orca.transform.ionospheric_dewarping

Ionospheric dewarping via VLSSr cross-match.

Ported from ExoPipe/extractor_pb_75.py into the orca package.

Computes pixel-level warp screens by cross-matching extracted LWA sources against the VLSSr catalog and interpolating positional offsets over the full image grid using scipy.interpolate.griddata.

Functions

parse_vlssr_text: Parse the OVRO-LWA VLSSr text catalog into a dict.
load_ref_catalog: Load a reference catalog (FITS or VLSSr text format).
generate_warp_screens: Build 2-D warp screens from LWA↔catalog cross-match.
apply_warp: Apply pre-computed warp screens to an image array.

Attributes

`logger`
`MATCH_RADIUS`
`DEFAULT_ALPHA`
`FLUX_RATIO_MIN`
`FLUX_RATIO_MAX`
`VLSS_MAX_SIZE_DEG`
`NVSS_MAX_SIZE_DEG`
`LWA_SIZE_TOLERANCE`

Functions

`parse_vlssr_text`(path)	Parse the OVRO-LWA VLSSr text catalog.
`load_ref_catalog`(path[, name])	Load a reference catalog (FITS table or VLSSr text).
`generate_warp_screens`(img_sources, cat_data, wcs_obj, ...)	Build 2-D ionospheric warp screens from LWA↔catalog cross-match.
`apply_warp`(data, screen_x, screen_y)	Apply pre-computed warp screens to an image array.

Module Contents

orca.transform.ionospheric_dewarping.logger[source]

orca.transform.ionospheric_dewarping.MATCH_RADIUS[source]

orca.transform.ionospheric_dewarping.DEFAULT_ALPHA = -0.7[source]

orca.transform.ionospheric_dewarping.FLUX_RATIO_MIN = 0.8[source]

orca.transform.ionospheric_dewarping.FLUX_RATIO_MAX = 1.2[source]

orca.transform.ionospheric_dewarping.VLSS_MAX_SIZE_DEG = 0.020833333333333332[source]

orca.transform.ionospheric_dewarping.NVSS_MAX_SIZE_DEG = 0.0125[source]

orca.transform.ionospheric_dewarping.LWA_SIZE_TOLERANCE = 1.2[source]

orca.transform.ionospheric_dewarping.parse_vlssr_text(path)[source]

Parse the OVRO-LWA VLSSr text catalog.

The text format has columns: RAh RAm RAs DECd DECm DECs … flux … where flux is in Jy and positions are sexagesimal.

Parameters:: path – Path to the VLSSr text file.
Returns:: Dict with keys ‘coords’, ‘flux’, ‘maj’, ‘ra’, ‘dec’, ‘type’, or None on failure.

orca.transform.ionospheric_dewarping.load_ref_catalog(path, name='VLSSr')[source]

Load a reference catalog (FITS table or VLSSr text).

Parameters:

path – Filesystem path to the catalog.
name – Catalog name (used to identify format).

Returns:

Dict with keys ‘coords’, ‘flux’, ‘maj’, ‘ra’, ‘dec’, ‘type’, or None on failure.

orca.transform.ionospheric_dewarping.generate_warp_screens(img_sources, cat_data, wcs_obj, shape, freq_mhz, cat_freq_mhz, lwa_bmaj_deg, clip_sigma, base_name='')[source]

Build 2-D ionospheric warp screens from LWA↔catalog cross-match.

Parameters:

img_sources – DataFrame with columns ‘ra’, ‘dec’, ‘flux_peak_I_app’, optionally ‘maj’.
cat_data – Dict from load_ref_catalog().
wcs_obj – astropy.wcs.WCS (celestial) of the reference image.
shape – (ny, nx) of the image.
freq_mhz – Observing frequency (MHz).
cat_freq_mhz – Reference catalog frequency (MHz), e.g. 74.
lwa_bmaj_deg – Beam FWHM of the LWA image (degrees).
clip_sigma – Sigma-clipping threshold (not currently applied — kept for API compatibility).
base_name – Prefix for diagnostic file names.

Returns:

Tuple (screen_x, screen_y, anchors_diag, raw_coords) where screens are 2-D arrays of pixel offsets, or (None, None, None, None) on failure.

orca.transform.ionospheric_dewarping.apply_warp(data, screen_x, screen_y)[source]

Apply pre-computed warp screens to an image array.

Parameters:

data – 2-D numpy array of image pixels.
screen_x – X-offset screen (same shape as data).
screen_y – Y-offset screen (same shape as data).

Returns:

Dewarped 2-D array, or None on shape mismatch.