ULTRA add epoch_delta to pset (IMAP-Science-Operations-Center#2355)

* add epoch delta var

Author: lacoak21

imap_processing/cdf/config/imap_ultra_l1c_variable_attrs.yaml

@@ -172,6 +172,18 @@ shcoarse:
   # TODO: come back to format
   UNITS: seconds
 
+epoch_delta:
+  <<: *default
+  CATDESC: Number of nanoseconds in spacecraft pointing covered by this pointing set product
+  FIELDNAM: epoch delta
+  UNITS: ns
+  VAR_TYPE: support_data
+  DISPLAY_TYPE: no_plot
+  TIME_SCALE: Terrestrial Time
+  SCALE_TYPE: linear
+  FORMAT: I20
+  dtype: int64
+
 energy_bin_delta:
   <<: *default_float32
   CATDESC: Difference between the energy bin edges.

imap_processing/tests/ultra/unit/test_ultra_l1c_pset_bins.py

@@ -302,8 +302,10 @@ def test_get_spacecraft_exposure_times(
         params,
         pixels_below_threshold,
         boundary_sf,
-        data_start_time,
-        data_start_time,
+        (
+            data_start_time,
+            data_start_time,
+        ),
         pix,
     )
     np.testing.assert_array_equal(exposure_pointing.shape, (24, pix))

imap_processing/ultra/l1c/helio_pset.py

@@ -128,17 +128,16 @@ def calculate_helio_pset(
     healpix = np.arange(n_pix)
 
     # Get midpoint timestamp for pointing.
-    pointing_start, pointing_stop = get_pointing_times(
-        et_to_met(species_dataset["event_times"].data[0])
+    pointing_range_met = get_pointing_times(
+        et_to_met(species_dataset["event_times"].mean())
     )
     logger.info("Calculating spacecraft exposure times with deadtime correction.")
     exposure_time, deadtime_ratios = get_spacecraft_exposure_times(
         rates_dataset,
         params_dataset,
         pixels_below_scattering,
         boundary_scale_factors,
-        pointing_start,
-        pointing_stop,
+        pointing_range_met,
         n_pix=n_pix,
     )
     logger.info("Calculating spun efficiencies and geometric function.")
@@ -164,7 +163,7 @@ def calculate_helio_pset(
         nside=nside,
     )
 
-    mid_time = ttj2000ns_to_et(met_to_ttj2000ns((pointing_start + pointing_stop) / 2))
+    mid_time = ttj2000ns_to_et(met_to_ttj2000ns((np.sum(pointing_range_met)) / 2))
 
     logger.info("Adjusting data for helio frame.")
     exposure_time, _efficiency, geometric_function = get_helio_adjusted_data(
@@ -191,9 +190,13 @@ def calculate_helio_pset(
         helio_pset_quality_flags,
         nside=nside,
     )
-    pointing_start = met_to_ttj2000ns(pointing_start)
+    # Convert pointing start and end time to ttj2000ns
+    pointing_range_ns = met_to_ttj2000ns(pointing_range_met)
     # Epoch should be the start of the pointing
-    pset_dict["epoch"] = np.atleast_1d(pointing_start).astype(np.int64)
+    pset_dict["epoch"] = np.atleast_1d(pointing_range_ns[0]).astype(np.int64)
+    pset_dict["epoch_delta"] = np.atleast_1d(np.diff(pointing_range_ns)).astype(
+        np.int64
+    )
     pset_dict["counts"] = counts[np.newaxis, ...]
     pset_dict["latitude"] = latitude[np.newaxis, ...]
     pset_dict["longitude"] = longitude[np.newaxis, ...]

imap_processing/ultra/l1c/spacecraft_pset.py

@@ -138,8 +138,8 @@ def calculate_spacecraft_pset(
     sensitivity = efficiencies * geometric_function
 
     # Get the start and stop times of the pointing period
-    pointing_start, pointing_stop = get_pointing_times(
-        float(et_to_met(species_dataset["event_times"].data[0]))
+    pointing_range_met = get_pointing_times(
+        float(et_to_met(species_dataset["event_times"].mean()))
     )
     # Calculate exposure times
     logger.info("Calculating spacecraft exposure times with deadtime correction.")
@@ -148,8 +148,7 @@ def calculate_spacecraft_pset(
         params_dataset,
         pixels_below_scattering,
         boundary_scale_factors,
-        pointing_start,
-        pointing_stop,
+        pointing_range_met,
         n_pix=n_pix,
     )
     logger.info("Calculating background rates.")
@@ -179,10 +178,13 @@ def calculate_spacecraft_pset(
         spacecraft_pset_quality_flags,
         nside=nside,
     )
-    # Convert pointing start time to ttj2000ns
-    pointing_start = met_to_ttj2000ns(pointing_start)
+    # Convert pointing start and end time to ttj2000ns
+    pointing_range_ns = met_to_ttj2000ns(pointing_range_met)
     # Epoch should be the start of the pointing
-    pset_dict["epoch"] = np.atleast_1d(pointing_start).astype(np.int64)
+    pset_dict["epoch"] = np.atleast_1d(pointing_range_ns[0]).astype(np.int64)
+    pset_dict["epoch_delta"] = np.atleast_1d(np.diff(pointing_range_ns)).astype(
+        np.int64
+    )
     pset_dict["counts"] = counts[np.newaxis, ...]
     pset_dict["latitude"] = latitude[np.newaxis, ...]
     pset_dict["longitude"] = longitude[np.newaxis, ...]

imap_processing/ultra/l1c/ultra_l1c_pset_bins.py

@@ -415,8 +415,7 @@ def get_spacecraft_exposure_times(
     params_dataset: xr.Dataset,
     pixels_below_scattering: list[list],
     boundary_scale_factors: NDArray,
-    pointing_start_met: float,
-    pointing_stop_met: float,
+    pointing_range_met: tuple[float, float],
     n_pix: int,
 ) -> tuple[NDArray, NDArray]:
     """
@@ -435,10 +434,8 @@ def get_spacecraft_exposure_times(
         below the FWHM scattering threshold.
     boundary_scale_factors : np.ndarray
         Boundary scale factors for each pixel at each spin phase.
-    pointing_start_met : float
-        Start time of the pointing period in mission elapsed time.
-    pointing_stop_met : float
-        Stop time of the pointing period in mission elapsed time.
+    pointing_range_met : tuple
+        Start and stop time of the pointing period in mission elapsed time.
     n_pix : int
         Number of HEALPix pixels.
 
@@ -465,8 +462,8 @@ def get_spacecraft_exposure_times(
     spin_data = get_spin_data()
     # Filter for spins only in pointing
     spin_data = spin_data[
-        (spin_data["spin_start_met"] >= pointing_start_met)
-        & (spin_data["spin_start_met"] <= pointing_stop_met)
+        (spin_data["spin_start_met"] >= pointing_range_met[0])
+        & (spin_data["spin_start_met"] <= pointing_range_met[1])
     ]
     # Get only valid spin data
     valid_mask = (spin_data["spin_phase_valid"].values == 1) & (

imap_processing/ultra/utils/ultra_l1_utils.py

@@ -102,6 +102,12 @@ def create_dataset(  # noqa: PLR0912
             "spin_phase_step",
         ]:
             continue
+        elif key == "epoch_delta":
+            dataset[key] = xr.DataArray(
+                data,
+                dims=["epoch"],
+                attrs=cdf_manager.get_variable_attributes(key, check_schema=False),
+            )
         elif key in velocity_keys:
             dataset[key] = xr.DataArray(
                 data,