1641 hi pset epoch should be pointing start time (#2346)

* Make PSET epoch time be start of pointing
Add epoch_delta varaible to PSET

* Use l1b met time rather than epoch to avoid extra time conversions

* Fix silly test mistake

Author: subagonsouth

imap_processing/cdf/config/imap_hi_variable_attrs.yaml

@@ -432,8 +432,18 @@ hi_de_nominal_bin:
 
 # Define override values for epoch as defined in imap_constant_attrs.yaml
 hi_pset_epoch:
-  CATDESC: Midpoint time of pointing, number of nanoseconds since J2000 with leap seconds included
-  BIN_LOCATION: 0.5
+  CATDESC: Start time of pointing, number of nanoseconds since J2000 with leap seconds included
+  DELTA_PLUS_VAR: epoch_delta
+  BIN_LOCATION: 0
+
+epoch_delta:
+  <<: *default_int64
+  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
 
 hi_pset_esa_energy_step:
   <<: *default_esa_energy_step

imap_processing/hi/hi_l1c.py

@@ -29,11 +29,12 @@
     frame_transform,
     frame_transform_az_el,
 )
+from imap_processing.spice.repoint import get_pointing_times
 from imap_processing.spice.spin import (
     get_instrument_spin_phase,
     get_spin_data,
 )
-from imap_processing.spice.time import ttj2000ns_to_et
+from imap_processing.spice.time import met_to_ttj2000ns, ttj2000ns_to_et
 
 N_SPIN_BINS = 3600
 SPIN_PHASE_BIN_EDGES = np.linspace(0, 1, N_SPIN_BINS + 1)
@@ -101,14 +102,14 @@ def generate_pset_dataset(
     config_df = CalibrationProductConfig.from_csv(calibration_prod_config_path)
 
     pset_dataset = empty_pset_dataset(
-        de_dataset.epoch.data[0],
+        de_dataset.ccsds_met.data.mean(),
         de_dataset.esa_energy_step,
         config_df.cal_prod_config.number_of_products,
         logical_source_parts["sensor"],
     )
-    pset_et = ttj2000ns_to_et(pset_dataset.epoch.data[0])
     # Calculate and add despun_z, hae_latitude, and hae_longitude variables to
     # the pset_dataset
+    pset_et = ttj2000ns_to_et(pset_dataset.epoch.data[0])
     pset_dataset.update(pset_geometry(pset_et, logical_source_parts["sensor"]))
     # Bin the counts into the spin-bins
     pset_dataset.update(pset_counts(pset_dataset.coords, config_df, de_dataset))
@@ -121,15 +122,16 @@ def generate_pset_dataset(
 
 
 def empty_pset_dataset(
-    epoch_val: int, l1b_energy_steps: xr.DataArray, n_cal_prods: int, sensor_str: str
+    l1b_met: float, l1b_energy_steps: xr.DataArray, n_cal_prods: int, sensor_str: str
 ) -> xr.Dataset:
     """
     Allocate an empty xarray.Dataset with appropriate pset coordinates.
 
     Parameters
     ----------
-    epoch_val : int
-        The starting epoch in J2000 TT nanoseconds for data in the PSET.
+    l1b_met : float
+        Any met from the input L1B DE dataset. This is used to query the
+        repoint-table data to get the start and end times of the pointing.
     l1b_energy_steps : xarray.DataArray
         The array of esa_energy_step data from the L1B DE product.
     n_cal_prods : int
@@ -148,13 +150,18 @@ def empty_pset_dataset(
 
     # preallocate coordinates xr.DataArrays
     coords = dict()
+
+    # Get the Pointing start and end times
+    pointing_mets = get_pointing_times(l1b_met)
+    epochs = met_to_ttj2000ns(np.asarray(pointing_mets))
+
     # epoch coordinate has only 1 entry for pointing set
     epoch_attrs = attr_mgr.get_variable_attributes("epoch", check_schema=False)
     epoch_attrs.update(
         attr_mgr.get_variable_attributes("hi_pset_epoch", check_schema=False)
     )
     coords["epoch"] = xr.DataArray(
-        np.array([epoch_val], dtype=np.int64),  # TODO: get dtype from cdf attrs?
+        np.array([epochs[0]], dtype=np.int64),
         name="epoch",
         dims=["epoch"],
         attrs=epoch_attrs,
@@ -201,6 +208,15 @@ def empty_pset_dataset(
 
     # Allocate the coordinate label variables
     data_vars = dict()
+    # Generate the epoch_delta variable
+    data_vars["epoch_delta"] = xr.DataArray(
+        np.diff(epochs),
+        name="epoch_delta",
+        dims=["epoch"],
+        attrs=attr_mgr.get_variable_attributes(
+            "hi_pset_epoch_delta", check_schema=False
+        ),
+    )
     # Generate label variables
     data_vars["esa_energy_step_label"] = xr.DataArray(
         coords["esa_energy_step"].values.astype(str),
@@ -257,7 +273,7 @@ def pset_geometry(pset_et: float, sensor_str: str) -> dict[str, xr.DataArray]:
     Returns
     -------
     geometry_vars : dict[str, xarray.DataArray]
-        Keys are variable names and values are data arrays.
+        Keys are variable names, and values are data arrays.
     """
     geometry_vars = create_dataset_variables(
         ["despun_z"], (1, 3), att_manager_lookup_str="hi_pset_{0}"

imap_processing/tests/hi/test_hi_l1c.py

@@ -32,17 +32,26 @@ def test_generate_pset_dataset(
     hi_l1_test_data_path,
     hi_test_cal_prod_config_path,
     use_fake_spin_data_for_time,
+    use_fake_repoint_data_for_time,
     imap_ena_sim_metakernel,
 ):
     """Test coverage for generate_pset_dataset function"""
     use_fake_spin_data_for_time(482372987.999)
     l1b_de_path = hi_l1_test_data_path / "imap_hi_l1b_45sensor-de_20250415_v999.cdf"
     l1b_dataset = load_cdf(l1b_de_path)
+    l1b_met = l1b_dataset["ccsds_met"].values[0]
+    # Set repoint start and end times.
+    seconds_per_day = 24 * 60 * 60
+    use_fake_repoint_data_for_time(
+        np.asarray([l1b_met - 15 * 60, l1b_met + seconds_per_day]),
+        np.asarray([l1b_met, l1b_met + seconds_per_day + 1]),
+    )
     l1c_dataset = hi_l1c.generate_pset_dataset(
         l1b_dataset, hi_test_cal_prod_config_path
     )
 
     assert l1c_dataset.epoch.data[0] == l1b_dataset.epoch.data[0].astype(np.int64)
+    assert l1c_dataset.epoch_delta.data[0] == seconds_per_day * 1e9
 
     np.testing.assert_array_equal(l1c_dataset.despun_z.data.shape, (1, 3))
     np.testing.assert_array_equal(l1c_dataset.hae_latitude.data.shape, (1, 3600))
@@ -59,7 +68,7 @@ def test_generate_pset_dataset(
     write_cdf(l1c_dataset)
 
 
-def test_empty_pset_dataset():
+def test_empty_pset_dataset(use_fake_repoint_data_for_time):
     """Test coverage for empty_pset_dataset function"""
     n_energy_steps = 8
     l1b_esa_energy_steps = xr.DataArray(
@@ -68,11 +77,17 @@ def test_empty_pset_dataset():
     )
     n_calibration_prods = 5
     sensor_str = HIAPID.H90_SCI_DE.sensor
+    l1b_met = 482373065
+    use_fake_repoint_data_for_time(
+        np.asarray([l1b_met - 15 * 60, l1b_met + 24 * 60 * 60])
+    )
+
     dataset = hi_l1c.empty_pset_dataset(
-        100, l1b_esa_energy_steps, n_calibration_prods, sensor_str
+        l1b_met, l1b_esa_energy_steps, n_calibration_prods, sensor_str
     )
 
     assert dataset.epoch.size == 1
+    assert dataset.epoch_delta.size == 1
     assert dataset.spin_angle_bin.size == 3600
     assert dataset.esa_energy_step.size == n_energy_steps
     np.testing.assert_array_equal(
@@ -127,7 +142,12 @@ def test_pset_geometry(mock_frame_transform, mock_geom_frame_transform, sensor_s
 
 
 @pytest.mark.external_test_data
-def test_pset_counts(hi_l1_test_data_path, hi_test_cal_prod_config_path):
+@mock.patch("imap_processing.hi.hi_l1c.get_pointing_times", return_value=(100, 200))
+def test_pset_counts(
+    mock_pointing_times,
+    hi_l1_test_data_path,
+    hi_test_cal_prod_config_path,
+):
     """Test coverage for pset_counts function."""
     l1b_de_path = hi_l1_test_data_path / "imap_hi_l1b_45sensor-de_20250415_v999.cdf"
     l1b_dataset = load_cdf(l1b_de_path)
@@ -145,7 +165,12 @@ def test_pset_counts(hi_l1_test_data_path, hi_test_cal_prod_config_path):
 
 
 @pytest.mark.external_test_data
-def test_pset_counts_empty_l1b(hi_l1_test_data_path, hi_test_cal_prod_config_path):
+@mock.patch("imap_processing.hi.hi_l1c.get_pointing_times", return_value=(100, 200))
+def test_pset_counts_empty_l1b(
+    mock_pointing_times,
+    hi_l1_test_data_path,
+    hi_test_cal_prod_config_path,
+):
     """Test coverage for pset_counts function when the input L1b contains no counts."""
     l1b_de_path = hi_l1_test_data_path / "imap_hi_l1b_45sensor-de_20250415_v999.cdf"
     l1b_dataset = load_cdf(l1b_de_path)
@@ -254,6 +279,7 @@ def test_pset_backgrounds():
     )
 
 
+@mock.patch("imap_processing.hi.hi_l1c.get_pointing_times", return_value=(100, 200))
 @mock.patch("imap_processing.hi.hi_l1c.get_spin_data", return_value=None)
 @mock.patch("imap_processing.hi.hi_l1c.get_instrument_spin_phase")
 @mock.patch("imap_processing.hi.hi_l1c.get_de_clock_ticks_for_esa_step")
@@ -263,6 +289,7 @@ def test_pset_exposure(
     mock_de_clock_ticks,
     mock_spin_phase,
     mock_spin_data,
+    mock_pointing_times,
 ):
     """Test coverage for pset_exposure function"""
     l1b_energy_steps = xr.DataArray(