AlreadyVisited Constraint

Only allow an object to be visited once. This is mostly useful for something like an engineering run where you have a set list of objects you want to observe once.

Note that the "best" object is still selected for each call, i.e. this is __not__ a sequential scheduler.

See also #402 for implementation.

Thanks @jermainegug !

pocs/scheduler/constraint.py

@@ -154,3 +154,31 @@ def get_score(self, time, observer, observation, **kwargs):
 
     def __str__(self):
         return "Moon Avoidance"
+
+
+class AlreadyVisited(BaseConstraint):
+
+    """ Simple Already Visited Constraint
+
+    A simple already visited constraint that determines if the given `observation`
+    has already been visited before. If given `observation` has already been
+    visited then it will not be considered for a call to become the `current observation`.
+    """
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    def get_score(self, time, observer, observation, **kwargs):
+        veto = False
+        score = self._score
+
+        observed_list = kwargs.get('observed_list')
+
+        observed_field_list = [obs.field for obs in observed_list.values()]
+
+        if observation.field in observed_field_list:
+            veto = True
+
+        return veto, score * self.weight
+
+    def __str__(self):
+        return "Already Visited"

pocs/scheduler/dispatch.py

@@ -49,7 +49,8 @@ def get_observation(self, time=None, show_all=False, reread_fields_file=False):
 
         common_properties = {
             'end_of_night': self.observer.tonight(time=time, horizon=-18 * u.degree)[-1],
-            'moon': get_moon(time, self.observer.location)
+            'moon': get_moon(time, self.observer.location),
+            'observed_list': self.observed_list
         }
 
         for constraint in listify(self.constraints):

pocs/tests/test_constraints.py

@@ -7,13 +7,17 @@
 from astropy.coordinates import get_moon
 from astropy.time import Time
 
+from collections import OrderedDict
+
 from pocs.scheduler.field import Field
 from pocs.scheduler.observation import Observation
 
 from pocs.scheduler.constraint import Altitude
 from pocs.scheduler.constraint import BaseConstraint
 from pocs.scheduler.constraint import Duration
 from pocs.scheduler.constraint import MoonAvoidance
+from pocs.scheduler.constraint import AlreadyVisited
+
 from pocs.utils import horizon as horizon_utils
 
 
@@ -229,3 +233,28 @@ def test_moon_avoidance(observer):
 
     assert veto1 is False and veto2 is False
     assert score2 > score1
+
+
+def test_already_visited(observer):
+    avc = AlreadyVisited()
+
+    time = Time('2016-08-13 10:00:00')
+
+    observation1 = Observation(Field('HD189733', '20h00m43.7135s +22d42m39.0645s'))  # HD189733
+    observation2 = Observation(Field('Hat-P-16', '00h38m17.59s +42d27m47.2s'))  # Hat-P-16
+    observation3 = Observation(Field('Sabik', '17h10m23s -15d43m30s'))  # Sabik
+
+    observed_list = OrderedDict()
+
+    observation1.seq_time = '01:00'
+    observation2.seq_time = '02:00'
+    observation3.seq_time = '03:00'
+
+    observed_list[observation1.seq_time] = observation1
+    observed_list[observation2.seq_time] = observation2
+
+    veto1, score1 = avc.get_score(time, observer, observation1, observed_list=observed_list)
+    veto2, score2 = avc.get_score(time, observer, observation3, observed_list=observed_list)
+
+    assert veto1 is True
+    assert veto2 is False