419 lines
8.3 KiB
C
419 lines
8.3 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 <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 LIM 1024
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#define XKE 0.07436680 // Guassian Gravitational Constant
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#define XKMPER 6378.135
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#define AE 1.0
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#define XMNPDA 1440.0
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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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// Dot product
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float dot(xyz_t a,xyz_t b)
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{
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return a.x*b.x+a.y*b.y+a.z*b.z;
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}
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// Magnitude
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double magnitude(xyz_t a)
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{
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return sqrt(dot(a,a));
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}
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// Cross product
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xyz_t cross(xyz_t a,xyz_t b)
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{
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xyz_t c;
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c.x=a.y*b.z-a.z*b.y;
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c.y=a.z*b.x-a.x*b.z;
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c.z=a.x*b.y-a.y*b.x;
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return c;
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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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// 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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// Clasical elements
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orbit_t classel(int ep_year,double ep_day,xyz_t r,xyz_t v)
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{
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int i;
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double rm,vm,vm2,rvm,mu=1.0;;
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double chi,xp,yp,sx,cx,b,ee;
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double a,ecc,incl,node,peri,mm,n;
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xyz_t h,e,kk,nn;
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orbit_t orb;
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r.x/=XKMPER;
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r.y/=XKMPER;
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r.z/=XKMPER;
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v.x/=(XKE*XKMPER/AE*XMNPDA/86400.0);
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v.y/=(XKE*XKMPER/AE*XMNPDA/86400.0);
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v.z/=(XKE*XKMPER/AE*XMNPDA/86400.0);
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rm=magnitude(r);
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vm2=dot(v,v);
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rvm=dot(r,v);
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h=cross(r,v);
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chi=dot(h,h)/mu;
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e.x=(vm2/mu-1.0/rm)*r.x-rvm/mu*v.x;
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e.y=(vm2/mu-1.0/rm)*r.y-rvm/mu*v.y;
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e.z=(vm2/mu-1.0/rm)*r.z-rvm/mu*v.z;
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a=pow(2.0/rm-vm2/mu,-1);
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ecc=magnitude(e);
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incl=acos(h.z/magnitude(h))*R2D;
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kk.x=0.0;
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kk.y=0.0;
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kk.z=1.0;
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nn=cross(kk,h);
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if (nn.x==0.0 && nn.y==0.0)
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nn.x=1.0;
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node=atan2(nn.y,nn.x)*R2D;
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if (node<0.0)
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node+=360.0;
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peri=acos(dot(nn,e)/(magnitude(nn)*ecc))*R2D;
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if (e.z<0.0)
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peri=360.0-peri;
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if (peri<0.0)
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peri+=360.0;
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// Elliptic motion
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if (ecc<1.0) {
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xp=(chi-rm)/ecc;
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yp=rvm/ecc*sqrt(chi/mu);
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b=a*sqrt(1.0-ecc*ecc);
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cx=xp/a+ecc;
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sx=yp/b;
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ee=atan2(sx,cx);
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n=XKE*sqrt(mu/(a*a*a));
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mm=(ee-ecc*sx)*R2D;
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}
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if (mm<0.0)
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mm+=360.0;
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// Fill
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orb.satno=0;
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orb.eqinc=incl*D2R;
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orb.ascn=node*D2R;
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orb.argp=peri*D2R;
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orb.mnan=mm*D2R;
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orb.ecc=ecc;
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orb.rev=XKE*pow(a,-3.0/2.0)*XMNPDA/(2.0*M_PI);
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orb.bstar=0.0;
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orb.ep_year=ep_year;
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orb.ep_day=ep_day;
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orb.norb=0;
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return orb;
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}
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orbit_t rv2el(int satno,double mjd,xyz_t r0,xyz_t v0)
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{
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int i,imode;
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orbit_t orb[5],orb1[5];
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xyz_t r,v;
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kep_t kep;
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char line1[70],line2[70];
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int ep_year;
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double ep_day;
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// Epoch
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ep_day=mjd2doy(mjd,&ep_year);
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// Initial guess
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orb[0]=classel(ep_year,ep_day,r0,v0);
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orb[0].satno=satno;
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for (i=0;i<5;i++) {
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// Propagate
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imode=init_sgdp4(&orb[i]);
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imode=satpos_xyz(mjd+2400000.5,&r,&v);
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// Compute initial orbital elements
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orb1[i]=classel(ep_year,ep_day,r,v);
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// Adjust
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orb[i+1].rev=orb[i].rev+orb[0].rev-orb1[i].rev;
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orb[i+1].ascn=orb[i].ascn+orb[0].ascn-orb1[i].ascn;
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orb[i+1].argp=orb[i].argp+orb[0].argp-orb1[i].argp;
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orb[i+1].mnan=orb[i].mnan+orb[0].mnan-orb1[i].mnan;
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orb[i+1].eqinc=orb[i].eqinc+orb[0].eqinc-orb1[i].eqinc;
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orb[i+1].ecc=orb[i].ecc+orb[0].ecc-orb1[i].ecc;
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orb[i+1].ep_year=orb[i].ep_year;
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orb[i+1].ep_day=orb[i].ep_day;
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orb[i+1].satno=orb[i].satno;
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orb[i+1].norb=orb[i].norb;
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orb[i+1].bstar=orb[i].bstar;
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// Keep in range
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if (orb[i+1].ecc<0.0)
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orb[i+1].ecc=0.0;
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if (orb[i+1].eqinc<0.0)
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orb[i+1].eqinc=0.0;
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}
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orb[i].mnan=modulo(orb[i].mnan,2.0*M_PI);
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orb[i].ascn=modulo(orb[i].ascn,2.0*M_PI);
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orb[i].argp=modulo(orb[i].argp,2.0*M_PI);
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return orb[i];
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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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// Present nfd
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void nfd_now(char *s)
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{
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time_t rawtime;
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struct tm *ptm;
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// Get UTC time
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time(&rawtime);
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ptm=gmtime(&rawtime);
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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);
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return;
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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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// 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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void usage(void)
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{
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printf("Usage: rv2tle -p XYZFILE [- i NORADID] [-d COSPARID] [-g] [-h]\n\n");
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printf("Arguments:\n");
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printf("-p XYZFILE File with cartesian position and velocity vector\n");
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printf(" Format: '{mjd} {x} {y} {z} {vx} {vy} {vz}'\n");
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printf(" Units: position in km, velocity in km/s\n");
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printf("-i NORADID Satellite Catalog Number (NORAD ID), default: 99000\n");
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printf("-d COSPARID International Designator (COSPAR ID), default: 14999A\n");
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printf("-g Use non-standard / GMAT's Modified Julian Date\n");
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printf("-h This help\n");
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return;
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}
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// Read a line of maximum length int lim from file FILE into string s
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int fgetline(FILE *file,char *s,int lim)
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{
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int c,i=0;
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while (--lim > 0 && (c=fgetc(file)) != EOF && c != '\n')
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s[i++] = c;
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if (c == '\n')
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s[i++] = c;
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s[i] = '\0';
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return i;
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}
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int main(int argc,char *argv[])
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{
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int imode,satno=99000,arg,gmat=0;
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FILE *file;
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orbit_t orb;
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xyz_t r,v;
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char xyzfile[LIM],nfd[32],line[LIM];
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char line1[80],line2[80],desig[20]="14999A";
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double mjd;
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char *env;
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// Decode options
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while ((arg=getopt(argc,argv,"p:i:d:gh"))!=-1) {
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switch (arg) {
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case 'p':
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strcpy(xyzfile,optarg);
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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 'd':
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strcpy(desig,optarg);
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break;
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case 'g':
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gmat=1;
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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(xyzfile,"r");
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while (fgetline(file,line,LIM)>0) {
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sscanf(line,"%lf %lf %lf %lf %lf %lf %lf",&mjd,&r.x,&r.y,&r.z,&v.x,&v.y,&v.z);
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// Convert to MJD
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if (gmat==1)
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mjd+=29999.5;
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// Convert
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orb=rv2el(orb.satno,mjd,r,v);
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orb.satno=satno;
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strcpy(orb.desig,desig);
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format_tle(orb,line1,line2);
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printf("%s\n%s\n",line1,line2);
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satno++;
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}
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fclose(file);
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return 0;
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}
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