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satpredict
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satpredict/satpredict.c

472 lines
11 KiB
C
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <getopt.h>
#include "sgdp4h.h"
#define LIM 256
#define NMAX 16
#define D2R M_PI/180.0
#define R2D 180.0/M_PI
#define XKMPER 6378.135 // Earth radius in km
#define XKMPAU 149597879.691 // AU in km
#define FLAT (1.0/298.257)
long Isat=0;
long Isatsel=0;
extern double SGDP4_jd0;
struct map {
double lat,lng;
float alt;
char observer[32];
int site_id;
} m;
struct point {
double mjd;
xyz_t obspos,sunpos;
double zeta,z,theta;
} *p;
double modulo(double,double);
void obspos_xyz(double,xyz_t *,xyz_t *);
void sunpos_xyz(double,xyz_t *);
double gmst(double);
double dgmst(double);
void precession_angles(double mjd0,double mjd,double *zeta,double *z,double *theta);
double nfd2mjd(char *date);
double date2mjd(int year,int month,double day);
// Compute Julian Day from Date
double date2mjd(int year,int month,double day)
{
int a,b;
double jd;
if (month<3) {
year--;
month+=12;
}
a=floor(year/100.);
b=2.-a+floor(a/4.);
if (year<1582) b=0;
if (year==1582 && month<10) b=0;
if (year==1582 && month==10 && day<=4) b=0;
jd=floor(365.25*(year+4716))+floor(30.6001*(month+1))+day+b-1524.5;
return jd-2400000.5;
}
// nfd2mjd
double nfd2mjd(char *date)
{
int year,month,day,hour,min;
float sec;
double mjd,dday;
sscanf(date,"%04d-%02d-%02dT%02d:%02d:%f",&year,&month,&day,&hour,&min,&sec);
dday=day+hour/24.0+min/1440.0+sec/86400.0;
mjd=date2mjd(year,month,dday);
return mjd;
}
// Greenwich Mean Sidereal Time
double gmst(double mjd)
{
double t,gmst;
t=(mjd-51544.5)/36525.0;
gmst=modulo(280.46061837+360.98564736629*(mjd-51544.5)+t*t*(0.000387933-t/38710000),360.0);
return gmst;
}
// Greenwich Mean Sidereal Time
double dgmst(double mjd)
{
double t,dgmst;
t=(mjd-51544.5)/36525.0;
dgmst=360.98564736629+t*(0.000387933-t/38710000);
return dgmst;
}
// Return x modulo y [0,y)
double modulo(double x,double y)
{
x=fmod(x,y);
if (x<0.0) x+=y;
return x;
}
// Observer position
void obspos_xyz(double mjd,xyz_t *pos,xyz_t *vel)
{
double ff,gc,gs,theta,s,dtheta;
s=sin(m.lat*D2R);
ff=sqrt(1.0-FLAT*(2.0-FLAT)*s*s);
gc=1.0/ff+m.alt/XKMPER;
gs=(1.0-FLAT)*(1.0-FLAT)/ff+m.alt/XKMPER;
theta=gmst(mjd)+m.lng;
dtheta=dgmst(mjd)*D2R/86400;
pos->x=gc*cos(m.lat*D2R)*cos(theta*D2R)*XKMPER;
pos->y=gc*cos(m.lat*D2R)*sin(theta*D2R)*XKMPER;
pos->z=gs*sin(m.lat*D2R)*XKMPER;
vel->x=-gc*cos(m.lat*D2R)*sin(theta*D2R)*XKMPER*dtheta;
vel->y=gc*cos(m.lat*D2R)*cos(theta*D2R)*XKMPER*dtheta;
vel->z=0.0;
return;
}
// Solar position
void sunpos_xyz(double mjd,xyz_t *pos)
{
double jd,t,l0,m,e,c,r;
double n,s,ecl,ra,de;
jd=mjd+2400000.5;
t=(jd-2451545.0)/36525.0;
l0=modulo(280.46646+t*(36000.76983+t*0.0003032),360.0)*D2R;
m=modulo(357.52911+t*(35999.05029-t*0.0001537),360.0)*D2R;
e=0.016708634+t*(-0.000042037-t*0.0000001267);
c=(1.914602+t*(-0.004817-t*0.000014))*sin(m)*D2R;
c+=(0.019993-0.000101*t)*sin(2.0*m)*D2R;
c+=0.000289*sin(3.0*m)*D2R;
r=1.000001018*(1.0-e*e)/(1.0+e*cos(m+c));
n=modulo(125.04-1934.136*t,360.0)*D2R;
s=l0+c+(-0.00569-0.00478*sin(n))*D2R;
ecl=(23.43929111+(-46.8150*t-0.00059*t*t+0.001813*t*t*t)/3600.0+0.00256*cos(n))*D2R;
ra=atan2(cos(ecl)*sin(s),cos(s));
de=asin(sin(ecl)*sin(s));
pos->x=r*cos(de)*cos(ra)*XKMPAU;
pos->y=r*cos(de)*sin(ra)*XKMPAU;
pos->z=r*sin(de)*XKMPAU;
return;
}
// Compute precession angles
void precession_angles(double mjd0,double mjd,double *zeta,double *z,double *theta)
{
double t0,t;
// Time in centuries
t0=(mjd0-51544.5)/36525.0;
t=(mjd-mjd0)/36525.0;
// Precession angles
*zeta=(2306.2181+1.39656*t0-0.000139*t0*t0)*t;
*zeta+=(0.30188-0.000344*t0)*t*t+0.017998*t*t*t;
*zeta*=D2R/3600.0;
*z=(2306.2181+1.39656*t0-0.000139*t0*t0)*t;
*z+=(1.09468+0.000066*t0)*t*t+0.018203*t*t*t;
*z*=D2R/3600.0;
*theta=(2004.3109-0.85330*t0-0.000217*t0*t0)*t;
*theta+=-(0.42665+0.000217*t0)*t*t-0.041833*t*t*t;
*theta*=D2R/3600.0;
return;
}
void compute_positions(char *tlefile,FILE *file,double ra0,double de0,double radius,int nmjd)
{
int i,imode;
orbit_t orb;
FILE *fp=NULL;
xyz_t satpos,satvel;
double dx,dy,dz,r,ra,de,d,rsun,rearth;
double psun,pearth,ptot;
double a,b,c,age;
char state[16];
// Open TLE file
fp=fopen(tlefile,"rb");
if (fp==NULL) {
printf("Error: TLE catalog %s not found, skipping\n",tlefile);
return;
}
// Read TLEs
while (read_twoline(fp,0,&orb)==0) {
Isat=orb.satno;
imode=init_sgdp4(&orb);
// Skip on error
if (imode==SGDP4_ERROR)
continue;
// Loop over times
for (i=0;i<nmjd;i++) {
// Satellite position
satpos_xyz(p[i].mjd+2400000.5,&satpos,&satvel);
// Check on radius
r=sqrt(satpos.x*satpos.x+satpos.y*satpos.y+satpos.z*satpos.z);
if (r>300000)
continue;
// Relative to observer
dx=satpos.x-p[i].obspos.x;
dy=satpos.y-p[i].obspos.y;
dz=satpos.z-p[i].obspos.z;
// Celestial position
r=sqrt(dx*dx+dy*dy+dz*dz);
ra=modulo(atan2(dy,dx),2.0*M_PI);
de=asin(dz/r);
// Correct for precession
a=cos(de)*sin(ra+p[i].zeta);
b=cos(p[i].theta)*cos(de)*cos(ra+p[i].zeta)-sin(p[i].theta)*sin(de);
c=sin(p[i].theta)*cos(de)*cos(ra+p[i].zeta)+cos(p[i].theta)*sin(de);
ra=modulo((atan2(a,b)+p[i].z)*R2D,360.0);
de=asin(c)*R2D;
// Check if nearby enough
r=acos(sin(de0*D2R)*sin(de*D2R)+cos(de0*D2R)*cos(de*D2R)*cos((ra0-ra)*D2R))*R2D;
if (r>radius)
continue;
// Satellite position relative to the Sun
dx=-satpos.x+p[i].sunpos.x;
dy=-satpos.y+p[i].sunpos.y;
dz=-satpos.z+p[i].sunpos.z;
// Distances
rsun=sqrt(dx*dx+dy*dy+dz*dz);
rearth=sqrt(satpos.x*satpos.x+satpos.y*satpos.y+satpos.z*satpos.z);
// Angles
psun=asin(696.0e3/rsun)*R2D;
pearth=asin(6378.135/rearth)*R2D;
ptot=acos((-dx*satpos.x-dy*satpos.y-dz*satpos.z)/(rsun*rearth))*R2D;
// Visibility state
if (ptot-pearth<-psun) {
strcpy(state,"eclipsed");
} else if (ptot-pearth>-psun && ptot-pearth<psun) {
strcpy(state,"umbra");
} else if (ptot-pearth>psun) {
strcpy(state,"sunlit");
}
// TLE age
age=p[i].mjd+2400000.5-SGDP4_jd0;
fprintf(file,"%05d,%s,%014.8lf,%010.6lf,%+010.6lf,%s,%s,%.3f\n",orb.satno,orb.desig,p[i].mjd,ra,de,state,tlefile,age);
}
}
fclose(fp);
return;
}
// Present nfd
void nfd_now(char *s)
{
time_t rawtime;
struct tm *ptm;
// Get UTC time
time(&rawtime);
ptm=gmtime(&rawtime);
sprintf(s,"%04d-%02d-%02dT%02d:%02d:%02d",ptm->tm_year+1900,ptm->tm_mon+1,ptm->tm_mday,ptm->tm_hour,ptm->tm_min,ptm->tm_sec);
return;
}
void usage()
{
printf("Usage: satpredict [OPTION]\n");
printf("Compute satellite predictions.\n\n");
printf("-t, --time date/time (yyyy-mm-ddThh:mm:ss.sss) [default: now]\n");
printf("-l, --length length (s) [default: 10s]\n");
printf("-n, --num number of points [default: 10]\n");
printf("-c, --catalog TLE catalog file [default: classfd.tle]\n");
printf("-R, --ra R.A. (deg) [default: 0.0 deg]\n");
printf("-D, --decl Decl. (deg) [default: 0.0 deg]\n");
printf("-r, --radius radius (deg) [default: 10.0 deg]\n");
printf("-L, --longitude manual site longitude (deg) [default: 0.0 deg]\n");
printf("-B, --latitude manual site latitude (deg) [default: 0.0 deg]\n");
printf("-H, --height manual site elevation (m) [default: 0.0 m]\n");
printf("-o, --output output csv file [default: results.csv]\n");
printf("-h, --help this help\n");
return;
}
int main(int argc,char *argv[])
{
int i,arg=0,nmjd=10,ntlefile=0;
char nfd[32]="",outfile[LIM]="results.csv";
char tlefile[NMAX][LIM];
float length=10.0;
double ra0=0.0,de0=0.0,radius=10.0;
double mjd0,t;
xyz_t obsvel;
FILE *file;
// Redirect stderr
freopen("/tmp/stderr.txt","w",stderr);
// Default options
nfd_now(nfd);
strcpy(tlefile[0],"classfd.tle");
// Decode options
if (argc>1) {
int c;
while (1)
{
static struct option long_options[] = {
{"time", required_argument, 0, 't'},
{"length", required_argument, 0, 'l'},
{"num", required_argument, 0, 'n'},
{"catalog", required_argument, 0, 'c'},
{"ra", required_argument, 0, 'R'},
{"decl", required_argument, 0, 'D'},
{"radius", required_argument, 0, 'r'},
{"longitude", required_argument, 0, 'L'},
{"latitude", required_argument, 0, 'B'},
{"height", required_argument, 0, 'H'},
{"output", no_argument, 0, 'o'},
{"help", no_argument, 0, 'h'},
{0, 0, 0, 0}
};
int option_index = 0;
c =
getopt_long (argc, argv,
"t:l:n:c:R:D:r:L:B:H:o:",
long_options, &option_index);
if (c == -1)
break;
switch (c)
{
case 0:
if (long_options[option_index].flag != 0)
break;
printf ("option %s", long_options[option_index].name);
if (optarg)
printf (" with arg %s", optarg);
printf ("\n");
break;
case 't':
strcpy(nfd,optarg);
mjd0=nfd2mjd(nfd);
break;
case 'l':
length=atof(optarg);
break;
case 'n':
nmjd=atoi(optarg);
break;
case 'c':
if (ntlefile==NMAX) {
printf("Error: Maximum number of TLE catalog files reached [%d]\n",NMAX);
return -1;
}
// strcpy(tlefile[ntlefile++],optarg);
snprintf(tlefile[ntlefile++],LIM-1,"%s",optarg);
break;
case 'o':
strcpy(outfile,optarg);
break;
case 'R':
ra0=(double) atof(optarg);
break;
case 'D':
de0=(double) atof(optarg);
break;
case 'r':
radius=(double) atof(optarg);
break;
case 'L':
m.lng=atof(optarg);
break;
case 'B':
m.lat=atof(optarg);
break;
case 'H':
m.alt=atof(optarg)/1000.0;
break;
default:
usage();
return 0;
}
}
} else {
usage();
return 0;
}
// Allocate
p=(struct point *) malloc(sizeof(struct point)*nmjd);
// Decode MJD
mjd0=nfd2mjd(nfd);
// Initialize
for (i=0;i<nmjd;i++) {
// Compute time
t=length*(float) i/(float) (nmjd-1);
p[i].mjd=mjd0+t/86400.0;
// Compute observer and sun position
obspos_xyz(p[i].mjd,&p[i].obspos,&obsvel);
sunpos_xyz(p[i].mjd,&p[i].sunpos);
// Compute precession angles
precession_angles(p[i].mjd,51544.5,&p[i].zeta,&p[i].z,&p[i].theta);
}
// Open output file
file=fopen(outfile,"w");
fprintf(file,"satno,cospar,mjd,ra,dec,state,tlefile,age\n");
// Compute positions
for (i=0;i<ntlefile;i++)
compute_positions(tlefile[i],file,ra0,de0,radius,nmjd);
// Close output file
fclose(file);
// Free
free(p);
// Close
fclose(stderr);
return 0;
}
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