-
Notifications
You must be signed in to change notification settings - Fork 41
/
sgp.cpp
169 lines (154 loc) · 4.64 KB
/
sgp.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
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
132
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
/* Copyright (C) 2018, Project Pluto. See LICENSE. */
#include <math.h>
#include "norad.h"
#include "norad_in.h"
#define ao params[0]
#define qo params[1]
#define xlo params[2]
#define d1o params[3]
#define d2o params[4]
#define d3o params[5]
#define d4o params[6]
#define omgdt params[7]
#define xnodot params[8]
#define c5 params[9]
#define c6 params[10]
void DLL_FUNC SGP_init( double *params, const tle_t *tle)
{
double c1, c2, c3, c4, r1, cosio, sinio, a1, d1, po, po2no;
c1 = ck2*1.5;
c2 = ck2/4.;
c3 = ck2/2.;
r1 = ae;
c4 = xj3*(r1*(r1*r1))/(ck2*4.);
cosio = cos(tle->xincl);
sinio = sin(tle->xincl);
a1 = pow( xke / tle->xno, two_thirds);
d1 = c1/a1/a1*(cosio*3.*cosio-1.)/pow( 1.-tle->eo*tle->eo, 1.5);
ao = a1*(1.-d1*.33333333333333331-d1*d1-d1*
1.654320987654321*d1*d1);
po = ao*(1.-tle->eo*tle->eo);
qo = ao*(1.-tle->eo);
xlo = tle->xmo+tle->omegao+tle->xnodeo;
d1o = c3*sinio*sinio;
d2o = c2*(cosio*7.*cosio-1.);
d3o = c1*cosio;
d4o = d3o*sinio;
po2no = tle->xno/(po*po);
omgdt = c1*po2no*(cosio*5.*cosio-1.);
xnodot = d3o*-2.*po2no;
c5 = c4*.5*sinio*(cosio*5.+3.)/(cosio+1.);
c6 = c4*sinio;
}
int DLL_FUNC SGP( const double tsince, const tle_t *tle, const double *params,
double *pos, double *vel)
{
double
temp, rdot, cosu, sinu, cos2u, sin2u, a, e,
p, rr, u, ecose, esine, omgas, cosik, xinck,
sinik, axnsl, aynsl,
sinuk, rvdot, cosuk, coseo1, sineo1, pl,
rk, uk, xl, su, ux, uy, uz, vx, vy, vz, pl2,
xnodek, cosnok, xnodes, el2, eo1, r1, sinnok,
xls, xmx, xmy, tem2, tem5;
const double chicken_factor_on_eccentricity = 1.e-6;
int i, rval = 0;
/* Update for secular gravity and atmospheric drag */
a = tle->xno+(tle->xndt2o*2.+tle->xndd6o*3.*tsince)*tsince;
if( a < 0.)
rval = SXPX_ERR_NEGATIVE_MAJOR_AXIS;
e = e6a;
if( e > 1. - chicken_factor_on_eccentricity)
rval = SXPX_ERR_NEARLY_PARABOLIC;
if( rval)
{
for( i = 0; i < 3; i++)
{
pos[i] = 0.;
if( vel)
vel[i] = 0.;
}
return( rval);
}
a = ao * pow( tle->xno / a, two_thirds);
if( a * (1. - e) < 1. && a * (1. + e) < 1.) /* entirely within earth */
rval = SXPX_WARN_ORBIT_WITHIN_EARTH; /* remember, e can be negative */
if( a * (1. - e) < 1. || a * (1. + e) < 1.) /* perigee within earth */
rval = SXPX_WARN_PERIGEE_WITHIN_EARTH;
if (a > qo) e = 1.-qo/a;
p = a*(1.-e*e);
xnodes = tle->xnodeo+xnodot*tsince;
omgas = tle->omegao+omgdt*tsince;
r1 = xlo+(tle->xno+omgdt+xnodot+
(tle->xndt2o+tle->xndd6o*tsince)*tsince)*tsince;
xls = FMod2p(r1);
/* Long period periodics */
axnsl = e*cos(omgas);
aynsl = e*sin(omgas)-c6/p;
r1 = xls-c5/p*axnsl;
xl = FMod2p(r1);
/* Solve Kepler's equation */
r1 = xl-xnodes;
u = FMod2p(r1);
eo1 = u;
tem5 = 1.;
i = 0;
do
{
sineo1 = sin(eo1);
coseo1 = cos(eo1);
if (fabs(tem5) < e6a) break;
tem5 = 1.-coseo1*axnsl-sineo1*aynsl;
tem5 = (u-aynsl*coseo1+axnsl*sineo1-eo1)/tem5;
tem2 = fabs(tem5);
if (tem2 > 1.) tem5 = tem2/tem5;
eo1 += tem5;
}
while(i++ < 10);
/* Short period preliminary quantities */
ecose = axnsl*coseo1+aynsl*sineo1;
esine = axnsl*sineo1-aynsl*coseo1;
el2 = axnsl*axnsl+aynsl*aynsl;
pl = a*(1.-el2);
pl2 = pl*pl;
rr = a*(1.-ecose);
rdot = xke*sqrt(a)/rr*esine;
rvdot = xke*sqrt(pl)/rr;
temp = esine/(sqrt(1.-el2)+1.);
sinu = a/rr*(sineo1-aynsl-axnsl*temp);
cosu = a/rr*(coseo1-axnsl+aynsl*temp);
su = atan2(sinu, cosu);
/* Update for short periodics */
sin2u = (cosu+cosu)*sinu;
cos2u = 1.-2.*sinu*sinu;
rk = rr+d1o/pl*cos2u;
uk = su-d2o/pl2*sin2u;
xnodek = xnodes+d3o*sin2u/pl2;
xinck = tle->xincl+d4o/pl2*cos2u;
/* Orientation vectors */
sinuk = sin(uk);
cosuk = cos(uk);
sinnok = sin(xnodek);
cosnok = cos(xnodek);
sinik = sin(xinck);
cosik = cos(xinck);
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 and velocity */
pos[0] = rk*ux*earth_radius_in_km;
pos[1] = rk*uy*earth_radius_in_km;
pos[2] = rk*uz*earth_radius_in_km;
if( vel)
{
vel[0] = (rdot*ux + rvdot * vx)*earth_radius_in_km;
vel[1] = (rdot*uy + rvdot * vy)*earth_radius_in_km;
vel[2] = (rdot*uz + rvdot * vz)*earth_radius_in_km;
}
return( rval);
} /* SGP */