278 lines
12 KiB
Go
278 lines
12 KiB
Go
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package orbit
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import (
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"errors"
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"time"
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"b612.me/astro/basic"
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)
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var (
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ERR_ORBIT_NEVER_RISE = errors.New("ERROR:轨道目标今日永远在地平线下！")
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ERR_ORBIT_NEVER_SET = errors.New("ERROR:轨道目标今日永远在地平线上！")
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)
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// Elements 日心二体圆锥曲线根数，参考系为 J2000 平黄道/平春分点。
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// EpochJD 与 TpJD 使用 TT/TDB 对应的儒略日。
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//
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// 经典椭圆根数：A/E/I/Omega/W/M0
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// 近日点形式：Q/E/I/Omega/W/TpJD
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//
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// 线性 rates 仅作用于经典椭圆根数，单位均为每天变化量。
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type Elements struct {
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EpochJD float64 // 历元儒略日（TT/TDB） / epoch Julian day in TT/TDB.
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A float64 // 半长径，单位 AU / semi-major axis in AU.
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E float64 // 离心率 / eccentricity.
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I float64 // 轨道倾角，单位度 / inclination in degrees.
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Omega float64 // 升交点黄经，单位度 / longitude of ascending node in degrees.
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W float64 // 近日点幅角，单位度 / argument of perihelion in degrees.
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M0 float64 // 历元平近点角，单位度 / mean anomaly at epoch in degrees.
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Q float64 // 近日点距离，单位 AU / perihelion distance in AU.
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TpJD float64 // 近日点通过时刻（TT/TDB JD） / perihelion passage time in TT/TDB Julian day.
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ADot float64 // 半长径日变化，单位 AU/day / daily rate of A.
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EDot float64 // 离心率日变化，单位 1/day / daily rate of E.
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IDot float64 // 倾角日变化，单位 deg/day / daily rate of I.
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OmegaDot float64 // 升交点黄经日变化，单位 deg/day / daily rate of Omega.
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WDot float64 // 近日点幅角日变化，单位 deg/day / daily rate of W.
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MDot float64 // 平近点角日变化，单位 deg/day / daily rate of M.
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}
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// EclipticPosition 黄道球坐标结果，Lon/Lat 单位度，Distance 单位 AU。
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type EclipticPosition struct {
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Lon float64
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Lat float64
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Distance float64
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}
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// EquatorialPosition 赤道球坐标结果，RA/Dec 单位度，Distance 单位 AU。
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type EquatorialPosition struct {
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RA float64
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Dec float64
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Distance float64
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}
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// MeanMotion 平均角速度 / mean motion.
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//
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// 返回平均角速度，单位度/日；对抛物线和双曲线轨道返回 `NaN`。
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func MeanMotion(elements Elements) float64 {
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return basic.OrbitMeanMotion(toBasicElements(elements))
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}
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// MeanAnomaly 平近点角 / mean anomaly.
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//
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// 返回给定时刻的平近点角，单位度；对抛物线和双曲线轨道返回 `NaN`。
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func MeanAnomaly(date time.Time, elements Elements) float64 {
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return basic.OrbitMeanAnomaly(ttJulianDay(date), toBasicElements(elements))
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}
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// TrueAnomaly 真近点角 / true anomaly.
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//
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// 返回给定时刻的真近点角，单位度。
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func TrueAnomaly(date time.Time, elements Elements) float64 {
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return basic.OrbitTrueAnomaly(ttJulianDay(date), toBasicElements(elements))
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}
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// HeliocentricEclipticJ2000 日心 J2000 平黄道坐标 / heliocentric J2000 ecliptic coordinates.
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//
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// 返回黄经、黄纬和距离；角度单位度，距离单位 AU。
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func HeliocentricEclipticJ2000(date time.Time, elements Elements) EclipticPosition {
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lon, lat, distance := basic.OrbitHeliocentricEclipticJ2000(ttJulianDay(date), toBasicElements(elements))
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return EclipticPosition{Lon: lon, Lat: lat, Distance: distance}
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}
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// HeliocentricEcliptic 日心历元黄道坐标 / heliocentric ecliptic coordinates of date.
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//
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// 返回历元黄经、黄纬和距离；角度单位度，距离单位 AU。
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func HeliocentricEcliptic(date time.Time, elements Elements) EclipticPosition {
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lon, lat, distance := basic.OrbitHeliocentricEcliptic(ttJulianDay(date), toBasicElements(elements))
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return EclipticPosition{Lon: lon, Lat: lat, Distance: distance}
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}
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// GeocentricEclipticJ2000 地心 J2000 平黄道坐标 / geocentric J2000 ecliptic coordinates.
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//
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// 返回黄经、黄纬和距离；角度单位度，距离单位 AU。
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func GeocentricEclipticJ2000(date time.Time, elements Elements) EclipticPosition {
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lon, lat, distance := basic.OrbitGeocentricEclipticJ2000(ttJulianDay(date), toBasicElements(elements))
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return EclipticPosition{Lon: lon, Lat: lat, Distance: distance}
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}
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// GeocentricEcliptic 地心历元黄道坐标 / geocentric ecliptic coordinates of date.
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//
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// 返回历元黄经、黄纬和距离；角度单位度，距离单位 AU。
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func GeocentricEcliptic(date time.Time, elements Elements) EclipticPosition {
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lon, lat, distance := basic.OrbitGeocentricEcliptic(ttJulianDay(date), toBasicElements(elements))
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return EclipticPosition{Lon: lon, Lat: lat, Distance: distance}
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}
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// GeocentricEquatorialJ2000 地心 J2000 平赤道坐标 / geocentric J2000 equatorial coordinates.
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//
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// 返回赤经、赤纬和距离；角度单位度，距离单位 AU。
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func GeocentricEquatorialJ2000(date time.Time, elements Elements) EquatorialPosition {
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ra, dec, distance := basic.OrbitGeocentricEquatorialJ2000(ttJulianDay(date), toBasicElements(elements))
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return EquatorialPosition{RA: ra, Dec: dec, Distance: distance}
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}
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// GeocentricEquatorial 地心历元平赤道坐标 / geocentric equatorial coordinates of date.
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//
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// 返回历元赤经、赤纬和距离；角度单位度，距离单位 AU。
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func GeocentricEquatorial(date time.Time, elements Elements) EquatorialPosition {
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ra, dec, distance := basic.OrbitGeocentricEquatorial(ttJulianDay(date), toBasicElements(elements))
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return EquatorialPosition{RA: ra, Dec: dec, Distance: distance}
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}
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// AstrometricGeocentricEquatorialJ2000 地心测算 J2000 赤道坐标 / astrometric geocentric J2000 equatorial coordinates.
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//
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// 返回加入光行时修正后的地心 J2000 赤经、赤纬和距离；角度单位度，距离单位 AU。
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func AstrometricGeocentricEquatorialJ2000(date time.Time, elements Elements) EquatorialPosition {
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ra, dec, distance := basic.OrbitAstrometricGeocentricEquatorialJ2000(ttJulianDay(date), toBasicElements(elements))
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return EquatorialPosition{RA: ra, Dec: dec, Distance: distance}
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}
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// ApparentGeocentricEcliptic 地心视黄道坐标 / apparent geocentric ecliptic coordinates.
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//
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// 返回加入光行时与章动修正后的地心视黄经、黄纬和距离；角度单位度，距离单位 AU。
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func ApparentGeocentricEcliptic(date time.Time, elements Elements) EclipticPosition {
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lon, lat, distance := basic.OrbitApparentGeocentricEcliptic(ttJulianDay(date), toBasicElements(elements))
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return EclipticPosition{Lon: lon, Lat: lat, Distance: distance}
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}
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// ApparentGeocentricEquatorial 地心视赤道坐标 / apparent geocentric equatorial coordinates.
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//
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// 返回加入光行时与章动修正后的地心视赤经、赤纬和距离；角度单位度，距离单位 AU。
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func ApparentGeocentricEquatorial(date time.Time, elements Elements) EquatorialPosition {
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ra, dec, distance := basic.OrbitApparentGeocentricEquatorial(ttJulianDay(date), toBasicElements(elements))
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return EquatorialPosition{RA: ra, Dec: dec, Distance: distance}
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}
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// ApparentTopocentricEquatorial 站心视赤道坐标 / apparent topocentric equatorial coordinates.
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//
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// 返回加入光行时、章动和站心修正后的视赤经、赤纬和距离；
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// `observerLon` 东经为正，`observerLat` 北纬为正，`observerHeight` 单位米。
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func ApparentTopocentricEquatorial(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64) EquatorialPosition {
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ra, dec, distance := basic.OrbitApparentTopocentricEquatorial(ttJulianDay(date), observerLon, observerLat, observerHeight, toBasicElements(elements))
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return EquatorialPosition{RA: ra, Dec: dec, Distance: distance}
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}
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// Altitude 视高度角 / apparent altitude.
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//
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// 返回目标在观测者所在地的视高度角，单位度；经度东正西负，纬度北正南负，海拔单位米。
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func Altitude(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64) float64 {
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jde := basic.Date2JDE(date)
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return basic.OrbitHeight(jde, observerLon, observerLat, observationTimezone(date), observerHeight, toBasicElements(elements))
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}
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// Zenith 天顶距 / zenith distance.
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//
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// 返回目标在观测者所在地的天顶距，单位度。
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func Zenith(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64) float64 {
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return 90 - Altitude(date, elements, observerLon, observerLat, observerHeight)
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}
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// Azimuth 视方位角 / apparent azimuth.
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//
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// 返回目标在观测者所在地的视方位角，按正北为 0°、向东增加。
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func Azimuth(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64) float64 {
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jde := basic.Date2JDE(date)
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return basic.OrbitAzimuth(jde, observerLon, observerLat, observationTimezone(date), observerHeight, toBasicElements(elements))
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}
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// HourAngle 站心视时角 / topocentric hour angle.
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//
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// 返回目标在观测者所在地的站心视时角，单位度。
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func HourAngle(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64) float64 {
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jde := basic.Date2JDE(date)
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return basic.OrbitHourAngle(jde, observerLon, observerLat, observationTimezone(date), observerHeight, toBasicElements(elements))
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}
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// CulminationTime 中天时刻 / culmination time.
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//
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// 返回目标在给定当地日期内的中天时刻，结果保持输入 `date` 的时区。
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func CulminationTime(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64) time.Time {
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if date.Hour() > 12 {
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date = date.Add(-12 * time.Hour)
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}
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timezone := observationTimezone(date)
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jde := basic.Date2JDE(date)
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calcJde := basic.OrbitCulminationTime(jde, observerLon, observerLat, timezone, observerHeight, toBasicElements(elements)) - timezone/24.0
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return basic.JDE2DateByZone(calcJde, date.Location(), false)
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}
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// RiseTime 升起时刻 / rise time.
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//
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// 返回目标在给定当地日期内的升起时刻；`aero=true` 时加入标准大气折射修正。
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func RiseTime(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64, aero bool) (time.Time, error) {
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var aeroFloat float64
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if aero {
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aeroFloat = 1
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}
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if date.Hour() > 12 {
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date = date.Add(-12 * time.Hour)
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}
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timezone := observationTimezone(date)
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jde := basic.Date2JDE(date)
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calcJde, err := basic.OrbitRiseTime(jde, observerLon, observerLat, timezone, aeroFloat, observerHeight, toBasicElements(elements))
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return orbitRiseSetResult(date, calcJde, err)
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}
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// SetTime 落下时刻 / set time.
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//
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// 返回目标在给定当地日期内的落下时刻；`aero=true` 时加入标准大气折射修正。
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func SetTime(date time.Time, elements Elements, observerLon, observerLat, observerHeight float64, aero bool) (time.Time, error) {
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var aeroFloat float64
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if aero {
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aeroFloat = 1
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}
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if date.Hour() > 12 {
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date = date.Add(-12 * time.Hour)
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}
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timezone := observationTimezone(date)
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jde := basic.Date2JDE(date)
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calcJde, err := basic.OrbitSetTime(jde, observerLon, observerLat, timezone, aeroFloat, observerHeight, toBasicElements(elements))
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return orbitRiseSetResult(date, calcJde, err)
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}
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func orbitRiseSetResult(date time.Time, jde float64, err error) (time.Time, error) {
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if err != nil {
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switch {
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case errors.Is(err, basic.ErrNeverRise):
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return time.Time{}, ERR_ORBIT_NEVER_RISE
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case errors.Is(err, basic.ErrNeverSet):
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return time.Time{}, ERR_ORBIT_NEVER_SET
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default:
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return time.Time{}, err
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}
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}
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return basic.JDE2DateByZone(jde, date.Location(), true), nil
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}
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func observationTimezone(date time.Time) float64 {
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_, loc := date.Zone()
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return float64(loc) / 3600.0
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}
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func ttJulianDay(date time.Time) float64 {
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jdeUTC := basic.Date2JDE(date.UTC())
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return basic.TD2UT(jdeUTC, true)
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}
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func toBasicElements(elements Elements) basic.OrbitElements {
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return basic.OrbitElements{
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EpochJD: elements.EpochJD,
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A: elements.A,
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E: elements.E,
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I: elements.I,
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Omega: elements.Omega,
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W: elements.W,
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M0: elements.M0,
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Q: elements.Q,
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TpJD: elements.TpJD,
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ADot: elements.ADot,
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EDot: elements.EDot,
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IDot: elements.IDot,
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OmegaDot: elements.OmegaDot,
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WDot: elements.WDot,
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MDot: elements.MDot,
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}
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}
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