JP-3677: Add maximum_shower_amplitude parameter to jump step

changes/8890.jump.rst

@@ -0,0 +1,2 @@
+Add maximum_shower_amplitude parameter to MIRI cosmic rays showers routine
+to fix accidental flagging of bright science pixels.

docs/jwst/jump/arguments.rst

@@ -111,6 +111,8 @@ is defined as:
 
 * ``--min_diffs_single_pass``: The minimum number of differences to switch to flagging all outliers at once
 
+* ``--max_shower_amplitude``: The maximum allowable amplitude for MIRI showers in DN/s
+
 **Parameter that affects both Snowball and Shower flagging**
 
 * ``--max_extended_radius``: The maxiumum extension of the jump and saturation that will be flagged for showers or snowballs

docs/jwst/jump/description.rst

@@ -49,7 +49,8 @@ detectors are almost always circles with a central region that is saturated.
 The saturated core allows the search for smaller events without false positives.
 The mid-IR (MIRI) detectors do not, in general, have a saturated center and are only rarely circular.
 Thus, we fit the minimum enclosing ellipse and do not require that there are saturated pixels
-within the ellipse.
+within the ellipse.  Likewise, MIRI showers are only flagged when detected features are consistent
+with the maximum known amplitude (in DN/s) of shower artifacts.
 
 Multiprocessing
 ---------------

jwst/jump/jump.py

@@ -28,7 +28,8 @@ def run_detect_jumps(output_model, gain_model, readnoise_model,
                      minimum_sigclip_groups=100,
                      only_use_ints=True,
                      mask_snowball_persist_next_int=True,
-                     snowball_time_masked_next_int=250
+                     snowball_time_masked_next_int=250,
+                     max_shower_amplitude=4
                      ):
 
     # Runs `detect_jumps` in stcal
@@ -43,6 +44,8 @@ def run_detect_jumps(output_model, gain_model, readnoise_model,
     after_jump_flag_n2 = int(after_jump_flag_time2 // gtime)
     grps_masked_after_shower = int(time_masked_after_shower // gtime)
     snowball_grps_masked_next_int = int(snowball_time_masked_next_int // gtime)
+    # Likewise, convert a max MIRI shower amplitude in DN/s to DN/group
+    max_shower_amplitude = max_shower_amplitude * gtime
     # Get 2D gain and read noise values from their respective models
     if reffile_utils.ref_matches_sci(output_model, gain_model):
         gain_2d = gain_model.data
@@ -85,7 +88,8 @@ def run_detect_jumps(output_model, gain_model, readnoise_model,
                                     minimum_sigclip_groups=minimum_sigclip_groups,
                                     only_use_ints=only_use_ints,
                                     mask_persist_grps_next_int = mask_snowball_persist_next_int,
-                                    persist_grps_flagged = snowball_grps_masked_next_int
+                                    persist_grps_flagged = snowball_grps_masked_next_int,
+                                    max_shower_amplitude = max_shower_amplitude
                                     )
 
 

jwst/jump/jump_step.py

@@ -38,6 +38,7 @@ class JumpStep(Step):
         mask_snowball_core_next_int = boolean(default=True) # Flag saturated cores of snowballs in the next integration?
         snowball_time_masked_next_int = integer(default=4000) # Time in seconds over which saturated cores are flagged in next integration
         find_showers = boolean(default=False) # Apply MIRI shower flagging?
+        max_shower_amplitude = float(default=4) # Maximum MIRI shower amplitude in DN/s
         extend_snr_threshold = float(default=1.2) # The SNR minimum for detection of extended showers in MIRI
         extend_min_area = integer(default=90) # Min area of emission after convolution for the detection of showers
         extend_inner_radius = float(default=1) # Inner radius of the ring_2D_kernel used for convolution
@@ -119,6 +120,7 @@ def process(self, step_input):
                                       min_sat_radius_extend=self.min_sat_radius_extend,
                                       sat_required_snowball=sat_required_snowball, sat_expand=self.sat_expand * 2,
                                       expand_large_events=expand_large_events, find_showers=self.find_showers,
+                                      max_shower_amplitude=self.max_shower_amplitude,
                                       edge_size=self.edge_size, extend_snr_threshold=self.extend_snr_threshold,
                                       extend_min_area=self.extend_min_area,
                                       extend_inner_radius=self.extend_inner_radius,