302 lines
6.3 KiB
C
302 lines
6.3 KiB
C
#include <stdio.h>
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#include <string.h>
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#include <math.h>
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#include <stdlib.h>
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#include <ctype.h>
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#include "sgdp4h.h"
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#include "satutl.h"
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#include <getopt.h>
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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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#define R2D 180.0/M_PI
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#define D2R M_PI/180.0
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extern double SGDP4_jd0;
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void orbit(orbit_t orb,float *aodp,float *perigee,float *apogee,float *period);
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void format_tle(orbit_t orb,char *line1,char *line2);
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double mjd2doy(double mjd,int *yr);
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double nfd2mjd(char *date);
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double date2mjd(int year,int month,double day);
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void mjd2date(double mjd,int *year,int *month,double *day);
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double gmst(double mjd);
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double modulo(double x,double y);
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void usage(void)
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{
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printf("faketle q:Q:i:I:w:t:m:n:d:\n\n");
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printf("-q Perigee altitude (km)\n");
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printf("-Q Apogee altitude (km)\n");
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printf("-I Orbital inclination (deg)\n");
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printf("-n RA of the ascending node (deg)\n");
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printf("-w Argument of perigee (deg)\n");
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printf("-m Mean anomaly (deg)\n");
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printf("-t Epoch (YYYY-mm-ddThh:mm:ss)\n");
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printf("-i Satellite number\n");
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printf("-d Time offset from epoch (s)\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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orbit_t orb;
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float aodp,perigee,apogee,period,dt=0.0;
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char line1[70],line2[70];
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int arg=0;
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double mjd,dh;
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// Initialize
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orb.satno=99999;
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orb.eqinc=0.0;
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orb.ascn=0.0;
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orb.argp=0.0;
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orb.mnan=0.0;
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orb.bstar=0.5e-4;
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orb.ep_day=1.000;
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orb.ep_year=2013;
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// Decode options
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while ((arg=getopt(argc,argv,"q:Q:i:I:w:t:m:n:hd:"))!=-1) {
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switch(arg) {
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case 'q':
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perigee=atof(optarg);
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break;
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case 'Q':
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apogee=atof(optarg);
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break;
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case 'I':
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orb.eqinc=atof(optarg)*D2R;
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break;
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case 'n':
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orb.ascn=atof(optarg)*D2R;
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break;
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case 'i':
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orb.satno=atoi(optarg);
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break;
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case 'w':
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orb.argp=atof(optarg)*D2R;
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break;
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case 'm':
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orb.mnan=atof(optarg)*D2R;
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break;
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case 't':
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mjd=nfd2mjd(optarg);
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break;
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case 'd':
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dt=atof(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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default:
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usage();
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return 0;
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}
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}
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orb.ep_day=mjd2doy(mjd+dt/86400.0,&orb.ep_year);
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perigee+=XKMPER;
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apogee+=XKMPER;
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aodp=0.5*(perigee+apogee)/XKMPER;
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orb.ecc=0.5*(apogee-perigee)/(aodp*XKMPER);
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orb.rev=XKE*pow(aodp,-1.5)*XMNPDA/(2.0*M_PI);
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if (orb.rev<10)
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orb.bstar=0.0;
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orbit(orb,&aodp,&perigee,&apogee,&period);
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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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void orbit(orbit_t orb,float *aodp,float *perigee,float *apogee,float *period)
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{
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float xno,eo,xincl;
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float a1,betao2,betao,temp0,del1,a0,del0,xnodp;
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xno=orb.rev*2.0*M_PI/XMNPDA;
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eo=orb.ecc;
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xincl=orb.eqinc;
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a1 = pow(XKE / xno, 2.0/3.0);
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betao2 = 1.0 - eo * eo;
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betao = sqrt(betao2);
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temp0 = (1.5 * CK2) * cos(xincl)*cos(xincl) / (betao * betao2);
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del1 = temp0 / (a1 * a1);
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a0 = a1 * (1.0 - del1 * (1.0/3.0 + del1 * (1.0 + del1 * 134.0/81.0)));
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del0 = temp0 / (a0 * a0);
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xnodp = xno / (1.0 + del0);
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*aodp = (a0 / (1.0 - del0));
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*perigee = (*aodp * (1.0 - eo) - 1) * XKMPER;
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*apogee = (*aodp * (1.0 + eo) - 1) * XKMPER;
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*period = (TWOPI * 1440.0 / XMNPDA) / xnodp;
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*aodp=(*aodp-1)*XKMPER;
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return;
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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 %2d%012.8f .00000000 00000-0 %8s 0 0",orb.satno,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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// 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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// 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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// 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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// 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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// 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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// 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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