Add function to add calibration exposures

doc/changes.rst

@@ -5,7 +5,8 @@ surveysim change log
 0.8.3 (unreleased)
 ------------------
 
-* No changes yet.
+* Add ``surveysim.util.add_calibration_exposures()``, to add simulated
+  calibration exposures to a set of science exposures.
 
 0.8.2 (2017-10-09)
 ------------------

py/surveysim/test/test_util.py

@@ -0,0 +1,44 @@
+import unittest
+import numpy as np
+from astropy.table import Table, Column
+from ..util import add_calibration_exposures
+
+class TestUtil(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        pass
+
+    @classmethod
+    def tearDownClass(cls):
+        pass
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def test_add_calibration_exposures(self):
+        exposures = Table()
+        exposures['TILEID'] = Column(np.array([0, 1], dtype=np.int32))
+        exposures['PASS'] = Column(np.array([0, 0], dtype=np.int16))
+        exposures['RA'] = Column(np.array([0.0, 1.0], dtype=np.float64))
+        exposures['DEC'] = Column(np.array([0.0, 1.0], dtype=np.float64))
+        exposures['EBMV'] = Column(np.array([0.0, 1.0], dtype=np.float64))
+        exposures['NIGHT'] = Column(np.array(['20200101', '20200102'], dtype=(str, 8)))
+        exposures['MJD'] = Column(np.array([0.0, 1.0], dtype=np.float64))
+        exposures['EXPTIME'] = Column(np.array([0.0, 1.0], dtype=np.float64), unit='s')
+        exposures['SEEING'] = Column(np.array([0.0, 1.0], dtype=np.float64), unit='arcsec')
+        exposures['TRANSPARENCY'] = Column(np.array([0.0, 1.0], dtype=np.float64))
+        exposures['AIRMASS'] = Column(np.array([0.0, 1.0], dtype=np.float64))
+        exposures['MOONFRAC'] = Column(np.array([0.0, 1.0], dtype=np.float64))
+        exposures['MOONALT'] = Column(np.array([0.0, 1.0], dtype=np.float64), unit='deg')
+        exposures['MOONSEP'] = Column(np.array([0.0, 1.0], dtype=np.float64), unit='deg')
+        exposures['PROGRAM'] = Column(np.array(['DARK', 'DARK'], dtype=(str, 6)))
+        exposures['FLAVOR'] = Column(np.array(['science', 'science'], dtype=(str, 7)))
+        output = add_calibration_exposures(exposures)
+        self.assertEqual(len(output), 14)
+        self.assertEqual('EXPID', output.colnames[0])
+        self.assertTrue(np.all(output['EXPID'] == np.arange(14, dtype=np.int32)))
+        self.assertEqual(output['RA'].unit, 'deg')

py/surveysim/util.py

@@ -0,0 +1,53 @@
+"""Simulation utilities that may be used by other packages.
+"""
+from __future__ import print_function, division, absolute_import
+import numpy as np
+from astropy.table import Column
+
+
+def add_calibration_exposures(exposures, arcs_per_night=3, flats_per_night=3):
+    """Adds calibration exposures to a set of science exposures and
+    assigns exposure IDs.
+
+    Parameters
+    ----------
+    exposures : :class:`astropy.table.Table`
+        A table of science exposures, produced by *e.g.*
+        ``desisurvey.progress.Progress.get_exposures()``.
+    arcs_per_night : :class:`int`, optional
+        Add this many arc exposures per night (default 3).
+    flats_per_night : :class:`int`, optional
+        Add this many arc exposures per night (default 3).
+
+    Returns
+    -------
+    :class:`astropy.table.Table`
+        A table augmented with calibration exposures.
+    """
+    if 'EXPID' not in exposures:
+        expidc = Column(np.arange(len(exposures), dtype=np.int32),
+                        name='EXPID', description='Exposure ID')
+        exposures.add_column(expidc, index=0)
+    for c in ('RA', 'DEC'):
+        if exposures[c].unit is None:
+            exposures[c].unit = 'deg'
+    output = exposures[:0].copy()
+    current_night = '19730703'
+    expid = 0
+    for i, night in enumerate(exposures['NIGHT']):
+        if night != current_night:
+            current_night = night
+            for j in range(flats_per_night):
+                output.add_row([expid, -1, -1, 0.0, 0.0, 0.0, night,
+                                0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
+                                'NONE', 'flat'])
+                expid += 1
+            for j in range(arcs_per_night):
+                output.add_row([expid, -1, -1, 0.0, 0.0, 0.0, night,
+                                0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
+                                'NONE', 'arc'])
+                expid += 1
+        output.add_row(exposures[i])
+        output['EXPID'][expid] = expid
+        expid += 1
+    return output