tsatel.c - plan9port - [fork] Plan 9 from user space
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tsatel.c (3832B)
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1 #include "astro.h"
2
3 char* satlst[] =
4 {
5 0
6 };
7
8 struct
9 {
10 double time;
11 double tilt;
12 double pnni;
13 double psi;
14 double ppi;
15 double d1pp;
16 double peri;
17 double d1per;
18 double e0;
19 double deo;
20 double rdp;
21 double st;
22 double ct;
23 double rot;
24 double semi;
25 } satl;
26
27 void
28 satels(void)
29 {
30 double ifa[10], t, t1, t2, tinc;
31 char **satp;
32 int flag, f, i, n;
33
34 satp = satlst;
35
36 loop:
37 if(*satp == 0)
38 return;
39 f = open(*satp, 0);
40 if(f < 0) {
41 fprint(2, "cannot open %s\n", *satp);
42 satp += 2;
43 goto loop;
44 }
45 satp++;
46 rline(f);
47 tinc = atof(skip(6));
48 rline(f);
49 rline(f);
50 for(i=0; i<9; i++)
51 ifa[i] = atof(skip(i));
52 n = ifa[0];
53 i = ifa[1];
54 t = dmo[i-1] + ifa[2] - 1.;
55 if(n%4 == 0 && i > 2)
56 t += 1.;
57 for(i=1970; i<n; i++) {
58 t += 365.;
59 if(i%4 == 0)
60 t += 1.;
61 }
62 t = (t * 24. + ifa[3]) * 60. + ifa[4];
63 satl.time = t * 60.;
64 satl.tilt = ifa[5] * radian;
65 satl.pnni = ifa[6] * radian;
66 satl.psi = ifa[7];
67 satl.ppi = ifa[8] * radian;
68 rline(f);
69 for(i=0; i<5; i++)
70 ifa[i] = atof(skip(i));
71 satl.d1pp = ifa[0] * radian;
72 satl.peri = ifa[1];
73 satl.d1per = ifa[2];
74 satl.e0 = ifa[3];
75 satl.deo = 0;
76 satl.rdp = ifa[4];
77
78 satl.st = sin(satl.tilt);
79 satl.ct = cos(satl.tilt);
80 satl.rot = pipi / (1440. + satl.psi);
81 satl.semi = satl.rdp * (1. + satl.e0);
82
83 n = PER*288.; /* 5 min steps */
84 t = day;
85 for(i=0; i<n; i++) {
86 if(sunel((t-day)/deld) > 0.)
87 goto out;
88 satel(t);
89 if(el > 0) {
90 t1 = t;
91 flag = 0;
92 do {
93 if(el > 30.)
94 flag++;
95 t -= tinc/(24.*3600.);
96 satel(t);
97 } while(el > 0.);
98 t2 = (t - day)/deld;
99 t = t1;
100 do {
101 t += tinc/(24.*3600.);
102 satel(t);
103 if(el > 30.)
104 flag++;
105 } while(el > 0.);
106 if(flag)
107 if((*satp)[0] == '-')
108 event("%s pass at ", (*satp)+1, "",
109 t2, SIGNIF+PTIME+DARK); else
110 event("%s pass at ", *satp, "",
111 t2, PTIME+DARK);
112 }
113 out:
114 t += 5./(24.*60.);
115 }
116 close(f);
117 satp++;
118 goto loop;
119 }
120
121 void
122 satel(double time)
123 {
124 int i;
125 double amean, an, coc, csl, d, de, enom, eo;
126 double pp, q, rdp, slong, ssl, t, tp;
127
128 i = 500;
129 el = -1;
130 time = (time-25567.5) * 86400;
131 t = (time - satl.time)/60;
132 if(t < 0)
133 return; /* too early for satelites */
134 an = floor(t/satl.peri);
135 while(an*satl.peri + an*an*satl.d1per/2. <= t) {
136 an += 1;
137 if(--i == 0)
138 return;
139 }
140 while((tp = an*satl.peri + an*an*satl.d1per/2.) > t) {
141 an -= 1;
142 if(--i == 0)
143 return;
144 }
145 amean = (t-tp)/(satl.peri+(an+.5)*satl.d1per);
146 pp = satl.ppi+(an+amean)*satl.d1pp;
147 amean *= pipi;
148 eo = satl.e0+satl.deo*an;
149 rdp = satl.semi/(1+eo);
150 enom = amean+eo*sin(amean);
151 do {
152 de = (amean-enom+eo*sin(enom))/(1.0-eo*cos(enom));
153 enom += de;
154 if(--i == 0)
155 return;
156 } while(fabs(de) >= 1.0e-6);
157 q = 3963.35*erad/(rdp*(1-eo*cos(enom))/(1-eo));
158 d = pp + 2*atan2(sqrt((1+eo)/(1-eo))*sin(enom/2),cos(enom/2));
159 slong = satl.pnni + t*satl.rot -
160 atan2(satl.ct*sin(d), cos(d));
161 ssl = satl.st*sin(d);
162 csl = pyth(ssl);
163 if(vis(time, atan2(ssl,csl), slong, q)) {
164 coc = ssl*sin(glat) + csl*cos(glat)*cos(wlong-slong);
165 el = atan2(coc-q, pyth(coc));
166 el /= radian;
167 }
168 }
169
170 int
171 vis(double t, double slat, double slong, double q)
172 {
173 double t0, t1, t2, d;
174
175 d = t/86400 - .005375 + 3653;
176 t0 = 6.238030674 + .01720196977*d;
177 t2 = t0 + .0167253303*sin(t0);
178 do {
179 t1 = (t0 - t2 + .0167259152*sin(t2)) /
180 (1 - .0167259152*cos(t2));
181 t2 = t2 + t1;
182 } while(fabs(t1) >= 1.e-4);
183 t0 = 2*atan2(1.01686816*sin(t2/2), cos(t2/2));
184 t0 = 4.926234925 + 8.214985538e-7*d + t0;
185 t1 = 0.91744599 * sin(t0);
186 t0 = atan2(t1, cos(t0));
187 if(t0 < -pi/2)
188 t0 = t0 + pipi;
189 d = 4.88097876 + 6.30038809*d - t0;
190 t0 = 0.43366079 * t1;
191 t1 = pyth(t0);
192 t2 = t1*cos(slat)*cos(d-slong) - t0*sin(slat);
193 if(t2 > 0.46949322e-2) {
194 if(0.46949322e-2*t2 + 0.999988979*pyth(t2) < q)
195 return 0;
196 }
197 t2 = t1*cos(glat)*cos(d-wlong) - t0*sin(glat);
198 if(t2 < .1)
199 return 0;
200 return 1;
201 }