Source code for lenstronomy.SimulationAPI.ObservationConfig.HST

"""Provisional HST instrument and observational settings.

See Optics and Observation Conditions spreadsheet at
https://docs.google.com/spreadsheets/d/1pMUB_OOZWwXON2dd5oP8PekhCT5MBBZJO1HV7IMZg4Y/edit?usp=sharing
for list of
sources.
"""
import lenstronomy.Util.util as util

__all__ = ["HST"]

# F160W filter configs
WFC3_F160W_band_obs = {
    "exposure_time": 5400.0,  # ~90mins orbit on HST, but this number corresponds to
    # approximately two HST orbits with overheads, guide star aquisition. ~2700s science exposure per orbit
    "sky_brightness": 22.3,
    "magnitude_zero_point": 25.96,
    "num_exposures": 1,
    "seeing": 0.08,  # set equal to the approx pixel size for drizzled PSF. Note that undrizzled PSF FWHM ~ 0.15" (Windhorst et al 2011)
    "psf_type": "GAUSSIAN",
}

# configs meant to simulate images close to those provided as part of the Time Delay Lens Modeling Challenge
TDLMC_F160W_band_obs = {
    "exposure_time": 5400.0,  # ~90mins orbit on HST, but this number corresponds to
    # approximately two HST orbits with overheads, guide star aquisition. ~2700s science exposure per orbit
    "sky_brightness": 22.0,
    "magnitude_zero_point": 25.9463,
    "num_exposures": 1,
    "seeing": None,
    "psf_type": "PIXEL",  # note kernel_point_source (the PSF map) must be provided separately
}

# - keyword exposure_time: exposure time per image (in seconds)
# - keyword sky_brightness: sky brightness (in magnitude per square arcseconds in units of electrons)
# - keyword magnitude_zero_point: magnitude in which 1 count (e-) per second per arcsecond square is registered
# - keyword num_exposures: number of exposures that are combined (depends on coadd_years)
# - keyword seeing: Full-Width-at-Half-Maximum (FWHM) of PSF
# - keyword psf_type: string, type of PSF ('GAUSSIAN' and 'PIXEL' supported)




class HST(object):
    """Class contains HST instrument and observation configurations."""



    def __init__(self, band="TDLMC_F160W", psf_type="PIXEL", coadd_years=None):
        """

        :param band: string, 'WFC3_F160W' or 'TDLMC_F160W' supported. Determines obs dictionary.
        :param psf_type: string, type of PSF ('GAUSSIAN', 'PIXEL' supported).
        :param coadd_years: int, number of years corresponding to num_exposures in obs dict. Currently supported: None.
        """

        if band == "TDLMC_F160W":
            self.obs = TDLMC_F160W_band_obs
        elif band == "WFC3_F160W" or band == "F160W":
            self.obs = WFC3_F160W_band_obs

        else:
            raise ValueError(
                "band %s not supported! Choose 'WFC3_F160W' or 'TDLMC_F160W'." % band
            )

        if psf_type == "GAUSSIAN":
            self.obs["psf_type"] = "GAUSSIAN"
        elif psf_type != "PIXEL":
            raise ValueError("psf_type %s not supported!" % psf_type)

        if coadd_years is not None:
            raise ValueError(
                " %s coadd_years not supported! "
                "You may manually adjust num_exposures in obs dict if required."
                % coadd_years
            )

        # WFC3 camera settings
        self.camera = {
            "read_noise": 4,
            "pixel_scale": 0.08,  # approx pixel size for drizzled PSF
            "ccd_gain": 2.5,
        }


        # - keyword read_noise: std of noise generated by read-out (in units of electrons)
        # - keyword pixel_scale: scale (in arcseconds) of pixels
        # - keyword ccd_gain: electrons/ADU (analog-to-digital unit)



    def kwargs_single_band(self):
        """

        :return: merged kwargs from camera and obs dicts
        """
        kwargs = util.merge_dicts(self.camera, self.obs)
        return kwargs