79 lines
2.9 KiB
Go
79 lines
2.9 KiB
Go
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package jupiter
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import (
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"time"
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"b612.me/astro/basic"
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)
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// GalileanSatellitePosition 木星伽利略卫星视位置 / apparent position of a Galilean satellite.
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//
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// Jovicentric* 为木心 J2000 平赤道直角坐标与速度，单位 AU / AU-day。
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// ApparentRA/Dec 为该卫星的地心天体测量赤经赤纬，单位度。
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// OffsetX/OffsetY 以木星中心为原点，分别沿天球东、北方向为正。
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// Jovicentric* are Jovicentric J2000 mean-equatorial coordinates and velocities in AU / AU-day.
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// ApparentRA/Dec are geocentric astrometric right ascension and declination in degrees.
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// OffsetX/OffsetY are measured from Jupiter's center, positive to celestial east and north.
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type GalileanSatellitePosition struct {
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JovicentricX float64
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JovicentricY float64
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JovicentricZ float64
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JovicentricVX float64
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JovicentricVY float64
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JovicentricVZ float64
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ApparentRA float64
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ApparentDec float64
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EarthDistance float64
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OffsetXArcsec float64
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OffsetYArcsec float64
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OffsetXJupiterR float64
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OffsetYJupiterR float64
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OffsetZJupiterR float64
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InFrontOfJupiter bool
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}
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// GalileanSatellitesInfo 四颗伽利略卫星视位置 / apparent positions of the four Galilean satellites.
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type GalileanSatellitesInfo struct {
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Io GalileanSatellitePosition
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Europa GalileanSatellitePosition
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Ganymede GalileanSatellitePosition
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Callisto GalileanSatellitePosition
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}
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// Satellites 木星四颗伽利略卫星视位置 / apparent positions of Jupiter's four Galilean satellites.
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//
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// date 表示观测绝对时刻；内部使用该时刻对应的 TT/TDB 历元做 L1 星历求值。
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// date is the observing instant; internally the corresponding TT/TDB epoch is used for the L1 ephemeris evaluation.
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func Satellites(date time.Time) GalileanSatellitesInfo {
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jde := basic.Date2JDE(date.UTC())
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observations := basic.JupiterGalileanSatelliteObservations(jde)
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return GalileanSatellitesInfo{
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Io: galileanSatellitePositionFromBasic(observations[0]),
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Europa: galileanSatellitePositionFromBasic(observations[1]),
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Ganymede: galileanSatellitePositionFromBasic(observations[2]),
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Callisto: galileanSatellitePositionFromBasic(observations[3]),
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}
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}
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func galileanSatellitePositionFromBasic(observation basic.JupiterGalileanObservation) GalileanSatellitePosition {
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return GalileanSatellitePosition{
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JovicentricX: observation.State.X,
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JovicentricY: observation.State.Y,
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JovicentricZ: observation.State.Z,
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JovicentricVX: observation.State.VX,
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JovicentricVY: observation.State.VY,
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JovicentricVZ: observation.State.VZ,
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ApparentRA: observation.RA,
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ApparentDec: observation.Dec,
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EarthDistance: observation.Distance,
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OffsetXArcsec: observation.OffsetXArcsec,
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OffsetYArcsec: observation.OffsetYArcsec,
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OffsetXJupiterR: observation.OffsetXJupiterRadii,
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OffsetYJupiterR: observation.OffsetYJupiterRadii,
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OffsetZJupiterR: observation.OffsetZJupiterRadii,
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InFrontOfJupiter: observation.InFrontOfJupiter,
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}
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}
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