feat: 扩展天文计算能力

- 新增日食、月食、本地可见性、中心线、半影区域、SVG 图示与沙罗周期信息
- 新增行星冲合、留、方照、物理星历、视直径、相位、亮肢角、轨道节点等计算
- 新增木星伽利略卫星位置、现象与接触事件计算
- 新增恒星星表、星座判定、自行修正与观测辅助能力
- 新增 coord、formula、orbit、sundial、lite/sun、lite/moon 等扩展包
- 完善农历年号、月相英文别名、视差角、大气质量、折射、日晷与双星计算
- 增加 NASA、JPL Horizons、IMCCE 等回归测试数据与基线测试
- 重构基础算法文件组织，补充大量公开 API 注释和语义回归测试
- 更新中文和英文 README，补充示例、精度说明、SVG 配图

jupiter/satellites.go

@@ -0,0 +1,78 @@
+package jupiter
+
+import (
+	"time"
+
+	"b612.me/astro/basic"
+)
+
+// GalileanSatellitePosition 木星伽利略卫星视位置 / apparent position of a Galilean satellite.
+//
+// Jovicentric* 为木心 J2000 平赤道直角坐标与速度，单位 AU / AU-day。
+// ApparentRA/Dec 为该卫星的地心天体测量赤经赤纬，单位度。
+// OffsetX/OffsetY 以木星中心为原点，分别沿天球东、北方向为正。
+// Jovicentric* are Jovicentric J2000 mean-equatorial coordinates and velocities in AU / AU-day.
+// ApparentRA/Dec are geocentric astrometric right ascension and declination in degrees.
+// OffsetX/OffsetY are measured from Jupiter's center, positive to celestial east and north.
+type GalileanSatellitePosition struct {
+	JovicentricX  float64
+	JovicentricY  float64
+	JovicentricZ  float64
+	JovicentricVX float64
+	JovicentricVY float64
+	JovicentricVZ float64
+
+	ApparentRA       float64
+	ApparentDec      float64
+	EarthDistance    float64
+	OffsetXArcsec    float64
+	OffsetYArcsec    float64
+	OffsetXJupiterR  float64
+	OffsetYJupiterR  float64
+	OffsetZJupiterR  float64
+	InFrontOfJupiter bool
+}
+
+// GalileanSatellitesInfo 四颗伽利略卫星视位置 / apparent positions of the four Galilean satellites.
+type GalileanSatellitesInfo struct {
+	Io       GalileanSatellitePosition
+	Europa   GalileanSatellitePosition
+	Ganymede GalileanSatellitePosition
+	Callisto GalileanSatellitePosition
+}
+
+// Satellites 木星四颗伽利略卫星视位置 / apparent positions of Jupiter's four Galilean satellites.
+//
+// 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。
+// date is the observing instant; internally the corresponding TT/TDB epoch is used for the L1 ephemeris evaluation.
+func Satellites(date time.Time) GalileanSatellitesInfo {
+	jde := basic.Date2JDE(date.UTC())
+	observations := basic.JupiterGalileanSatelliteObservations(jde)
+	return GalileanSatellitesInfo{
+		Io:       galileanSatellitePositionFromBasic(observations[0]),
+		Europa:   galileanSatellitePositionFromBasic(observations[1]),
+		Ganymede: galileanSatellitePositionFromBasic(observations[2]),
+		Callisto: galileanSatellitePositionFromBasic(observations[3]),
+	}
+}
+
+func galileanSatellitePositionFromBasic(observation basic.JupiterGalileanObservation) GalileanSatellitePosition {
+	return GalileanSatellitePosition{
+		JovicentricX:  observation.State.X,
+		JovicentricY:  observation.State.Y,
+		JovicentricZ:  observation.State.Z,
+		JovicentricVX: observation.State.VX,
+		JovicentricVY: observation.State.VY,
+		JovicentricVZ: observation.State.VZ,
+
+		ApparentRA:       observation.RA,
+		ApparentDec:      observation.Dec,
+		EarthDistance:    observation.Distance,
+		OffsetXArcsec:    observation.OffsetXArcsec,
+		OffsetYArcsec:    observation.OffsetYArcsec,
+		OffsetXJupiterR:  observation.OffsetXJupiterRadii,
+		OffsetYJupiterR:  observation.OffsetYJupiterRadii,
+		OffsetZJupiterR:  observation.OffsetZJupiterRadii,
+		InFrontOfJupiter: observation.InFrontOfJupiter,
+	}
+}