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sattools/xyz2tle.c

709 lines
14 KiB
C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <getopt.h>
#include <ctype.h>
#include "sgdp4h.h"
#include "satutl.h"
#define LIM 80
#define NMAX 256
#define D2R M_PI/180.0
#define R2D 180.0/M_PI
#define XKE 0.07436680 // Guassian Gravitational Constant
#define XKMPER 6378.135
#define AE 1.0
#define XMNPDA 1440.0
struct data {
int n,nsel;
struct point *p;
double chisq,rms;
} d;
struct point {
int flag;
double mjd;
xyz_t r;
};
orbit_t orb;
void versafit(int m,int n,double *a,double *da,double (*func)(double *),double dchisq,double tol,char *opt);
// Dot product
float dot(xyz_t a,xyz_t b)
{
return a.x*b.x+a.y*b.y+a.z*b.z;
}
// Magnitude
double magnitude(xyz_t a)
{
return sqrt(dot(a,a));
}
// Cross product
xyz_t cross(xyz_t a,xyz_t b)
{
xyz_t c;
c.x=a.y*b.z-a.z*b.y;
c.y=a.z*b.x-a.x*b.z;
c.z=a.x*b.y-a.y*b.x;
return c;
}
// Return x modulo y [0,y)
double modulo(double x,double y)
{
x=fmod(x,y);
if (x<0.0) x+=y;
return x;
}
// 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;
}
// Read a line of maximum length int lim from file FILE into string s
int fgetline(FILE *file,char *s,int lim)
{
int c,i=0;
while (--lim > 0 && (c=fgetc(file)) != EOF && c != '\n')
s[i++] = c;
if (c == '\t')
c=' ';
if (c == '\n')
s[i++] = c;
s[i] = '\0';
return i;
}
// Format TLE
void format_tle(orbit_t orb,char *line1,char *line2)
{
int i,csum;
char sbstar[]=" 00000-0",bstar[13];
// Format Bstar term
if (fabs(orb.bstar)>1e-9) {
sprintf(bstar,"%11.4e",10*orb.bstar);
sbstar[0] = bstar[0]; sbstar[1] = bstar[1]; sbstar[2] = bstar[3]; sbstar[3] = bstar[4];
sbstar[4] = bstar[5]; sbstar[5] = bstar[6]; sbstar[6] = bstar[8]; sbstar[7] = bstar[10]; sbstar[8] = '\0';
}
// Print lines
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);
sprintf(line2,"2 %05d %8.4f %8.4f %07.0f %8.4f %8.4f %11.8f%5ld",orb.satno,DEG(orb.eqinc),DEG(orb.ascn),1E7*orb.ecc,DEG(orb.argp),DEG(orb.mnan),orb.rev,orb.norb);
// Compute checksums
for (i=0,csum=0;i<strlen(line1);i++) {
if (isdigit(line1[i]))
csum+=line1[i]-'0';
else if (line1[i]=='-')
csum++;
}
sprintf(line1,"%s%d",line1,csum%10);
for (i=0,csum=0;i<strlen(line2);i++) {
if (isdigit(line2[i]))
csum+=line2[i]-'0';
else if (line2[i]=='-')
csum++;
}
sprintf(line2,"%s%d",line2,csum%10);
return;
}
// Precess a celestial position
void precess(double mjd0,double ra0,double de0,double mjd,double *ra,double *de)
{
double t0,t;
double zeta,z,theta;
double a,b,c;
// Angles in radians
ra0*=D2R;
de0*=D2R;
// 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;
a=cos(de0)*sin(ra0+zeta);
b=cos(theta)*cos(de0)*cos(ra0+zeta)-sin(theta)*sin(de0);
c=sin(theta)*cos(de0)*cos(ra0+zeta)+cos(theta)*sin(de0);
*ra=(atan2(a,b)+z)*R2D;
*de=asin(c)*R2D;
if (*ra<360.0)
*ra+=360.0;
if (*ra>360.0)
*ra-=360.0;
return;
}
// Read data file
struct data read_data(char *filename,double mjd0)
{
int i=0,status;
char line[LIM];
FILE *file;
struct data d;
int min;
double ra,de,ra0,de0,r;
double x,y,z;
// Open file
file=fopen(filename,"r");
if (file==NULL) {
fprintf(stderr,"Failed to open %s\n",filename);
exit(1);
}
// Count lines
while (fgetline(file,line,LIM)>0)
i++;
d.n=i;
// Allocate
d.p=(struct point *) malloc(sizeof(struct point)*d.n);
// Rewind file
rewind(file);
// Read data
i=0;
while (fgetline(file,line,LIM)>0) {
status=sscanf(line,"%d,%lf,%lf,%lf",&min,&x,&y,&z);
if (d.n==1008)
min*=10;
d.p[i].mjd=mjd0+(double) min/1440.0;
// Precess position
r=sqrt(x*x+y*y+z*z);
ra0=atan2(y,x)*R2D;
de0=asin(z/r)*R2D;
precess(51544.5,ra0,de0,d.p[i].mjd,&ra,&de);
d.p[i].r.x=r*cos(de*D2R)*cos(ra*D2R);
d.p[i].r.y=r*cos(de*D2R)*sin(ra*D2R);
d.p[i].r.z=r*sin(de*D2R);
d.p[i].flag=0;
i++;
}
// Close file
fclose(file);
return d;
}
// Read tle
orbit_t read_tle(char *filename,int satno)
{
int i;
FILE *file;
orbit_t orb;
file=fopen(filename,"r");
if (file==NULL)
fatal_error("Failed to open %s\n",filename);
// Read TLE
read_twoline(file,satno,&orb);
fclose(file);
return orb;
}
// Chi-squared
double chisq(double *a)
{
int i,imode,n;
double chisq;
xyz_t satpos,satvel,dr;
// Construct struct
// a[0]: inclination
// a[1]: RA of ascending node
// a[2]: eccentricity
// a[3]: argument of periastron
// a[4]: mean anomaly
// a[5]: revs per day
// a[6]: bstar drag
if (a[2]<0.0)
a[2]=0.0;
if (a[0]<0.0) {
a[0]*=-1;
a[1]+=180.0;
} else if (a[0]>180.0) {
a[0]=180.0;
}
if (a[5]>20.0)
a[5]=20.0;
if (a[5]<0.1)
a[5]=0.1;
// Set parameters
orb.eqinc=RAD(a[0]);
orb.ascn=RAD(modulo(a[1],360.0));
orb.ecc=a[2];
orb.argp=RAD(modulo(a[3],360.0));
orb.mnan=RAD(modulo(a[4],360.0));
orb.rev=a[5];
orb.bstar=a[6];
// Initialize
imode=init_sgdp4(&orb);
if (imode==SGDP4_ERROR)
printf("Error\n");
// Loop over points
for (i=0,chisq=0.0,n=0;i<d.n;i++) {
// Skip unflagged positions
if (d.p[i].flag!=1)
continue;
// Get satellite position
satpos_xyz(d.p[i].mjd+2400000.5,&satpos,&satvel);
dr.x=(satpos.x-d.p[i].r.x);
dr.y=(satpos.y-d.p[i].r.y);
dr.z=(satpos.z-d.p[i].r.z);
// Add
chisq+=dr.x*dr.x+dr.y*dr.y+dr.z*dr.z;
n++;
}
chisq/=(double) n;
d.rms=sqrt(chisq);
d.nsel=n;
return chisq;
}
double decode_filename(char *filename,int *satno)
{
int year,month,day,hour,min,sec;
int status;
double mjd;
status=sscanf(filename,"%6d_%4d%2d%2d_%2d%2d%2d",satno,&year,&month,&day,&hour,&min,&sec);
mjd=date2mjd(year,month,(double) day+hour/24.0+min/1440.0+sec/86400.0);
return mjd;
}
// Compute Date from Julian Day
void mjd2date(double mjd,int *year,int *month,double *day)
{
double f,jd;
int z,alpha,a,b,c,d,e;
jd=mjd+2400000.5;
jd+=0.5;
z=floor(jd);
f=fmod(jd,1.);
if (z<2299161)
a=z;
else {
alpha=floor((z-1867216.25)/36524.25);
a=z+1+alpha-floor(alpha/4.);
}
b=a+1524;
c=floor((b-122.1)/365.25);
d=floor(365.25*c);
e=floor((b-d)/30.6001);
*day=b-d-floor(30.6001*e)+f;
if (e<14)
*month=e-1;
else
*month=e-13;
if (*month>2)
*year=c-4716;
else
*year=c-4715;
return;
}
// MJD to DOY
double mjd2doy(double mjd,int *yr)
{
int year,month,k=2;
double day,doy;
mjd2date(mjd,&year,&month,&day);
if (year%4==0 && year%400!=0)
k=1;
doy=floor(275.0*month/9.0)-k*floor((month+9.0)/12.0)+day-30;
*yr=year;
return doy;
}
// Clasical elements
orbit_t classel(int ep_year,double ep_day,xyz_t r,xyz_t v)
{
int i;
double rm,vm,vm2,rvm,mu=1.0;;
double chi,xp,yp,sx,cx,b,ee;
double a,ecc,incl,node,peri,mm,n;
xyz_t h,e,kk,nn;
orbit_t orb;
r.x/=XKMPER;
r.y/=XKMPER;
r.z/=XKMPER;
v.x/=(XKE*XKMPER/AE*XMNPDA/86400.0);
v.y/=(XKE*XKMPER/AE*XMNPDA/86400.0);
v.z/=(XKE*XKMPER/AE*XMNPDA/86400.0);
rm=magnitude(r);
vm2=dot(v,v);
rvm=dot(r,v);
h=cross(r,v);
chi=dot(h,h)/mu;
e.x=(vm2/mu-1.0/rm)*r.x-rvm/mu*v.x;
e.y=(vm2/mu-1.0/rm)*r.y-rvm/mu*v.y;
e.z=(vm2/mu-1.0/rm)*r.z-rvm/mu*v.z;
a=pow(2.0/rm-vm2/mu,-1);
ecc=magnitude(e);
incl=acos(h.z/magnitude(h))*R2D;
kk.x=0.0;
kk.y=0.0;
kk.z=1.0;
nn=cross(kk,h);
if (nn.x==0.0 && nn.y==0.0)
nn.x=1.0;
node=atan2(nn.y,nn.x)*R2D;
if (node<0.0)
node+=360.0;
peri=acos(dot(nn,e)/(magnitude(nn)*ecc))*R2D;
if (e.z<0.0)
peri=360.0-peri;
if (peri<0.0)
peri+=360.0;
// Elliptic motion
if (ecc<1.0) {
xp=(chi-rm)/ecc;
yp=rvm/ecc*sqrt(chi/mu);
b=a*sqrt(1.0-ecc*ecc);
cx=xp/a+ecc;
sx=yp/b;
ee=atan2(sx,cx);
n=XKE*sqrt(mu/(a*a*a));
mm=(ee-ecc*sx)*R2D;
}
if (mm<0.0)
mm+=360.0;
// Fill
orb.satno=0;
orb.eqinc=incl*D2R;
orb.ascn=node*D2R;
orb.argp=peri*D2R;
orb.mnan=mm*D2R;
orb.ecc=ecc;
orb.rev=XKE*pow(a,-3.0/2.0)*XMNPDA/(2.0*M_PI);
orb.bstar=0.0;
orb.ep_year=ep_year;
orb.ep_day=ep_day;
orb.norb=0;
return orb;
}
// State vector to SGP4 elements
orbit_t rv2el(int satno,double mjd,xyz_t r0,xyz_t v0)
{
int i,imode;
orbit_t orb[5],orb1[5];
xyz_t r,v;
kep_t kep;
char line1[70],line2[70];
int ep_year;
double ep_day;
// Epoch
ep_day=mjd2doy(mjd,&ep_year);
// Initial guess
orb[0]=classel(ep_year,ep_day,r0,v0);
orb[0].satno=satno;
for (i=0;i<4;i++) {
// Propagate
imode=init_sgdp4(&orb[i]);
imode=satpos_xyz(mjd+2400000.5,&r,&v);
// Compute initial orbital elements
orb1[i]=classel(ep_year,ep_day,r,v);
// Adjust
orb[i+1].rev=orb[i].rev+orb[0].rev-orb1[i].rev;
orb[i+1].ascn=orb[i].ascn+orb[0].ascn-orb1[i].ascn;
orb[i+1].argp=orb[i].argp+orb[0].argp-orb1[i].argp;
orb[i+1].mnan=orb[i].mnan+orb[0].mnan-orb1[i].mnan;
orb[i+1].eqinc=orb[i].eqinc+orb[0].eqinc-orb1[i].eqinc;
orb[i+1].ecc=orb[i].ecc+orb[0].ecc-orb1[i].ecc;
orb[i+1].ep_year=orb[i].ep_year;
orb[i+1].ep_day=orb[i].ep_day;
orb[i+1].satno=orb[i].satno;
orb[i+1].norb=orb[i].norb;
orb[i+1].bstar=orb[i].bstar;
// Keep in range
if (orb[i+1].ecc<0.0)
orb[i+1].ecc=0.0;
if (orb[i+1].eqinc<0.0)
orb[i+1].eqinc=0.0;
}
orb[i].mnan=modulo(orb[i].mnan,2.0*M_PI);
orb[i].ascn=modulo(orb[i].ascn,2.0*M_PI);
orb[i].argp=modulo(orb[i].argp,2.0*M_PI);
return orb[i];
}
// Fit
void fit(orbit_t orb,int *ia)
{
int i,n;
double a[7],da[7];
double db[7]={0.1,0.1,0.002,0.1,0.1,0.01,0.0001};
// Copy parameters
a[0]=orb.eqinc*R2D;
da[0]=da[0]*R2D;
a[1]=orb.ascn*R2D;
da[1]=da[1]*R2D;
a[2]=orb.ecc;
a[3]=orb.argp*R2D;
da[3]=da[3]*R2D;
a[4]=orb.mnan*R2D;
da[4]=da[4]*R2D;
a[5]=orb.rev;
a[6]=orb.bstar;
for (i=0;i<7;i++) {
if (ia[i]==1)
da[i]=db[i];
else
da[i]=0.0;
}
// Construct struct
// a[0]: inclination
// a[1]: RA of ascending node
// a[2]: eccentricity
// a[3]: argument of periastron
// a[4]: mean anomaly
// a[5]: revs per day
// a[6]: bstar
// Count highlighted points
for (i=0,n=0;i<d.n;i++)
if (d.p[i].flag==1)
n++;
if (n>0)
versafit(n,7,a,da,chisq,0.0,1e-7,"n");
// Return parameters
orb.eqinc=RAD(a[0]);
orb.ascn=RAD(modulo(a[1],360.0));
orb.ecc=a[2];
orb.argp=RAD(modulo(a[3],360.0));
orb.mnan=RAD(modulo(a[4],360.0));
orb.rev=a[5];
orb.bstar=a[6];
return;
}
int main(int argc,char *argv[])
{
int i,j,k,arg=0,satno=0,satname=0,usecatalog=0,imode,m=10;
long norb;
char *datafile,*catalog,filename[32];
int ia[7]={0,0,0,0,0,0,0};
char line1[70],line2[70],desig[10];
double mjd,sma,perigee,apogee,xno;
float mag=0.0,dm;
xyz_t r,v;
FILE *file;
// Decode options
while ((arg=getopt(argc,argv,"d:c:i:n:m:"))!=-1) {
switch(arg) {
case 'd':
datafile=optarg;
break;
case 'c':
catalog=optarg;
usecatalog=1;
break;
case 'i':
satno=atoi(optarg);
break;
case 'n':
norb=atoi(optarg);
if (norb<0)
norb=0;
break;
case 'm':
mag=atof(optarg);
break;
default:
return 0;
}
}
// Magnitude offset
dm=5.0*log10(1000.0/40000.0);
// Reloop stderr
freopen("/tmp/stderr.txt","w",stderr);
// Decode filename
mjd=decode_filename(datafile,&satname);
// Read data
d=read_data(datafile,mjd);
// Write data
sprintf(filename,"%06d.xyz",satname);
file=fopen(filename,"w");
for (i=0;i<d.n;i++)
fprintf(file,"%lf %f %f %f\n",d.p[i].mjd,d.p[i].r.x,d.p[i].r.y,d.p[i].r.z);
fclose(file);
// Open elements
sprintf(filename,"%06d.tle",satname);
file=fopen(filename,"w");
// Estimate orbit
k=504;
if (usecatalog==0) {
// Set initial state vector
r.x=d.p[k].r.x;
r.y=d.p[k].r.y;
r.z=d.p[k].r.z;
v.x=(d.p[k+1].r.x-d.p[k].r.x)/60.0;
v.y=(d.p[k+1].r.y-d.p[k].r.y)/60.0;
v.z=(d.p[k+1].r.z-d.p[k].r.z)/60.0;
// Estimate initial orbit from elements
orb=rv2el(99999,d.p[k].mjd,r,v);
strcpy(orb.desig,"14999A");
orb.norb=norb;
} else {
// Read orbit
orb=read_tle(catalog,satno);
strcpy(desig,orb.desig);
// Propagate
imode=init_sgdp4(&orb);
imode=satpos_xyz(d.p[k].mjd+2400000.5,&r,&v);
orb=rv2el(orb.satno,d.p[k].mjd,r,v);
// orb.satno=99999;
// strcpy(orb.desig,"14999A");
strcpy(orb.desig,desig);
orb.norb=norb;
}
// Set flags
for (j=0;j<d.n;j++)
d.p[j].flag=0;
for (j=0;j<d.n;j++)
d.p[j].flag=1;
// Fit orbit
for (j=0;j<10;j++) {
if (j==1) ia[4]=1;
if (j==2) ia[1]=1;
if (j==3) ia[0]=1;
if (j==4) ia[5]=1;
if (j==5) ia[3]=1;
if (j==6) ia[2]=1;
if (j==7) ia[6]=1;
fit(orb,ia);
}
// Compute orbit size
xno=orb.rev*2.0*M_PI/XMNPDA;
sma=pow(XKE/xno,2.0/3.0)*XKMPER;
perigee=sma*(1.0-orb.ecc)-XKMPER;
apogee=sma*(1.0+orb.ecc)-XKMPER;
// Format TLE
format_tle(orb,line1,line2);
fprintf(file,"SO %6d %4.1f %7.0fkm x%7.0fkm\n%s\n%s\n# %d positions, %.1f km rms\n",satname,mag+dm,perigee,apogee,line1,line2,d.nsel,d.rms);
printf("SO %6d %4.1f %7.0fkm x%7.0fkm\n%s\n%s\n# %d positions, %.1f km rms\n",satname,mag+dm,perigee,apogee,line1,line2,d.nsel,d.rms);
// Close output file
fclose(file);
return 0;
}