Implement use of an initial fid drift correction

proseco/fid.py

@@ -5,10 +5,13 @@
 Get a catalog of fid lights.
 """
 
+import os
 import weakref
 
 import numpy as np
+from chandra_aca.fid_drift import get_drift
 from chandra_aca.transform import yagzag_to_pixels
+from cxotime import CxoTime
 
 from . import characteristics as ACA
 from . import characteristics_acq as ACQ
@@ -316,7 +319,7 @@ def get_fid_candidates(self):
         Result is updating self.cand_fids.
         """
         yang, zang = get_fid_positions(
-            self.detector, self.focus_offset, self.sim_offset
+            self.detector, self.focus_offset, self.sim_offset, self.t_ccd_acq, self.date
         )
         row, col = yagzag_to_pixels(yang, zang, allow_bad=True)
         ids = np.arange(len(yang), dtype=np.int64) + 1  # E.g. 1 to 6 for ACIS
@@ -472,7 +475,7 @@ def set_spoilers_score(self, fid):
                 )
 
 
-def get_fid_positions(detector, focus_offset, sim_offset):
+def get_fid_positions(detector, focus_offset, sim_offset, t_ccd_acq=None, date=None):
     """Calculate the fid light positions for all fids for ``detector``.
 
     This is adapted from the Matlab
@@ -518,4 +521,22 @@ def get_fid_positions(detector, focus_offset, sim_offset):
 
     yang, zang = np.degrees(yfid) * 3600, np.degrees(zfid) * 3600
 
+    # Apply fid drift
+    enable_fid_drift_env = os.environ.get("PROSECO_ENABLE_FID_DRIFT", "True")
+    if enable_fid_drift_env not in ("True", "False"):
+        raise ValueError(
+            f'PROSECO_ENABLE_FID_DRIFT env var must be either "True" or "False" '
+            f"got {enable_fid_drift}"
+        )
+
+    # The env var is still just a string so do a string equals on it
+    if enable_fid_drift_env == "True":
+        if t_ccd_acq is None or date is None:
+            raise ValueError(
+                "t_ccd_acq and date must be provided if fid drift is enabled"
+            )
+        dy, dz = get_drift(date, t_ccd_acq)
+        yang += dy
+        zang += dz
+
     return yang, zang

proseco/tests/conftest.py

@@ -7,6 +7,11 @@ def use_fixed_chandra_models(monkeypatch):
     monkeypatch.setenv("CHANDRA_MODELS_DEFAULT_VERSION", "3.48")
 
 
+@pytest.fixture(autouse=True)
+def disable_fid_drift(monkeypatch):
+    monkeypatch.setenv("PROSECO_ENABLE_FID_DRIFT", "False")
+
+
 # By default test with the latest AGASC version available including release candidates
 @pytest.fixture(autouse=True)
 def proseco_agasc_rc(monkeypatch):

proseco/tests/test_fid.py

@@ -10,14 +10,16 @@
 from ..fid import get_fid_catalog, get_fid_positions
 from .test_common import DARK40, OBS_INFO, STD_INFO, mod_std_info
 
-# Reference fid positions for spoiling tests
+# Reference fid positions for spoiling tests.  Because this is done outside
+# a test the fixture to generally disable fid drift is not in effect.
+os.environ["PROSECO_ENABLE_FID_DRIFT"] = "False"
 FIDS = get_fid_catalog(stars=StarsTable.empty(), **STD_INFO)
 
 # Do not use the AGASC supplement in testing by default since mags can change
 os.environ[agasc.SUPPLEMENT_ENABLED_ENV] = "False"
 
 
-def test_get_fid_position():
+def test_get_fid_position(monkeypatch):
     """
     Compare computed fid positions to flight values from starcheck reports.
     """
@@ -48,6 +50,20 @@ def test_get_fid_position():
     assert np.allclose(yang[fidset], [-1174, 1224, -1177], rtol=0, atol=1.1)
     assert np.allclose(zang[fidset], [-468, -460, 561], rtol=0, atol=1.1)
 
+    yang1, zang1 = get_fid_positions("ACIS-S", focus_offset=0.0, sim_offset=0.0)
+    monkeypatch.setenv("CHANDRA_MODELS_DEFAULT_VERSION", "fid-drift")
+    monkeypatch.setenv("PROSECO_ENABLE_FID_DRIFT", "True")
+    yang2, zang2 = get_fid_positions(
+        "ACIS-S", focus_offset=0.0, sim_offset=0.0, date="2023:235", t_ccd_acq=-13.65
+    )
+    yang3, zang3 = get_fid_positions(
+        "ACIS-S", focus_offset=0.0, sim_offset=0.0, date="2019:001", t_ccd_acq=-13.65
+    )
+    assert np.allclose(yang1, yang3, rtol=0, atol=0.1)
+    assert np.allclose(zang1, zang3, rtol=0, atol=0.1)
+    assert np.allclose(yang1 - yang2, -36.35, rtol=0, atol=0.1)
+    assert np.allclose(zang1 - zang2, -11.83, rtol=0, atol=0.1)
+
 
 def test_get_initial_catalog():
     """Test basic catalog with no stars in field using standard 2-4-5 config."""