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# This file is part of astro_metadata_translator. 

# 

# Developed for the LSST Data Management System. 

# This product includes software developed by the LSST Project 

# (http://www.lsst.org). 

# See the COPYRIGHT file at the top-level directory of this distribution 

# for details of code ownership. 

# 

# This program is free software: you can redistribute it and/or modify 

# it under the terms of the GNU General Public License as published by 

# the Free Software Foundation, either version 3 of the License, or 

# (at your option) any later version. 

# 

# This program is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

# GNU General Public License for more details. 

# 

# You should have received a copy of the GNU General Public License 

# along with this program. If not, see <http://www.gnu.org/licenses/>. 

 

"""Generically useful translation helpers which translation classes 

can use. 

 

They are written as free functions. Some of them are written 

as if they are methods of `MetadataTranslator`, allowing them to be attached 

to translator classes that need them. These methods have full access to 

the translator methods. 

 

Other functions are pure helpers that can be imported and used to help 

translation classes without using `MetadataTranslator` properties. 

 

""" 

 

__all__ = ("to_location_via_telescope_name", 

"is_non_science", 

"tracking_from_degree_headers", 

"altitude_from_zenith_distance") 

 

from astropy.coordinates import EarthLocation, SkyCoord 

import astropy.units as u 

 

 

def to_location_via_telescope_name(self): 

"""Calculate the observatory location via the telescope name. 

 

Returns 

------- 

loc : `astropy.coordinates.EarthLocation` 

Location of the observatory. 

""" 

return EarthLocation.of_site(self.to_telescope()) 

 

 

def is_non_science(self): 

"""Raise an exception if this is a science observation. 

 

Raises 

------ 

KeyError 

Is a science observation. 

""" 

if self.to_observation_type() == "science": 

raise KeyError("Header represents science observation and can not default") 

return 

 

 

def altitude_from_zenith_distance(zd): 

"""Convert zenith distance to altitude 

 

Parameters 

---------- 

zd : `astropy.units.Quantity` 

Zenith distance as an angle. 

 

Returns 

------- 

alt : `astropy.units.Quantity` 

Altitude. 

""" 

return 90.*u.deg - zd 

 

 

def tracking_from_degree_headers(self, radecsys, radecpairs, unit=u.deg): 

"""Calculate the tracking coordinates from lists of headers. 

 

Parameters 

---------- 

radecsys : `list` or `tuple` 

Header keywords to try corresponding to the tracking system. If none 

match ICRS will be assumed. 

pairs : `tuple` of `tuple` of pairs of `str` 

Pairs of keywords containing the RA/Dec in units of ``unit``. 

unit : `astropy.unit.BaseUnit` or `tuple` 

Unit definition suitable for the `~astropy.coordinate.SkyCoord` 

constructor. 

 

Returns 

------- 

radec = `astropy.coordinates.SkyCoord` 

The RA/Dec coordinates. None if this is a moving target or a 

non-science observation without any RA/Dec definition. 

 

Raises 

------ 

KeyError 

No RA/Dec keywords were found and this observation is a science 

observation. 

""" 

used = [] 

for k in radecsys: 

if k in self._header: 

frame = self._header[k].strip().lower() 

used.append(k) 

if frame == "gappt": 

self._used_these_cards(*used) 

# Moving target 

return None 

break 

else: 

frame = "icrs" 

for ra_key, dec_key in radecpairs: 

if ra_key in self._header and dec_key in self._header: 

radec = SkyCoord(self._header[ra_key], self._header[dec_key], 

frame=frame, unit=unit, obstime=self.to_datetime_begin(), 

location=self.to_location()) 

self._used_these_cards(ra_key, dec_key, *used) 

return radec 

if self.to_observation_type() == "science": 

raise KeyError("Unable to determine tracking RA/Dec of science observation") 

return None