descwl.survey module¶
Manage the parameters that define a simulated survey’s camera design and observing conditions.
- class descwl.survey.Survey(**args)[source]¶
Bases: object
Survey camera and observing parameters.
No default values are assigned to constructor args since these are handled at run time based on a requested (survey_name,filter_band) combination using get_defaults().Parameters: - survey_name (str) – Use default camera and observing parameters appropriate for this survey.
- filter_band (str) – LSST imaging band to simulate. Must be one of ‘u’,’g’,’r’,’i’,’z’,’y’.
- image_width (int) – Simulated camera image width in pixels.
- image_height (int) – Simulated camera image height in pixels.
- pixel_scale (float) – Simulated camera pixel scale in arcseconds per pixel.
- exposure_time (float) – Simulated camera total exposure time seconds.
- zero_point (float) – Simulated camera zero point in electrons per second at 24th magnitude.
- mirror_diameter (float) – Size of the primary mirror’s clear aperture in meters to use for the optical PSF, or zero if no optical PSF should be simulated.
- effective_area (float) – Effective total light collecting area in square meters. Used to determine the obscuration fraction in the simulated optical PSF. Ignored if mirror_diameter is zero.
- zenith_psf_fwhm (float) – FWHM of the atmospheric PSF at zenith in arcseconds.
- atmospheric_psf_beta (float) – Moffat beta parameter of the atmospheric PSF, or use a Kolmogorov PSF if beta <= 0.
- atmospheric_psf_e1 (float) – Atmospheric ellipticity component e1 (+) with |e| = (a-b)/(a+b).
- atmospheric_psf_e2 (float) – Atmospheric ellipticity component e2 (x) with |e| = (a-b)/(a+b).
- sky_brightness (float) – Sky brightness in mags/sq.arcsec during the observation.
- airmass (float) – Optical path length through the atmosphere relative to the zenith path length.
- extinction (float) – Exponential exctinction coefficient for atmospheric absorption.
- cosmic_shear_g1 (float) – Cosmic shear ellipticity component g1 (+) with |g| = (a-b)/(a+b).
- cosmic_shear_g2 (float) – Cosmic shear ellipticity component g2 (x) with |g| = (a-b)/(a+b).
Raises: RuntimeError – Missing or extra arguments provided or unable to calculate PSF size.
- static add_args(parser)[source]¶
Add command-line arguments for constructing a new Survey.
The added arguments are our constructor parameters with ‘_’ replaced by ‘-‘ in the names. No default values are assigned to the added args since these are handled at run time based on a requested (survey_name,filter_band) combination using get_defaults().
Parameters: parser (argparse.ArgumentParser) – Arguments will be added to this parser object using its add_argument method.
- description()[source]¶
Describe the survey we simulate.
Returns: Description of the camera design and observing conditions we simulate. Return type: str
- classmethod from_args(args)[source]¶
Create a new Survey object from a set of arguments.
Parameters: args (object) – A set of arguments accessed as a dict using the built-in vars() function. The argument set must include those defined in add_args(). Two additional arguments are also required: survey_name and filter_band. These establish the constructor parameter defaults via :func:get_defaults. Any extra arguments beyond those defined in add_args(), survey_name, and filter_band will be silently ignored. Returns: A newly constructed Survey object. Return type: Survey Raises: RuntimeError – Defaults not yet defined for requested combination.
- static get_defaults(survey_name, filter_band)[source]¶
Get survey camera and observing parameter default values.
Parameters: Returns: Dictionary of parameter (name,value) pairs.
Return type: dict
Raises: RuntimeError – Defaults not yet defined for requested combination.
- get_flux(ab_magnitude)[source]¶
Convert source magnitude to flux.
The calculation includes the effects of atmospheric extinction.
Parameters: ab_magnitude (float) – AB magnitude of source. Returns: Flux in detected electrons. Return type: float
- get_image_coordinates(dx_arcsecs, dy_arcsecs)[source]¶
Convert a physical offset from the image center into image coordinates.
Parameters: Returns: Corresponding floating-point image coordinates (x_pixels,y_pixels) whose math.floor() value gives pixel indices and whose...
Return type: tuple