JP-3609: Change treatment of MIRI MRS values with no photom info (#8453)

Co-authored-by: Howard Bushouse <bushouse@stsci.edu>

CHANGES.rst

@@ -76,6 +76,12 @@ outlier_detection
   ``OutlierDetectionStackStep``, ``outlierpars`` reference file handling,
   and ``scale_detection`` (an unused argument). [#8438]
 
+photom
+------
+
+- Ensure that NaNs in MRS photom files are not replaced with ones by
+  pipeline code for consistency with other modes [#8453]
+
 pipeline
 --------
 

jwst/photom/photom.py

@@ -508,18 +508,10 @@ def calc_miri(self, ftab):
         # MRS detectors
         elif self.detector == 'MIRIFUSHORT' or self.detector == 'MIRIFULONG':
 
-            # Reset conversion and pixel size values with DQ=NON_SCIENCE to 1,
-            # so no conversion is applied
-            where_dq = np.bitwise_and(ftab.dq, dqflags.pixel['NON_SCIENCE'])
-            ftab.data[where_dq > 0] = 1.0
-
-            # Reset NaN's in conversion array to 1
+            # Make sure all NaN's have DO_NOT_USE flag set
             where_nan = np.isnan(ftab.data)
-            ftab.data[where_nan] = 1.0
-
-            # Make sure all NaN's and zeros have DQ flags set
             ftab.dq[where_nan] = np.bitwise_or(ftab.dq[where_nan],
-                                               dqflags.pixel['NON_SCIENCE'])
+                                               dqflags.pixel['DO_NOT_USE'])
 
             # Compute the combined 2D sensitivity factors
             sens2d = ftab.data