864 hi l1b compute coincidence type and time deltas

docs/source/conf.py

@@ -107,6 +107,8 @@
     (r"py:.*", r".*CoDICECompression.*"),
     (r"py:.*", r".*.lo.l0.utils.*"),
     (r"py:.*", r".*.lo.l0.data_classes.*"),
+    (r"py:.*", r".*.hi.l1b.hi_l1b.CoincidenceBitmap.*"),
+    (r"py:.*", r".*.hi.l1b.hi_l1b.TriggerId.*"),
     (r"py:.*", r".*.hit.l0.utils.*"),
     (r"py:.*", r".*.hit.l0.data_classes.*"),
     (r"py:.*", r".*.hit.l1a.*"),

imap_processing/hi/l1b/hi_l1b.py

@@ -1,14 +1,34 @@
 """IMAP-HI L1B processing module."""
 
 import logging
+from enum import IntEnum
 
+import numpy as np
 import xarray as xr
 
 from imap_processing import imap_module_directory
 from imap_processing.cdf.imap_cdf_manager import ImapCdfAttributes
-from imap_processing.hi.utils import HIAPID, create_dataset_variables
+from imap_processing.hi.utils import HIAPID, HiConstants, create_dataset_variables
 from imap_processing.utils import convert_raw_to_eu
 
+
+class TriggerId(IntEnum):
+    """IntEnum class for trigger id values."""
+
+    A = 1
+    B = 2
+    C = 3
+
+
+class CoincidenceBitmap(IntEnum):
+    """IntEnum class for coincidence type bitmap values."""
+
+    A = 2**3
+    B = 2**2
+    C1 = 2**1
+    C2 = 2**0
+
+
 logger = logging.getLogger(__name__)
 ATTR_MGR = ImapCdfAttributes()
 ATTR_MGR.add_instrument_global_attrs("hi")
@@ -90,28 +110,149 @@ def annotate_direct_events(l1a_dataset: xr.Dataset) -> xr.Dataset:
     l1b_dataset : xarray.Dataset
         L1B direct event data.
     """
-    n_epoch = l1a_dataset["epoch"].size
+    l1b_dataset = compute_coincidence_type_and_time_deltas(l1a_dataset)
     l1b_de_var_names = [
-        "coincidence_type",
         "esa_energy_step",
-        "delta_t_ab",
-        "delta_t_ac1",
-        "delta_t_bc1",
-        "delta_t_c1c2",
         "spin_phase",
         "hae_latitude",
         "hae_longitude",
         "quality_flag",
         "nominal_bin",
     ]
     new_data_vars = create_dataset_variables(
-        l1b_de_var_names, (n_epoch,), att_manager_lookup_str="hi_de_{0}"
+        l1b_de_var_names, l1a_dataset["epoch"].size, att_manager_lookup_str="hi_de_{0}"
     )
-    l1b_dataset = l1a_dataset.assign(new_data_vars)
+    l1b_dataset = l1b_dataset.assign(new_data_vars)
     l1b_dataset = l1b_dataset.drop_vars(
         ["tof_1", "tof_2", "tof_3", "de_tag", "ccsds_met", "meta_event_met"]
     )
 
     de_global_attrs = ATTR_MGR.get_global_attributes("imap_hi_l1b_de_attrs")
     l1b_dataset.attrs.update(**de_global_attrs)
     return l1b_dataset
+
+
+def compute_coincidence_type_and_time_deltas(dataset: xr.Dataset) -> xr.Dataset:
+    """
+    Compute coincidence type and time deltas.
+
+    Adds the new variables "coincidence_type", "delta_t_ab", "delta_t_ac1",
+    "delta_t_bc1", and "delta_t_c1c2" to the input xarray.Dataset and returns
+    the updated xarray.Dataset.
+
+    Parameters
+    ----------
+    dataset : xarray.Dataset
+        The L1A/B dataset that results from reading in the L1A CDF and
+        allocating the new L1B DataArrays.
+
+    Returns
+    -------
+    xarray.Dataset
+        Updated xarray.Dataset with 5 new variables added.
+    """
+    new_data_vars = create_dataset_variables(
+        [
+            "coincidence_type",
+            "delta_t_ab",
+            "delta_t_ac1",
+            "delta_t_bc1",
+            "delta_t_c1c2",
+        ],
+        len(dataset.epoch),
+        "hi_de_{0}",
+    )
+    out_ds = dataset.assign(new_data_vars)
+
+    # compute masks needed for coincidence type and delta t calculations
+    a_mask = out_ds.trigger_id.values == TriggerId.A
+    b_mask = out_ds.trigger_id.values == TriggerId.B
+    c_mask = out_ds.trigger_id.values == TriggerId.C
+
+    tof_1_valid_mask = np.isin(
+        out_ds.tof_1.values, HiConstants.TOF1_BAD_VALUES, invert=True
+    )
+    tof_2_valid_mask = np.isin(
+        out_ds.tof_2.values, HiConstants.TOF2_BAD_VALUES, invert=True
+    )
+    tof_1and2_valid_mask = tof_1_valid_mask & tof_2_valid_mask
+    tof_3_valid_mask = np.isin(
+        out_ds.tof_3.values, HiConstants.TOF3_BAD_VALUES, invert=True
+    )
+
+    # Table denoting how hit-first mask and valid TOF masks are used to set
+    # coincidence type bitmask
+    # -----------------------------------------------------------------------
+    # | Trigger ID  |  Hit First  | TOF 1 Valid | TOF 2 Valid | TOF 3 Valid |
+    # -----------------------------------------------------------------------
+    # |      1      |      A      |     A,B     |     A,C1    |    C1,C2    |
+    # |      2      |      B      |     A,B     |     B,C1    |    C1,C2    |
+    # |      3      |      C1     |     A,C1    |     B,C1    |    C1,C2    |
+    # Set coincidence type bitmask
+    out_ds.coincidence_type[a_mask | tof_1_valid_mask] |= CoincidenceBitmap.A
+    out_ds.coincidence_type[
+        b_mask | (a_mask & tof_1_valid_mask) | (c_mask & tof_2_valid_mask)
+    ] |= CoincidenceBitmap.B
+    out_ds.coincidence_type[c_mask | tof_2_valid_mask | tof_2_valid_mask] |= (
+        CoincidenceBitmap.C1.value
+    )
+    out_ds.coincidence_type[tof_3_valid_mask] |= CoincidenceBitmap.C2
+
+    # Table denoting how TOF is interpreted for each Trigger ID
+    # -----------------------------------------------------------------------
+    # | Trigger ID  |  Hit First  |    TOF 1    |    TOF 2    |    TOF 3    |
+    # -----------------------------------------------------------------------
+    # |      1      |      A      |  t_b - t_a  | t_c1 - t_a  | t_c2 - t_c1 |
+    # |      2      |      B      |  t_a - t_b  | t_c1 - t_b  | t_c2 - t_c1 |
+    # |      3      |      C      |  t_a - t_c1 | t_b  - t_c1 | t_c2 - t_c1 |
+    # delta_t_ab
+    out_ds.delta_t_ab.values[a_mask & tof_1_valid_mask] = (
+        out_ds.tof_1.values[a_mask & tof_1_valid_mask].astype(np.float32)
+        * HiConstants.TOF1_TICK_PER_NS
+    )
+    out_ds.delta_t_ab.values[b_mask & tof_1_valid_mask] = (
+        -out_ds.tof_1.values[b_mask & tof_1_valid_mask].astype(np.float32)
+        * HiConstants.TOF1_TICK_PER_NS
+    )
+    out_ds.delta_t_ab.values[c_mask & tof_1and2_valid_mask] = (
+        out_ds.tof_2.values[c_mask & tof_1and2_valid_mask].astype(np.float32)
+        * HiConstants.TOF2_TICK_PER_NS
+        - out_ds.tof_1.values[c_mask & tof_1and2_valid_mask].astype(np.float32)
+        * HiConstants.TOF1_TICK_PER_NS
+    )
+
+    # delta_t_ac1
+    out_ds.delta_t_ac1.values[a_mask & tof_2_valid_mask] = (
+        out_ds.tof_2.values[a_mask & tof_2_valid_mask].astype(np.float32)
+        * HiConstants.TOF2_TICK_PER_NS
+    )
+    out_ds.delta_t_ac1.values[b_mask & tof_1and2_valid_mask] = (
+        out_ds.tof_2.values[b_mask & tof_1and2_valid_mask]
+        * HiConstants.TOF2_TICK_PER_NS
+        - out_ds.tof_1.values[b_mask & tof_1and2_valid_mask]
+        * HiConstants.TOF1_TICK_PER_NS
+    )
+    out_ds.delta_t_ac1.values[c_mask & tof_1_valid_mask] = (
+        -out_ds.tof_1.values[c_mask & tof_1_valid_mask] * HiConstants.TOF1_TICK_PER_NS
+    )
+
+    # delta_t_bc1
+    out_ds.delta_t_bc1.values[a_mask & tof_1_valid_mask & tof_2_valid_mask] = (
+        out_ds.tof_2.values[a_mask & tof_1and2_valid_mask]
+        * HiConstants.TOF2_TICK_PER_NS
+        - out_ds.tof_1.values[a_mask & tof_1and2_valid_mask]
+        * HiConstants.TOF1_TICK_PER_NS
+    )
+    out_ds.delta_t_bc1.values[b_mask & tof_2_valid_mask] = (
+        out_ds.tof_2.values[b_mask & tof_2_valid_mask] * HiConstants.TOF2_TICK_PER_NS
+    )
+    out_ds.delta_t_bc1.values[c_mask & tof_2_valid_mask] = (
+        -out_ds.tof_2.values[c_mask & tof_2_valid_mask] * HiConstants.TOF2_TICK_PER_NS
+    )
+
+    # delta_t_c1c2
+    out_ds.delta_t_c1c2.values[tof_3_valid_mask] = (
+        out_ds.tof_3.values[tof_3_valid_mask] * HiConstants.TOF3_TICK_PER_NS
+    )
+
+    return out_ds

imap_processing/hi/utils.py

@@ -1,6 +1,7 @@
 """IMAP-Hi utils functions."""
 
 from collections.abc import Sequence
+from dataclasses import dataclass
 from enum import IntEnum
 from typing import Optional, Union
 
@@ -34,6 +35,38 @@ def sensor(self) -> str:
         return self.name[1:3] + "sensor"
 
 
+@dataclass(frozen=True)
+class HiConstants:
+    """
+    Constants for Hi instrument.
+
+    Attributes
+    ----------
+    TOF1_TICK_PER_NS : int
+        Duration of Time-of-Flight 1 clock tick in nanoseconds.
+    TOF2_TICK_PER_NS : int
+        Duration of Time-of-Flight 2 clock tick in nanoseconds.
+    TOF3_TICK_PER_NS : int
+        Duration of Time-of-Flight 3 clock tick in nanoseconds.
+    TOF1_BAD_VALUES : tuple[int]
+        Tuple of values indicating TOF1 does not contain a valid time.
+    TOF2_BAD_VALUES : tuple[int]
+        Tuple of values indicating TOF2 does not contain a valid time.
+    TOF3_BAD_VALUES : tuple[int]
+        Tuple of values indicating TOF3 does not contain a valid time.
+    """
+
+    TOF1_TICK_PER_NS = 1  # 1 ns
+    TOF2_TICK_PER_NS = 1  # 1 ns
+    TOF3_TICK_PER_NS = 2  # 0.5 ns
+
+    # These values are stored in the TOF telemetry when the TOF timer
+    # does not have valid data.
+    TOF1_BAD_VALUES = (511, 1023)
+    TOF2_BAD_VALUES = (1023,)
+    TOF3_BAD_VALUES = (1023,)
+
+
 def full_dataarray(
     name: str,
     attrs: dict,

imap_processing/tests/hi/test_hi_l1b.py

@@ -1,8 +1,16 @@
 """Test coverage for imap_processing.hi.l1b.hi_l1b.py"""
 
+import numpy as np
+import pytest
+import xarray as xr
+
 from imap_processing.hi.l1a.hi_l1a import hi_l1a
-from imap_processing.hi.l1b.hi_l1b import hi_l1b
-from imap_processing.hi.utils import HIAPID
+from imap_processing.hi.l1b.hi_l1b import (
+    CoincidenceBitmap,
+    compute_coincidence_type_and_time_deltas,
+    hi_l1b,
+)
+from imap_processing.hi.utils import HIAPID, HiConstants
 
 
 def test_hi_l1b_hk(hi_l0_test_data_path):
@@ -29,3 +37,109 @@ def test_hi_l1b_de(create_de_data, tmp_path):
     l1b_dataset = hi_l1b(processed_data[0], data_version=data_version)
     assert l1b_dataset.attrs["Logical_source"] == "imap_hi_l1b_45sensor-de"
     assert len(l1b_dataset.data_vars) == 14
+
+
+@pytest.fixture()
+def synthetic_trigger_id_and_tof_data():
+    """Create synthetic minimum dataset for testing the
+    coincidence_type_and_time_deltas algorithm."""
+    # The following coincidence type table shows possible values to consider
+    # Value| # Exp | Requirements to get this value
+    # -----|-------|-------------------------------
+    #   0  |   0   | Non-event not recorded
+    #   1  |   0   | Can't trigger c2 only
+    #   2  |   2   | trigger_id = 3, tof_3 invalid
+    #   3  |   2   | trigger_id = 3, tof_3 valid
+    #   4  |   2   | trigger_id = 2, no valid tofs
+    #   5  |   0   | B and C2 not possible?
+    #   6  |   4   | trigger_id = 2 OR 3, tof_2 valid
+    #   7  |   4   | trigger_id = 2 OR 3, tof_2/3 valid
+    #   8  |   2   | trigger_id = 3, no valid tofs
+    #   9  |   0   | A and C2 not possible?
+    #  10  |   3   | trigger_id = 1, tof_2 OR trigger_id = 3, tof_1
+    #  11  |   3   | trigger_id = 1, tof_2/3, OR trigger_id = 3, tof_1/3
+    #  12  |   2   | trigger_id = 1 OR 2, tof_1
+    #  13  |   0   | A/B and C2 not possible?
+    #  14  |   3   | trigger_id = 1 OR 2 OR 3, tof_1/2
+    #  15  |   3   | trigger_id = 1, 2, 3, tof_1/2/3
+
+    # Use meshgrid to get all combinations of trigger_id and tof valid/invalid
+    # Note: this generates 6 impossible occurrences where C1 is not triggered
+    #    but C2 is. Those are manually removed below.
+    ids = np.arange(3) + 1
+    tof1s = np.array(np.concatenate((HiConstants.TOF1_BAD_VALUES, [1])))
+    tof2s = np.array(np.concatenate((HiConstants.TOF2_BAD_VALUES, [2])))
+    tof3s = np.array(np.concatenate((HiConstants.TOF3_BAD_VALUES, [3])))
+    var_names = ["trigger_id", "tof_1", "tof_2", "tof_3"]
+    data = np.meshgrid(ids, tof1s, tof2s, tof3s)
+    data = [arr.flatten() for arr in data]
+    # Remove impossible combinations
+    good_inds = np.nonzero(
+        np.logical_not(
+            np.logical_and(data[0] != 3, ((data[2] >= 511) & (data[3] < 511)))
+        )
+    )
+    data = [arr[good_inds] for arr in data]
+    data_vars = {
+        n: xr.DataArray(arr, dims=["epoch"]) for n, arr in zip(var_names, data)
+    }
+    synthetic_l1a_ds = xr.Dataset(
+        coords={
+            "epoch": xr.DataArray(
+                np.arange(data_vars["trigger_id"].size), name="epoch", dims=["epoch"]
+            )
+        },
+        data_vars=data_vars,
+    )
+    expected_histogram = np.array([0, 0, 2, 2, 2, 0, 4, 4, 2, 0, 3, 3, 2, 0, 3, 3])
+    return synthetic_l1a_ds, expected_histogram
+
+
+def test_compute_coincidence_type_and_time_deltas(synthetic_trigger_id_and_tof_data):
+    """Test coverage for
+    `imap_processing.hi.hi_l1b.compute_coincidence_type_and_time_deltas`."""
+    # l1a_dataset = load_cdf(hi_l1a_test_file_path)
+    updated_dataset = compute_coincidence_type_and_time_deltas(
+        synthetic_trigger_id_and_tof_data[0]
+    )
+    for var_name in [
+        "coincidence_type",
+        "delta_t_ab",
+        "delta_t_ac1",
+        "delta_t_bc1",
+        "delta_t_c1c2",
+    ]:
+        assert var_name in updated_dataset.data_vars
+    # verify coincidence type values
+    coincidence_hist, bins = np.histogram(
+        updated_dataset.coincidence_type, bins=np.arange(17)
+    )
+    np.testing.assert_array_equal(
+        coincidence_hist, synthetic_trigger_id_and_tof_data[1]
+    )
+    # verify delta_t values are valid in the correct locations
+    np.testing.assert_array_equal(
+        updated_dataset.delta_t_ab != updated_dataset.delta_t_ab.FILLVAL,
+        updated_dataset.coincidence_type >= 12,
+    )
+    np.testing.assert_array_equal(
+        updated_dataset.delta_t_ac1 != updated_dataset.delta_t_ac1.FILLVAL,
+        np.logical_and(
+            np.bitwise_and(updated_dataset.coincidence_type, CoincidenceBitmap.A.value),
+            np.bitwise_and(updated_dataset.coincidence_type, CoincidenceBitmap.C1),
+        ),
+    )
+    np.testing.assert_array_equal(
+        updated_dataset.delta_t_bc1 != updated_dataset.delta_t_bc1.FILLVAL,
+        np.logical_and(
+            np.bitwise_and(updated_dataset.coincidence_type, CoincidenceBitmap.B.value),
+            np.bitwise_and(updated_dataset.coincidence_type, CoincidenceBitmap.C1),
+        ),
+    )
+    np.testing.assert_array_equal(
+        updated_dataset.delta_t_c1c2 != updated_dataset.delta_t_c1c2.FILLVAL,
+        np.logical_and(
+            np.bitwise_and(updated_dataset.coincidence_type, CoincidenceBitmap.C1),
+            np.bitwise_and(updated_dataset.coincidence_type, CoincidenceBitmap.C2),
+        ),
+    )