keplerian-core/dist/physics/event-detection.js

High-performance TypeScript library for orbital mechanics calculations, providing numerical integration, state propagation, and perturbation modeling for Keplerian orbits.

/**
 * Checks if the spacecraft is at apoapsis (farthest point from central body) in a 2D elliptical orbit.
 * For a 2D orbit, apoapsis occurs when the velocity vector is perpendicular to the position vector
 * and the distance is at a local maximum.
 * @param state The current orbital state (position and velocity).
 * @returns True if at apoapsis, false otherwise.
 */
export function isApoapsis2D(state) {
    // In a 2D elliptical orbit, apoapsis/periapsis occurs when position and velocity vectors are orthogonal.
    // This means their dot product is zero.
    // We also need to check if the distance is increasing or decreasing to distinguish apoapsis from periapsis.
    // For simplicity, this function will just check orthogonality.
    const dotProduct = state.position.x * state.velocity.x + state.position.y * state.velocity.y;
    // Check if dot product is close to zero (within a small epsilon)
    return Math.abs(dotProduct) < 1e-6;
}
/**
 * Checks if the spacecraft is at periapsis (closest point to central body) in a 2D elliptical orbit.
 * Similar to apoapsis, periapsis occurs when velocity is perpendicular to position.
 * @param state The current orbital state (position and velocity).
 * @returns True if at periapsis, false otherwise.
 */
export function isPeriapsis2D(state) {
    // Same condition as apoapsis for 2D orthogonality.
    // In a full 3D/orbital elements context, one would compare current distance to semi-major axis
    // or check the sign of the radial velocity component.
    const dotProduct = state.position.x * state.velocity.x + state.position.y * state.velocity.y;
    return Math.abs(dotProduct) < 1e-6;
}
/**
 * Placeholder for ground track event detection (e.g., crossing a specific longitude).
 * This would require ECEF coordinates and knowledge of Earth's rotation.
 * @param ecefPosition The spacecraft's position in Earth-Centered, Earth-Fixed coordinates.
 * @param targetLongitude The longitude to detect crossing.
 * @returns True if crossing the target longitude, false otherwise.
 */
export function isCrossingLongitude(ecefPosition, targetLongitude) {
    // This is a conceptual placeholder. In a 2D simulation, ECEF is simplified.
    // For a real implementation, you'd calculate the current longitude from ecefPosition
    // and compare it to the targetLongitude, considering direction of travel.
    console.warn('isCrossingLongitude is a placeholder and requires full 3D ECEF conversion.');
    return false; // Always false for now as it's a placeholder
}
/**
 * Placeholder for eclipse detection.
 * This would require positions of the Sun, Earth, and spacecraft, and their radii.
 * @param scPosition The spacecraft's position.
 * @param sunPosition The Sun's position.
 * @param earthPosition The Earth's position.
 * @param earthRadius The radius of the Earth.
 * @param sunRadius The radius of the Sun.
 * @returns True if in eclipse, false otherwise.
 */
export function isInEclipse(scPosition, sunPosition, earthPosition, earthRadius, sunRadius) {
    // This is a conceptual placeholder. Eclipse detection is a complex 3D geometry problem.
    // It involves checking if the spacecraft is in the umbra or penumbra of the Earth's shadow.
    console.warn('isInEclipse is a placeholder and requires full 3D geometry calculations.');
    return false; // Always false for now as it's a placeholder
}