Updated bright star treatment and addition of saturation

euclidlike/instrument_params.py

@@ -18,6 +18,7 @@
 short_exptime_nisp = 112  # s (for the shorter NISP imaging exposures)
 short_exptime_vis = 95 # s (for the shorter exposures with VIS taken in parallel with NISP imaging)
 read_noise = 4.4  # e-, https://www.euclid-ec.org/public/mission/vis/
+saturation = 200000 # e-, from https://www.euclid-ec.org/public/mission/vis/#:~:text=VIS%20pixels%20are%20saturated%20at,IE(AB)%3D16.0.
 n_dithers = 4
 n_ccd = 36
 n_ccd_row = 6

euclidlike_imsim/ccd.py

@@ -8,7 +8,7 @@
 import numpy as np
 
 import euclidlike
-from euclidlike.instrument_params import gain
+from euclidlike.instrument_params import gain, saturation
 from .noise import cfg_noise_key, parse_noise_config, get_noise
 
 
@@ -199,7 +199,11 @@ def addNoise(self, image, config, base, image_num, obj_num, current_var, logger)
         image.quantize()
 
         image += base["noise_image"]
-
+
+        # Apply saturation
+        saturation_ADU = np.round(saturation/gain)
+        image.array[image.array > saturation_ADU] = saturation_ADU
+
         if self.cfg_noise["sky_subtract"]:
             image -= base["sky_image"]
 

euclidlike_imsim/stamp.py

@@ -6,6 +6,10 @@
 # import os, psutil
 # process = psutil.Process()
 
+# Parameter below determines the flux at which we switch from using Euclid-like PSF to the bright star PSF
+# This is done to avoid visual artifacts from using the Euclid-like PSF for very bright objects.
+# Tests to determine this value can be found here: https://github.com/GalSim-developers/GalSim-Euclid-Like/issues/46
+psf_switch_limit = 8e5
 
 class Euclidlike_stamp(StampBuilder):
     """This performs the tasks necessary for building the stamp for a single object.
@@ -89,7 +93,7 @@ def setup(self, config, base, xsize, ysize, ignore, logger):
             gal_achrom = gal.evaluateAtWavelength(bandpass.effective_wavelength)
             if (hasattr(gal_achrom, 'original') and isinstance(gal_achrom.original, galsim.DeltaFunction)):
                 # For bright stars, set the following stamp size limits
-                if self.flux < 1e6:
+                if self.flux < psf_switch_limit:
                     image_size = 500
                     self.pupil_bin = 8
                 elif self.flux < 6e6: