaseCorrection

Purpose

MHO_ManualChannelPhaseCorrection applies user-specified, per-channel phase corrections to visibility data. For each channel matching a configured label, the operator constructs a constant phase phasor and multiplies all visibility data within that channel (across all polarization products matching the configured polarization, all spectral points, and all accumulation periods). The operator handles conjugation based on both the channel’s sideband (lower vs.upper) and the station index (reference vs.remote).

Control File Trigger

  • Keywords: pc_phases, pc_phases_x, pc_phases_y, pc_phases_r, pc_phases_l

  • Category: calibration

  • Priority: 3.5

The suffix-free keyword (pc_phases) applies to all polarizations; suffixed variants (_x, _y, _r, _l) restrict the correction to the named polarization.

Parameters for pc_phases variants

Parameter

Type

Description

channel_names

string

Comma-separated channel labels to which the correction applies.

pc_phases

list_real

Phase correction in degrees, one per channel name.

Input Data

This operator acts on the visibility_type container.

Algorithm

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

The builder (MHO_ManualChannelPhaseCorrectionBuilder) parses the polarization from the keyword name, constructs a channel-label-to-phase map from the channel_names and pc_phases parameters, and retrieves target station identifiers.

Execution (``ExecuteInPlace``):

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

  2. For each station, check applicability via IsApplicable (same station-identity matching as MHO_LSBOffset).

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

  4. For each polarization product:

    1. Check polarization match via PolMatch: if the operator’s polarization is ? (wildcard), all products match; otherwise, the character at the station’s index in the pol-product label must equal the configured polarization (case-insensitive).

    2. Determine a metadata key for storing the applied phase: ref_pcphase_<pol> for the reference station, rem_pcphase_<pol> for the remote station.

    3. For each (channel-label, phase) pair in the configured map:

      1. Iterate over all channels in the visibility container. For each channel, retrieve the channel_label and compare via LabelMatch: if the configured label contains no + or -, the given label’s +/- suffixes (used for DSB halves) are stripped before comparison.

      2. On label match, retrieve the channel’s net_sideband label (if present).

      3. Construct the base phasor from the phase value in degrees:

      \[\Phi = \exp\!\left(i \cdot \phi_{\rm pc} \cdot \pi/180\right)\]

      1. Apply conjugation rules:

        • If net_sideband equals L (lower sideband), conjugate: Phi = conj(Phi).

        • If the station is the reference station (st_idx = 0), conjugate: Phi = conj(Phi).

      2. Multiply the visibility sub-view for (pol-product, channel, all APs, all spectral points) by Phi.

      3. Store the phase value (converted to radians) as metadata on the channel axis under the ref_pcphase_<pol> or rem_pcphase_<pol> key.

Effect on Data

For each matching station and polarization, the operator multiplies all visibility data within each matching channel (across all spectral points and accumulation periods) by a constant complex phasor exp(i * phi_pc * pi/180). The phasor is conjugated for lower-sideband channels and for the reference station. The phase value (in radians) is stored as metadata on the channel axis for later inspection. The correction is independent of frequency and time within the channel.