Source code for gammapy.data.pointing

# 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)