# Licensed under a 3-clause BSD style license - see LICENSE.rst
from __future__ import absolute_import, division, print_function, unicode_literals
from scipy.interpolate import interp1d
from astropy.version import version as astropy_version
from astropy.utils import lazyproperty
from astropy.units import Quantity
from astropy.table import Table
from astropy.coordinates import SkyCoord, AltAz, CartesianRepresentation
from ..utils.scripts import make_path
from ..utils.time import time_ref_from_dict
from ..utils.fits import earth_location_from_dict
__all__ = ["PointingInfo"]
[docs]class PointingInfo(object):
"""IACT array pointing info.
Data format specification: :ref:`gadf:iact-pnt`
Parameters
----------
table : `~astropy.table.Table`
Table (with meta header info) on pointing
Examples
--------
>>> from gammapy.data import PointingInfo
>>> pointing_info = PointingInfo.read('$GAMMAPY_DATA/tests/hess_event_list.fits')
>>> print(pointing_info)
"""
def __init__(self, table):
self.table = table
[docs] @classmethod
def read(cls, filename, hdu="POINTING"):
"""Read `PointingInfo` table from file.
Parameters
----------
filename : str
File name
hdu : int or str
HDU number or name
Returns
-------
pointing_info : `PointingInfo`
Pointing info object
"""
filename = make_path(filename)
table = Table.read(str(filename), hdu=hdu)
return cls(table=table)
def __str__(self):
ss = "Pointing info:\n\n"
ss += "Location: {}\n".format(self.location.geodetic)
m = self.table.meta
ss += "MJDREFI, MJDREFF, TIMESYS = {}\n".format(
(m["MJDREFI"], m["MJDREFF"], m["TIMESYS"])
)
ss += "Time ref: {}\n".format(self.time_ref.fits)
ss += "Time ref: {} MJD (TT)\n".format(self.time_ref.mjd)
sec = self.duration.to("second").value
hour = self.duration.to("hour").value
ss += "Duration: {} sec = {} hours\n".format(sec, hour)
ss += "Table length: {}\n".format(len(self.table))
ss += "\nSTART:\n" + self._str_for_index(0) + "\n"
ss += "\nEND:\n" + self._str_for_index(-1) + "\n"
return ss
def _str_for_index(self, idx):
"""Information for one point in the pointing table."""
ss = "Time: {}\n".format(self.time[idx].fits)
ss += "Time: {} MJD (TT)\n".format(self.time[idx].mjd)
ss += "RADEC: {} deg\n".format(self.radec[idx].to_string())
ss += "ALTAZ: {} deg\n".format(self.altaz[idx].to_string())
return ss
@lazyproperty
def location(self):
"""Observatory location (`~astropy.coordinates.EarthLocation`)."""
return earth_location_from_dict(self.table.meta)
@lazyproperty
def time_ref(self):
"""Time reference (`~astropy.time.Time`)"""
return time_ref_from_dict(self.table.meta)
@lazyproperty
def duration(self):
"""Pointing table duration (`~astropy.time.TimeDelta`).
The time difference between the first and last entry.
"""
return self.time[-1] - self.time[0]
@lazyproperty
def time(self):
"""Time array (`~astropy.time.Time`)"""
met = Quantity(self.table["TIME"].astype("float64"), "second")
time = self.time_ref + met
return time.tt
@lazyproperty
def radec(self):
"""RA / DEC position from table (`~astropy.coordinates.SkyCoord`)"""
lon = self.table["RA_PNT"]
lat = self.table["DEC_PNT"]
return SkyCoord(lon, lat, unit="deg", frame="icrs")
@lazyproperty
def altaz_frame(self):
"""ALT / AZ frame (`~astropy.coordinates.AltAz`)."""
return AltAz(obstime=self.time, location=self.location)
@lazyproperty
def altaz(self):
"""ALT / AZ position computed from RA / DEC (`~astropy.coordinates.SkyCoord`)"""
return self.radec.transform_to(self.altaz_frame)
@lazyproperty
def altaz_from_table(self):
"""ALT / AZ position from table (`~astropy.coordinates.SkyCoord`)"""
lon = self.table["AZ_PNT"]
lat = self.table["ALT_PNT"]
return SkyCoord(lon, lat, unit="deg", frame=self.altaz_frame)
[docs] def altaz_interpolate(self, time):
"""Interpolate pointing for a given time."""
t_new = time.mjd
t = self.time.mjd
xyz = self.altaz.cartesian
x_new = interp1d(t, xyz.x)(t_new)
y_new = interp1d(t, xyz.y)(t_new)
z_new = interp1d(t, xyz.z)(t_new)
xyz_new = CartesianRepresentation(x_new, y_new, z_new)
altaz_frame = AltAz(obstime=time, location=self.location)
# FIXME: an API change in Astropy in 3.1 broke this
# See https://github.com/gammapy/gammapy/pull/1906
if astropy_version >= "3.1":
kwargs = {"representation_type": "unitspherical"}
else:
kwargs = {"representation": "unitspherical"}
return SkyCoord(xyz_new, frame=altaz_frame, unit="deg", **kwargs)