State Representations

Astrea uses strongly typed element sets to allow an easier user interface for conversions, and common operators. Currently, there are 3 supported orbital element sets: - Classical Orbital Elements (Keplerian) - Modified Equinoctial Elements (Equinoctial) - Cartesian State Vectors (Cartesian)

as well as a host of angular element sets such as geodetic and spherical coordinates.

// Build out a Cartesian element set using strongly typed, united quantities
Cartesian cartesian{
    7000.0 * km, 0.0 * km, 0.0 * km, 0.0 * km / s, 7.5 * km / s, 1.0 * km / s,
};
std::cout << "Cartesian: " << cartesian << std::endl;

// Conversions are done through the constructors for each element set type
GravParam mu = 398600.44189 * pow<3>(km) / pow<2>(s); // Earth
Keplerian keplerian{ cartesian, mu };
Equinoctial equinoctial{ keplerian, mu };

std::cout << "Converted to Keplerian: " << keplerian << std::endl;
std::cout << "Converted to Equinoctial: " << equinoctial << std::endl;
std::cout << "Converted back to Cartesian: " << Cartesian(equinoctial, mu) << std::endl << std::endl;

// Outputs:
// Cartesian: [7000 km, 0 km, 0 km, 0 km/s, 7.5 km/s, 1 km/s] (Cartesian)
// Converted to Keplerian: [7037.95 km, 0.00539276, 0.132552 rad, 0 rad, 0 rad, 0 rad] (Keplerian)
// Converted to Equinoctial: [7037.75 km, 0.00539276, 0, 0.066373, 0, 0 rad] (Equinoctial)
// Converted back to Cartesian: [7000 km, 0 km, 0 km, -0 km/s, 7.5 km/s, 1 km/s] (Cartesian)