# Licensed under a 3-clause BSD style license - see LICENSE.rst
from __future__ import absolute_import, division, print_function, unicode_literals
from ..utils.energy import Energy
from . import EnergyDependentTablePSF, IRFStacker
__all__ = ["make_psf", "make_mean_psf", "make_mean_edisp"]
[docs]def make_psf(observation, position, energy=None, rad=None):
"""Make energy-dependent PSF for a given source position.
Parameters
----------
observation : `~gammapy.data.DataStoreObservation`
Observation for which to compute the PSF
position : `~astropy.coordinates.SkyCoord`
Position at which to compute the PSF
energy : `~astropy.units.Quantity`
1-dim energy array for the output PSF.
If none is given, the energy array of the PSF from the observation is used.
rad : `~astropy.coordinates.Angle`
1-dim offset wrt source position array for the output PSF.
If none is given, the offset array of the PSF from the observation is used.
Returns
-------
psf : `~gammapy.irf.EnergyDependentTablePSF`
Energy dependent psf table
"""
offset = position.separation(observation.pointing_radec)
if energy is None:
energy = observation.psf.to_energy_dependent_table_psf(theta=offset).energy
if rad is None:
rad = observation.psf.to_energy_dependent_table_psf(theta=offset).rad
psf_value = observation.psf.to_energy_dependent_table_psf(
theta=offset, rad=rad
).evaluate(energy)
arf = observation.aeff.data.evaluate(offset=offset, energy=energy)
exposure = arf * observation.observation_live_time_duration
psf = EnergyDependentTablePSF(
energy=energy, rad=rad, exposure=exposure, psf_value=psf_value
)
return psf
[docs]def make_mean_psf(observations, position, energy=None, rad=None):
"""Compute mean energy-dependent PSF.
Parameters
----------
observations : `~gammapy.data.Observations`
Observations for which to compute the PSF
position : `~astropy.coordinates.SkyCoord`
Position at which to compute the PSF
energy : `~astropy.units.Quantity`
1-dim energy array for the output PSF.
If none is given, the energy array of the PSF from the first
observation is used.
rad : `~astropy.coordinates.Angle`
1-dim offset wrt source position array for the output PSF.
If none is given, the energy array of the PSF from the first
observation is used.
Returns
-------
psf : `~gammapy.irf.EnergyDependentTablePSF`
Mean PSF
"""
psf = make_psf(observations[0], position, energy, rad)
if rad is None:
rad = psf.rad
if energy is None:
energy = psf.energy
exposure = psf.exposure
psf_value = psf.psf_value.T * psf.exposure
for obs in observations[1:]:
psf = make_psf(obs, position, energy, rad)
exposure += psf.exposure
psf_value += psf.psf_value.T * psf.exposure
psf_value /= exposure
psf_tot = EnergyDependentTablePSF(
energy=energy, rad=rad, exposure=exposure, psf_value=psf_value.T
)
return psf_tot
[docs]def make_mean_edisp(
observations,
position,
e_true,
e_reco,
low_reco_threshold=Energy(0.002, "TeV"),
high_reco_threshold=Energy(150, "TeV"),
):
"""Compute mean energy dispersion.
Compute the mean edisp of a set of observations j at a given position
The stacking is implemented in :func:`~gammapy.irf.IRFStacker.stack_edisp`
Parameters
----------
observations : `~gammapy.data.Observations`
Observations for which to compute the EDISP
position : `~astropy.coordinates.SkyCoord`
Position at which to compute the EDISP
e_true : `~gammapy.utils.energy.EnergyBounds`
True energy axis
e_reco : `~gammapy.utils.energy.EnergyBounds`
Reconstructed energy axis
low_reco_threshold : `~gammapy.utils.energy.Energy`
low energy threshold in reco energy, default 0.002 TeV
high_reco_threshold : `~gammapy.utils.energy.Energy`
high energy threshold in reco energy , default 150 TeV
Returns
-------
stacked_edisp : `~gammapy.irf.EnergyDispersion`
Stacked EDISP for a set of observation
"""
list_aeff = []
list_edisp = []
list_livetime = []
list_low_threshold = [low_reco_threshold] * len(observations)
list_high_threshold = [high_reco_threshold] * len(observations)
for obs in observations:
offset = position.separation(obs.pointing_radec)
list_aeff.append(obs.aeff.to_effective_area_table(offset, energy=e_true))
list_edisp.append(
obs.edisp.to_energy_dispersion(offset, e_reco=e_reco, e_true=e_true)
)
list_livetime.append(obs.observation_live_time_duration)
irf_stack = IRFStacker(
list_aeff=list_aeff,
list_edisp=list_edisp,
list_livetime=list_livetime,
list_low_threshold=list_low_threshold,
list_high_threshold=list_high_threshold,
)
irf_stack.stack_edisp()
return irf_stack.stacked_edisp