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csst_mci_sim/zodiacal.py

+import numpy as np
+import julian
+from datetime import datetime
+from astropy.time import Time
+from astropy.coordinates import get_sun
+from astropy.coordinates import SkyCoord
+import pandas as pd
+from astropy import units as u
+
+from scipy import interpolate
+
+
+def zodiacal(ra, dec, time, path):
+    """
+        For given RA, DEC and TIME, return the interpolated zodical spectrum in Leinert-1998.
+
+    :param ra: RA in unit of degree, ICRS frame
+    :param dec: DEC in unit of degree, ICRS frame
+    :param time: the specified string that in ISO format i.e., yyyy-mm-dd.
+    :param path: the relative file path
+    :return:
+        wave_A: wavelength of the zodical spectrum
+
+        spec_erg: flux of the zodical spectrum, in unit of erg/s/cm^2/A/sr
+
+    """
+
+    # get solar position
+    dt = datetime.fromisoformat(time)
+    jd = julian.to_jd(dt, fmt='jd')
+
+    ###jd = time2jd(dt)
+    t = Time(jd, format='jd', scale='utc')
+
+    astro_sun = get_sun(t)
+    ra_sun, dec_sun = astro_sun.gcrs.ra.deg, astro_sun.gcrs.dec.deg
+
+    radec_sun = SkyCoord(ra=ra_sun*u.degree,
+                         dec=dec_sun*u.degree, frame='gcrs')
+    lb_sun = radec_sun.transform_to('geocentrictrueecliptic')
+
+    # get offsets between the target and sun.
+    radec_obj = SkyCoord(ra=ra*u.degree, dec=dec*u.degree, frame='icrs')
+    lb_obj = radec_obj.transform_to('geocentrictrueecliptic')
+
+    beta = abs(lb_obj.lat.degree)
+    lamda = abs(lb_obj.lon.degree - lb_sun.lon.degree)
+
+    # interpolated zodical surface brightness at 0.5 um
+    zodi = pd.read_csv(path+'MCI_inputData/refs/zodi_map.dat',
+                       sep='\s+', header=None, comment='#')
+    beta_angle = np.array([0, 5, 10, 15, 20, 25, 30, 45, 60, 75])
+    lamda_angle = np.array([0, 5, 10, 15, 20, 25, 30, 35, 40, 45,
+                            60, 75, 90, 105, 120, 135, 150, 165, 180])
+    xx, yy = np.meshgrid(beta_angle, lamda_angle)
+    f = interpolate.interp2d(xx, yy, zodi, kind='linear')
+    zodi_obj = f(beta, lamda)       # 10^�? W m�? sr�? um�?
+
+    # read the zodical spectrum in the ecliptic
+    cat_spec = pd.read_csv(
+        path+'MCI_inputData/refs/solar_spec.dat', sep='\s+', header=None, comment='#')
+    wave = cat_spec[0].values       # A
+    spec0 = cat_spec[1].values      # 10^-8 W m^�? sr^�? μm^�?
+    zodi_norm = 252                 # 10^-8 W m^�? sr^�? μm^�?
+
+    spec = spec0 * (zodi_obj / zodi_norm) * 1e-8  # W m^�? sr^�? μm^�?
+
+    # convert to the commonly used unit of MJy/sr, erg/s/cm^2/A/sr
+    wave_A = wave                                               # A
+    # spec_mjy = spec * 0.1 * wave_A**2 / 3e18 * 1e23 * 1e-6      # MJy/sr
+    spec_erg = spec * 0.1                                       # erg/s/cm^2/A/sr
+    # erg/s/cm^2/A/arcsec^2
+    spec_erg2 = spec_erg / 4.25452e10
+
+    return wave_A, spec_erg2
+
+
+###############################
+# path='/home/yan/MCI/'
+# wave0, zodi0=zodiacal(10.0, 20.0, '2024-04-04', path)