keplerian::keplerian(
const epoch& ref_epoch,
const array3D& r0,
const array3D& v0,
double mu_central_body,
double mu_self,
double radius,
double safe_radius,
const std::string &name) : base(mu_central_body, mu_self, radius, safe_radius, name), m_r(r0), m_v(v0), m_ref_mjd2000(ref_epoch.mjd2000())
{
// This line is singular (small e and small i) in which case the orbital elements are (simply) not defined
ic2par(r0,v0, get_mu_central_body(), m_keplerian_elements);
m_keplerian_elements[5] = e2m(m_keplerian_elements[5],m_keplerian_elements[1]);
m_mean_motion = sqrt(get_mu_central_body() / pow(m_keplerian_elements[0],3));
}
void keplerian::eph_impl(double mjd2000, array3D &r, array3D &v) const {
double dt = (mjd2000 - m_ref_mjd2000) * ASTRO_DAY2SEC;
if (m_keplerian_elements[1] > 1e-3 && m_keplerian_elements[2] > 1e-3)
{
double elements[6];
std::copy(m_keplerian_elements.begin(), m_keplerian_elements.end(), elements);
elements[5] += m_mean_motion * dt;
elements[5] = m2e(elements[5],elements[1]);
par2ic(elements, get_mu_central_body(), r, v);
} else { // Small inclinations and eccentricities (including nans), we use lagrangian propagation
r = m_r;
v = m_v;
propagate_lagrangian(r, v, dt, get_mu_central_body());
}
}
/// Computes the low-precision ephemerides
void jpl_lp::eph_impl(double mjd2000, array3D &r, array3D &v) const {
if (mjd2000 <=-73048.0 || mjd2000>=18263.0) {
throw_value_error("Ephemeris are out of range [1800-2050]");
}
// algorithm from http://ssd.jpl.nasa.gov/txt/p_elem_t1.txt downloded 2013
array6D elements, elements2;
double dt = (mjd2000 - ref_mjd2000) / 36525.0; // Number of centuries passed since J2000.0
for(unsigned int i= 0;i<6;++i) {
elements[i] = (jpl_elements[i] + jpl_elements_dot[i] * dt);
}
elements2[0] = elements[0] * ASTRO_AU;
elements2[1] = elements[1];
elements2[2] = elements[2] * ASTRO_DEG2RAD;
elements2[3] = elements[5] * ASTRO_DEG2RAD;
elements2[4] = (elements[4] - elements[5]) * ASTRO_DEG2RAD;
elements2[5] = (elements[3] - elements[4]) * ASTRO_DEG2RAD;
elements2[5] = m2e(elements2[5],elements2[1]);
par2ic(elements2, get_mu_central_body(), r, v);
}
/**
* Constructs a planet from its elements and its phyisical parameters
* \param[in] ref_epoch epoch to which the elements are referred to
* \param[in] elem A STL vector containing the keplerian parameters (a,e,i,Om,om,M). (SI units)
* \param[in] mu_central_body The gravitational parameter of the attracting body (SI units)
* \param[in] mu_self The gravitational parameter of the planet (SI units)
* \param[in] radius radius of the planet (SI units)
* \param[in] safe_radius mimimual radius that is safe during a fly-by of the planet (SI units)
* \param[in] name C++ string containing the planet name. Default value is "Unknown"
*/
keplerian::keplerian(
const epoch& ref_epoch,
const array6D& keplerian_elements,
double mu_central_body,
double mu_self,
double radius,
double safe_radius,
const std::string &name)
: base(mu_central_body, mu_self, radius, safe_radius, name), m_keplerian_elements(keplerian_elements), m_ref_mjd2000(ref_epoch.mjd2000())
{
if (keplerian_elements[0] <=0) {
throw_value_error("The planet semi-major axis needs to a positive number");
}
if (keplerian_elements[1] < 0 || keplerian_elements[1] >=1) {
throw_value_error("The planet eccentricity needs to be in [0,1)");
}
m_mean_motion = sqrt(mu_central_body / pow(keplerian_elements[0],3));
par2ic(m_keplerian_elements, get_mu_central_body(), m_r, m_v);
}
/// Sets the keplerian elements (and computes the mean motion)
void keplerian::set_elements(const array6D& el) {
m_keplerian_elements = el;
m_mean_motion = sqrt(get_mu_central_body() / pow(m_keplerian_elements[0],3));
}
double planet::compute_period() const {
return 2* boost::math::constants::pi<double>() * std::sqrt(std::pow(get_elements()[0],3) / get_mu_central_body());
}
