Calculate sensitivity

esbo_etc/classes/Config.py

@@ -142,10 +142,10 @@ class Configuration(object):
         if hasattr(self.conf.common, "exposure_time"):
             mes = self.conf.common.exposure_time.check_quantity("val", u.s)
             mes is not None and error("Configuration check: common -> exposure_time: " + mes)
-        elif hasattr(self.conf.common, "snr"):
+        if hasattr(self.conf.common, "snr"):
             mes = self.conf.common.snr.check_quantity("val", u.dimensionless_unscaled)
             mes is not None and error("Configuration check: common -> snr: " + mes)
-        else:
+        if not (hasattr(self.conf.common, "exposure_time") or hasattr(self.conf.common, "snr")):
             error("Configuration check: common: Expected one of the containers 'exposure_time' or 'snr' but got none.")
 
         # Check astroscene
@@ -162,7 +162,10 @@ class Configuration(object):
                                                                                  dir(tg), 1)[0] + "'?")
         mes = getattr(tg, self.conf.astroscene.target.type).check_config(self.conf.astroscene.target)
         mes is not None and error("Configuration check: astroscene -> target: " + mes)
-
+        if hasattr(self.conf.common, "exposure_time") and hasattr(self.conf.common, "snr"):
+            if self.conf.astroscene.target.type.lower() != "blackbodytarget":
+                error("Configuration check: astroscene -> target: Sensitivity calculation only possible for " +
+                      "a target of the type 'BlackBodyTarget'.")
         mes = self.__check_optical_components(self.conf.astroscene)
         mes is not None and error("Configuration check: astroscene -> " + mes)
 

esbo_etc/classes/sensor/ASensor.py

@@ -39,13 +39,14 @@ class ASensor:
         pass
 
     @abstractmethod
-    def getExpTime(self, snr: float):
+    @u.quantity_input(snr=u.dimensionless_unscaled)
+    def getExpTime(self, snr: u.Quantity):
         """
         Calculate the necessary exposure time in order to achieve the given SNR.
 
         Parameters
         ----------
-        snr : float
+        snr : Quantity
             The SNR for which the necessary exposure time shall be calculated.
 
         Returns
@@ -55,6 +56,28 @@ class ASensor:
         """
         pass
 
+    @abstractmethod
+    @u.quantity_input(exp_time="time", snr=u.dimensionless_unscaled, target_brightness=u.mag)
+    def getSensitivity(self, exp_time: u.Quantity, snr: u.Quantity, target_brightness: u.Quantity):
+        """
+        Calculate the sensitivity of the telescope detector combination.
+
+        Parameters
+        ----------
+        exp_time : Quantity
+            The exposure time in seconds.
+        snr : Quantity
+            The SNR for which the sensitivity time shall be calculated.
+        target_brightness : Quantity
+            The target brightness in magnitudes.
+
+        Returns
+        -------
+        sensitivity: Quantity
+            The sensitivity as limiting apparent star magnitude in mag.
+        """
+        pass
+
     @staticmethod
     def check_config(sensor: Entry, conf: Entry) -> Union[None, str]:
         """

esbo_etc/classes/sensor/Imager.py

@@ -149,6 +149,34 @@ class Imager(ASensor):
         self.__calcSNR(signal_current * exp_time, background_current * exp_time, read_noise, dark_current * exp_time)
         return exp_time
 
+    @u.quantity_input(exp_time="time", snr=u.dimensionless_unscaled, target_brightness=u.mag)
+    def getSensitivity(self, exp_time: u.Quantity, snr: u.Quantity, target_brightness: u.Quantity):
+        """
+        Calculate the sensitivity of the telescope detector combination.
+
+        Parameters
+        ----------
+        exp_time : Quantity
+            The exposure time in seconds.
+        snr : Quantity
+            The SNR for which the sensitivity time shall be calculated.
+        target_brightness : Quantity
+            The target brightness in magnitudes.
+
+        Returns
+        -------
+        sensitivity: Quantity
+            The sensitivity as limiting apparent star magnitude in mag.
+        """
+        # Calculate the electron currents
+        signal_current, background_current, read_noise, dark_current = self.__exposePixels()
+        # Fix the physical units of the SNR
+        snr = snr * u.electron ** 0.5
+        signal_current_lim = snr * (snr + np.sqrt(
+            snr ** 2 + 4 * (exp_time * (background_current.sum() + dark_current.sum()) + (read_noise ** 2).sum()))) / (
+                                         2 * exp_time)
+        return target_brightness - 2.5 * np.log10(signal_current_lim / signal_current.sum()) * u.mag
+
     @u.quantity_input(signal=u.electron, background=u.electron, read_noise=u.electron ** 0.5, dark=u.electron)
     def __calcSNR(self, signal: u.Quantity, background: u.Quantity, read_noise: u.Quantity,
                   dark: u.Quantity) -> u.dimensionless_unscaled:

esbo_etc/esbo-etc.py

@@ -23,9 +23,12 @@ if __name__ == "__main__":
     parent = oc_factory.fromConfigBatch(conf)
     sensor_factory = etc.SensorFactory(parent, conf.common)
     imager = sensor_factory.create(conf.instrument.sensor)
-    if hasattr(conf.common, "exposure_time"):
+    if hasattr(conf.common, "exposure_time") and hasattr(conf.common, "snr"):
+        sensitivity = imager.getSensitivity(conf.common.exposure_time(), conf.common.snr(), conf.astroscene.target.mag)
+        print("The limiting apparent magnitude is: %.2f mag." % sensitivity.value)
+    elif hasattr(conf.common, "exposure_time"):
         snr = imager.getSNR(conf.common.exposure_time())
-        print("The SNR is: %.2f" % snr)
+        print("The SNR is: %.2f." % snr.value)
     elif hasattr(conf.common, "snr"):
         exp_time = imager.getExpTime(conf.common.snr())
-        print("The necessary exposure time is: %.2f s" % exp_time.value)
+        print("The necessary exposure time is: %.2f s." % exp_time.value)