def SolarSpectrum():
    """Spectrum of direct solar irradiance at ground level.
    
    TODO: add source?
    """
    solar_spectrum = [[0.28, 1.755832e-22], [0.285, 3.294496e-13], [0.29, 
        9.825731e-07], [0.295, 0.004867814], [0.3, 0.5930555], [0.305, 
        10.09141], [0.31, 34.18097], [0.315, 80.42174], [0.32, 126.9513], [
        0.325, 175.5832], [0.33, 280.2401], [0.335, 285.3227], [0.34, 
        316.5119], [0.345, 302.188], [0.35, 361.3318], [0.355, 423.9411], [
        0.36, 405.2276], [0.365, 473.0351], [0.37, 541.7667], [0.375, 
        469.4541], [0.38, 561.8663], [0.385, 508.3828], [0.39, 648.7338], [
        0.395, 648.2718], [0.4, 955.0803], [0.405, 982.573], [0.41, 
        981.4178], [0.415, 1076.949], [0.42, 1098.781], [0.425, 1125.35], [
        0.43, 867.7508], [0.435, 1148.568], [0.44, 1220.997], [0.445, 
        1329.581], [0.45, 1492.457], [0.455, 1458.958], [0.46, 1491.302], [
        0.465, 1502.854], [0.47, 1461.268], [0.475, 1546.75], [0.48, 
        1581.404], [0.485, 1485.527], [0.49, 1568.698], [0.495, 1591.801],
        [0.5, 1539.819], [0.505, 1549.06], [0.51, 1569.853], [0.515, 
        1554.836], [0.52, 1516.716], [0.525, 1613.748], [0.53, 1609.128], [
        0.535, 1610.283], [0.54, 1515.56], [0.545, 1592.956], [0.55, 
        1595.266], [0.555, 1618.369], [0.56, 1557.146], [0.565, 1554.836],
        [0.57, 1515.56], [0.575, 1542.129], [0.58, 1561.767], [0.585, 
        1582.559], [0.59, 1363.08], [0.595, 1440.476], [0.6, 1523.647], [
        0.605, 1558.301], [0.61, 1539.819], [0.615, 1543.284], [0.62, 
        1555.991], [0.625, 1473.975], [0.63, 1460.113], [0.635, 1519.026],
        [0.64, 1524.802], [0.645, 1524.802], [0.65, 1461.268], [0.655, 
        1398.89], [0.66, 1465.889], [0.665, 1490.147], [0.67, 1493.613], [
        0.675, 1482.061], [0.68, 1473.975], [0.685, 1438.165], [0.69, 
        1227.927], [0.695, 1281.064], [0.7, 1282.22], [0.705, 1331.891], [
        0.71, 1342.288], [0.715, 1306.478], [0.72, 867.1732], [0.725, 
        953.2321], [0.73, 1061.239], [0.735, 1217.531], [0.74, 1253.341], [
        0.745, 1311.098], [0.75, 1303.012], [0.755, 1293.771], [0.76, 
        283.128], [0.765, 723.3567], [0.77, 1226.772], [0.775, 1236.014], [
        0.78, 1237.169], [0.785, 1229.083], [0.79, 1118.765], [0.795, 
        1164.394], [0.8, 1134.014], [0.805, 1121.307], [0.81, 1091.042], [
        0.815, 850.77], [0.82, 831.71], [0.825, 1000.362], [0.83, 919.5016],
        [0.835, 1049.456], [0.84, 1061.354], [0.845, 1078.22], [0.85, 
        1017.921], [0.855, 982.9195], [0.86, 1063.665], [0.865, 1007.64], [
        0.87, 1043.219], [0.875, 1036.288], [0.88, 1023.003], [0.885, 
        1012.145], [0.89, 1000.016], [0.895, 809.5311], [0.9, 726.8221], [
        0.905, 825.7032], [0.91, 552.7406], [0.915, 615.812], [0.92, 
        734.6772], [0.925, 660.0543], [0.93, 304.9603], [0.935, 147.513], [
        0.94, 361.4473], [0.945, 258.1767], [0.95, 61.59275], [0.955, 
        230.3375], [0.96, 313.7395], [0.965, 429.3703], [0.97, 596.983], [
        0.975, 564.7542], [0.98, 568.2197], [0.985, 682.3488], [0.99, 
        767.4835], [0.995, 819.2344], [1.0, 801.214], [1.005, 782.2695], [
        1.01, 775.8006], [1.015, 779.4971], [1.02, 765.7508], [1.025, 
        767.599], [1.03, 757.2027], [1.035, 746.4597], [1.04, 738.0271], [
        1.045, 725.667], [1.05, 719.0826], [1.055, 709.0328], [1.06, 
        690.4348], [1.065, 685.4677], [1.07, 658.7836], [1.075, 643.8822],
        [1.08, 639.6081], [1.085, 642.265], [1.09, 593.402], [1.095, 
        530.4462], [1.1, 464.718], [1.105, 491.633], [1.11, 429.7168], [
        1.115, 178.2401], [1.12, 64.23805], [1.125, 69.67882], [1.13, 
        22.60634], [1.135, 4.263669], [1.14, 169.923], [1.145, 65.58958], [
        1.15, 65.21993], [1.155, 232.7633], [1.16, 216.5912], [1.165, 
        333.1461], [1.17, 447.3907], [1.175, 457.2095], [1.18, 436.6478], [
        1.185, 385.4745], [1.19, 480.8901], [1.195, 451.0872], [1.2, 
        458.7112], [1.205, 449.1234], [1.21, 470.4937], [1.215, 426.829], [
        1.22, 488.5141], [1.225, 498.2174], [1.23, 497.4088], [1.235, 
        517.3929], [1.24, 516.0068], [1.245, 513.0034], [1.25, 510.231], [
        1.255, 501.5674], [1.26, 479.2729], [1.265, 442.7701], [1.27, 
        432.1427], [1.275, 459.6353], [1.28, 459.9818], [1.285, 464.4869],
        [1.29, 453.9751], [1.295, 433.1823], [1.3, 350.4734], [1.305, 
        400.7225], [1.31, 275.2729], [1.315, 249.8596], [1.32, 232.7633], [
        1.325, 307.8482], [1.33, 172.0023], [1.335, 182.2831], [1.34, 
        125.3341], [1.345, 50.43397], [1.35, 1.852865], [1.355, 
        1.421993e-06], [1.36, 4.201291e-07], [1.365, 2.019207e-16], [1.37, 
        8.799954e-09], [1.375, 0.0007149241], [1.38, 0.0002424666], [1.385,
        1.4347e-06], [1.39, 0.001954519], [1.395, 2.606025e-07], [1.4, 
        3.272548e-12], [1.405, 6.190464e-08], [1.41, 0.005661404], [1.415, 
        0.001804349], [1.42, 0.7145775], [1.425, 4.718799], [1.43, 23.7846],
        [1.435, 3.674541], [1.44, 12.69513], [1.445, 13.81563], [1.45, 
        7.487701], [1.455, 30.16104], [1.46, 47.2342], [1.465, 58.45073], [
        1.47, 13.75787], [1.475, 132.1495], [1.48, 25.21699], [1.485, 
        81.32276], [1.49, 140.4666], [1.495, 150.6319], [1.5, 245.701], [
        1.505, 167.9592], [1.51, 283.821], [1.515, 280.3556], [1.52, 
        270.9988], [1.525, 274.2333], [1.53, 281.2797], [1.535, 292.1381],
        [1.54, 301.2639], [1.545, 309.9275], [1.55, 304.2673], [1.555, 
        300.3397], [1.56, 300.6863], [1.565, 299.0691], [1.57, 273.5402], [
        1.575, 279.3159], [1.58, 274.6953], [1.585, 287.402], [1.59, 
        269.4972], [1.595, 285.6693], [1.6, 264.6455], [1.605, 266.8403], [
        1.61, 249.8596], [1.615, 266.7248], [1.62, 266.4938], [1.625, 
        270.0747], [1.63, 268.6885], [1.635, 259.6784], [1.64, 240.0408], [
        1.645, 247.0872], [1.65, 250.2061], [1.655, 250.5526], [1.66, 
        250.3216], [1.665, 237.846], [1.67, 248.2423], [1.675, 239.6942], [
        1.68, 230.684], [1.685, 239.1166], [1.69, 228.7203], [1.695, 
        235.0736], [1.7, 219.5945], [1.705, 217.7463], [1.71, 206.5413], [
        1.715, 204.0], [1.72, 204.0], [1.725, 188.2899], [1.73, 187.9434],
        [1.735, 170.0385], [1.74, 174.7746], [1.745, 159.4111], [1.75, 
        172.5798], [1.755, 152.3647], [1.76, 163.9162], [1.765, 123.8324],
        [1.77, 127.6444], [1.775, 94.67632], [1.78, 76.52887], [1.785, 
        48.759], [1.79, 62.26274], [1.795, 19.64915], [1.8, 15.96421], [
        1.805, 2.68111], [1.81, 1.351529], [1.815, 0.1782401], [1.82, 
        0.02100068], [1.825, 0.0295026], [1.83, 5.069966e-06], [1.835, 
        3.109671e-06], [1.84, 1.12639e-08], [1.845, 7.945141e-07], [1.85, 
        2.736557e-07], [1.855, 5.976761e-08], [1.86, 3.084258e-05], [1.865,
        2.34496e-05], [1.87, 4.700317e-13], [1.875, 1.05373e-12], [1.88, 
        0.0003766953], [1.885, 0.0001557146], [1.89, 0.0008908538], [1.895,
        0.0008015605], [1.9, 3.690713e-07], [1.905, 3.564802e-07], [1.91, 
        3.483941e-05], [1.915, 8.942038e-05], [1.92, 0.003726523], [1.925, 
        0.02120861], [1.93, 0.01522491], [1.935, 0.3087723], [1.94, 
        0.3988743], [1.945, 2.781608], [1.95, 6.680249], [1.955, 2.853227],
        [1.96, 11.02131], [1.965, 17.3735], [1.97, 37.48471], [1.975, 
        52.94065], [1.98, 65.99388], [1.985, 76.25164], [1.99, 76.12457], [
        1.995, 75.84733], [2.0, 34.13477], [2.005, 11.3332], [2.01, 
        39.80657], [2.015, 23.13771], [2.02, 42.45187], [2.025, 75.89354],
        [2.03, 84.88063], [2.035, 103.6519], [2.04, 94.67632], [2.045, 
        96.95198], [2.05, 72.00067], [2.055, 56.48697], [2.06, 71.66568], [
        2.065, 64.71166], [2.07, 68.33884], [2.075, 83.71392], [2.08, 
        94.0872], [2.085, 92.65481], [2.09, 99.14677], [2.095, 98.85798], [
        2.1, 91.55741], [2.105, 104.345], [2.11, 98.29195], [2.115, 
        102.4158], [2.12, 95.31166], [2.125, 97.82989], [2.13, 99.74745], [
        2.135, 100.5561], [2.14, 102.1848], [2.145, 100.8102], [2.15, 
        91.93861], [2.155, 92.73567], [2.16, 92.6086], [2.165, 82.61653], [
        2.17, 91.29173], [2.175, 86.97146], [2.18, 91.36104], [2.185, 
        77.70713], [2.19, 86.27836], [2.195, 85.74699], [2.2, 77.0949], [
        2.205, 80.19071], [2.21, 88.48471], [2.215, 83.80634], [2.22, 
        87.44507], [2.225, 83.78323], [2.23, 85.83941], [2.235, 83.45979],
        [2.24, 82.87066], [2.245, 79.90192], [2.25, 81.72706], [2.255, 
        76.52887], [2.26, 75.98595], [2.265, 77.31438], [2.27, 73.53703], [
        2.275, 72.57825], [2.28, 75.51234], [2.285, 71.41155], [2.29, 
        71.59637], [2.295, 69.21676], [2.3, 65.64733], [2.305, 65.86681], [
        2.31, 69.74813], [2.315, 63.78754], [2.32, 55.89784], [2.325, 
        58.43918], [2.33, 60.36829], [2.335, 62.96738], [2.34, 44.14994], [
        2.345, 53.89943], [2.35, 40.24552], [2.355, 48.50487], [2.36, 
        51.93567], [2.365, 48.63193], [2.37, 26.24507], [2.375, 43.12185],
        [2.38, 38.00453], [2.385, 24.28131], [2.39, 32.51755], [2.395, 
        37.68108], [2.4, 40.99637], [2.405, 27.09988], [2.41, 26.48765], [
        2.415, 19.16399], [2.42, 19.44122], [2.425, 26.25662], [2.43, 
        39.42537], [2.435, 8.307859], [2.44, 36.68765], [2.445, 13.12254],
        [2.45, 6.917055], [2.455, 15.29422], [2.46, 24.75492], [2.465, 
        14.68199], [2.47, 7.535062], [2.475, 7.232412], [2.48, 2.036534], [
        2.485, 1.159773], [2.49, 0.4409218], [2.495, 0.38894], [2.5, 
        1.192118], [2.505, 0.1178256], [2.51, 0.230222], [2.515, 0.02307995
        ], [2.52, 0.005186636], [2.525, 8.529648e-05], [2.53, 5.429218e-08],
        [2.535, 2.57137e-09], [2.54, 1.254496e-08], [2.545, 7.580113e-14],
        [2.55, 1.089194e-20], [2.555, 1.036288e-12], [2.56, 6.137327e-14],
        [2.565, 1.341132e-19], [2.57, 4.495855e-27], [2.575, 2.718519e-43],
        [2.58, 8.27898e-35], [2.585, 0.0], [2.59, 0.0], [2.595, 0.0], [2.6,
        1.401298e-45], [2.605, 0.0], [2.61, 0.0], [2.615, 0.0], [2.62, 
        6.389921e-43], [2.625, 0.0], [2.63, 0.0], [2.635, 8.24317e-23], [
        2.64, 1.977622e-25], [2.645, 3.870917e-28], [2.65, 5.282514e-31], [
        2.655, 2.101948e-44], [2.66, 7.691007e-38], [2.665, 0.0], [2.67, 
        0.0], [2.675, 0.0], [2.68, 0.0], [2.685, 0.0], [2.69, 4.203895e-45],
        [2.695, 0.0], [2.7, 0.0], [2.705, 0.0], [2.71, 0.0], [2.715, 
        9.111803e-41], [2.72, 0.0], [2.725, 1.520181e-30], [2.73, 
        1.561767e-30], [2.735, 7.793816e-32], [2.74, 3.076172e-38], [2.745,
        1.721178e-37], [2.75, 5.867237e-42], [2.755, 0.0], [2.76, 0.0], [
        2.765, 2.810487e-38], [2.77, 6.439977e-34], [2.775, 0.0], [2.78, 
        3.463169e-41], [2.785, 1.364235e-36], [2.79, 8.396806e-22], [2.795,
        9.365979e-23], [2.8, 1.356149e-14], [2.805, 2.779298e-16], [2.81, 
        4.397667e-12], [2.815, 3.218256e-12], [2.82, 7.425322e-14], [2.825,
        1.903692e-08], [2.83, 3.691868e-06], [2.835, 4.135447e-13], [2.84, 
        6.42496e-08], [2.845, 0.0002679955], [2.85, 4.470441e-07], [2.855, 
        3.652593e-07], [2.86, 0.0002067724], [2.865, 0.003345323], [2.87, 
        1.24872e-05], [2.875, 0.01402356], [2.88, 0.008862332], [2.885, 
        0.01924485], [2.89, 0.007473839], [2.895, 0.4261359], [2.9, 
        0.09198482], [2.905, 0.002128947], [2.91, 0.6100362], [2.915, 
        0.1715402], [2.92, 0.6144258], [2.925, 0.2073499], [2.93, 1.656489],
        [2.935, 2.313771], [2.94, 0.2400408], [2.945, 0.196607], [2.95, 
        1.638007], [2.955, 0.7849263], [2.96, 1.492457], [2.965, 3.734609],
        [2.97, 0.04676059], [2.975, 0.1094623], [2.98, 0.2450079], [2.985, 
        3.056534], [2.99, 6.057621], [2.995, 1.480906], [3.0, 3.981812], [
        3.005, 0.9241222], [3.01, 3.634111], [3.015, 2.126636], [3.02, 
        0.0498795], [3.025, 3.859366], [3.03, 2.861314], [3.035, 0.740453],
        [3.04, 0.5771143], [3.045, 1.351529], [3.05, 0.1505164], [3.055, 
        0.0204462], [3.06, 3.115447], [3.065, 0.8756058], [3.07, 0.3492027],
        [3.075, 2.830124], [3.08, 1.386183], [3.085, 0.3766953], [3.09, 
        0.5635991], [3.095, 0.07939365], [3.1, 1.830917], [3.105, 0.2093137
        ], [3.11, 0.08597802], [3.115, 0.5444235], [3.12, 5.816194], [3.125,
        1.196738], [3.13, 3.370736], [3.135, 7.649422], [3.14, 1.336512], [
        3.145, 1.344598], [3.15, 3.883624], [3.155, 3.158188], [3.16, 
        6.340634], [3.165, 12.8684], [3.17, 9.983986], [3.175, 7.336376], [
        3.18, 8.348289], [3.185, 5.731868], [3.19, 2.19479], [3.195, 
        0.8751438], [3.2, 0.04146999], [3.205, 0.0200419], [3.21, 
        0.009394858], [3.215, 0.04889762], [3.22, 0.4417304], [3.225, 
        0.02447769], [3.23, 0.05661404], [3.235, 4.23017], [3.24, 1.881744],
        [3.245, 0.1957984], [3.25, 1.468199], [3.255, 6.91821], [3.26, 
        0.5117327], [3.265, 0.714462], [3.27, 0.3461993], [3.275, 3.131619],
        [3.28, 1.364235], [3.285, 8.155379], [3.29, 6.398391], [3.295, 
        0.3224031], [3.3, 0.6914745], [3.305, 1.679592], [3.31, 2.510147],
        [3.315, 0.01062972], [3.32, 0.008433771], [3.325, 2.253703], [3.33,
        3.401925], [3.335, 7.758006], [3.34, 1.736195], [3.345, 2.252548],
        [3.35, 6.016036], [3.355, 2.031914], [3.36, 3.4747], [3.365, 
        5.899365], [3.37, 2.852072], [3.375, 6.88009], [3.38, 4.453114], [
        3.385, 6.382219], [3.39, 10.68632], [3.395, 9.365979], [3.4, 
        13.2034], [3.405, 3.969105], [3.41, 5.988312], [3.415, 7.733748], [
        3.42, 14.55493], [3.425, 11.14838], [3.43, 10.07986], [3.435, 
        11.71325], [3.44, 8.677508], [3.445, 11.64394], [3.45, 12.97237], [
        3.455, 8.471891], [3.46, 13.51529], [3.465, 11.25581], [3.47, 
        13.54994], [3.475, 11.90963], [3.48, 12.79909], [3.485, 13.38822],
        [3.49, 11.01785], [3.495, 13.78097], [3.5, 13.14564], [3.505, 
        13.18029], [3.51, 13.11098], [3.515, 11.64394], [3.52, 13.28426], [
        3.525, 12.0829], [3.53, 11.86342], [3.535, 9.63513], [3.54, 
        9.058708], [3.545, 9.734473], [3.55, 10.95316], [3.555, 8.415288],
        [3.56, 11.49146], [3.565, 12.14066], [3.57, 7.699093], [3.575, 
        8.362151], [3.58, 11.20383], [3.585, 9.255084], [3.59, 9.442219], [
        3.595, 9.932004], [3.6, 10.9393], [3.605, 11.56308], [3.61, 
        9.555424], [3.615, 9.627044], [3.62, 13.19185], [3.625, 10.99243],
        [3.63, 10.4576], [3.635, 10.72906], [3.64, 12.96081], [3.645, 
        11.89807], [3.65, 10.92312], [3.655, 11.93273], [3.66, 11.82876], [
        3.665, 11.05135], [3.67, 7.242808], [3.675, 2.920226], [3.68, 
        7.257825], [3.685, 9.436443], [3.69, 10.0094], [3.695, 10.6147], [
        3.7, 12.23307], [3.705, 12.0598], [3.71, 9.839592], [3.715, 
        9.526545], [3.72, 11.34938], [3.725, 12.0829], [3.73, 9.712525], [
        3.735, 8.408357], [3.74, 9.006726], [3.745, 11.60929], [3.75, 
        9.896194], [3.755, 9.29436], [3.76, 8.864643], [3.765, 8.670577], [
        3.77, 9.617802], [3.775, 9.493046], [3.78, 10.45991], [3.785, 
        8.957055], [3.79, 7.537372], [3.795, 9.389082], [3.8, 11.33089], [
        3.805, 10.09604], [3.81, 8.170396], [3.815, 7.491166], [3.82, 
        11.01207], [3.825, 10.56734], [3.83, 10.79721], [3.835, 7.306342],
        [3.84, 9.927383], [3.845, 9.710215], [3.85, 9.877712], [3.855, 
        9.170758], [3.86, 8.479977], [3.865, 9.136104], [3.87, 8.273204], [
        3.875, 7.29479], [3.88, 7.233567], [3.885, 7.67137], [3.89, 
        7.663284], [3.895, 8.552751], [3.9, 8.527338], [3.905, 9.039071], [
        3.91, 8.155379], [3.915, 7.950917], [3.92, 7.851574], [3.925, 
        7.636715], [3.93, 8.031777], [3.935, 8.475356], [3.94, 8.463805], [
        3.945, 8.571234], [3.95, 8.652095], [3.955, 8.907383], [3.96, 
        8.891211], [3.965, 8.962831], [3.97, 8.746817], [3.975, 8.585096],
        [3.98, 8.561993], [3.985, 8.552751], [3.99, 8.494994], [3.995, 
        8.284756], [4.0, 8.193499]]
    return solar_spectrum
