Merge pull request #87 from lsst-sitcom/tickets/DM-43169

DM-43169: Create utility function to check for timebase errors

python/lsst/summit/utils/auxtel/__init__.py

@@ -0,0 +1,22 @@
+# This file is part of summit_utils.
+#
+# Developed for the LSST Data Management System.
+# This product includes software developed by the LSST Project
+# (https://www.lsst.org).
+# See the COPYRIGHT file at the top-level directory of this distribution
+# for details of code ownership.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+from .mount import hasTimebaseErrors

python/lsst/summit/utils/auxtel/mount.py

@@ -0,0 +1,79 @@
+# This file is part of summit_utils.
+#
+# Developed for the LSST Data Management System.
+# This product includes software developed by the LSST Project
+# (https://www.lsst.org).
+# See the COPYRIGHT file at the top-level directory of this distribution
+# for details of code ownership.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+import logging
+
+import numpy as np
+
+from ..efdUtils import getEfdData
+
+
+def hasTimebaseErrors(expRecord, client, maxDiff=1.05):
+    """Check if an exposure has cRIO timebase errors.
+
+    Data in the lsst.sal.ATMCS.mount_AzEl_Encoders topic is a packed
+    time-series, and if the amount of data that is packed in isn't packed for a
+    period of almost exactly one second then the unpacking code will
+    incorrectly assign the intra-second timestamps, causing misalignment, as
+    this breaks the fundamental assumption required to have a packed
+    timeseries.
+
+    Parameters
+    ----------
+    expRecord : `lsst.daf.butler.dimensions.DimensionRecord`
+        The exposure record to query.
+    client : `lsst_efd_client.efd_helper.EfdClient`
+        The EFD client to use.
+    maxDiff : `float`, optional
+        The maximum difference in cRIO timestamps to consider as a timebase
+        error, in seconds. The correct spacing is 1s, so 1.05 denotes a 50ms
+        difference when the jitter should be on the order of microseconds.
+
+    Returns
+    -------
+    containsErrors : `bool`
+        `True` if the exposure has timebase errors, `False` otherwise.
+    """
+    log = logging.getLogger(__name__)
+    mountPosition = getEfdData(
+        client, "lsst.sal.ATMCS.mount_AzEl_Encoders", expRecord=expRecord, warn=False
+    )
+
+    if mountPosition.empty:
+        log.warning(
+            f"No mount data was found for {expRecord.obs_id}, so there is technically no"
+            " timebase error present"
+        )
+        return False
+
+    cRIOtimestamps = mountPosition["cRIO_timestamp"]
+    if len(cRIOtimestamps) == 1:
+        log.warning(
+            f"cRIO_timestamp data had length 1 for {expRecord.obs_id}, so timebase errors are"
+            " impossible"
+        )
+        return False
+
+    diff = np.diff(cRIOtimestamps.values)
+    if np.min(diff) < 0:
+        raise ValueError("cRIO timestamps are not monotonically increasing - time is running backwards!")
+
+    return np.max(diff) > maxDiff