Source code for sunpy.map.sources.gong
"""
GONG Map subclass definitions
"""
import numpy as np
import astropy.units as u
from astropy.time import Time
from sunpy.coordinates import get_earth
from sunpy.map import GenericMap
__all__ = ['GONGSynopticMap']
from sunpy.map.mapbase import SpatialPair
[docs]
class GONGSynopticMap(GenericMap):
"""
GONG Synoptic Map.
The Global Oscillation Network Group (GONG) operates a six-station network of velocity
imagers located around the Earth that observe the Sun nearly continuously. GONG
produces hourly photospheric magnetograms using the Ni I 676.8 nm spectral line with an
array of 242×256 pixels covering the solar disk. These magnetograms are used to derive
synoptic maps which show a full-surface picture of the solar magnetic field.
Notes
-----
If you have ``pfsspy`` installed this map source will be used instead of the one built into ``pfsspy``.
References
----------
* `GONG Page <https://gong.nso.edu/>`_
* `Magnetogram Synoptic Map Images Page <https://gong.nso.edu/data/magmap/>`_
* `FITS header keywords <https://gong.nso.edu/data/DMAC_documentation/General/fitsdesc.html>`_
* `Instrument Paper (pp. 203–208) <https://inis.iaea.org/collection/NCLCollectionStore/_Public/20/062/20062491.pdf>`_
* `GONG+ Documentation <https://gong.nso.edu/data/DMAC_documentation/PipelineMap/GlobalMap.html>`_
"""
[docs]
@classmethod
def is_datasource_for(cls, data, header, **kwargs):
return (str(header.get('TELESCOP', '')).endswith('GONG') and
str(header.get('CTYPE1', '').startswith('CRLN')))
@property
def date(self):
return Time(f"{self.meta.get('date-obs')} {self.meta.get('time-obs')}")
@property
def scale(self):
# Since, this map uses the cylindrical equal-area (CEA) projection,
# the spacing should be modified to 180/pi times the original value
# Reference: Section 5.5, Thompson 2006
return SpatialPair(self.meta['cdelt1'] * self.spatial_units[0] / u.pixel,
self.meta['cdelt2'] * 180 / np.pi * self.spatial_units[0] / u.pixel)
@property
def spatial_units(self):
return SpatialPair(u.deg, u.deg)
@property
def observer_coordinate(self):
return get_earth(self.date)