astro 2.0.0

Advanced algorithms for astronomy
Documentation 
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/*
Copyright (c) 2015, 2016 Saurav Sachidanand

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

//! The dwarf planet Pluto

use angle;
use time;

/**
Computes the geocentric equatorial semidiameter of Pluto

# Returns

* `semidiameter`: Geocentric equatorial semidiameter
                  *| in radians per AU*

# Arguments

* `pluto_earth_dist`: Pluto-Earth distance *| in AU*
**/
#[inline]
pub fn semdiameter(pluto_earth_dist: f64) -> f64 {

    angle::deg_frm_dms(0, 0, 2.07).to_radians() / pluto_earth_dist

}

/**
Computes the apparent magnitude of Pluto using the Astronomical
Almanac's method adopted in 1984

# Returns

* `app_mag`: Apparent magnitude of Pluto

# Arguments

* `delta`: Pluto-Earth distance *| in AU*
* `r`    : Pluto-Sun distance *| in AU*
**/
#[inline]
pub fn apprnt_mag_84(delta: f64, r: f64) -> f64 {

    (r * delta).log10()*5.0 - 1.0

}

/**
Computes the heliocentric coordinates of Pluto, referred to the
standard equinox of J2000.0

This function is valid only for the years 1885 AD to 2099 AD.

# Returns

`(long, lat, rad_vec)`

* `long`   : Heliocentric longitude of Pluto *| in radians*
* `lat`    : Heliocentric latitude of Pluto *| in radians*
* `rad_vec`: Heliocentric radius vector of Pluto *| in AU*

The error in

* `long` is less than 0.07 arcseconds
* `lat` is less than 0.02 arcseconds
* `rad_vec` is less than 0.000006 AU

# Arguments

* `JD`: Julian (Ephemeris) day
**/
pub fn heliocent_pos(JD: f64) -> (f64, f64, f64) {

    let JC = time::julian_cent(JD);

    struct terms(i8, i8, i8, f64, f64, f64, f64, f64, f64);
    let tuple_terms = [
        terms(0,  0,  1, -19.799805,  19.850055, -5.452852, -14.974862,  6.6865439,  6.8951812),
        terms(0,  0,  2,   0.897144,  -4.954829,  3.527812,   1.672790, -1.1827535, -0.0332538),
        terms(0,  0,  3,   0.611149,   1.211027, -1.050748,   0.327647,  0.1593179, -0.1438890),
        terms(0,  0,  4,  -0.341243,  -0.189585,  0.178690,  -0.292153, -0.0018444,  0.0483220),
        terms(0,  0,  5,   0.129287,  -0.034992,  0.018650,   0.100340, -0.0065977, -0.0085431),
        terms(0,  0,  6,  -0.038164,   0.030893, -0.030697,  -0.025823,  0.0031174, -0.0006032),
        terms(0,  1, -1,   0.020442,  -0.009987,  0.004878,   0.011248, -0.0005794,  0.0022161),
      	terms(0,  1,  0,  -0.004063,  -0.005071,  0.000226,  -0.000064,  0.0004601,  0.0004032),
      	terms(0,  1,  1,  -0.006016,  -0.003336,  0.00203,   -0.000836, -0.0001729,  0.0000234),
      	terms(0,  1,  2,  -0.003956,   0.003039,  0.000069,  -0.000604, -0.0000415,  0.0000702),
      	terms(0,  1,  3,  -0.000667,   0.003572, -0.000247,  -0.000567,  0.0000239,  0.0000723),
      	terms(0,  2, -2,   0.001276,   0.000501, -0.000057,   0.000001,  0.0000067, -0.0000067),
      	terms(0,  2, -1,   0.001152,  -0.000917, -0.000122,   0.000175,  0.0001034, -0.0000451),
      	terms(0,  2,  0,   0.00063,   -0.001277, -0.000049,  -0.000164, -0.0000129,  0.0000504),
      	terms(1, -1,  0,   0.002571,  -0.000459, -0.000197,   0.000199,  0.000048,  -0.0000231),
      	terms(1, -1,  1,   0.000899,  -0.001449, -0.000025,   0.000217,  0.0000002, -0.0000441),
      	terms(1,  0, -3,  -0.001016,   0.001043,  0.000589,  -0.000248, -0.0003359,  0.0000265),
      	terms(1,  0, -2,  -0.002343,  -0.001012, -0.000269,   0.000711,  0.0007856, -0.0007832),
      	terms(1,  0, -1,   0.007042,   0.000788,  0.000185,   0.000193,  0.0000036,  0.0045763),
      	terms(1,  0,  0,   0.001199,  -0.000338,  0.000315,   0.000807,  0.0008663,  0.0008547),
      	terms(1,  0,  1,   0.000418,  -0.000067, -0.00013,   -0.000043, -0.0000809, -0.0000769),
      	terms(1,  0,  2,   0.00012,   -0.000274,  0.000005,   0.000003,  0.0000263, -0.0000144),
      	terms(1,  0,  3,  -0.00006,   -0.000159,  0.000002,   0.000017, -0.0000126,  0.0000032),
      	terms(1,  0,  4,  -0.000082,  -0.000029,  0.000002,   0.000005, -0.0000035, -0.0000016),
      	terms(1,  1, -3,  -0.000036,  -0.000029,  0.000002,   0.000003, -0.0000019, -0.0000004),
      	terms(1,  1, -2,  -0.00004,    0.000007,  0.000003,   0.000001, -0.0000015,  0.0000008),
      	terms(1,  1, -1,  -0.000014,   0.000022,  0.000002,  -0.000001, -0.0000004,  0.0000012),
      	terms(1,  1,  0,   0.000004,   0.000013,  0.000001,  -0.000001,  0.0000005,  0.0000006),
      	terms(1,  1,  1,   0.000005,   0.000002,  0.0,       -0.000001,  0.0000003,  0.0000001),
      	terms(1,  1,  3,  -0.000001,   0.0,       0.0,        0.0,       0.0000006, -0.0000002),
      	terms(2,  0, -6,   0.000002,   0.0,       0.0,       -0.000002,  0.0000002,  0.0000002),
      	terms(2,  0, -5,  -0.000004,   0.000005,  0.000002,   0.000002, -0.0000002, -0.0000002),
      	terms(2,  0, -4,   0.000004,  -0.000007, -0.000007,   0.0,       0.0000014,  0.0000013),
      	terms(2,  0, -3,   0.000014,   0.000024,  0.00001,   -0.000008, -0.0000063,  0.0000013),
      	terms(2,  0, -2,  -0.000049,  -0.000034, -0.000003,   0.00002,   0.0000136, -0.0000236),
      	terms(2,  0, -1,   0.000163,  -0.000048,  0.000006,   0.000005,  0.0000273,  0.0001065),
      	terms(2,  0,  0,   0.000009,  -0.000024,  0.000014,   0.000017,  0.0000251,  0.0000149),
      	terms(2,  0,  1,  -0.000004,   0.000001, -0.000002,   0.0,      -0.0000025, -0.0000009),
      	terms(2,  0,  2,  -0.000003,   0.000001,  0.0,        0.0,       0.0000009, -0.0000002),
      	terms(2,  0,  3,   0.000001,   0.000003,  0.0,        0.0,      -0.0000008,  0.0000007),
      	terms(3,  0, -2,  -0.000003,  -0.000001,  0.0,        0.000001,  0.0000002, -0.000001),
      	terms(3,  0, -1,   0.000005,  -0.000003,  0.0,        0.0,       0.0000019,  0.0000035),
      	terms(3,  0,  0,   0.0,        0.0,       0.000001,   0.0,       0.000001,   0.0000003)
    ];

    let j = 34.350 + 3034.9057 * JC;
    let s = 50.080 + 1222.1138 * JC;
    let p = 238.96 + 144.96000 * JC;

    let mut long = (238.958116f64 + 144.96 * JC).to_radians();
    let mut lat  = -3.908239_f64.to_radians();
    let mut r    =  40.7241346;

    for x in tuple_terms.iter() {
        let alpha = ((x.0 as f64)*j + (x.1 as f64)*s + (x.2 as f64)*p).to_radians();
        let alpha_sin = alpha.sin();
        let alpha_cos = alpha.cos();

        long += x.3.to_radians()*alpha_sin + x.4.to_radians()*alpha_cos;
        lat  += x.5.to_radians()*alpha_sin + x.6.to_radians()*alpha_cos;
        r    += x.7*alpha_sin + x.8*alpha_cos;
    }

    (long, lat, r)

}

/**
Returns the mean orbital elements of Pluto near 2000 AD

# Returns

`(a, e, i, omega, w)`

* `a`    : Semimajor axis of the orbit *| in AU*
* `e`    : Eccentricity of the orbit
* `i`    : Inclination of the plane of the orbit with the
           plane of the ecliptic *| in radians*
* `omega`: Longitude of the ascending node *| in radians*
* `w`    : Argument of the perihelion *| in radians*
**/
pub fn mn_orb_elements_2000AD() -> (f64, f64, f64, f64, f64) {
    
    (
        039.543,                  // a
        000.249,                  // e
        017.140_f64.to_radians(), // i
        110.307_f64.to_radians(), // omega
        113.768_f64.to_radians()  // w
    )

}