From b62f60e7bc39242542aae8dff5c8c6067733e0b2 Mon Sep 17 00:00:00 2001
From: Roy Smart <roytsmart@gmail.com>
Date: Mon, 4 Nov 2024 19:52:32 -0700
Subject: [PATCH] Added `iris.sg.SpectrographObservation.timedelta` field which
 stores the exposure time of each frame.

---
 iris/sg/_spectrograph.py | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/iris/sg/_spectrograph.py b/iris/sg/_spectrograph.py
index 41abe07..e37f996 100644
--- a/iris/sg/_spectrograph.py
+++ b/iris/sg/_spectrograph.py
@@ -101,6 +101,11 @@ class SpectrographObservation(
             ax[1].set_ylim(wavelength_min, wavelength_max)
     """
 
+    timedelta: u.Quantity | na.AbstractScalar = 0 * u.s
+    """
+    The exposure time for each frame in the observation.
+    """
+
     wavelength_center: None | u.Quantity | na.AbstractScalar = None
     """
     TThe rest wavelength of the dominant spectral line in the observation.
@@ -270,8 +275,13 @@ def from_fits(
 
             hdul = astropy.io.fits.open(file)
             hdu = hdul[index_window]
+            hdu_aux = hdul[~1]
 
-            wcs = astropy.wcs.WCS(hdu).wcs
+            detector_type = hdul[0].header[f"TDET{index_window}"]
+
+            key_timedelta = "EXPTIMEF" if "FUV" in detector_type else "EXPTIMEN"
+            timedelta = hdu_aux.data[..., hdu_aux.header[key_timedelta]] << u.s
+            self.timedelta[index] = na.ScalarArray(timedelta, axis_detector_x)
 
             self.outputs[index] = na.ScalarArray(
                 ndarray=hdu.data << u.DN,
@@ -281,6 +291,8 @@ def from_fits(
             time = astropy.time.Time(hdul[0].header["DATE_OBS"]).jd
             self.inputs.time[index] = time
 
+            wcs = astropy.wcs.WCS(hdu).wcs
+
             crval = self.inputs.crval
             crval.wavelength[index] = wcs.crval[~iw] << u.m
             crval.position.x[index] = wcs.crval[~ix] << u.deg
@@ -405,11 +417,15 @@ def empty(
         shape = na.broadcast_shapes(shape_base, shape_wcs)
         outputs = na.ScalarArray.empty(shape) << u.DN
 
+        shape_timedelta = shape_base | {axis_wavelength: shape_wcs[axis_wavelength]}
+        timedelta = na.ScalarArray.empty(shape_timedelta) * u.s
+
         wavelength_center = na.ScalarArray.empty(shape_base) << u.AA
 
         return cls(
             inputs=inputs,
             outputs=outputs,
+            timedelta=timedelta,
             wavelength_center=wavelength_center,
             axis_time=axis_time,
             axis_wavelength=axis_wavelength,