remove_lightleak#

xrtpy.image_correction.remove_lightleak(in_map, scale=1.0, leak_map=None)[source]#

Subtract visible stray light image from XRT synoptic composite images.

Parameters:#

in_map~sunpy.map.sources.hinode.XRTMap

sunpy.map.Map for the synoptic composite image which the visible stray light will be subtracted from

scalefloat, default: 1.0

Scaling factor to apply when subtracting the light leak image: out_data = in_data - scale * leak_img

leak_mapMap, optional

A leak image to subtract, if a non-default image is desired. It’s assumed that the image is 1024x1024, prepped and exposure normalized.

Returns:#

out_mapXRTMap

sunpy.map.Map of input image with the light leak removed. The metadata HISTORY is also updated to reflect the fact that the light leak was removed.

Example:#

>>> file = ``"comp_XRT20200220_061539.6.fits"``
>>> in_map = Map(file)
>>> out_map = remove_lightleak(in_map)

Notes:#

(Taken from the IDL routine xrt_synleaksub.pro) 1. XRT images obtained after 9-May-2021 suffer visible stray light contamination (light leak) due to the pre-filter failure, i.e. tiny rupture development occurred multiple times as follows:

phase 1 : 9-May-2012 12:00 phase 2 : 14-Jun-2015 12:30 phase 3 : 27-May-2017 11:00 phase 4 : 29-May-2018 00:00 phase 5 : 8-Jun-2022 12:40

2. The light leak correction is done by simply subtracting the light leak image (visible stray light component included in each X-ray filter pair) obtained during the Hinode satellite’s eclipse season, which occurs roughly May to August each year. The light leak image has the following characteristics:

  • Leak pattern and intensity differ with each filter and also with the satellite pointing.

  • Leak pattern and intensity of the same filter and pointing are roughly constant during each stray light phase (above), but vary by ~10% depending on the growth of the contamination layer on the CCD (that repeats gradual increase and jump down after CCD bakeouts).

3. The image for the light leak correction should therefore be selected for the same filter, same satellite pointing, same stray light phase then ideally be adjusted for the level of CCD contamination at the time of observation. However, as a practical matter, preparing the leak image for every possible pointing is hard to achieve, while we have good amount of light leak measurements at the disk center pointing. The full-disk composite images are therefore corrected most reliably for the light leak.

4. Intensity variation of the leak image due to the growth of CCD contamination layer is well determined for Ti_poly at the stray light phase 1 by using the intensity correlation between Ti_poly and Al_mesh images (cg. [Takeda et al., 2016], p.317). The resulting k-factor is obtained with the function GET_SLCORFACT_RAW.PRO, and the leak image subtraction has been already performed only for the Ti_poly SCIA images at the phase 1 (as of Feb-2022).