Class: Orbit::OrbitGlobals

Inherits:
Object
  • Object
show all
Defined in:
lib/orbit/orbit_globals.rb

Constant Summary collapse

PI = 
3.141592653589793
TWO_PI = 
2.0 * OrbitGlobals::PI
RADS_PER_DEGREE = 
OrbitGlobals::PI / 180.0
DEGREES_PER_RAD = 
180.0 / OrbitGlobals::PI
GM =

Earth gravitational constant, km^3/sec^2

398601.2
GEO_SYNC_ALT =

km

42241.892
EARTHDIAM =

km

12800.0
DAYSIDEREAL =

sec

(23 * 3600) + (56 * 60) + 4.09
DAYSOLAR =

sec

(24 * 3600.0)
AE = 
1.0
AU =

Astronomical unit (km) (IAU 76)

149597870.0
SR =

Solar radius (km) (IAU 76)

696000.0
XKMPER =

Earth equatorial radius - kilometers (WGS ‘72)

6378.135
F =

Earth flattening (WGS ‘72)

1.0 / 298.26
GE =

Earth gravitational constant (WGS ‘72)

398600.8
J2 =

J2 harmonic (WGS ‘72)

1.0826158E-3
J3 =

J3 harmonic (WGS ‘72)

-2.53881E-6  # J3 harmonic (WGS '72)
J4 =

J4 harmonic (WGS ‘72)

-1.65597E-6  # J4 harmonic (WGS '72)
CK2 = 
OrbitGlobals::J2 / 2.0
CK4 = 
-3.0 * OrbitGlobals::J4 / 8.0
XJ3 = 
OrbitGlobals::J3
QO = 
OrbitGlobals::AE + 120.0 / OrbitGlobals::XKMPER
S = 
OrbitGlobals::AE + 78.0  / OrbitGlobals::XKMPER
MIN_PER_DAY =

Minutes per day (solar)

1440.0
SEC_PER_DAY =

Seconds per day (solar)

86400.0
OMEGAE =

Earth rotation per sidereal day

1.00273790934
XKE = 
Math.sqrt(3600.0 * OrbitGlobals::GE /
(OrbitGlobals::XKMPER * OrbitGlobals::XKMPER * OrbitGlobals::XKMPER))
QOMS2T =

(QO - S)^4 ER^4

((OrbitGlobals::QO - OrbitGlobals::S) ** 4.0)

Class Method Summary collapse

Class Method Details

.actan(sinx, cosx) ⇒ Object

// ///////////////////////////////////////////////////////////////////////////

// Globals.AcTan()
// ArcTangent of sin(x) / cos(x). The advantage of this function over arctan()
// is that it returns the correct quadrant of the angle.



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# File 'lib/orbit/orbit_globals.rb', line 65

def self.actan( sinx,  cosx)
  ret = nil

  if (cosx == 0.0)
     if (sinx > 0.0)
        ret = PI / 2.0
     else
        ret = 3.0 * PI / 2.0
    end
  else
     if (cosx > 0.0)
        ret = Math.atan(sinx / cosx)
     else
        ret = PI + Math.atan(sinx / cosx)
      end
    end

  return ret
end

.deg_to_rad(deg) ⇒ Object 



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# File 'lib/orbit/orbit_globals.rb', line 42

def self.deg_to_rad( deg )
  deg * RADS_PER_DEGREE;
end

.fmod2p(arg) ⇒ Object 



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# File 'lib/orbit/orbit_globals.rb', line 51

def self.fmod2p(arg)
  modu = (arg % TWO_PI);

  if (modu < 0.0)
     modu += TWO_PI
   end

  return modu
end

.rad_to_deg(rad) ⇒ Object 



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# File 'lib/orbit/orbit_globals.rb', line 46

def self.rad_to_deg( rad )
  rad * DEGREES_PER_RAD;
end

.sqr(n) ⇒ Object 



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# File 'lib/orbit/orbit_globals.rb', line 38

def self.sqr( n )
  n ** 2
end

.time_to_gmst(t) ⇒ Object 



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# File 'lib/orbit/orbit_globals.rb', line 85

def self.time_to_gmst(t)
  jd = t.to_date.jd - 0.5
  seconds = (t.hour * 3600) + (t.min * 60) + (t.sec).to_f + (t.subsec).to_f
  fraction_of_day = seconds / 86400.0

  jd += fraction_of_day

  #puts "jd: #{jd}"

  ut = (jd + 0.5 ) % 1.0;
  jd = jd - ut
  tu = (jd - 2451545.0) / 36525.0
  gmst = 24110.54841 + tu * (8640184.812866 + tu * (0.093104 - tu * 6.2E-6));
  gmst =  ( gmst + 86400.0 * 1.00273790934 * ut ) % 86400.0
  if (gmst < 0.0)
    gmst += 86400.0 # "wrap" negative modulo value
  end

  gmst = (OrbitGlobals::TWO_PI * (gmst / 86400.0))

  # puts "gmst: #{gmst}"

  gmst
end

.time_to_lmst(t, lon) ⇒ Object

///////////////////////////////////////////////////////////////////// ToLmst() Calculate Local Mean Sidereal Time for given longitude (for this date). The longitude is assumed to be in radians measured west from Greenwich. The return value is the angle, in radians, measuring eastward from the Vernal Equinox to the given longitude.



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# File 'lib/orbit/orbit_globals.rb', line 116

def self.time_to_lmst (t, lon)
  gmst = OrbitGlobals.time_to_gmst( t )
  lmst = ( gmst + lon ) % TWO_PI

  # puts "long: #{lon}"
  # puts "gmst: #{gmst}"
  # puts "lmst: #{lmst}"

  lmst
end