ref: dc96f164a2b72ccb209ae98ce50a11087cbe44f8
dir: /sys/src/cmd/astro/satel.c/
#include "astro.h"
char* satlst[] =
{
0,
};
struct
{
double time;
double tilt;
double pnni;
double psi;
double ppi;
double d1pp;
double peri;
double d1per;
double e0;
double deo;
double rdp;
double st;
double ct;
double rot;
double semi;
} satl;
void
satels(void)
{
double ifa[10], t, t1, t2, tinc;
char **satp;
int flag, f, i, n;
satp = satlst;
loop:
if(*satp == 0)
return;
f = open(*satp, 0);
if(f < 0) {
fprint(2, "cannot open %s\n", *satp);
satp += 2;
goto loop;
}
satp++;
rline(f);
tinc = atof(skip(6));
rline(f);
rline(f);
for(i=0; i<9; i++)
ifa[i] = atof(skip(i));
n = ifa[0];
i = ifa[1];
t = dmo[i-1] + ifa[2] - 1.;
if(n%4 == 0 && i > 2)
t += 1.;
for(i=1970; i<n; i++) {
t += 365.;
if(i%4 == 0)
t += 1.;
}
t = (t * 24. + ifa[3]) * 60. + ifa[4];
satl.time = t * 60.;
satl.tilt = ifa[5] * radian;
satl.pnni = ifa[6] * radian;
satl.psi = ifa[7];
satl.ppi = ifa[8] * radian;
rline(f);
for(i=0; i<5; i++)
ifa[i] = atof(skip(i));
satl.d1pp = ifa[0] * radian;
satl.peri = ifa[1];
satl.d1per = ifa[2];
satl.e0 = ifa[3];
satl.deo = 0;
satl.rdp = ifa[4];
satl.st = sin(satl.tilt);
satl.ct = cos(satl.tilt);
satl.rot = pipi / (1440. + satl.psi);
satl.semi = satl.rdp * (1. + satl.e0);
n = PER*288.; /* 5 min steps */
t = day;
for(i=0; i<n; i++) {
if(sunel((t-day)/deld) > 0.)
goto out;
satel(t);
if(el > 0) {
t1 = t;
flag = 0;
do {
if(el > 30.)
flag++;
t -= tinc/(24.*3600.);
satel(t);
} while(el > 0.);
t2 = (t - day)/deld;
t = t1;
do {
t += tinc/(24.*3600.);
satel(t);
if(el > 30.)
flag++;
} while(el > 0.);
if(flag)
if((*satp)[0] == '-')
event("%s pass at ", (*satp)+1, "",
t2, SIGNIF+PTIME+DARK); else
event("%s pass at ", *satp, "",
t2, PTIME+DARK);
}
out:
t += 5./(24.*60.);
}
close(f);
satp++;
goto loop;
}
void
satel(double time)
{
int i;
double amean, an, coc, csl, d, de, enom, eo;
double pp, q, rdp, slong, ssl, t, tp;
i = 500;
el = -1;
time = (time-25567.5) * 86400;
t = (time - satl.time)/60;
if(t < 0)
return; /* too early for satelites */
an = floor(t/satl.peri);
while(an*satl.peri + an*an*satl.d1per/2. <= t) {
an += 1;
if(--i == 0)
return;
}
while((tp = an*satl.peri + an*an*satl.d1per/2.) > t) {
an -= 1;
if(--i == 0)
return;
}
amean = (t-tp)/(satl.peri+(an+.5)*satl.d1per);
pp = satl.ppi+(an+amean)*satl.d1pp;
amean *= pipi;
eo = satl.e0+satl.deo*an;
rdp = satl.semi/(1+eo);
enom = amean+eo*sin(amean);
do {
de = (amean-enom+eo*sin(enom))/(1.0-eo*cos(enom));
enom += de;
if(--i == 0)
return;
} while(fabs(de) >= 1.0e-6);
q = 3963.35*erad/(rdp*(1-eo*cos(enom))/(1-eo));
d = pp + 2*atan2(sqrt((1+eo)/(1-eo))*sin(enom/2),cos(enom/2));
slong = satl.pnni + t*satl.rot -
atan2(satl.ct*sin(d), cos(d));
ssl = satl.st*sin(d);
csl = pyth(ssl);
if(vis(time, atan2(ssl,csl), slong, q)) {
coc = ssl*sin(glat) + csl*cos(glat)*cos(wlong-slong);
el = atan2(coc-q, pyth(coc));
el /= radian;
}
}
int
vis(double t, double slat, double slong, double q)
{
double t0, t1, t2, d;
d = t/86400 - .005375 + 3653;
t0 = 6.238030674 + .01720196977*d;
t2 = t0 + .0167253303*sin(t0);
do {
t1 = (t0 - t2 + .0167259152*sin(t2)) /
(1 - .0167259152*cos(t2));
t2 = t2 + t1;
} while(fabs(t1) >= 1.e-4);
t0 = 2*atan2(1.01686816*sin(t2/2), cos(t2/2));
t0 = 4.926234925 + 8.214985538e-7*d + t0;
t1 = 0.91744599 * sin(t0);
t0 = atan2(t1, cos(t0));
if(t0 < -pi/2)
t0 = t0 + pipi;
d = 4.88097876 + 6.30038809*d - t0;
t0 = 0.43366079 * t1;
t1 = pyth(t0);
t2 = t1*cos(slat)*cos(d-slong) - t0*sin(slat);
if(t2 > 0.46949322e-2) {
if(0.46949322e-2*t2 + 0.999988979*pyth(t2) < q)
return 0;
}
t2 = t1*cos(glat)*cos(d-wlong) - t0*sin(glat);
if(t2 < .1)
return 0;
return 1;
}