Module: Korba::OrbitUtils

Included in:
Car, Kep, KeplersEquation, Propagator::Kepler, Tle
Defined in:
lib/korba/orbit_utils.rb

Instance Method Summary collapse

Instance Method Details

#deg_to_rad(deg) ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 51

def deg_to_rad(deg)
  rad = deg * Math::PI / 180.0
  normalize_rad(rad)
end

#distance ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 36

def distance
  semi_major_axis * (1 - eccentricity * Math.cos(deg_to_rad(eccentric_anomaly)))
end

#eccentric_anomaly ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 22

def eccentric_anomaly
  kepler = KeplersEquation.new(eccentricity:, mean_anomaly:)
  rad_to_deg(kepler.solve)
end

#height_at_apogee ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 18

def height_at_apogee
  semi_major_axis * (1 + eccentricity) - Constant::EARTH_RADIUS
end

#height_at_perigee ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 14

def height_at_perigee
  semi_major_axis * (1 - eccentricity) - Constant::EARTH_RADIUS
end

#normalize_deg(deg) ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 65

def normalize_deg(deg)
  deg % 360.0
end

#normalize_rad(rad) ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 56

def normalize_rad(rad)
  rad % (2.0 * Math::PI)
end

#path_angle ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 44

def path_angle
  return 0.0 if eccentricity < 1e-15

  factor = Math.sqrt(Constant::GME * semi_major_axis * (1 - eccentricity ** 2)) / (distance * velocity)
  rad_to_deg(Math.acos(factor))
end

#period ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 10

def period
  2.0 * Math::PI * Math.sqrt(semi_major_axis ** 3 / Constant::GME)
end

#rad_to_deg(rad) ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 60

def rad_to_deg(rad)
  deg = rad * 180.0 / Math::PI
  normalize_deg(deg)
end

#semi_major_axis ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 5

def semi_major_axis
  # a = (μ / n^2)^(1/3) m
  (Constant::GME / (mean_motion * 2.0 * Math::PI / 86400.0) ** 2.0) ** (1.0 / 3.0)
end

#true_anomaly ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 27

def true_anomaly
  e_rad = deg_to_rad(eccentric_anomaly)
  y = Math.sqrt(1 - eccentricity ** 2) * Math.sin(e_rad)
  x = Math.cos(e_rad) - eccentricity

  # atan2(y, x) で正確な位相（-pi から pi）を求める
  rad_to_deg(Math.atan2(y, x))
end

#velocity ⇒ Object 



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# File 'lib/korba/orbit_utils.rb', line 40

def velocity
  Math.sqrt(Constant::GME * (2.0 / distance - 1.0 / semi_major_axis))
end