Method: Orbit::Eci#setup

Defined in:
lib/orbit/eci.rb

#setup(geo, date) ⇒ Object 



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# File 'lib/orbit/eci.rb', line 25

def setup( geo, date )
# puts "Eci.setup( geo, #{date} )"
   mfactor = OrbitGlobals::TWO_PI * (OrbitGlobals::OMEGAE / OrbitGlobals::SEC_PER_DAY)
   lat = geo.latitude_rad
   lon = geo.longitude_rad
   alt = geo.altitude

   # Calculate Local Mean Sidereal Time (theta)
   theta = OrbitGlobals.time_to_lmst( date, lon )
   c = 1.0 / Math.sqrt(1.0 + OrbitGlobals::F * (OrbitGlobals::F - 2.0) * OrbitGlobals::sqr(Math.sin(lat)))
   s = ((1.0 - OrbitGlobals::F) ** 2 ) * c
   achcp = (OrbitGlobals::XKMPER * c + alt) * Math.cos(lat)

   @m_Date = date
   @m_Position = Vector.new()

   @m_Position.m_x = achcp * Math.cos(theta)                    # km
   @m_Position.m_y = achcp * Math.sin(theta)                    # km
   @m_Position.m_z = (OrbitGlobals::XKMPER * s + alt) * Math.sin(lat) # km
   @m_Position.m_w = Math.sqrt(OrbitGlobals::sqr(@m_Position.m_x) +
      OrbitGlobals::sqr(@m_Position.m_y) +
      OrbitGlobals::sqr(@m_Position.m_z))            # range, km

   @m_Velocity = Vector.new()

   @m_Velocity.m_x = -mfactor * @m_Position.m_y               # km / sec
   @m_Velocity.m_y =  mfactor * @m_Position.m_x
   @m_Velocity.m_z = 0.0
   @m_Velocity.m_w = Math.sqrt(OrbitGlobals::sqr(@m_Velocity.m_x) +  # range rate km/sec^2
      OrbitGlobals::sqr(@m_Velocity.m_y))
end