/* Function to return xyz coords of a JPL ephemeris body in
* standard coordinate system.
*/
void
body3d(double t, /* time is in years here */
int body,
double *x, double *y, double *z,
double *vxyz)
{
double xxx[3];
double xec, yec, zec;
/* get observatory posn wrt barycenter */
bodycenter_ssbary(t/DAY+jd0, xxx, body, vxyz);
/*fprintf(stderr,"bodycenter for %d: %f %f %f\n",body,xxx[0],xxx[1],xxx[2]);*/
/* convert to tangent-point coord system */
/* via ecliptic */
xyz_eq_to_ec(xxx[0], xxx[1], xxx[2], &xec, &yec, &zec,NULL);
xyz_ec_to_proj(xec, yec, zec, x, y, z, lat0, lon0, NULL);
/* Translate to our origin */
*x += xBary;
*y += yBary;
*z += zBary;
/* Rotate velocity if it has bee requested: */
if (vxyz != NULL) {
xyz_eq_to_ec(vxyz[0], vxyz[1], vxyz[2], &xec, &yec, &zec,NULL);
xyz_ec_to_proj(xec, yec, zec, vxyz, vxyz+1, vxyz+2, lat0, lon0, NULL);
}
return;
}
/* Transform from an orbital element representation to a PBASIS
* description. Sets up projected coordinate system to the proper
* situation for the desired epoch as well, so the global lat0, lon0,
* etc. will be changed.
*/
void
elements_to_pbasis(ORBIT *o,
double jd,
int obscode,
PBASIS *p) {
XVBASIS xv;
double xec, yec, zec;
elements_to_xv(o, jd, &xv);
/* Set up a new coordinate system that centers on current-epoch
* positions */
earth_ssbary(jd, obscode, &xBary, &yBary, &zBary);
/* Get target vector in ecliptic coords, set lat0/lon0 */
xBary *= -1.; yBary *= -1.; zBary *= -1.;
xyz_eq_to_ec(xBary, yBary, zBary, &xec, &yec, &zec,NULL);
xv.x += xec; xv.y+=yec; xv.z+=zec;
lon0 = atan2(xv.y, xv.x);
lat0 = asin( xv.z / sqrt(xv.x*xv.x + xv.y*xv.y + xv.z*xv.z));
jd0 = jd;
/* Rotate target and bary into the projected system */
xyz_ec_to_proj(xec, yec, zec, &xBary, &yBary, &zBary, lat0, lon0, NULL);
xyz_ec_to_proj(xv.x, xv.y, xv.z, &xv.x, &xv.y, &xv.z, lat0, lon0, NULL);
xyz_ec_to_proj(xv.xdot, xv.ydot, xv.zdot,
&xv.xdot, &xv.ydot, &xv.zdot, lat0, lon0, NULL);
p->g = 1./xv.z;
p->a = xv.x * p->g;
p->b = xv.y * p->g;
p->adot = xv.xdot * p->g;
p->bdot = xv.ydot * p->g;
p->gdot = xv.zdot * p->g;
return;
}
/* Input file is stdin if fname==NULL */
int
read_radec(OBSERVATION obsarray[], char *fname, int *nobs)
{
FILE *fptr;
OBSERVATION *obs;
int i;
char inbuff[256];
double jd,ra,dec,elat,elon;
if (fname==NULL)
fptr = stdin;
else if ( (fptr=fopen(fname,"r"))==NULL) {
fprintf(stderr,"Error opening observations file %s\n",fname);
exit(1);
}
*nobs=0;
while ( fgets_nocomment(inbuff,255,fptr,NULL)!=NULL) {
if ( scan_observation(inbuff, &(obsarray[*nobs]))) {
fprintf(stderr,"Quitting on format error\n");
exit(1);
}
obs = &(obsarray[*nobs]);
(*nobs)++;
eq_to_ec(obs->thetax,obs->thetay,&elat,&elon,NULL);
if (*nobs==1) {
double xec, yec, zec;
/* Use first observation to set the reference frame */
jd0 = obs->obstime;
lat0 = elat;
lon0 = elon;
/* Find location of SSBARY wrt observatory at zero time */
earth_ssbary(jd0, obs->obscode, &xBary, &yBary, &zBary);
/* Negate the vector to make it earth->SSBARY*/
/* And rotate equatorial into the tangent-point coords */
xBary *= -1.; yBary *= -1.; zBary *= -1.;
xyz_eq_to_ec(xBary, yBary, zBary, &xec, &yec, &zec,NULL);
xyz_ec_to_proj(xec, yec, zec, &xBary, &yBary, &zBary, lat0, lon0, NULL);
}
/* Set time to years after jd0, rotate to tangent plane coords */
obs->obstime = (obs->obstime-jd0)*DAY;
ec_to_proj(elat,elon,&(obs->thetax),&(obs->thetay),
lat0,lon0,NULL);
/* Calculate the position of Earth at this time to avoid doing
* it many times later: */
earth3d(obs->obstime, obs->obscode,
&(obs->xe),&(obs->ye),&(obs->ze));
}
if (fname!=NULL) fclose(fptr);
return(0);
}
/* Function to return xyz coords of observatory in the current
* standard coordinate system.
*/
void
earth3d(double t, /* time is in years here */
int obscode,
double *x, double *y, double *z)
{
double x1,y1,z1,xTelEq,yTelEq,zTelEq;
double xec, yec, zec;
/* get observatory posn wrt barycenter */
earth_ssbary(t/DAY+jd0, obscode, &x1, &y1, &z1);
/* convert to tangent-point coord system */
/* via ecliptic */
xyz_eq_to_ec(x1, y1, z1, &xec, &yec, &zec,NULL);
xyz_ec_to_proj(xec, yec, zec, x, y, z, lat0, lon0, NULL);
/* Translate to our origin */
*x += xBary;
*y += yBary;
*z += zBary;
return;
}
/* Function to return xyz coords of observatory in the current
* standard coordinate system based on 2line MPC supplied values
*/
void
mpc3d(double t, /* time is in years here */
double *x, double *y, double *z)
{
double xTelEq,yTelEq,zTelEq;
double xec, yec, zec;
double xgeo[3];
geo_to_ssbary(t/DAY+jd0, x, y, z);
/* convert to tangent-point coord system */
/* via ecliptic */
xyz_eq_to_ec(*x, *y, *z, &xec, &yec, &zec,NULL);
xyz_ec_to_proj(xec, yec, zec, x, y, z, lat0, lon0, NULL);
/* Translate to our origin */
*x += xBary;
*y += yBary;
*z += zBary;
return;
}
/* Return the angle btwn zenith (anti-earth) direction and target*/
double
zenith_angle(OBSERVATION *obs)
{
double xobs, yobs, zobs, r;
double xec, yec, zec, cosb;
/* Get the anti-Earth vector (in ICRS) for this observation */
observatory_geocenter(obs->obstime/DAY+jd0, obs->obscode,
&xobs, &yobs, &zobs);
r = sqrt(xobs*xobs+yobs*yobs+zobs*zobs);
if (r<=0.) {
fprintf(stderr,"Non-positive geocentric radius in zenith_angle()\n");
exit(1);
}
xobs /=r; yobs/=r; zobs/=r;
/* Rotate this ICRS vector into ecliptic, then projected coords */
xyz_eq_to_ec(xobs, yobs, zobs, &xec, &yec, &zec,NULL);
xyz_ec_to_proj(xec, yec, zec, &xobs, &yobs, &zobs, lat0, lon0, NULL);
/* dot the observation direction into the (Earth->bary) vector*/
cosb = obs->thetax*xobs + obs->thetay*yobs + zobs;
cosb /= sqrt(1+obs->thetax*obs->thetax+obs->thetay*obs->thetay);
return acos(cosb);
}
/* Input file is stdin if fname==NULL */
int
read_radec(OBSERVATION obsarray[], char *fname, int *nobs)
{
FILE *fptr;
OBSERVATION *obs;
int scan_status_flag;
int i;
char inbuff[256];
double jd,ra,dec,elat,elon;
if (fname==NULL)
fptr = stdin;
else if ( (fptr=fopen(fname,"r"))==NULL) {
fprintf(stderr,"Error opening observations file %s\n",fname);
exit(1);
}
*nobs=0;
while ( fgets_nocomment(inbuff,255,fptr,NULL)!=NULL) {
// obs refers to the previous observation, after the first loop.
scan_status_flag = scan_observation(inbuff, &(obsarray[*nobs]), obs);
// scanned line was 2nd line of two line format so don't advance nobs as all we did was reset the observer x/y
if (scan_status_flag == -1) {
mpc3d(obs->obstime, &(obs->xe), &(obs->ye), &(obs->ze));
continue;
}
// all other non-zero status values indicate an error.
if ( scan_status_flag == 1) {
fprintf(stderr,"Quitting on format error\n");
exit(1);
}
obs = &(obsarray[*nobs]);
(*nobs)++;
eq_to_ec(obs->thetax,obs->thetay,&elat,&elon,NULL);
if (*nobs==1) {
double xec, yec, zec;
/* Use first observation to set the reference frame */
jd0 = obs->obstime;
lat0 = elat;
lon0 = elon;
/* fprintf(stderr, "%f %f %f %d\n", elat, elon, obs->obstime, obs->obscode); */
/* Find location of SSBARY wrt observatory at zero time */
earth_ssbary(jd0, obs->obscode, &xBary, &yBary, &zBary);
/* fprintf(stderr, "%f %f %f %d\n", elat, elon, obs->obstime, obs->obscode); */
/* Negate the vector to make it earth->SSBARY*/
/* And rotate equatorial into the tangent-point coords */
xBary *= -1.; yBary *= -1.; zBary *= -1.;
xyz_eq_to_ec(xBary, yBary, zBary, &xec, &yec, &zec,NULL);
xyz_ec_to_proj(xec, yec, zec, &xBary, &yBary, &zBary, lat0, lon0, NULL);
}
/* fprintf(stderr,"%f %f", lat0, lon0); */
/* Set time to years after jd0, rotate to tangent plane coords */
obs->obstime = (obs->obstime-jd0)*DAY;
ec_to_proj(elat,elon,&(obs->thetax),&(obs->thetay),
lat0,lon0,NULL);
/* Calculate the position of Earth at this time to avoid doing
* it many times later: */
if (scan_status_flag == -2) {
mpc3d(obs->obstime, &(obs->xe), &(obs->ye), &(obs->ze));
} else {
earth3d(obs->obstime, obs->obscode,
&(obs->xe), &(obs->ye), &(obs->ze));
}
}
if (fname!=NULL) fclose(fptr);
return(0);
}
