112 lines
3.9 KiB
Rust
112 lines
3.9 KiB
Rust
//! Tests for the anomaly conversions.
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//!
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//! 近点角换算的测试。
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use apsis_kepler::{
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eccentric_from_mean, eccentric_from_true, mean_from_eccentric, mean_from_true,
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true_from_eccentric, true_from_mean, wrap_to_pi,
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};
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use core::f64::consts::PI;
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#[test]
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fn wrap_places_angles_in_the_half_open_interval() {
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for turns in -3..=3 {
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for offset in [0.0, 0.25, 0.5, 0.75] {
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let angle = PI + (f64::from(turns) + offset) * 2.0 * PI;
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let wrapped = wrap_to_pi(angle);
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assert!(
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(-PI..PI).contains(&wrapped),
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"angle {angle} wrapped to {wrapped}"
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);
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// The result differs from the input by a whole number of turns.
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// 结果与输入相差整数圈。
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let turns_removed = (angle - wrapped) / (2.0 * PI);
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assert!((turns_removed - turns_removed.round()).abs() < 1e-9);
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}
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}
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}
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#[test]
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fn wrap_keeps_values_already_in_range() {
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for angle in [-3.0, -1.0, 0.0, 1.0, 3.0] {
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assert!((wrap_to_pi(angle) - angle).abs() < 1e-12);
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}
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}
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#[test]
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fn keplers_equation_holds_for_the_solution() {
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// M = E - e sin E must be satisfied by the returned eccentric anomaly.
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// 所返回的偏近点角必须满足 M = E - e sin E。
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for eccentricity in [0.0, 0.01, 0.1, 0.5, 0.9, 0.99] {
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for mean in [-3.0, -1.0, 0.0, 0.5, 1.5, 3.0] {
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let eccentric = eccentric_from_mean(mean, eccentricity);
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let recovered = mean_from_eccentric(eccentric, eccentricity);
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assert!(
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(recovered - mean).abs() < 1e-9,
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"e={eccentricity} M={mean} recovered={recovered}"
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);
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}
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}
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}
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#[test]
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fn eccentric_and_true_anomaly_round_trip() {
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for eccentricity in [0.0, 0.05, 0.3, 0.7, 0.95] {
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for true_anomaly in [-3.0, -1.0, 0.0, 0.25, 1.0, 3.0] {
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let eccentric = eccentric_from_true(true_anomaly, eccentricity);
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let back = true_from_eccentric(eccentric, eccentricity);
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assert!(
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(back - true_anomaly).abs() < 1e-9,
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"e={eccentricity} nu={true_anomaly} back={back}"
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);
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}
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}
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}
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#[test]
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fn mean_and_true_anomaly_round_trip() {
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for eccentricity in [0.0, 0.05, 0.3, 0.7, 0.95] {
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for true_anomaly in [-2.5, -0.5, 0.0, 0.75, 2.0] {
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let mean = mean_from_true(true_anomaly, eccentricity);
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let back = true_from_mean(mean, eccentricity);
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assert!(
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(back - true_anomaly).abs() < 1e-8,
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"e={eccentricity} nu={true_anomaly} back={back}"
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);
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}
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}
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}
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#[test]
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fn a_circular_orbit_has_equal_anomalies() {
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// With zero eccentricity every anomaly is the same angle.
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// 偏心率为零时每种近点角都是同一个角。
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for angle in [-2.0, -0.5, 0.0, 1.0, 2.5] {
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assert!((eccentric_from_mean(angle, 0.0) - angle).abs() < 1e-12);
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assert!((true_from_eccentric(angle, 0.0) - angle).abs() < 1e-12);
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assert!((true_from_mean(angle, 0.0) - angle).abs() < 1e-12);
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}
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}
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#[test]
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fn anomalies_at_perigee_are_zero() {
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for eccentricity in [0.0, 0.3, 0.8] {
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assert!(eccentric_from_mean(0.0, eccentricity).abs() < 1e-12);
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assert!(true_from_mean(0.0, eccentricity).abs() < 1e-12);
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assert!(mean_from_true(0.0, eccentricity).abs() < 1e-12);
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}
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}
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#[test]
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fn true_anomaly_exceeds_mean_anomaly_before_apogee() {
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// For an eccentric orbit the satellite spends less time near perigee,
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// so the true anomaly runs ahead of the mean anomaly in the first half
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// of the orbit.
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// 对偏心轨道，卫星在近地点附近花的时间较少，故在轨道的上半段真近点角领先于平
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// 近点角。
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let eccentricity = 0.5;
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let mean = 1.0;
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let true_anomaly = true_from_mean(mean, eccentricity);
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assert!(true_anomaly > mean, "nu={true_anomaly} M={mean}");
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}
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