GCRS¶
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class
astropy.coordinates.
GCRS
(*args, **kwargs)[source] [edit on github]¶ Bases:
astropy.coordinates.BaseRADecFrame
A coordinate or frame in the Geocentric Celestial Reference System (GCRS).
GCRS is distinct form ICRS mainly in that it is relative to the Earth’s center-of-mass rather than the solar system Barycenter. That means this frame includes the effects of aberration (unlike ICRS). For more background on the GCRS, see the references provided in the See Also section of the documentation. (Of particular note is Section 1.2 of USNO Circular 179)
This frame also includes frames that are defined relative to the Earth, but that are offset (in both position and velocity) from the Earth.
The frame attributes are listed under Other Parameters.
Parameters: representation :
BaseRepresentation
or NoneA representation object or
None
to have no data (or use the other keywords below).ra :
Angle
, optional, must be keywordThe RA for this object (
dec
must also be given andrepresentation
must be None).dec :
Angle
, optional, must be keywordThe Declination for this object (
ra
must also be given andrepresentation
must be None).distance :
Quantity
, optional, must be keywordThe Distance for this object along the line-of-sight. (
representation
must be None).pm_ra_cosdec :
Quantity
, optional, must be keywordThe proper motion in Right Ascension (including the
cos(dec)
factor) for this object (pm_dec
must also be given).pm_dec :
Quantity
, optional, must be keyword Theproper motion in Declination for this object (
pm_ra_cosdec
must also be given).radial_velocity :
Quantity
, optional, must be keywordThe radial velocity of this object.
copy : bool, optional
If
True
(default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.Other Parameters: obstime :
Time
The time at which the observation is taken. Used for determining the position of the Earth.
obsgeoloc :
CartesianRepresentation
,Quantity
The position of the observer relative to the center-of-mass of the Earth, oriented the same as BCRS/ICRS. Either [0, 0, 0],
CartesianRepresentation
, or proper input for one, i.e., aQuantity
with shape (3, ...) and length units. Defaults to [0, 0, 0], meaning “true” GCRS.obsgeovel :
CartesianRepresentation
,Quantity
The velocity of the observer relative to the center-of-mass of the Earth, oriented the same as BCRS/ICRS. Either [0, 0, 0],
CartesianRepresentation
, or proper input for one, i.e., aQuantity
with shape (3, ...) and velocity units. Defaults to [0, 0, 0], meaning “true” GCRS.Attributes Summary
default_differential
default_representation
frame_attributes
frame_specific_representation_info
name
obsgeoloc
obsgeovel
obstime
Attributes Documentation
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default_differential
¶
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default_representation
¶
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frame_attributes
= OrderedDict([('obstime', <astropy.coordinates.frame_attributes.TimeFrameAttribute object>), ('obsgeoloc', <astropy.coordinates.frame_attributes.CartesianRepresentationFrameAttribute object>), ('obsgeovel', <astropy.coordinates.frame_attributes.CartesianRepresentationFrameAttribute object>)])¶
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frame_specific_representation_info
¶
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name
= 'gcrs'¶
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obsgeoloc
= <CartesianRepresentation (x, y, z) in m ( 0., 0., 0.)>¶
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obsgeovel
= <CartesianRepresentation (x, y, z) in m / s ( 0., 0., 0.)>¶
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obstime
= <Time object: scale='utc' format='jyear_str' value=J2000.000>¶
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