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- /*
- * Copyright (C) 2023 Christopher J. Howard
- *
- * This file is part of Antkeeper source code.
- *
- * Antkeeper source code is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * Antkeeper source code is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
- */
-
- #ifndef ANTKEEPER_PHYSICS_ORBIT_ELEMENTS_HPP
- #define ANTKEEPER_PHYSICS_ORBIT_ELEMENTS_HPP
-
- #include "utility/fundamental-types.hpp"
- #include "math/numbers.hpp"
- #include <cmath>
-
- namespace physics {
- namespace orbit {
-
- /**
- * Set of six Keplerian elements required to uniquely identify an orbit.
- *
- * @tparam T Scalar type.
- */
- template <class T>
- struct elements
- {
- /// Scalar type.
- typedef T scalar_type;
-
- /// Eccentricity (e).
- scalar_type ec;
-
- /// Semimajor axis (a).
- scalar_type a;
-
- /// Inclination (i), in radians.
- scalar_type in;
-
- /// Right ascension of the ascending node (OMEGA), in radians.
- scalar_type om;
-
- /// Argument of periapsis (omega), in radians.
- scalar_type w;
-
- /// Mean anomaly (M) at epoch, in radians.
- scalar_type ma;
- };
-
- /**
- * Calculates the period of an elliptical orbit according to Kepler's third law.
- *
- * @param a Semimajor axis (a).
- * @param gm Standard gravitational parameter (GM).
- * @return Orbital period (T).
- */
- template <class T>
- T period(T a, T gm);
-
- /**
- * Calculates the mean motion (n) of an orbit.
- *
- * @param a Semimajor axis (a).
- * @param gm Standard gravitational parameter (GM).
- * @return Mean motion (n), in radians per unit time.
- */
- template <class T>
- T mean_motion(T a, T gm);
-
- /**
- * Calculates the mean motion (n) of an orbit.
- *
- * @param t Orbital period (T).
- * @return Mean motion (n), in radians per unit time.
- */
- template <class T>
- T mean_motion(T t);
-
- /**
- * Derives the argument of the periapsis (omega) of an orbit, given the longitude of periapsis (pomega) and longitude of the ascending node (OMEGA).
- *
- * @param lp Longitude of the periapsis (pomega), in radians.
- * @param om Right ascension of the ascending node (OMEGA), in radians.
- * @return Argument of the periapsis (omega), in radians.
- */
- template <class T>
- T argument_periapsis(T om, T lp);
-
- /**
- * Derives the longitude of the periapsis (pomega) of an orbit, given the argument of periapsis (omega) and longitude of the ascending node (OMEGA).
- *
- * @param w Argument of the periapsis (omega), in radians.
- * @param om Right ascension of the ascending node (OMEGA), in radians.
- * @return Longitude of the periapsis (pomega), in radians.
- */
- template <class T>
- T longitude_periapsis(T om, T w);
-
- /**
- * Derives the semiminor axis (b) of an orbit, given the semimajor axis (a) and eccentricity (e).
- *
- * @param a Semimajor axis (a).
- * @param ec Eccentricity (e).
- * @return Semiminor axis (b).
- */
- template <class T>
- T semiminor_axis(T a, T ec);
-
- /**
- * Derives the semi-latus rectum (l) of an orbit, given the semimajor axis (a) and eccentricity (e).
- *
- * @param a Semimajor axis (a).
- * @param ec Eccentricity (e).
- * @return Semi-latus rectum (l).
- */
- template <class T>
- T semilatus_rectum(T a, T ec);
-
- template <class T>
- T period(T a, T gm)
- {
- return math::two_pi<T> * std::sqrt((a * a * a) / gm);
- }
-
- template <class T>
- T mean_motion(T a, T gm)
- {
- return std::sqrt((a * a * a) / gm);
- }
-
- template <class T>
- T mean_motion(T t)
- {
- return math::two_pi<T> / t;
- }
-
- template <class T>
- T argument_periapsis(T om, T lp)
- {
- return lp - om;
- }
-
- template <class T>
- T longitude_periapsis(T om, T w)
- {
- return w + om;
- }
-
- template <class T>
- T semiminor_axis(T a, T ec)
- {
- return a * std::sqrt(T(1) - ec * ec);
- }
-
- template <class T>
- T semilatus_rectum(T a, T ec)
- {
- return a * (T(1) - ec * ec);
- }
-
- } // namespace orbit
- } // namespace physics
-
- #endif // ANTKEEPER_PHYSICS_ORBIT_ELEMENTS_HPP
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