sun_dist.py

# David R Thompson
# Earth/Sun distance

import datetime
import scipy as s

esd_table = s.array([[1,  0.98331],
  [2,  0.98330],
  [3,  0.98330],
  [4,  0.98330],
  [5,  0.98330],
  [6,  0.98332],
  [7,  0.98333],
  [8,  0.98335],
  [9,  0.98338],
  [10, 0.98341],
  [11, 0.98345],
  [12, 0.98349],
  [13, 0.98354],
  [14, 0.98359],
  [15, 0.98365],
  [16, 0.98371],
  [17, 0.98378],
  [18, 0.98385],
  [19, 0.98393],
  [20, 0.98401],
  [21, 0.98410],
  [22, 0.98419],
  [23, 0.98428],
  [24, 0.98439],
  [25, 0.98449],
  [26, 0.98460],
  [27, 0.98472],
  [28, 0.98484],
  [29, 0.98496],
  [30, 0.98509],
  [31, 0.98523],
  [32, 0.98536],
  [33, 0.98551],
  [34, 0.98565],
  [35, 0.98580],
  [36, 0.98596],
  [37, 0.98612],
  [38, 0.98628],
  [39, 0.98645],
  [40, 0.98662],
  [41, 0.98680],
  [42, 0.98698],
  [43, 0.98717],
  [44, 0.98735],
  [45, 0.98755],
  [46, 0.98774],
  [47, 0.98794],
  [48, 0.98814],
  [49, 0.98835],
  [50, 0.98856],
  [51, 0.98877],
  [52, 0.98899],
  [53, 0.98921],
  [54, 0.98944],
  [55, 0.98966],
  [56, 0.98989],
  [57, 0.99012],
  [58, 0.99036],
  [59, 0.99060],
  [60, 0.99084],
  [61, 0.99108],
  [62, 0.99133],
  [63, 0.99158],
  [64, 0.99183],
  [65, 0.99208],
  [66, 0.99234],
  [67, 0.99260],
  [68, 0.99286],
  [69, 0.99312],
  [70, 0.99339],
  [71, 0.99365],
  [72, 0.99392],
  [73, 0.99419],
  [74, 0.99446],
  [75, 0.99474],
  [76, 0.99501],
  [77, 0.99529],
  [78, 0.99556],
  [79, 0.99584],
  [80, 0.99612],
  [81, 0.99640],
  [82, 0.99669],
  [83, 0.99697],
  [84, 0.99725],
  [85, 0.99754],
  [86, 0.99782],
  [87, 0.99811],
  [88, 0.99840],
  [89, 0.99868],
  [90, 0.99897],
  [91, 0.99926],
  [92, 0.99954],
  [93, 0.99983],
  [94, 1.00012],
  [95, 1.00041],
  [96, 1.00069],
  [97, 1.00098],
  [98, 1.00127],
  [99, 1.00155],
  [100,1.00184],
  [101,1.00212],
  [102,1.00240],
  [103,1.00269],
  [104,1.00297],
  [105,1.00325],
  [106,1.00353],
  [107,1.00381],
  [108,1.00409],
  [109,1.00437],
  [110,1.00464],
  [111,1.00492],
  [112,1.00519],
  [113,1.00546],
  [114,1.00573],
  [115,1.00600],
  [116,1.00626],
  [117,1.00653],
  [118,1.00679],
  [119,1.00705],
  [120,1.00731],
  [121,1.00756],
  [122,1.00781],
  [123,1.00806],
  [124,1.00831],
  [125,1.00856],
  [126,1.00880],
  [127,1.00904],
  [128,1.00928],
  [129,1.00952],
  [130,1.00975],
  [131,1.00998],
  [132,1.01020],
  [133,1.01043],
  [134,1.01065],
  [135,1.01087],
  [136,1.01108],
  [137,1.01129],
  [138,1.01150],
  [139,1.01170],
  [140,1.01191],
  [141,1.01210],
  [142,1.01230],
  [143,1.01249],
  [144,1.01267],
  [145,1.01286],
  [146,1.01304],
  [147,1.01321],
  [148,1.01338],
  [149,1.01355],
  [150,1.01371],
  [151,1.01387],
  [152,1.01403],
  [153,1.01418],
  [154,1.01433],
  [155,1.01447],
  [156,1.01461],
  [157,1.01475],
  [158,1.01488],
  [159,1.01500],
  [160,1.01513],
  [161,1.01524],
  [162,1.01536],
  [163,1.01547],
  [164,1.01557],
  [165,1.01567],
  [166,1.01577],
  [167,1.01586],
  [168,1.01595],
  [169,1.01603],
  [170,1.01610],
  [171,1.01618],
  [172,1.01625],
  [173,1.01631],
  [174,1.01637],
  [175,1.01642],
  [176,1.01647],
  [177,1.01652],
  [178,1.01656],
  [179,1.01659],
  [180,1.01662],
  [181,1.01665],
  [182,1.01667],
  [183,1.01668],
  [184,1.01670],
  [185,1.01670],
  [186,1.01670],
  [187,1.01670],
  [188,1.01669],
  [189,1.01668],
  [190,1.01666],
  [191,1.01664],
  [192,1.01661],
  [193,1.01658],
  [194,1.01655],
  [195,1.01650],
  [196,1.01646],
  [197,1.01641],
  [198,1.01635],
  [199,1.01629],
  [200,1.01623],
  [201,1.01616],
  [202,1.01609],
  [203,1.01601],
  [204,1.01592],
  [205,1.01584],
  [206,1.01575],
  [207,1.01565],
  [208,1.01555],
  [209,1.01544],
  [210,1.01533],
  [211,1.01522],
  [212,1.01510],
  [213,1.01497],
  [214,1.01485],
  [215,1.01471],
  [216,1.01458],
  [217,1.01444],
  [218,1.01429],
  [219,1.01414],
  [220,1.01399],
  [221,1.01383],
  [222,1.01367],
  [223,1.01351],
  [224,1.01334],
  [225,1.01317],
  [226,1.01299],
  [227,1.01281],
  [228,1.01263],
  [229,1.01244],
  [230,1.01225],
  [231,1.01205],
  [232,1.01186],
  [233,1.01165],
  [234,1.01145],
  [235,1.01124],
  [236,1.01103],
  [237,1.01081],
  [238,1.01060],
  [239,1.01037],
  [240,1.01015],
  [241,1.00992],
  [242,1.00969],
  [243,1.00946],
  [244,1.00922],
  [245,1.00898],
  [246,1.00874],
  [247,1.00850],
  [248,1.00825],
  [249,1.00800],
  [250,1.00775],
  [251,1.00750],
  [252,1.00724],
  [253,1.00698],
  [254,1.00672],
  [255,1.00646],
  [256,1.00620],
  [257,1.00593],
  [258,1.00566],
  [259,1.00539],
  [260,1.00512],
  [261,1.00485],
  [262,1.00457],
  [263,1.00430],
  [264,1.00402],
  [265,1.00374],
  [266,1.00346],
  [267,1.00318],
  [268,1.00290],
  [269,1.00262],
  [270,1.00234],
  [271,1.00205],
  [272,1.00177],
  [273,1.00148],
  [274,1.00119],
  [275,1.00091],
  [276,1.00062],
  [277,1.00033],
  [278,1.00005],
  [279,0.99976],
  [280,0.99947],
  [281,0.99918],
  [282,0.99890],
  [283,0.99861],
  [284,0.99832],
  [285,0.99804],
  [286,0.99775],
  [287,0.99747],
  [288,0.99718],
  [289,0.99690],
  [290,0.99662],
  [291,0.99634],
  [292,0.99605],
  [293,0.99577],
  [294,0.99550],
  [295,0.99522],
  [296,0.99494],
  [297,0.99467],
  [298,0.99440],
  [299,0.99412],
  [300,0.99385],
  [301,0.99359],
  [302,0.99332],
  [303,0.99306],
  [304,0.99279],
  [305,0.99253],
  [306,0.99228],
  [307,0.99202],
  [308,0.99177],
  [309,0.99152],
  [310,0.99127],
  [311,0.99102],
  [312,0.99078],
  [313,0.99054],
  [314,0.99030],
  [315,0.99007],
  [316,0.98983],
  [317,0.98961],
  [318,0.98938],
  [319,0.98916],
  [320,0.98894],
  [321,0.98872],
  [322,0.98851],
  [323,0.98830],
  [324,0.98809],
  [325,0.98789],
  [326,0.98769],
  [327,0.98750],
  [328,0.98731],
  [329,0.98712],
  [330,0.98694],
  [331,0.98676],
  [332,0.98658],
  [333,0.98641],
  [334,0.98624],
  [335,0.98608],
  [336,0.98592],
  [337,0.98577],
  [338,0.98562],
  [339,0.98547],
  [340,0.98533],
  [341,0.98519],
  [342,0.98506],
  [343,0.98493],
  [344,0.98481],
  [345,0.98469],
  [346,0.98457],
  [347,0.98446],
  [348,0.98436],
  [349,0.98426],
  [350,0.98416],
  [351,0.98407],
  [352,0.98399],
  [353,0.98391],
  [354,0.98383],
  [355,0.98376],
  [356,0.98370],
  [357,0.98363],
  [358,0.98358],
  [359,0.98353],
  [360,0.98348],
  [361,0.98344],
  [362,0.98340],
  [363,0.98337],
  [364,0.98335],
  [365,0.98333],
  [366,0.98331]])
   

def sun_dist_au(year, month, day):
  d   = datetime.date(year, month, day)
  doy = d.timetuple().tm_yday
  return esd_table[doy-1,1]


if __name__ == '__main__':
  t = datetime.datetime.now().timetuple()
  esd = sun_dist_au(t[0],t[1],t[2])
  print(esd)