BUG FIX: Updated get_turnaround_flags so that it can catch stationary…

sotodlib/tod_ops/flags.py

@@ -157,7 +157,8 @@ def get_det_bias_flags(aman, detcal=None, rfrac_range=(0.1, 0.7),
 def get_turnaround_flags(aman, az=None, method='scanspeed', name='turnarounds',
                          merge=True, merge_lr=True, overwrite=True, 
                          t_buffer=2., kernel_size=400, peak_threshold=0.1, rel_distance_peaks=0.3,
-                         truncate=False, qlim=1, merge_subscans=True, turnarounds_in_subscan=False):
+                         truncate=False, qlim=1, merge_subscans=True, turnarounds_in_subscan=False,
+                         az_throw_threshold=None):
     """
     Compute turnaround flags for a dataset.
 
@@ -195,15 +196,30 @@ def get_turnaround_flags(aman, az=None, method='scanspeed', name='turnarounds',
         (Optional). Also merge an AxisManager with subscan information.
     turnarounds_in_subscan : bool
         (Optional). Turnarounds are included as part of a subscan.
+    az_throw_threshold : float
+        Minimum azimuth throw required to attempt turnaround flagging. If ``aman.obs_info.az_throw`` falls below this value, 
+        the obs is treated as stationary or incomplete and a ``ValueError`` is raised instead.
 
     Returns
     -------
     Ranges : RangesMatrix
         The turnaround flags as a Ranges object.
     """
+    if az_throw_threshold is None:
+        raise ValueError(
+                "`az_throw_threshold` is required and cannot be None"
+                )
+
     if az is None : 
         az = aman.boresight.az
-
+
+    # Check that telescope was scanning. 
+    if aman.obs_info.az_throw < az_throw_threshold:
+        raise ValueError(
+                f"""Azimuth motion {aman.obs_info.az_throw} is too small compared to threshold {az_throw_threshold} 
+                to compute turnaround flags"""
+                )
+
     if method not in ['az', 'scanspeed']:
         raise ValueError('Unsupported method. Supported methods are `az` or `scanspeed`')
 

sotodlib/tod_ops/sub_polyf.py

@@ -48,7 +48,7 @@ def subscan_polyfilter(aman, degree, signal_name="signal", exclude_turnarounds=F
     if exclude_turnarounds:
         if ("left_scan" not in aman.flags) or ("turnarounds" not in aman.flags):
             logger.warning('aman does not have left/right scan or turnarounds flag. `sotodlib.flags.get_turnaround_flags` will be ran with default parameters')
-            _ = flags.get_turnaround_flags(aman,truncate=True)
+            _ = flags.get_turnaround_flags(aman,az_throw_threshold=0.,truncate=True)
         ls_mask = aman.flags["left_scan"].mask()
         rs_mask = aman.flags["right_scan"].mask()
         ta_mask = aman.flags["turnarounds"].mask()
@@ -60,7 +60,7 @@ def subscan_polyfilter(aman, degree, signal_name="signal", exclude_turnarounds=F
     else:
         if ("left_scan" not in aman.flags):
             logger.warning('aman does not have left/right scan. `sotodlib.flags.get_turnaround_flags` will be ran with default parameters')
-            _ = flags.get_turnaround_flags(aman,truncate=True)
+            _ = flags.get_turnaround_flags(aman,az_throw_threshold=0.,truncate=True)
 
         ls_mask = aman.flags["left_scan"].mask()
         rs_mask = aman.flags["right_scan"].mask()

tests/test_psd.py

@@ -84,7 +84,7 @@ def test_wn_debias(self):
         boresight.wrap("az", az, [(0, "samps")])
         aman.wrap('boresight', boresight)
         aman.wrap('flags', core.AxisManager(aman.dets, aman.samps))
-        get_turnaround_flags(aman)
+        get_turnaround_flags(aman, az_throw_threshold = 0.1)
 
         # test default arguments, this is biased
         calc_psd(aman, merge=True, nperseg=2**18)