Class: Orbit::NoradBase

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

Direct Known Subclasses

NoradSGP4

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(nothing) ⇒ NoradBase

Returns a new instance of NoradBase.



39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
 
# File 'lib/orbit/norad_base.rb', line 39

def initialize( nothing )
  # Initialize any variables which are time-independent when
  # calculating the ECI coordinates of the satellite.
  @m_satInc = @orbit.inclination
  @m_satEcc = @orbit.eccentricity

  @m_cosio  = Math.cos(@m_satInc)
  @m_theta2 = @m_cosio * @m_cosio
  @m_x3thm1 = 3.0 * @m_theta2 - 1.0
  @m_eosq   = @m_satEcc * @m_satEcc
  @m_betao2 = 1.0 - @m_eosq
  @m_betao  = Math.sqrt(@m_betao2)

  # The "recovered" semimajor axis and mean motion.
  @m_aodp  = @orbit.semi_major
  @m_xnodp = @orbit.mean_motion

  # For perigee below 156 km, the values of OrbitGlobals::S and OrbitGlobals::QOMS2T are altered.
  @m_perigee = OrbitGlobals::XKMPER * (@m_aodp * (1.0 - @m_satEcc) - OrbitGlobals::AE)

  @m_s4      = OrbitGlobals::S
  @m_qoms24  = OrbitGlobals::QOMS2T

  if (@m_perigee < 156.0)
     @m_s4 = @m_perigee - 78.0

     if (@m_perigee <= 98.0)
        @m_s4 = 20.0
      end

     @m_qoms24 = (((120.0 - @m_s4) * OrbitGlobals::AE / OrbitGlobals::XKMPER ) ** 4.0)
     @m_s4 = @m_s4 / OrbitGlobals::XKMPER + OrbitGlobals::AE
   end

  pinvsq = 1.0 / (@m_aodp * @m_aodp * @m_betao2 * @m_betao2)

  @m_tsi   = 1.0 / (@m_aodp - @m_s4)
  @m_eta   = @m_aodp * @m_satEcc * @m_tsi
  @m_etasq = @m_eta * @m_eta
  @m_eeta  = @m_satEcc * @m_eta

  psisq  = (1.0 - @m_etasq).abs

  @m_coef  = @m_qoms24 * (@m_tsi ** 4.0)
  @m_coef1 = @m_coef / (psisq ** 3.5)

  c2 = @m_coef1 * @m_xnodp *
              (@m_aodp * (1.0 + 1.5 * @m_etasq + @m_eeta * (4.0 + @m_etasq)) +
              0.75 * OrbitGlobals::CK2 * @m_tsi / psisq * @m_x3thm1 *
              (8.0 + 3.0 * @m_etasq * (8.0 + @m_etasq)))

  @m_c1    = @orbit.bstar * c2
  @m_sinio = Math.sin(@m_satInc)

  a3ovk2 = -OrbitGlobals::XJ3 / OrbitGlobals::CK2 * (OrbitGlobals::AE ** 3.0)

  @m_c3     = @m_coef * @m_tsi * a3ovk2 * @m_xnodp * OrbitGlobals::AE * @m_sinio / @m_satEcc
  @m_x1mth2 = 1.0 - @m_theta2
  @m_c4     = 2.0 * @m_xnodp * @m_coef1 * @m_aodp * @m_betao2 *
             (@m_eta * (2.0 + 0.5 * @m_etasq) +
             @m_satEcc * (0.5 + 2.0 * @m_etasq) -
             2.0 * OrbitGlobals::CK2 * @m_tsi / (@m_aodp * psisq) *
             (-3.0 * @m_x3thm1 * (1.0 - 2.0 * @m_eeta + @m_etasq * (1.5 - 0.5 * @m_eeta)) +
             0.75 * @m_x1mth2 *
             (2.0 * @m_etasq - @m_eeta * (1.0 + @m_etasq)) *
             Math.cos(2.0 * @orbit.arg_perigee)))

  theta4 = @m_theta2 * @m_theta2
  temp1  = 3.0 * OrbitGlobals::CK2 * pinvsq * @m_xnodp
  temp2  = temp1 * OrbitGlobals::CK2 * pinvsq
  temp3  = 1.25 * OrbitGlobals::CK4 * pinvsq * pinvsq * @m_xnodp

  @m_xmdot = @m_xnodp + 0.5 * temp1 * @m_betao * @m_x3thm1 +
            0.0625 * temp2 * @m_betao *
            (13.0 - 78.0 * @m_theta2 + 137.0 * theta4)

  x1m5th = 1.0 - 5.0 * @m_theta2

  @m_omgdot = -0.5 * temp1 * x1m5th + 0.0625 * temp2 *
             (7.0 - 114.0 * @m_theta2 + 395.0 * theta4) +
             temp3 * (3.0 - 36.0 * @m_theta2 + 49.0 * theta4)

  xhdot1 = -temp1 * @m_cosio

  @m_xnodot = xhdot1 + (0.5 * temp2 * (4.0 - 19.0 * @m_theta2) +
             2.0 * temp3 * (3.0 - 7.0 * @m_theta2)) * @m_cosio
  @m_xnodcf = 3.5 * @m_betao2 * xhdot1 * @m_c1
  @m_t2cof  = 1.5 * @m_c1
  @m_xlcof  = 0.125 * a3ovk2 * @m_sinio *
             (3.0 + 5.0 * @m_cosio) / (1.0 + @m_cosio)
  @m_aycof  = 0.25 * a3ovk2 * @m_sinio
  @m_x7thm1 = 7.0 * @m_theta2 - 1.0
end

Instance Attribute Details

#m_aodp ⇒ Object

Returns the value of attribute m_aodp.



24
25
26
 
# File 'lib/orbit/norad_base.rb', line 24

def m_aodp
  @m_aodp
end

#m_aycof ⇒ Object

Returns the value of attribute m_aycof.



14
15
16
 
# File 'lib/orbit/norad_base.rb', line 14

def m_aycof
  @m_aycof
end

#m_betao ⇒ Object

Returns the value of attribute m_betao.



31
32
33
 
# File 'lib/orbit/norad_base.rb', line 31

def m_betao
  @m_betao
end

#m_betao2 ⇒ Object

Returns the value of attribute m_betao2.



8
9
10
 
# File 'lib/orbit/norad_base.rb', line 8

def m_betao2
  @m_betao2
end

#m_c1 ⇒ Object

Returns the value of attribute m_c1.



34
35
36
 
# File 'lib/orbit/norad_base.rb', line 34

def m_c1
  @m_c1
end

#m_c3 ⇒ Object

Returns the value of attribute m_c3.



27
28
29
 
# File 'lib/orbit/norad_base.rb', line 27

def m_c3
  @m_c3
end

#m_c4 ⇒ Object

Returns the value of attribute m_c4.



20
21
22
 
# File 'lib/orbit/norad_base.rb', line 20

def m_c4
  @m_c4
end

#m_coef ⇒ Object

Returns the value of attribute m_coef.



19
20
21
 
# File 'lib/orbit/norad_base.rb', line 19

def m_coef
  @m_coef
end

#m_coef1 ⇒ Object

Returns the value of attribute m_coef1.



11
12
13
 
# File 'lib/orbit/norad_base.rb', line 11

def m_coef1
  @m_coef1
end

#m_cosio ⇒ Object

Returns the value of attribute m_cosio.



7
8
9
 
# File 'lib/orbit/norad_base.rb', line 7

def m_cosio
  @m_cosio
end

#m_eeta ⇒ Object

Returns the value of attribute m_eeta.



26
27
28
 
# File 'lib/orbit/norad_base.rb', line 26

def m_eeta
  @m_eeta
end

#m_eosq ⇒ Object

Returns the value of attribute m_eosq.



16
17
18
 
# File 'lib/orbit/norad_base.rb', line 16

def m_eosq
  @m_eosq
end

#m_eta ⇒ Object

Returns the value of attribute m_eta.



10
11
12
 
# File 'lib/orbit/norad_base.rb', line 10

def m_eta
  @m_eta
end

#m_etasq ⇒ Object

Returns the value of attribute m_etasq.



33
34
35
 
# File 'lib/orbit/norad_base.rb', line 33

def m_etasq
  @m_etasq
end

#m_omgdot ⇒ Object

Returns the value of attribute m_omgdot.



21
22
23
 
# File 'lib/orbit/norad_base.rb', line 21

def m_omgdot
  @m_omgdot
end

#m_perigee ⇒ Object

Returns the value of attribute m_perigee.



25
26
27
 
# File 'lib/orbit/norad_base.rb', line 25

def m_perigee
  @m_perigee
end

#m_qoms24 ⇒ Object

Returns the value of attribute m_qoms24.



32
33
34
 
# File 'lib/orbit/norad_base.rb', line 32

def m_qoms24
  @m_qoms24
end

#m_s4 ⇒ Object

Returns the value of attribute m_s4.



9
10
11
 
# File 'lib/orbit/norad_base.rb', line 9

def m_s4
  @m_s4
end

#m_satEcc ⇒ Object

eccentricity



5
6
7
 
# File 'lib/orbit/norad_base.rb', line 5

def m_satEcc
  @m_satEcc
end

#m_satInc ⇒ Object

inclination



4
5
6
 
# File 'lib/orbit/norad_base.rb', line 4

def m_satInc
  @m_satInc
end

#m_sinio ⇒ Object

Returns the value of attribute m_sinio.



12
13
14
 
# File 'lib/orbit/norad_base.rb', line 12

def m_sinio
  @m_sinio
end

#m_t2cof ⇒ Object

Returns the value of attribute m_t2cof.



29
30
31
 
# File 'lib/orbit/norad_base.rb', line 29

def m_t2cof
  @m_t2cof
end

#m_theta2 ⇒ Object

Returns the value of attribute m_theta2.



30
31
32
 
# File 'lib/orbit/norad_base.rb', line 30

def m_theta2
  @m_theta2
end

#m_tsi ⇒ Object

Returns the value of attribute m_tsi.



18
19
20
 
# File 'lib/orbit/norad_base.rb', line 18

def m_tsi
  @m_tsi
end

#m_x1mth2 ⇒ Object

Returns the value of attribute m_x1mth2.



35
36
37
 
# File 'lib/orbit/norad_base.rb', line 35

def m_x1mth2
  @m_x1mth2
end

#m_x3thm1 ⇒ Object

Returns the value of attribute m_x3thm1.



23
24
25
 
# File 'lib/orbit/norad_base.rb', line 23

def m_x3thm1
  @m_x3thm1
end

#m_x7thm1 ⇒ Object

Returns the value of attribute m_x7thm1.



37
38
39
 
# File 'lib/orbit/norad_base.rb', line 37

def m_x7thm1
  @m_x7thm1
end

#m_xlcof ⇒ Object

Returns the value of attribute m_xlcof.



22
23
24
 
# File 'lib/orbit/norad_base.rb', line 22

def m_xlcof
  @m_xlcof
end

#m_xmdot ⇒ Object

Returns the value of attribute m_xmdot.



28
29
30
 
# File 'lib/orbit/norad_base.rb', line 28

def m_xmdot
  @m_xmdot
end

#m_xnodcf ⇒ Object

Returns the value of attribute m_xnodcf.



36
37
38
 
# File 'lib/orbit/norad_base.rb', line 36

def m_xnodcf
  @m_xnodcf
end

#m_xnodot ⇒ Object

Returns the value of attribute m_xnodot.



13
14
15
 
# File 'lib/orbit/norad_base.rb', line 13

def m_xnodot
  @m_xnodot
end

#m_xnodp ⇒ Object

Returns the value of attribute m_xnodp.



17
18
19
 
# File 'lib/orbit/norad_base.rb', line 17

def m_xnodp
  @m_xnodp
end

Instance Method Details

#final_position(incl, omega, e, a, xl, xnode, xn, tsince) ⇒ Object 



133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
 
# File 'lib/orbit/norad_base.rb', line 133

def final_position( incl, omega,      e,
                               a,    xl,  xnode,
                              xn, tsince)
  if (e * e) > 1.0
    Exception.new( "Error in satellite data" )
     #throw new PropagationException("Error in satellite data")
   end

  beta = Math.sqrt(1.0 - e * e)

  # Long period periodics
  axn  = e * Math.cos(omega)
  temp = 1.0 / (a * beta * beta)
  xll  = temp * @m_xlcof * axn
  aynl = temp * @m_aycof
  xlt  = xl + xll
  ayn  = e * Math.sin(omega) + aynl

  # Solve Kepler's Equation
  capu   = OrbitGlobals::fmod2p(xlt - xnode)
  temp2  = capu
  temp3  = 0.0
  temp4  = 0.0
  temp5  = 0.0
  temp6  = 0.0
  sinepw = 0.0
  cosepw = 0.0

  fDone  = false
  i = 1
  while i <= 10 && !fDone do
  #for (int i = 1 (i <= 10) && !fDone i++)
     sinepw = Math.sin(temp2)
     cosepw = Math.cos(temp2)
     temp3 = axn * sinepw
     temp4 = ayn * cosepw
     temp5 = axn * cosepw
     temp6 = ayn * sinepw

     epw = (capu - temp4 + temp3 - temp2) /
                  (1.0 - temp5 - temp6) + temp2

     if ((epw - temp2).abs <= 1.0e-06)
       fDone = true
     else
      temp2 = epw
     end

     i += 1
   end

  # Short period preliminary quantities
  ecose = temp5 + temp6
  esine = temp3 - temp4
  elsq  = axn * axn + ayn * ayn
  temp  = 1.0 - elsq
  pl = a * temp
  r  = a * (1.0 - ecose)
  temp1 = 1.0 / r
  rdot  = OrbitGlobals::XKE * Math.sqrt(a) * esine * temp1
  rfdot = OrbitGlobals::XKE * Math.sqrt(pl) * temp1
  temp2 = a * temp1
  betal = Math.sqrt(temp)
  temp3 = 1.0 / (1.0 + betal)
  cosu  = temp2 * (cosepw - axn + ayn * esine * temp3)
  sinu  = temp2 * (sinepw - ayn - axn * esine * temp3)
  u     = OrbitGlobals.actan(sinu, cosu)
  sin2u = 2.0 * sinu * cosu
  cos2u = 2.0 * cosu * cosu - 1.0

  temp  = 1.0 / pl
  temp1 = OrbitGlobals::CK2 * temp
  temp2 = temp1 * temp

  # Update for short periodics
  rk = r * (1.0 - 1.5 * temp2 * betal * @m_x3thm1) +
              0.5 * temp1 * @m_x1mth2 * cos2u
  uk = u - 0.25 * temp2 * @m_x7thm1 * sin2u
  xnodek = xnode + 1.5 * temp2 * @m_cosio * sin2u
  xinck  = incl + 1.5 * temp2 * @m_cosio * @m_sinio * cos2u
  rdotk  = rdot - xn * temp1 * @m_x1mth2 * sin2u
  rfdotk = rfdot + xn * temp1 * (@m_x1mth2 * cos2u + 1.5 * @m_x3thm1)

  # Orientation vectors
  sinuk  = Math.sin(uk)
  cosuk  = Math.cos(uk)
  sinik  = Math.sin(xinck)
  cosik  = Math.cos(xinck)
  sinnok = Math.sin(xnodek)
  cosnok = Math.cos(xnodek)
  xmx = -sinnok * cosik
  xmy = cosnok * cosik
  ux  = xmx * sinuk + cosnok * cosuk
  uy  = xmy * sinuk + sinnok * cosuk
  uz  = sinik * sinuk
  vx  = xmx * cosuk - cosnok * sinuk
  vy  = xmy * cosuk - sinnok * sinuk
  vz  = sinik * cosuk

  # Position
  x = rk * ux
  y = rk * uy
  z = rk * uz

  vecPos = Vector.new(x, y, z)

  # puts "@orbit.epoch_time : #{@orbit.epoch_time}"

  gmt = @orbit.epoch_time  + ( tsince * 60.0 )

  # Validate on altitude
  altKm = (vecPos.magnitude * (OrbitGlobals::XKMPER / OrbitGlobals::AE))

  if (altKm < OrbitGlobals::XKMPER)
     Exception.new( "Decay Exception" )
     #throw new DecayException(gmt, @orbit.SatNameLong)
   end

  # Velocity
  xdot = rdotk * ux + rfdotk * vx
  ydot = rdotk * uy + rfdotk * vy
  zdot = rdotk * uz + rfdotk * vz

 vecVel = Vector.new(xdot, ydot, zdot)

  return Eci.new_with_pos_vel_gmt(vecPos, vecVel, gmt)
end