46 lines
1.4 KiB
Go
46 lines
1.4 KiB
Go
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package basic
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import "math"
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// OrbitAsteroidMagnitudeHG 返回小行星 H-G 模型的视星等。
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func OrbitAsteroidMagnitudeHG(jd float64, elements OrbitElements, absoluteMagnitude, slopeParameter float64) float64 {
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if !isFinite(jd) || !isFinite(absoluteMagnitude) || !isFinite(slopeParameter) {
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return math.NaN()
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}
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sunDistance := OrbitSunDistance(jd, elements)
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earthDistance := OrbitEarthDistance(jd, elements)
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phaseAngle := OrbitPhaseAngle(jd, elements)
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if !isFinitePositive(sunDistance) || !isFinitePositive(earthDistance) || !isFinite(phaseAngle) {
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return math.NaN()
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}
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phaseBlend := orbitHGSlopeBlend(phaseAngle, slopeParameter)
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if phaseBlend == 0 {
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return math.Inf(1)
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}
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if !isFinitePositive(phaseBlend) {
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return math.NaN()
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}
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return absoluteMagnitude + 5*math.Log10(sunDistance*earthDistance) - 2.5*math.Log10(phaseBlend)
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}
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func orbitHGSlopeBlend(phaseAngle, slopeParameter float64) float64 {
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phi1 := orbitHGPhaseFunction1(phaseAngle)
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phi2 := orbitHGPhaseFunction2(phaseAngle)
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return (1-slopeParameter)*phi1 + slopeParameter*phi2
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}
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func orbitHGPhaseFunction1(phaseAngle float64) float64 {
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return math.Exp(-3.33 * math.Pow(orbitHGTanHalfPhaseAngle(phaseAngle), 0.63))
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}
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func orbitHGPhaseFunction2(phaseAngle float64) float64 {
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return math.Exp(-1.87 * math.Pow(orbitHGTanHalfPhaseAngle(phaseAngle), 1.22))
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}
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func orbitHGTanHalfPhaseAngle(phaseAngle float64) float64 {
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return math.Tan((phaseAngle * math.Pi / 180) / 2)
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}
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