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 }