Solar Orbiter/STIX Visibility Imaging

Imports

import pickle

import astropy.units as apu
import matplotlib.pyplot as plt
import numpy as np

from xrayvision.clean import vis_clean
from xrayvision.imaging import vis_psf_map, vis_to_map
from xrayvision.mem import mem, resistant_mean

Create images from STIX visibility data.

The STIX data has already been prepared and stored in python pickle format the variables can be simply restored.

with open("./stix_vis.pkl", "rb") as file:
    stix_data = pickle.load(file)

time_range = stix_data["time_range"]
energy_range = stix_data["energy_range"]
stix_vis = stix_data["stix_visibilities"]

Lets have a look at the point spread function (PSF) or dirty beam

psf_map = vis_psf_map(stix_vis, shape=(129, 129) * apu.pixel, pixel_size=2 * apu.arcsec / apu.pix, scheme="uniform")
psf_map.plot()

/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:892: SunpyMetadataWarning: Missing metadata for observation time, setting observation time to current time. Set the 'DATE-AVG' FITS keyword to prevent this warning.
  warn_metadata("Missing metadata for observation time, "
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:633: SunpyMetadataWarning: Missing metadata for observer: assuming Earth-based observer.
For frame 'heliographic_stonyhurst' the following metadata is missing: hgln_obs,dsun_obs,hglt_obs
For frame 'heliographic_carrington' the following metadata is missing: crln_obs,crlt_obs,dsun_obs

  obs_coord = self.observer_coordinate

<matplotlib.image.AxesImage object at 0x76d58b44f220>

Back projection

backproj_map = vis_to_map(stix_vis, shape=(129, 129) * apu.pixel, pixel_size=2 * apu.arcsec / apu.pix, scheme="uniform")
backproj_map.plot()

/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:892: SunpyMetadataWarning: Missing metadata for observation time, setting observation time to current time. Set the 'DATE-AVG' FITS keyword to prevent this warning.
  warn_metadata("Missing metadata for observation time, "
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:633: SunpyMetadataWarning: Missing metadata for observer: assuming Earth-based observer.
For frame 'heliographic_stonyhurst' the following metadata is missing: hgln_obs,dsun_obs,hglt_obs
For frame 'heliographic_carrington' the following metadata is missing: crln_obs,crlt_obs,dsun_obs

  obs_coord = self.observer_coordinate

<matplotlib.image.AxesImage object at 0x76d58b335fd0>

Clean

clean_map, model_map, resid_map = vis_clean(
    stix_vis,
    shape=[129, 129] * apu.pixel,
    pixel_size=[2, 2] * apu.arcsec / apu.pix,
    clean_beam_width=20 * apu.arcsec,
    niter=100,
)
clean_map.plot()

/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:892: SunpyMetadataWarning: Missing metadata for observation time, setting observation time to current time. Set the 'DATE-AVG' FITS keyword to prevent this warning.
  warn_metadata("Missing metadata for observation time, "
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:633: SunpyMetadataWarning: Missing metadata for observer: assuming Earth-based observer.
For frame 'heliographic_stonyhurst' the following metadata is missing: hgln_obs,dsun_obs,hglt_obs
For frame 'heliographic_carrington' the following metadata is missing: crln_obs,crlt_obs,dsun_obs

  obs_coord = self.observer_coordinate

<matplotlib.image.AxesImage object at 0x76d58b2b1f10>

MEM

# Compute percent_lambda
snr_value, _ = resistant_mean((np.abs(stix_vis.visibilities) / stix_vis.amplitude_uncertainty).flatten(), 3)
percent_lambda = 2 / (snr_value**2 + 90)

mem_map = mem(
    stix_vis, shape=[129, 129] * apu.pixel, pixel_size=[2, 2] * apu.arcsec / apu.pix, percent_lambda=percent_lambda
)
mem_map.plot()

/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:892: SunpyMetadataWarning: Missing metadata for observation time, setting observation time to current time. Set the 'DATE-AVG' FITS keyword to prevent this warning.
  warn_metadata("Missing metadata for observation time, "
INFO: Missing metadata for solar radius: assuming the standard radius of the photosphere. [sunpy.map.mapbase]
/home/docs/checkouts/readthedocs.org/user_builds/xrayvision/envs/latest/lib/python3.9/site-packages/sunpy/map/mapbase.py:633: SunpyMetadataWarning: Missing metadata for observer: assuming Earth-based observer.
For frame 'heliographic_stonyhurst' the following metadata is missing: hgln_obs,dsun_obs,hglt_obs
For frame 'heliographic_carrington' the following metadata is missing: crln_obs,crlt_obs,dsun_obs

  obs_coord = self.observer_coordinate

<matplotlib.image.AxesImage object at 0x76d58b236ca0>

Comparison

fig = plt.figure(figsize=(10, 10))
fig.add_subplot(221, projection=psf_map)
fig.add_subplot(222, projection=backproj_map)
fig.add_subplot(223, projection=clean_map)
fig.add_subplot(224, projection=mem_map)
axs = fig.get_axes()
psf_map.plot(axes=axs[0])
axs[0].set_title("PSF")
backproj_map.plot(axes=axs[1])
axs[1].set_title("Back Projection")
clean_map.plot(axes=axs[2])
axs[2].set_title("Clean")
mem_map.plot(axes=axs[3])
axs[3].set_title("MEM")
plt.show()