279 lines
5.4 KiB
C
279 lines
5.4 KiB
C
#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <math.h>
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#include <getopt.h>
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#include "sgdp4h.h"
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#include "satutl.h"
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#define LIM 128
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#define XKMPER 6378.135 /* Km per earth radii */
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#define XMNPDA 1440.0 /* Minutes per day */
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#define AE 1.0 /* Earth radius in "chosen units". */
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#define XKE 0.743669161e-1
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#define CK2 5.413080e-4 /* (0.5 * XJ2 * AE * AE) */
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extern double SGDP4_jd0;
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// Compute Julian Day from Date
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double date2mjd(int year,int month,double day)
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{
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int a,b;
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double jd;
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if (month<3) {
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year--;
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month+=12;
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}
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a=floor(year/100.);
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b=2.-a+floor(a/4.);
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if (year<1582) b=0;
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if (year==1582 && month<10) b=0;
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if (year==1582 && month==10 && day<=4) b=0;
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jd=floor(365.25*(year+4716))+floor(30.6001*(month+1))+day+b-1524.5;
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return jd-2400000.5;
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}
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// nfd2mjd
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double nfd2mjd(char *date)
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{
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int year,month,day,hour,min,sec;
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double mjd,dday;
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sscanf(date,"%04d-%02d-%02dT%02d:%02d:%02d",&year,&month,&day,&hour,&min,&sec);
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dday=day+hour/24.0+min/1440.0+sec/86400.0;
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mjd=date2mjd(year,month,dday);
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return mjd;
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}
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// Return x modulo y [0,y)
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double modulo(double x,double y)
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{
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x=fmod(x,y);
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if (x<0.0) x+=y;
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return x;
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}
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// DOY to MJD
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double doy2mjd(int year,double doy)
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{
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int month,k=2;
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double day;
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if (year%4==0 && year%400!=0)
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k=1;
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month=floor(9.0*(k+doy)/275.0+0.98);
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if (doy<32)
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month=1;
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day=doy-floor(275.0*month/9.0)+k*floor((month+9.0)/12.0)+30.0;
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return date2mjd(year,month,day);
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}
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// Greenwich Mean Sidereal Time
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double gmst(double mjd)
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{
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double t,gmst;
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t=(mjd-51544.5)/36525.0;
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gmst=modulo(280.46061837+360.98564736629*(mjd-51544.5)+t*t*(0.000387933-t/38710000),360.0);
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return gmst;
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}
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// Compute Date from Julian Day
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void mjd2date(double mjd,int *year,int *month,double *day)
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{
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double f,jd;
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int z,alpha,a,b,c,d,e;
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jd=mjd+2400000.5;
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jd+=0.5;
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z=floor(jd);
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f=fmod(jd,1.);
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if (z<2299161)
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a=z;
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else {
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alpha=floor((z-1867216.25)/36524.25);
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a=z+1+alpha-floor(alpha/4.);
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}
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b=a+1524;
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c=floor((b-122.1)/365.25);
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d=floor(365.25*c);
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e=floor((b-d)/30.6001);
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*day=b-d-floor(30.6001*e)+f;
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if (e<14)
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*month=e-1;
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else
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*month=e-13;
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if (*month>2)
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*year=c-4716;
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else
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*year=c-4715;
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return;
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}
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// MJD to DOY
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double mjd2doy(double mjd,int *yr)
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{
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int year,month,k=2;
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double day,doy;
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mjd2date(mjd,&year,&month,&day);
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if (year%4==0 && year%400!=0)
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k=1;
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doy=floor(275.0*month/9.0)-k*floor((month+9.0)/12.0)+day-30;
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*yr=year;
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return doy;
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}
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// Format TLE
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void format_tle(orbit_t orb,char *line1,char *line2)
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{
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int i,csum;
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char sbstar[]=" 00000-0",bstar[13];
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// Format Bstar term
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if (fabs(orb.bstar)>1e-9) {
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sprintf(bstar,"%11.4e",10*orb.bstar);
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sbstar[0] = bstar[0]; sbstar[1] = bstar[1]; sbstar[2] = bstar[3]; sbstar[3] = bstar[4];
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sbstar[4] = bstar[5]; sbstar[5] = bstar[6]; sbstar[6] = bstar[8]; sbstar[7] = bstar[10]; sbstar[8] = '\0';
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}
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// Print lines
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sprintf(line1,"1 %05dU %-8s %2d%012.8f .00000000 00000-0 %8s 0 0",orb.satno,orb.desig,orb.ep_year-2000,orb.ep_day,sbstar);
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sprintf(line2,"2 %05d %8.4f %8.4f %07.0f %8.4f %8.4f %11.8f 0",orb.satno,DEG(orb.eqinc),DEG(orb.ascn),1E7*orb.ecc,DEG(orb.argp),DEG(orb.mnan),orb.rev);
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// Compute checksums
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for (i=0,csum=0;i<strlen(line1);i++) {
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if (isdigit(line1[i]))
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csum+=line1[i]-'0';
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else if (line1[i]=='-')
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csum++;
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}
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sprintf(line1,"%s%d",line1,csum%10);
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for (i=0,csum=0;i<strlen(line2);i++) {
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if (isdigit(line2[i]))
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csum+=line2[i]-'0';
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else if (line2[i]=='-')
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csum++;
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}
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sprintf(line2,"%s%d",line2,csum%10);
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return;
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}
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void usage(void)
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{
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printf("launch tle c:i:t:T:I:d:\n\n");
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printf("-c reference tle\n-i reference satno\n-t reference launch time\n-T launch time\n-I output satno\n-d output desig\n");
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return;
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}
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int main(int argc,char *argv[])
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{
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int arg=0,satno=0,satno1=84001;
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char tlefile[LIM];
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char nfd0[32],nfd1[32];
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char line1[70],line2[70];
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FILE *file;
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orbit_t orb;
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double mjd0,mjd1,h0,h1,dmjd,dh;
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char *env;
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char desig[]="14900A";
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env=getenv("ST_TLEDIR");
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sprintf(tlefile,"%s/classfd.tle",env);
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// Decode options
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while ((arg=getopt(argc,argv,"c:i:t:T:I:d:"))!=-1) {
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switch (arg) {
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case 'c':
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strcpy(tlefile,optarg);
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break;
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case 't':
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strcpy(nfd0,optarg);
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mjd0=nfd2mjd(nfd0);
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break;
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case 'T':
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strcpy(nfd1,optarg);
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mjd1=nfd2mjd(nfd1);
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break;
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case 'i':
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satno=atoi(optarg);
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break;
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case 'I':
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satno1=atoi(optarg);
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break;
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case 'd':
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strcpy(desig,optarg);
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break;
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case 'h':
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usage();
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return 0;
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break;
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default:
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usage();
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return 0;
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}
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}
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// Open file
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file=fopen(tlefile,"rb");
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if (file==NULL)
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fatal_error("File open failed for reading \"%s\"",tlefile);
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// Find elements
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read_twoline(file,satno,&orb);
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fclose(file);
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// Difference between epoch and launch time
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dmjd=doy2mjd(orb.ep_year,orb.ep_day)-mjd0;
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// Difference in RAAN
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orb.ascn=RAD(modulo(gmst(mjd1)-gmst(mjd0)+DEG(orb.ascn),360.0));
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// New epoch
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mjd0=mjd1+dmjd;
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// Format epoch
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orb.ep_day=mjd2doy(mjd0,&orb.ep_year);
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// Update desig
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strcpy(orb.desig,desig);
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orb.satno=satno1;
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// Print output
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format_tle(orb,line1,line2);
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printf("%s\n%s\n",line1,line2);
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return 0;
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}
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