aperture

Module to handle SIAF apertures.

The aperture module defined classes and functions to support working with SIAF apertures. The main class is Aperture, JwstAperture and HstAperture inherit from it. The class methods support transformations between any of the 4 SIAF frames (detector, science/DMS, ideal, V-frame/telescope). Aperture attributes correspond to entries in the SIAF xml files in the Project Reference Database (PRD), and are checked for format compliance. Methods for aperture validation and plotting are provided. The nomenclature is adapted from the JWST SIAF document Cox & Lallo: JWST-STScI-001550.

Authors

• Johannes Sahlmann

Notes

Numerous contributions and code snippets by Colin Cox were incorporated. Some methods were adapted from the jwxml package (https://github.com/mperrin/jwxml). Some of the polynomial transformation code was adapted from (https://github.com/spacetelescope/ramp_simulator/).

class pysiaf.aperture.Aperture

A class for aperture definitions of astronomical telescopes.

HST and JWST SIAF entries are supported via class inheritance. Frames, transformations, conventions and property/attribute names are as defined for JWST in JWST-STScI-001550.

Transformations between four coordinate systems (“frames”) are supported:

• Detector (“det”) : units of pixels, according to detector read out axes orientation as defined by SIAF. This system generally differs from the JWST-DMS detector frame definition.

• Science (“sci”) : units of pixels, corresponds to DMS coordinate system.

• Ideal (“idl”) : units of arcseconds, usually a tangent plane projection with reference point at aperture reference location.

• Telescope or V2/V3 (“tel”) : units of arcsecs, spherical coordinate system.

Examples

extract one aperture from a Siaf object: ap = some_siaf['desired_aperture_name']

convert pixel coordinates to V2V3 / tel coords (takes pixel coords, returns arcsec): ap.det_to_tel(1024, 512)

convert idl coords to sci pixels: ap.idl_to_sci( 10, 3)

Frames can also be defined by strings: ap.convert(1024, 512, from_frame='det', to_frame='tel')

Get aperture vertices/corners in tel frame: ap.corners('tel')

Get the reference point defined in the SIAF: ap.reference_point('tel')

plot coordinates in idl frame: ap.plot('tel')

There exist methods for all of the possible {tel,idl,sci,det}_to_{tel,idl,sci,det} combinations.

Set attributes required for PRD.

closed_polygon_points(to_frame, rederive=True)

Compute closed polygon points of aperture outline. Used for plotting and path generation.

Parameters:

to_framestr

Name of frame.

rederivebool

Whether to rederive vertices from scratch (if True) or use idl values stored in SIAF.

Returns:

points_x, points_ytuple of numpy arrays

x and y coordinates of aperture vertices

complement()

Complement the attributes of an aperture.

This method is useful when generating new apertures. The attributes that will be added are:

• X[Y]IdlVert1[2,3,4]

• X[Y]SciScale

convert(x, y, from_frame, to_frame)

Convert input coordinates from one frame to another frame.

Parameters:

xfloat

first coordinate

yfloat

second coordinate

from_framestr

Frame in which x,y are given

to_framestr

Frame to transform into

Returns:

x’, y’tuple

Coordinates in to_frame

corners(to_frame, rederive=True)

Return coordinates of the aperture vertices in the specified frame.

The positions refer to the outside corners of the corner pixels, not the pixel centers.

Parameters:

to_framestr

Frame of returned coordinates

rederivebool

If True, the parameters given in the aperture definition file are used to derive the vertices. Otherwise computations are made on the basis of the IdlVert attributes.

Returns:

x, ytuple of float arrays

coordinates of vertices in to_frame

correct_for_dva(v2_arcsec, v3_arcsec, verbose=False)

Apply differential velocity aberration correction to input arrays of V2/V3 coordinates.

Currently only implemented for HST apertures.

Parameters:

v2_arcsecfloat

v2 coordinates

v3_arcsecfloat

v3 coordinates

verbosebool

verbosity

Returns:

v2,v3tuple ot floats

Corrected coordinates

det_to_idl(*args)

Detector to ideal frame transformation.

det_to_raw(*args)

Detector to raw frame transformation.

det_to_sci(x_det, y_det, *args)

Detector to science frame transformation, following Section 4.1 of JWST-STScI-001550.

det_to_sky(*args)

det_to_tel(*args)

Detector to telescope frame transformation.

detector_transform(from_system, to_system, angle_deg=None, parity=None)

Generate transformation model to transform between det <-> sci.

DetSciYAngle_deg, DetSciParity can be defined externally to override aperture attribute.

Parameters:

from_systemstr

Originating system

to_systemstr

System to transform into

angle_degfloat, int

DetSciYAngle

parityint

DetSciParity

Returns:

x_model, y_modeltuple of astropy.modeling models

distortion_transform(from_system, to_system, include_offset=True)

Return polynomial distortion transformation between sci<->idl.

Parameters:

from_systemstr

Starting system (e.g. “sci”, “idl”)

to_systemstr

Ending coordinate system (e.g. “sci” , “idl”)

include_offsetbool

Whether to include the zero-point offset.

Returns:

x_modelastropy.modeling.Model

Correction in x

y_modelastropy.modeling.Model

Correction in y

dms_corner()

Compute the pixel value of the lower left corner of an aperture.

This corresponds to the OSS corner position (x: ColCorner, y: RowCorner). The notation for OSS is 1-based, i.e. the lower left corner of a FULL subarray is (1,1)

get_polynomial_coefficients()

Return a dictionary of arrays holding the significant idl/sci coefficients.

get_polynomial_derivatives(location='fiducial', coefficient_seed='Sci2Idl')

Return derivative values for scale and rotation derivation.

The four partial derivatives of coefficients that transform between two frames E and R are:

b=(dx_E)/(dx_R ) c=(dx_E)/(dy_R ) e=(dy_E)/(dx_R ) f=(dy_E)/(dy_R )

Parameters:

locationstr or dict

if dict, has to have ‘x’ and ‘y’ elements

coefficient_seed

Returns:

dict

get_polynomial_linear_parameters(location='fiducial', coefficient_seed='Sci2Idl')

Return linear polynomial parameters.

Parameters:

location

coefficient_seed

Returns:

idl_to_det(*args)

Ideal to detector frame transformation.

idl_to_raw(*args)

Ideal to raw frame transformation.

idl_to_sci(x_idl, y_idl)

Ideal to science frame transformation.

idl_to_sky(*args)

idl_to_tel(x_idl, y_idl, V3IdlYAngle_deg=None, V2Ref_arcsec=None, V3Ref_arcsec=None, method='planar_approximation', input_coordinates='tangent_plane', output_coordinates='tangent_plane', verbose=False)

Convert from ideal to telescope (V2/V3) coordinate system.

By default, this implements the planar approximation, which is adequate for most purposes but may not be for all. Error is about 1.7 mas at 10 arcminutes from the tangent point. See JWST-STScI-1550 for more details. For higher accuracy, set method=’spherical_transformation’ in which case 3D matrix rotations are applied. Also by default, the input coordinates are in a tangent plane with a reference points at the origin (0,0) of the ideal frame. input_coordinates can be set to ‘spherical’.

Parameters:

x_idl: float

ideal X coordinate in arcsec

y_idl: float

ideal Y coordinate in arcsec

V3IdlYAngle_deg: float

overwrites self.V3IdlYAngle

V2Ref_arcsecfloat

overwrites self.V2Ref

V3Ref_arcsecfloat

overwrites self.V3Ref

methodstr

must be one of [‘planar_approximation’, ‘spherical_transformation’, ‘spherical’]

input_coordinatesstr

must be one of [‘tangent_plane’, ‘spherical’, ‘planar’]

Returns:

tuple of floats containing V2, V3 coordinates in arcsec

path(to_frame)

Return matplotlib path generated from aperture vertices.

Parameters:

to_framestr

Coordinate frame.

Returns:

pathmatplotlib.path.Path object

Path describing the aperture outline

plot(frame='tel', label=False, ax=None, title=False, units='arcsec', show_frame_origin=None, mark_ref=False, fill=True, fill_color='cyan', fill_alpha=None, label_rotation=0.0, **kwargs)

Plot this aperture.

Parameters:

framestr

Which coordinate system to plot in: ‘tel’, ‘idl’, ‘sci’, ‘det’

labelstr or bool

Add text label. If True, text will be the default aperture name.

axmatplotlib.Axes

Desired destination axes to plot into (If None, current axes are inferred)

titlestr

Figure title. If set, add a label to the plot indicating which frame was plotted.

unitsstr

one of ‘arcsec’, ‘arcmin’, ‘deg’

show_frame_originstr or list

Plot frame origin (goes to plot_frame_origin()): None, ‘all’, ‘det’, ‘sci’, ‘raw’, ‘idl’, or a list of these.

mark_refbool

Add marker for the (V2Ref, V3Ref) reference point defining this aperture.

fillbool

Whether to color fill the aperture

fill_colorstr

Fill color

fill_alphafloat

alpha parameter for filled aperture

colormatplotlib-compatible color

Color specification for this aperture’s outline, passed through to matplotlib.Axes.plot

kwargsdict

Dictionary of optional parameters passed to matplotlib

.. todo:: plotting in Sky frame, requires attitude

#elif system == ‘radec’:

# if attitude_ref is not None:

# vertices = np.array(

# siaf_rotations.pointing(attitude_ref, self.points_closed.T[0],

#self.points_closed.T[1])).T

# self.path_radec = matplotlib.path.Path(vertices)

# else:

# error(‘Please provide attitude_ref’)

plot_detector_channels(frame, color='0.5', alpha=0.3, evenoddratio=0.5, ax=None)

Outline the detector readout channels.

These are depicted as alternating light/dark bars to show the regions read out by each of the output amps.

Parameters:

framestr

Which coordinate system to plot in: “tel”, “idl”, “sci”, “det”

colormatplotlib-compatible color

Color specification for the amplifier shaded region, passed through to matplotlib.patches.Polygon as facecolor

alphafloat

Opacity of odd-numbered amplifier region overlays (for even, see “evenoddratio”)

evenoddratiofloat

Ratio of opacity between even and odd amplifier region overlays

axmatplotlib.Axes

Desired destination axes to plot into (If None, current axes are inferred from pyplot.)

plot_frame_origin(frame, which='sci', units='arcsec', ax=None)

Indicate the origins of the detector and science frames.

Red and blue squares indicate the detector and science frame origin, respectively.

Parameters:

framestr

Which coordinate system to plot in: ‘tel’, ‘idl’, ‘sci’, ‘det’

whichstr of list

Which origin to plot: ‘all’, ‘det’, ‘sci’, ‘raw’, ‘idl’, or a list

unitsstr

one of ‘arcsec’, ‘arcmin’, ‘deg’

axmatplotlib.Axes

Desired destination axes to plot into (If None, current axes are inferred from pyplot.)

raw_to_det(*args)

Raw to detector frame transformation.

raw_to_idl(*args)

Raw to raw ideal transformation.

raw_to_sci(x_raw, y_raw)

Convert from raw/native coordinates to SIAF-Science coordinates.

SIAF-Science coordinates are the same as DMS coordinates for FULLSCA apertures. Implements the fits_generator description described the table attached to https://jira.stsci.edu/browse/JWSTSIAF-25 (except for Guider 2) and implemented in https://github.com/STScI-JWST/jwst/blob/master/jwst/fits_generator/create_dms_data.py

Parameters:

x_rawfloat

Raw x coordinate

y_rawfloat

Raw y coordinate

Returns:

x_sci, y_scituple of science coordinates

References

See https://jwst-docs.stsci.edu/display/JDAT/Coordinate+Systems+and+Transformations See also JWST-STScI-002566 and JWST-STScI-003222 Rev A

raw_to_tel(*args)

Raw to telescope frame transformation.

reference_point(to_frame)

Return the defining reference point of the aperture in to_frame.

sci_to_det(x_sci, y_sci, *args)

Science to detector frame transformation, following Section 4.1 of JWST-STScI-001550.

sci_to_idl(x_sci, y_sci)

Science to ideal frame transformation.

sci_to_raw(x_sci, y_sci)

Convert from Science coordinates to raw/native coordinates.

Implements the fits_generator description described the table attached to https://jira.stsci.edu/browse/JWSTSIAF-25 (except for Guider 2) and implemented in https://github.com/STScI-JWST/jwst/blob/master/jwst/fits_generator/create_dms_data.py

Parameters:

x_scifloat

Science x coordinate

y_scifloat

Science y coordinate

Returns:

x_raw, y_rawtuple of raw coordinates

References

See https://jwst-docs.stsci.edu/display/JDAT/Coordinate+Systems+and+Transformations See also JWST-STScI-002566 and JWST-STScI-003222 Rev A

sci_to_sky(*args)

sci_to_tel(*args)

Science to telescope frame transformation.

set_attitude_matrix(attmat)

Set an atttude matrix, for use in subsequent transforms to sky frame.

set_distortion_coefficients_from_file(file_name)

Set polynomial from standardized file.

Parameters:

file_namestr

Reference file containing coefficients

Returns:

set_polynomial_coefficients(sci2idlx, sci2idly, idl2scix, idl2sciy)

Set the values of polynomial coefficients.

Parameters:

sci2idlxarray

Coefficients

sci2idlyarray

Coefficients

idl2scixarray

Coefficients

idl2sciyarray

Coefficients

sky_to_det(*args)

sky_to_idl(*args)

sky_to_sci(*args)

sky_to_tel(*args)

Sky to Tel frame transformation. Requires an attitude matrix.

Input sky coords should be given in degrees RA and Dec, or equivalent astropy.Quantities

Results are returned as floats with implicit units of arcseconds, for consistency with the other *_to_tel functions.

tel_to_det(*args)

Telescope to detector frame transformation.

tel_to_idl(v2_arcsec, v3_arcsec, V3IdlYAngle_deg=None, V2Ref_arcsec=None, V3Ref_arcsec=None, method='planar_approximation', output_coordinates='tangent_plane', input_coordinates='tangent_plane')

Convert from telescope (V2/V3) to ideal coordinate system.

By default, this implements the planar approximation, which is adequate for most purposes but may not be for all. Error is about 1.7 mas at 10 arcminutes from the tangent point. See JWST-STScI-1550 for more details. For higher accuracy, set method=’spherical_transformation’ in which case 3D matrix rotations are applied.

Also by default, the output coordinates are in a tangent plane with a reference point at the origin (0,0) of the ideal frame.

Parameters:

v2_arcsecfloat

V2 coordinate in arcsec

v3_arcsecfloat

V3 coordinate in arcsec

V3IdlYAngle_degfloat

overwrites self.V3IdlYAngle

V2Ref_arcsecfloat

overwrites self.V2Ref

V3Ref_arcsecfloat

overwrites self.V3Ref

methodstr

must be one of [‘planar_approximation’, ‘spherical_transformation’]

output_coordinatesstr

must be one of [‘tangent_plane’, ‘spherical’]

Returns:

tuple of floats containing x_idl, y_idl coordinates in arcsec

tel_to_raw(*args)

Telescope to raw frame transformation.

tel_to_sci(*args)

Telescope to science frame transformation.

tel_to_sky(*args)

Tel to sky frame transformation. Requires an attitude matrix.

Note, sky coordinates are returned as floats with angles in degrees. It’s easy to cast into an astropy SkyCoord and then convert into any desired other representation. For instance:

>>> sc = astropy.coordinates.SkyCoord( *aperture.tel_to_sky(xtel, ytel), unit='deg' )
>>> sc.to_string('hmsdms')

telescope_transform(from_system, to_system, V3IdlYAngle_deg=None, V2Ref_arcsec=None, V3Ref_arcsec=None, verbose=False)

Return transformation model between tel<->idl.

V3IdlYAngle_deg, V2Ref_arcsec, V3Ref_arcsec can be given as arguments to override aperture attributes.

Parameters:

from_systemstr

Starting system (“tel” or “idl”)

to_systemstr

Ending coordinate system (“tel” or “idl”)

V3IdlYAngle_degfloat

Angle

V2Ref_arcsecfloat

Reference coordinate

V3Ref_arcsecfloat

Reference coordinate

verbosebool

verbosity

Returns:

x_model, y_modeltuple of astropy.modeling models

validate()

Verify that the instance’s attributes fully qualify the aperture.

# http: // ssb.stsci.edu / doc / jwst / _modules / jwst / datamodels / #wcs_ref_models.html # DistortionModel.validate

verify()

Perform internal verification of aperture parameters.

class pysiaf.aperture.HstAperture

Class for apertures of HST instruments.

Initialize HST aperture by inheriting from Aperture class.

closed_polygon_points(to_frame, rederive=False)

Compute closed polygon points of aperture outline.

compute_tvs_matrix(v2_arcsec=None, v3_arcsec=None, pa_deg=None, verbose=False)

Compute the TVS matrix from tvs-specific v2,v3,pa parameters.

Parameters:

v2_arcsecfloat

offset

v3_arcsecfloat

offset

pa_degfloat

angle

verbosebool

verbosity

Returns:

tvsnumpy matrix

TVS matrix

corners(to_frame, rederive=False)

Return coordinates of the aperture vertices in the specified frame.

idl_to_tel(x_idl, y_idl, V3IdlYAngle_deg=None, V2Ref_arcsec=None, V3Ref_arcsec=None, method='planar_approximation', input_coordinates='tangent_plane', output_coordinates=None, verbose=False)

Convert ideal coordinates to telescope (V2/V3) coordinates for HST.

INPUT COORDINATES HAVE TO BE FGS OBJECT SPACE CARTESIAN X,Y coordinates

For HST FGS, transformation is implemented using the FGS TVS matrix. Parameter names are overloaded for simplicity: tvs_pa_deg = V3IdlYAngle_deg tvs_v2_arcsec = V2Ref_arcsec tvs_v3_arcsec = V3Ref_arcsec

Parameters:

x_idlfloat

ideal x coordinates in arcsec

y_idlfloat

ideal y coordinates in arcsec

V3IdlYAngle_degfloat

angle

V2Ref_arcsecfloat

Reference coordinate

V3Ref_arcsecfloat

Reference coordinate

methodstr

input_coordinatesstr

Returns:

v2, v3tuple of float

Telescope coordinates in arcsec

rearrange_fgs_alignment_parameters(pa_deg_in, v2_arcsec_in, v3_arcsec_in, direction)

Convert to/from alignment parameters make FGS look like a regular camera aperture.

Parameters:

pa_deg_infloat

v2_arcsec_infloat

v3_arcsec_infloat

directionstr

One of [‘fgs_to_camera’, ]

Returns:

pa, v2, v3tuple

re-arranged and sometimes sign-inverted alignment parameters

set_idl_reference_point(v2_ref, v3_ref, verbose=False)

Determine the reference point in the Ideal frame.

V2Ref and V3Ref are determined via the TVS matrix. The tvs parameters that determine the TVS matrix itself are derived and added to the attribute list.

Parameters:

v2_reffloat

reference coordinate

v3_reffloat

reference coordinate

verbosebool

verbosity

set_tel_reference_point(verbose=True)

Recompute and set V2Ref and V3Ref to actual position in tel/V frame.

This is after using those V2Ref and V3Ref attributes for TVS matrix update.

tel_to_idl(v2_arcsec, v3_arcsec, V3IdlYAngle_deg=None, V2Ref_arcsec=None, V3Ref_arcsec=None, method='planar_approximation', output_coordinates='tangent_plane', input_coordinates='tangent_plane')

Convert from telescope (V2/V3) to ideal coordinate system.

By default, this implements the planar approximation, which is adequate for most purposes but may not be for all. Error is about 1.7 mas at 10 arcminutes from the tangent point. See JWST-STScI-1550 for more details. For higher accuracy, set method=’spherical_transformation’ in which case 3D matrix rotations are applied.

Also by default, the output coordinates are in a tangent plane with a reference point at the origin (0,0) of the ideal frame.

Parameters:

v2_arcsecfloat

V2 coordinate in arcsec

v3_arcsecfloat

V3 coordinate in arcsec

V3IdlYAngle_degfloat

overwrites self.V3IdlYAngle

V2Ref_arcsecfloat

overwrites self.V2Ref

V3Ref_arcsecfloat

overwrites self.V3Ref

methodstr

must be one of [‘planar_approximation’, ‘spherical_transformation’]

output_coordinatesstr

must be one of [‘tangent_plane’, ‘spherical’]

Returns:

tuple of floats containing x_idl, y_idl coordinates in arcsec

class pysiaf.aperture.JwstAperture

Class for apertures of JWST instruments.

Initialize JWST aperture by inheriting from Aperture.

class pysiaf.aperture.NirspecAperture(tilt=None, filter_name='CLEAR')

Class for apertures of the JWST NIRSpec instrument.

Initialize NIRSpec aperture by inheriting from JWSTAperture.

corners(to_frame, rederive=True)

Return coordinates of aperture vertices.

det_to_sci(x_det, y_det, *args)

Detector to science frame transformation. Use parent aperture if SLIT.

gwa_to_ote(gwa_x, gwa_y)

NIRSpec transformation from GWA sky side to OTE frame XAN, YAN.

Parameters:

gwa_xfloat

GWA coordinate

gwa_yfloat

GWA coordinate

Returns:

xan, yantuple of floats

XAN, YAN in degrees

gwa_to_sci(x_gwa, y_gwa)

NIRSpec transformation from GWA detector side to Science frame.

Parameters:

x_gwafloat

GWA coordinate

y_scifloat

GWA coordinate

Returns:

x_sci, y_scituple of floats

Science coordinates

gwain_to_gwaout(x_gwa, y_gwa)

Transform from GWA detector side to GWA skyward side. This is the effect of the mirror.

Parameters:

x_gwafloat

GWA coordinate

y_gwafloat

GWA coordinate

Returns:

x_gwap, y_gwaptuple of floats

GWA skyward side coordinates

References

Giardino, Ferruit, and Alves de Oliveira (2014), ESA NTN-2014-005 Proffitt et al. (2018), JWST-STScI-005921

gwaout_to_gwain(x_gwa, y_gwa)

Transform from GWA skyward side to GWA detector side. Effect of mirror.

Parameters:

x_gwafloat

GWA coordinate

y_gwafloat

GWA coordinate

Returns:

x_gwap, y_gwaptuple of floats

GWA detector side coordinates

References

Equations for the reverse transform T. Keyes (private communication) will be documented in next update of JWST-STScI-005921.

idl_to_sci(x_idl, y_idl)

Transform to Science frame using special implementation for NIRSpec via tel frame.

Parameters:

x_idlfloat

Ideal coordinate

y_idlfloat

Ideal coordinate

Returns:

x_sci, y_scituple of floats

Science coordinates

ote_to_gwa(ote_x, ote_y)

NIRSpec transformation from OTE frame XAN, YAN to GWA sky side.

Parameters:

ote_xfloat

XAN coordinate in degrees

ote_yfloat

YAN coordinate in degrees

Returns:

gwa_x, gwa_ytuple of floats

GWA coordinates

sci_to_det(x_sci, y_sci, *args)

Science to detector frame transformation. Use parent aperture if SLIT.

sci_to_gwa(x_sci, y_sci)

NIRSpec transformation from Science frame to GWA detector side.

Parameters:

x_scifloat

Science frame coordinate

y_scifloat

Science frame coordinate

Returns:

x_gwa, y_gwatuple of floats

GWA detector side coordinates

sci_to_idl(x_sci, y_sci)

Transform to ideal frame, using special implementation for NIRSpec via tel frame.

Parameters:

x_scifloat

Science coordinate

y_scifloat

Science coordinate

Returns:

v2, v3tuple of floats

telescope coordinates

sci_to_tel(x_sci, y_sci)

Science to telescope frame transformation. Overwrite standard behaviour for NIRSpec.

tel_to_sci(x_tel, y_tel)

Telescope to science frame transformation for NIRSpec.

class pysiaf.aperture.RomanAperture

A class that defines the accepted aperture types for the Roman SIAF. This is built upon the pysiaf.aperture.Aperture base class.

Set attributes required for PRD.

class pysiaf.aperture.SiafCoordinates(x, y, frame)

A helper class to hold coordinate arrays associated with a SIAF frame.

Initialize object.

pysiaf.aperture.compare_apertures(reference_aperture, comparison_aperture, absolute_tolerance=None, attribute_list=None, print_file=<_io.TextIOWrapper name='<stdout>' mode='w' encoding='utf-8'>, fractional_tolerance=1e-06, verbose=False, ignore_attributes=None)

Compare the attributes of two apertures.

Parameters:

reference_aperture

comparison_aperture

absolute_tolerance

attribute_list

print_file

fractional_tolerance

verbose

ignore_attributes

pysiaf.aperture.get_hst_to_jwst_coefficient_order(polynomial_degree)

Return array of indices that convert an aeeay of HST coefficients to JWST ordering.

This assumes that the coefficient orders are as follows HST: 1, y, x, y^2, xy, x^2, y^3, xy^2, x^2y, x^3 … (according to Cox’s /grp/hst/OTA/alignment/FocalPlane.xlsx) JWST: 1, x, y, x^2, xy, y^2, x^3, x^2y, xy^2, y^3 …

Parameters:

polynomial_degreeint

polynomial degree

Returns:

conversion_indexnumpy array

Array of indices

pysiaf.aperture.linear_transform_model(from_system, to_system, parity, angle_deg)

Create an astropy.modeling.Model object for linear transforms: det <-> sci and idl <-> tel.

See sics_to_v2v3 (HST): x_v2v3 = v2_origin + parity * x_sics * np.cos(np.deg2rad(theta_deg)) + y_sics * np.sin( np.deg2rad(theta_deg)) y_v2v3 = v3_origin - parity * x_sics * np.sin(np.deg2rad(theta_deg)) + y_sics * np.cos( np.deg2rad(theta_deg))

Parameters:

from_systemstr

Starting system

to_systemstr

End system

parityint

Parity

angle_degfloat

Angle in degrees

Returns:

xmodel, ymodeltuple of astropy models

Transformation models

pysiaf.aperture.points_on_arc(x0, y0, radius, phi1_deg, phi2_deg, N=100)

Compute points that lie on a circular arc between angles phi1 and phi2.

Parameters:

x0float

offset

y0float

offset

radiusfloat

Radius of circle

phi1_degfloat

Start angle of pie in deg

phi2_degfloat

End angle of pie in deg

Nint

Number of sampled points

Returns:

x, ytuple of floats

Coordinates on circle

pysiaf.aperture.to_distortion_model(coefficients, degree=5)

Create an astropy.modeling.Model object for distortion polynomial.

Parameters:

coefficientsarray like

Coefficients from the ISIM transformations file.

degreeint

Degree of polynomial. Default is 5 as in the ISIM file but many of the polynomials are of a smaller degree.

Returns:

polyastropy.modeling.Polynomial2D

Polynomial model transforming one coordinate (x or y) between two systems.