Merge pull request #263 from lsst/tickets/DM-27298

DM-27298: Calculate observation_counter and observing_day

python/lsst/obs/lsst/ingest.py

@@ -24,7 +24,6 @@
 from lsst.pipe.tasks.ingestCalibs import CalibsParseTask
 from astro_metadata_translator import ObservationInfo
 import lsst.log as lsstLog
-from .translators.lsst import ROLLOVERTIME
 from .translators import LsstCamTranslator
 from .lsstCamMapper import LsstCamMapper
 from ._fitsHeader import readRawFitsHeader
@@ -195,20 +194,8 @@ def translate_dayObs(self, md):
         dayObs : `str`
             The day that the data was taken, e.g. ``1958-02-05``.
         """
-        # Trust DAYOBS if it is there
-        if "DAYOBS" in md:
-            dayObs = str(md.getScalar("DAYOBS"))
-
-            if re.match(r"^\d{8}$", dayObs):
-                dateObs = f"{dayObs[:4]}-{dayObs[4:6]}-{dayObs[6:8]}"
-                return dateObs
-
-        # Try to work it out from date of observation
-        dateObs = self.observationInfo.datetime_begin
-        dateObs -= ROLLOVERTIME
-        dateObs.format = "iso"
-        dateObs.out_subfmt = "date"  # YYYY-MM-DD format
-        return str(dateObs)
+        dayObs = str(self.observationInfo.observing_day)
+        return "-".join([dayObs[:4], dayObs[4:6], dayObs[6:]])
 
     def translate_snap(self, md):
         """Extract snap number from metadata.

python/lsst/obs/lsst/translators/lsst.py

@@ -10,7 +10,7 @@
 
 """Metadata translation support code for LSST headers"""
 
-__all__ = ("ROLLOVERTIME", "TZERO", "SIMONYI_LOCATION", "read_detector_ids",
+__all__ = ("TZERO", "SIMONYI_LOCATION", "read_detector_ids",
            "compute_detector_exposure_id_generic", "LsstBaseTranslator",
            "SIMONYI_TELESCOPE")
 
@@ -32,8 +32,7 @@
 from astro_metadata_translator.translators.helpers import tracking_from_degree_headers, \
     altaz_from_degree_headers
 
-# LSST day clock starts at UTC+8
-ROLLOVERTIME = TimeDelta(8*60*60, scale="tai", format="sec")
+
 TZERO = Time("2015-01-01T00:00", format="isot", scale="utc")
 TZERO_DATETIME = TZERO.to_datetime()
 
@@ -162,6 +161,10 @@ class LsstBaseTranslator(FitsTranslator):
     _DEFAULT_LOCATION = SIMONYI_LOCATION
     """Default telescope location in absence of relevant FITS headers."""
 
+    _ROLLOVER_TIME = TimeDelta(12*60*60, scale="tai", format="sec")
+    """Time delta for the definition of a Rubin Observatory start of day.
+    Used when the header is missing. See LSE-400 for details."""
+
     @classmethod
     def __init_subclass__(cls, **kwargs):
         """Ensure that subclasses clear their own detector mapping entries
@@ -711,3 +714,44 @@ def _determine_primary_filter(self):
                             self.to_observation_id())
 
         return physical_filter
+
+    @cache_translation
+    def to_observing_day(self):
+        """Return the day of observation as YYYYMMDD integer.
+
+        For LSSTCam and other compliant instruments this is the value
+        of the DAYOBS header.
+
+        Returns
+        -------
+        obs_day : `int`
+            The day of observation.
+        """
+        if self.is_key_ok("DAYOBS"):
+            self._used_these_cards("DAYOBS")
+            return int(self._header["DAYOBS"])
+
+        # Calculate it ourselves correcting for the Rubin offset
+        date = self.to_datetime_begin().tai
+        date -= self._ROLLOVER_TIME
+        return int(date.strftime("%Y%m%d"))
+
+    @cache_translation
+    def to_observation_counter(self):
+        """Return the sequence number within the observing day.
+
+        Returns
+        -------
+        counter : `int`
+            The sequence number for this day.
+        """
+        if self.is_key_ok("SEQNUM"):
+            # Some older LATISS data may not have the header
+            # but this is corrected in fix_header for LATISS.
+            self._used_these_cards("SEQNUM")
+            return int(self._header["SEQNUM"])
+
+        # This indicates a problem so we warn and return a 0
+        log.warning("%s: Unable to determine the observation counter so returning 0",
+                    self.to_observation_id())
+        return 0

python/lsst/obs/lsst/translators/lsst_ucdcam.py

@@ -17,7 +17,7 @@
 import os.path
 
 import astropy.units as u
-from astropy.time import Time
+from astropy.time import Time, TimeDelta
 
 from astro_metadata_translator import cache_translation
 
@@ -79,6 +79,9 @@ class LsstUCDCamTranslator(LsstBaseTranslator):
     """Maximum number of detectors to use when calculating the
     detector_exposure_id."""
 
+    _ROLLOVER_TIME = TimeDelta(8*60*60, scale="tai", format="sec")
+    """Time delta for the definition of a Rubin Test Stand start of day."""
+
     @classmethod
     def can_translate(cls, header, filename=None):
         """Indicate whether this translation class can translate the

python/lsst/obs/lsst/translators/lsstsim.py

@@ -28,8 +28,11 @@ class LsstSimTranslator(LsstBaseTranslator):
     """Shared routines for LSST Simulated Data.
     """
 
-    # No constant or trivial mappings defined
-    _const_map = {}
+    # Reset mappings
+    _const_map = {
+        # neither phosim nor imsim report a counter
+        "observation_counter": 0,
+    }
     _trivial_map = {}
 
     @classmethod

python/lsst/obs/lsst/translators/ts3.py

@@ -17,7 +17,7 @@
 import os.path
 
 import astropy.units as u
-from astropy.time import Time
+from astropy.time import Time, TimeDelta
 
 from astro_metadata_translator import cache_translation
 
@@ -69,6 +69,9 @@ class LsstTS3Translator(LsstBaseTranslator):
 
     cameraPolicyFile = "policy/ts3.yaml"
 
+    _ROLLOVER_TIME = TimeDelta(8*60*60, scale="tai", format="sec")
+    """Time delta for the definition of a Rubin Test Stand start of day."""
+
     @classmethod
     def can_translate(cls, header, filename=None):
         """Indicate whether this translation class can translate the

python/lsst/obs/lsst/translators/ts8.py

@@ -16,7 +16,7 @@
 import re
 
 import astropy.units as u
-from astropy.time import Time
+from astropy.time import Time, TimeDelta
 
 from astro_metadata_translator import cache_translation
 
@@ -59,6 +59,9 @@ class LsstTS8Translator(LsstBaseTranslator):
 
     cameraPolicyFile = "policy/ts8.yaml"
 
+    _ROLLOVER_TIME = TimeDelta(8*60*60, scale="tai", format="sec")
+    """Time delta for the definition of a Rubin Test Stand start of day."""
+
     @classmethod
     def can_translate(cls, header, filename=None):
         """Indicate whether this translation class can translate the