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vadd.c
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vadd.c
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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include "cpgplot.h"
#include "sgdp4h.h"
#include "satutl.h"
#include <getopt.h>
#define LIM 128
#define XKE 0.07436680 // Guassian Gravitational Constant
#define XKMPER 6378.135
#define AE 1.0
#define XMNPDA 1440.0
#define R2D 180.0/M_PI
#define D2R M_PI/180.0
extern double SGDP4_jd0;
// Dot product
float dot(xyz_t a,xyz_t b)
{
return a.x*b.x+a.y*b.y+a.z*b.z;
}
// Return x modulo y [0,y)
double modulo(double x,double y)
{
x=fmod(x,y);
if (x<0.0) x+=y;
return x;
}
// 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;
}
// 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;
}
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];
}
// 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 0",orb.satno,DEG(orb.eqinc),DEG(orb.ascn),1E7*orb.ecc,DEG(orb.argp),DEG(orb.mnan),orb.rev);
// 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;
}
// 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;
}
// 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,sec;
double mjd,dday;
sscanf(date,"%04d-%02d-%02dT%02d:%02d:%02d",&year,&month,&day,&hour,&min,&sec);
dday=day+hour/24.0+min/1440.0+sec/86400.0;
mjd=date2mjd(year,month,dday);
return mjd;
}
void usage(void)
{
printf("propagate c:i:t:m:\n\nPropagates orbital elements to a new epoch using the SGP4/SDP4 model.\nDefault operation propagates classfd.tle to now,\n\n-c input catalog\n-i Satellite number\n-t New epoch (YYYY-MM-DDTHH:MM:SS)\n-m New epoch (MJD)\n");
return;
}
int main(int argc,char *argv[])
{
int imode,satno=0,arg,satnomin,flag=0,satnonew=-1;
FILE *file;
orbit_t orb;
xyz_t r,v,n,dv;
char tlefile[LIM],nfd[32];
char line1[80],line2[80],desig[20];
double mjd,ra,de,dr,drmin;
float vadd=0.0;
char direction[16]="radial";
char *env;
// Get environment variable
env=getenv("ST_TLEDIR");
sprintf(tlefile,"%s/classfd.tle",env);
// Set date
nfd_now(nfd);
mjd=nfd2mjd(nfd);
// Decode options
while ((arg=getopt(argc,argv,"c:i:t:m:hv:d:I:"))!=-1) {
switch (arg) {
case 't':
strcpy(nfd,optarg);
mjd=nfd2mjd(nfd);
break;
case 'm':
mjd=(double) atof(optarg);
break;
case 'c':
strcpy(tlefile,optarg);
break;
case 'i':
satno=atoi(optarg);
break;
case 'h':
usage();
return 0;
break;
case 'v':
vadd=atof(optarg);
break;
case 'd':
strcpy(direction,optarg);
break;
case 'I':
satnonew=atoi(optarg);
break;
default:
usage();
return 0;
}
}
// Reloop stderr
freopen("/tmp/stderr.txt","w",stderr);
// Open file
file=fopen(tlefile,"r");
while (read_twoline(file,satno,&orb)==0) {
format_tle(orb,line1,line2);
strcpy(desig,orb.desig);
// Propagate
imode=init_sgdp4(&orb);
imode=satpos_xyz(mjd+2400000.5,&r,&v);
// Compute normal
n=cross(r,v);
// Add velocity
if (strcmp(direction,"prograde")==0) {
dv.x=vadd*v.x/magnitude(v);
dv.y=vadd*v.y/magnitude(v);
dv.z=vadd*v.z/magnitude(v);
} else if (strcmp(direction,"radial")==0) {
dv.x=vadd*r.x/magnitude(r);
dv.y=vadd*r.y/magnitude(r);
dv.z=vadd*r.z/magnitude(r);
} else if (strcmp(direction,"normal")==0) {
dv.x=vadd*n.x/magnitude(n);
dv.y=vadd*n.y/magnitude(n);
dv.z=vadd*n.z/magnitude(n);
} else {
dv.x=0.0;
dv.y=0.0;
dv.z=0.0;
}
v.x+=dv.x/1000.0;
v.y+=dv.y/1000.0;
v.z+=dv.z/1000.0;
// Convert
orb=rv2el(orb.satno,mjd,r,v);
if (satnonew==-1) {
strcpy(orb.desig,desig);
} else {
strcpy(orb.desig,"15999A");
orb.satno=satnonew;
}
// Print tle
format_tle(orb,line1,line2);
printf("%s\n%s\n# %05d + %g m/s %s\n",line1,line2,satno,vadd,direction);
}
fclose(file);
return 0;
}