HIT L0 - Add sectorate angles (IMAP-Science-Operations-Center#1493)

* Replace declination and azimuth indices with angles provided by HIT

* Test new angle dimensions have correct values

Author: vmartinez-cu

imap_processing/hit/l0/constants.py

@@ -116,3 +116,12 @@
 # decompressing data
 MANTISSA_BITS = 12
 EXPONENT_BITS = 4
+
+# Define sectorate angles
+DECLINATION_ANGLES = np.array(
+    [11.25, 33.75, 56.25, 78.75, 101.25, 123.75, 146.25, 168.75], dtype=np.float32
+)
+AZIMUTH_ANGLES = np.array(
+    [12, 36, 60, 84, 108, 132, 156, 180, 204, 228, 252, 276, 300, 324, 348],
+    dtype=np.float32,
+)

imap_processing/hit/l0/decom_hit.py

@@ -4,7 +4,9 @@
 import xarray as xr
 
 from imap_processing.hit.l0.constants import (
+    AZIMUTH_ANGLES,
     COUNTS_DATA_STRUCTURE,
+    DECLINATION_ANGLES,
     EXPONENT_BITS,
     FLAG_PATTERN,
     FRAME_SIZE,
@@ -93,6 +95,17 @@ def parse_count_rates(sci_dataset: xr.Dataset) -> None:
                 # Reshape data to 8x15 for declination and azimuth look directions
                 parsed_data = np.array(parsed_data).reshape((-1, *field_meta.shape))
                 dims = ["epoch", "declination", "azimuth"]
+                # Add angle values to coordinates
+                sci_dataset.coords["declination"] = xr.DataArray(
+                    data=DECLINATION_ANGLES,
+                    dims=["declination"],
+                    name="declination",
+                )
+                sci_dataset.coords["azimuth"] = xr.DataArray(
+                    data=AZIMUTH_ANGLES,
+                    dims=["azimuth"],
+                    name="azimuth",
+                )
             elif "sngrates" in field:
                 dims = ["epoch", "gain", f"{field}_index"]
         elif field_meta.shape[0] > 1:
@@ -102,11 +115,12 @@ def parse_count_rates(sci_dataset: xr.Dataset) -> None:
 
         sci_dataset[field] = xr.DataArray(parsed_data, dims=dims, name=field)
         # Add dimensions to coordinates
-        # TODO: confirm that dtype int16 is correct
         for dim in dims:
             if dim not in sci_dataset.coords:
                 sci_dataset.coords[dim] = xr.DataArray(
-                    np.arange(sci_dataset.sizes[dim], dtype=np.int16),
+                    np.arange(sci_dataset.sizes[dim], dtype=np.int16)
+                    if dim == "gain"
+                    else np.arange(sci_dataset.sizes[dim], dtype=np.int32),
                     dims=[dim],
                     name=dim,
                 )

imap_processing/tests/hit/test_decom_hit.py

@@ -7,6 +7,7 @@
 from imap_processing.hit.hit_utils import (
     HitAPID,
 )
+from imap_processing.hit.l0.constants import AZIMUTH_ANGLES, DECLINATION_ANGLES
 from imap_processing.hit.l0.decom_hit import (
     assemble_science_frames,
     decom_hit,
@@ -122,6 +123,9 @@ def test_parse_count_rates(sci_dataset):
     if count_rate_vars in list(sci_dataset.keys()):
         assert True
 
+    assert np.allclose(sci_dataset["declination"].values, DECLINATION_ANGLES)
+    assert np.allclose(sci_dataset["azimuth"].values, AZIMUTH_ANGLES)
+
 
 def test_is_sequential():
     """Test the is_sequential function."""