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eph_manager.c
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/*
Naval Observatory Vector Astrometry Software (NOVAS)
C Edition, Version 3.1
eph_manager.c: C version of JPL Ephemeris Manager for use with solsys1
U. S. Naval Observatory
Astronomical Applications Dept.
Washington, DC
http://www.usno.navy.mil/USNO/astronomical-applications
*/
#ifndef _EPHMAN_
#include "eph_manager.h"
#endif
/*
Define global variables
*/
short int KM;
/*
IPT and LPT defined as int to support 64 bit systems.
*/
int IPT[3][12], LPT[3];
long int NRL, NP, NV;
long int RECORD_LENGTH;
double SS[3], JPLAU, PC[18], VC[18], TWOT, EM_RATIO;
double *BUFFER;
FILE *EPHFILE = NULL;
/********ephem_open */
short int ephem_open (char *ephem_name,
double *jd_begin, double *jd_end,
short int *de_number)
/*
------------------------------------------------------------------------
PURPOSE:
This function opens a JPL planetary ephemeris file and
sets initial values. This function must be called
prior to calls to the other JPL ephemeris functions.
REFERENCES:
Standish, E.M. and Newhall, X X (1988). "The JPL Export
Planetary Ephemeris"; JPL document dated 17 June 1988.
INPUT
ARGUMENTS:
*ephem_name (char)
Name of the direct-access ephemeris file.
OUTPUT
ARGUMENTS:
*jd_begin (double)
Beginning Julian date of the ephemeris file.
*jd_end (double)
Ending Julian date of the ephemeris file.
*de_number (short int)
DE number of the ephemeris file opened.
RETURNED
VALUE:
(short int)
0 ...file exists and is opened correctly.
1 ...file does not exist/not found.
2-10...error reading from file header.
11 ...unable to set record length; ephemeris (DE number)
not in look-up table.
GLOBALS
USED:
SS eph_manager.h
JPLAU eph_manager.h
PC eph_manager.h
VC eph_manager.h
TWOT eph_manager.h
EM_RATIO eph_manager.h
BUFFER eph_manager.h
IPT eph_manager.h
LPT eph_manager.h
NRL eph_manager.h
KM eph_manager.h
NP eph_manager.h
NV eph_manager.h
RECORD_LENGTH eph_manager.h
EPHFILE eph_manager.h
FUNCTIONS
CALLED:
fclose stdio.h
free stdlib.h
fopen stdio.h
fread stdio.h
calloc stdlib.h
VER./DATE/
PROGRAMMER:
V1.0/06-90/JAB (USNO/NA)
V1.1/06-92/JAB (USNO/AA): Restructure and add initializations.
V1.2/07-98/WTH (USNO/AA): Modified to open files for different
ephemeris types. (200,403,404,405,406)
V1.3/11-07/WKP (USNO/AA): Updated prolog.
V1.4/09-10/WKP (USNO/AA): Changed ncon and denum variables and
sizeof ipt array to type 'int' for
64-bit system compatibility.
V1.5/09-10/WTH (USNO/AA): Added support for DE421, default case
for switch, close file on error.
V1.6/10-10/WKP (USNO/AA): Renamed function to lowercase to
comply with coding standards.
NOTES:
KM...flag defining physical units of the output states.
= 1, km and km/sec
= 0, AU and AU/day
Default value is 0 (KM determines time unit for nutations.
Angle unit is always radians.)
------------------------------------------------------------------------
*/
{
char ttl[252], cnam[2400];
short int i, j;
int ncon, denum;
if (EPHFILE)
{
fclose (EPHFILE);
free (BUFFER);
}
/*
Open file ephem_name.
*/
if ((EPHFILE = fopen (ephem_name, "rb")) == NULL)
{
return 1;
}
else
{
/*
File found. Set initializations and default values.
*/
KM = 0;
NRL = 0;
NP = 2;
NV = 3;
TWOT = 0.0;
for (i = 0; i < 18; i++)
{
PC[i] = 0.0;
VC[i] = 0.0;
}
PC[0] = 1.0;
VC[1] = 1.0;
/*
Read in values from the first record, aka the header.
*/
if (fread (ttl, sizeof ttl, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 2;
}
if (fread (cnam, sizeof cnam, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 3;
}
if (fread (SS, sizeof SS, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 4;
}
if (fread (&ncon, sizeof ncon, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 5;
}
if (fread (&JPLAU, sizeof JPLAU, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 6;
}
if (fread (&EM_RATIO, sizeof EM_RATIO, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 7;
}
for (i = 0; i < 12; i++)
for (j = 0; j < 3; j++)
if (fread (&IPT[j][i], sizeof(int), 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 8;
}
if (fread (&denum, sizeof denum, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 9;
}
if (fread (LPT, sizeof LPT, 1, EPHFILE) != 1)
{
fclose (EPHFILE);
return 10;
}
/*
Set the value of the record length according to what JPL ephemeris is
being opened.
*/
switch (denum)
{
case 102:
RECORD_LENGTH = 6184;
break;
case 200: case: 202:
RECORD_LENGTH = 6608;
break;
case 403: case 405: case 410: case 413: case 414:
case 418: case 421: case 422: case 423: case 424:
case 430: case 431: case 433: case 434: case 435:
case 436: case 438: case 440: case 441:
RECORD_LENGTH = 8144;
break;
case 404: case 406:
RECORD_LENGTH = 5824;
break;
case 432:
RECORD_LENGTH = 7504;
break;
/*
An unknown DE file was opened. Close the file and return an error
code.
*/
default:
*jd_begin = 0.0;
*jd_end = 0.0;
*de_number = 0;
fclose (EPHFILE);
return 11;
break;
}
BUFFER = (double *) calloc (RECORD_LENGTH / 8, sizeof(double));
*de_number = (short int) denum;
*jd_begin = SS[0];
*jd_end = SS[1];
}
return 0;
}
/********ephem_close */
short int ephem_close (void)
/*
------------------------------------------------------------------------
PURPOSE:
This function closes a JPL planetary ephemeris file and frees the
memory.
REFERENCES:
Standish, E.M. and Newhall, X X (1988). "The JPL Export
Planetary Ephemeris"; JPL document dated 17 June 1988.
INPUT
ARGUMENTS:
None.
OUTPUT
ARGUMENTS:
None.
RETURNED
VALUE:
(short int)
0 ...file was already closed or closed correctly.
EOF...error closing file.
GLOBALS
USED:
BUFFER eph_manager.h
EPHFILE eph_manager.h
FUNCTIONS
CALLED:
fclose stdio.h
free stdlib.h
VER./DATE/
PROGRAMMER:
V1.0/11-07/WKP (USNO/AA)
V1.1/09-10/WKP (USNO/AA): Explicitly cast fclose return value to
type 'short int'.
V1.2/10-10/WKP (USNO/AA): Renamed function to lowercase to
comply with coding standards.
NOTES:
None.
------------------------------------------------------------------------
*/
{
short int error = 0;
if (EPHFILE)
{
error = (short int) fclose (EPHFILE);
EPHFILE = NULL; // new line, reset pointer
free (BUFFER);
}
return error;
}
/********planet_ephemeris */
short int planet_ephemeris (double tjd[2], short int target,
short int center,
double *position, double *velocity)
/*
------------------------------------------------------------------------
PURPOSE:
This function accesses the JPL planetary ephemeris to give the
position and velocity of the target object with respect to the
center object.
REFERENCES:
Standish, E.M. and Newhall, X X (1988). "The JPL Export
Planetary Ephemeris"; JPL document dated 17 June 1988.
INPUT
ARGUMENTS:
tjd[2] (double)
Two-element array containing the Julian date, which may be
split any way (although the first element is usually the
"integer" part, and the second element is the "fractional"
part). Julian date is in the TDB or "T_eph" time scale.
target (short int)
Number of 'target' point.
center (short int)
Number of 'center' (origin) point.
The numbering convention for 'target' and'center' is:
0 = Mercury 7 = Neptune
1 = Venus 8 = Pluto
2 = Earth 9 = Moon
3 = Mars 10 = Sun
4 = Jupiter 11 = Solar system bary.
5 = Saturn 12 = Earth-Moon bary.
6 = Uranus 13 = Nutations (long int. and obliq.)
(If nutations are desired, set 'target' = 13;
'center' will be ignored on that call.)
OUTPUT
ARGUMENTS:
*position (double)
Position vector array of target relative to center, measured
in AU.
*velocity (double)
Velocity vector array of target relative to center, measured
in AU/day.
RETURNED
VALUE:
(short int)
0 ...everything OK.
1,2...error returned from State.
GLOBALS
USED:
EM_RATIO eph_manager.h
FUNCTIONS
CALLED:
state eph_manager.h
VER./DATE/
PROGRAMMER:
V1.0/03-93/WTH (USNO/AA): Convert FORTRAN to C.
V1.1/07-93/WTH (USNO/AA): Update to C standards.
V2.0/07-98/WTH (USNO/AA): Modified for ease of use and linearity.
V3.0/11-06/JAB (USNO/AA): Allowed for use of input 'split' Julian
date for higher precision.
V3.1/11-07/WKP (USNO/AA): Updated prolog and error codes.
V3.1/12-07/WKP (USNO/AA): Removed unreferenced variables.
V3.2/10-10/WKP (USNO/AA): Renamed function to lowercase to
comply with coding standards.
NOTES:
None.
------------------------------------------------------------------------
*/
{
short int i, error = 0, earth = 2, moon = 9;
short int do_earth = 0, do_moon = 0;
double jed[2];
double pos_moon[3] = {0.0,0.0,0.0}, vel_moon[3] = {0.0,0.0,0.0},
pos_earth[3] = {0.0,0.0,0.0}, vel_earth[3] = {0.0,0.0,0.0};
double target_pos[3] = {0.0,0.0,0.0}, target_vel[3] = {0.0,0.0,0.0},
center_pos[3] = {0.0,0.0,0.0}, center_vel[3] = {0.0,0.0,0.0};
/*
Initialize 'jed' for 'state' and set up component count.
*/
jed[0] = tjd[0];
jed[1] = tjd[1];
/*
Check for target point = center point.
*/
if (target == center)
{
for (i = 0; i < 3; i++)
{
position[i] = 0.0;
velocity[i] = 0.0;
}
return 0;
}
/*
Check for instances of target or center being Earth or Moon,
and for target or center being the Earth-Moon barycenter.
*/
if ((target == earth) || (center == earth))
do_moon = 1;
if ((target == moon) || (center == moon))
do_earth = 1;
if ((target == 12) || (center == 12))
do_earth = 1;
if (do_earth)
{
error = state (jed,2, pos_earth,vel_earth);
if (error)
return error;
}
if (do_moon)
{
error = state (jed,9, pos_moon,vel_moon);
if (error)
return error;
}
/*
Make call to State for target object.
*/
if (target == 11)
{
for (i = 0; i < 3; i++)
{
target_pos[i] = 0.0;
target_vel[i] = 0.0;
}
}
else if (target == 12)
{
for (i = 0; i < 3; i++)
{
target_pos[i] = pos_earth[i];
target_vel[i] = vel_earth[i];
}
}
else
error = state (jed,target, target_pos,target_vel);
if (error)
return error;
/*
Make call to State for center object.
*/
/*
If the requested center is the Solar System barycenter,
then don't bother with a second call to State.
*/
if (center == 11)
{
for (i = 0; i < 3; i++)
{
center_pos[i] = 0.0;
center_vel[i] = 0.0;
}
}
/*
Center is Earth-Moon barycenter, which was already computed above.
*/
else if (center == 12)
{
for (i = 0; i < 3; i++)
{
center_pos[i] = pos_earth[i];
center_vel[i] = vel_earth[i];
}
}
else
error = state (jed,center, center_pos,center_vel);
if (error)
return error;
/*
Check for cases of Earth as target and Moon as center or vice versa.
*/
if ((target == earth) && (center == moon))
{
for (i = 0; i < 3; i++)
{
position[i] = -center_pos[i];
velocity[i] = -center_vel[i];
}
return 0;
}
else if ((target == moon) && (center == earth))
{
for (i = 0; i < 3; i++)
{
position[i] = target_pos[i];
velocity[i] = target_vel[i];
}
return 0;
}
/*
Check for Earth as target, or as center.
*/
else if (target == earth)
{
for (i = 0; i < 3; i++)
{
target_pos[i] = target_pos[i] - (pos_moon[i] /
(1.0 + EM_RATIO));
target_vel[i] = target_vel[i] - (vel_moon[i] /
(1.0 + EM_RATIO));
}
}
else if (center == earth)
{
for (i = 0; i < 3; i++)
{
center_pos[i] = center_pos[i] - (pos_moon[i] /
(1.0 + EM_RATIO));
center_vel[i] = center_vel[i] - (vel_moon[i] /
(1.0 + EM_RATIO));
}
}
/*
Check for Moon as target, or as center.
*/
else if (target == moon)
{
for (i = 0; i < 3; i++)
{
target_pos[i] = (pos_earth[i] - (target_pos[i] /
(1.0 + EM_RATIO))) + target_pos[i];
target_vel[i] = (vel_earth[i] - (target_vel[i] /
(1.0 + EM_RATIO))) + target_vel[i];
}
}
else if (center == moon)
{
for (i = 0; i < 3; i++)
{
center_pos[i] = (pos_earth[i] - (center_pos[i] /
(1.0 + EM_RATIO))) + center_pos[i];
center_vel[i] = (vel_earth[i] - (center_vel[i] /
(1.0 + EM_RATIO))) + center_vel[i];
}
}
/*
Compute position and velocity vectors.
*/
for (i = 0; i < 3; i++)
{
position[i] = target_pos[i] - center_pos[i];
velocity[i] = target_vel[i] - center_vel[i];
}
return 0;
}
/********state */
short int state (double *jed, short int target,
double *target_pos, double *target_vel)
/*
------------------------------------------------------------------------
PURPOSE:
This function reads and interpolates the JPL planetary
ephemeris file.
REFERENCES:
Standish, E.M. and Newhall, X X (1988). "The JPL Export
Planetary Ephemeris"; JPL document dated 17 June 1988.
INPUT
ARGUMENTS:
*jed (double)
2-element Julian date (TDB) at which interpolation is wanted.
Any combination of jed[0]+jed[1] which falls within the time
span on the file is a permissible epoch. See Note 1 below.
target (short int)
The requested body to get data for from the ephemeris file.
The designation of the astronomical bodies is:
0 = Mercury 6 = Uranus
1 = Venus 7 = Neptune
2 = Earth-Moon barycenter 8 = Pluto
3 = Mars 9 = geocentric Moon
4 = Jupiter 10 = Sun
5 = Saturn
OUTPUT
ARGUMENTS:
*target_pos (double)
The barycentric position vector array of the requested object,
in AU.
(If target object is the Moon, then the vector is geocentric.)
*target_vel (double)
The barycentric velocity vector array of the requested object,
in AU/Day.
Both vectors are referenced to the Earth mean equator and
equinox of epoch.
RETURNED
VALUE:
(short int)
0...everything OK.
1...error reading ephemeris file.
2...epoch out of range.
GLOBALS
USED:
KM eph_manager.h
EPHFILE eph_manager.h
IPT eph_manager.h
BUFFER eph_manager.h
NRL eph_manager.h
RECORD_LENGTH eph_manager.h
SS eph_manager.h
JPLAU eph_manager.h
FUNCTIONS
CALLED:
split eph_manager.h
fseek stdio.h
fread stdio.h
interpolate eph_manager.h
ephem_close eph_manager.h
VER./DATE/
PROGRAMMER:
V1.0/03-93/WTH (USNO/AA): Convert FORTRAN to C.
V1.1/07-93/WTH (USNO/AA): Update to C standards.
V2.0/07-98/WTH (USNO/AA): Modify to make position and velocity
two distinct vector arrays. Routine set
to compute one state per call.
V2.1/11-07/WKP (USNO/AA): Updated prolog.
V2.2/10-10/WKP (USNO/AA): Renamed function to lowercase to
comply with coding standards.
NOTES:
1. For ease in programming, the user may put the entire epoch in
jed[0] and set jed[1] = 0. For maximum interpolation accuracy,
set jed[0] = the most recent midnight at or before
interpolation epoch, and set jed[1] = fractional part of a day
elapsed between jed[0] and epoch. As an alternative, it may
prove convenient to set jed[0] = some fixed epoch, such as
start of the integration and jed[1] = elapsed interval between
then and epoch.
------------------------------------------------------------------------
*/
{
short int i;
long int nr, rec;
double t[2], aufac = 1.0, jd[4], s;
/*
Set units based on value of the 'KM' flag.
*/
if (KM)
t[1] = SS[2] * 86400.0;
else
{
t[1] = SS[2];
aufac = 1.0 / JPLAU;
}
/*
Check epoch.
*/
s = jed[0] - 0.5;
split (s, &jd[0]);
split (jed[1], &jd[2]);
jd[0] += jd[2] + 0.5;
jd[1] += jd[3];
split (jd[1], &jd[2]);
jd[0] += jd[2];
/*
Return error code if date is out of range.
*/
if ((jd[0] < SS[0]) || ((jd[0] + jd[3]) > SS[1]))
return 2;
/*
Calculate record number and relative time interval.
*/
nr = (long int) ((jd[0] - SS[0]) / SS[2]) + 3;
if (jd[0] == SS[1])
nr -= 2;
t[0] = ((jd[0] - ((double) (nr-3) * SS[2] + SS[0])) + jd[3]) / SS[2];
/*
Read correct record if it is not already in memory.
*/
if (nr != NRL)
{
NRL = nr;
rec = (nr - 1) * RECORD_LENGTH;
fseek (EPHFILE, rec, SEEK_SET);
if (!fread (BUFFER, RECORD_LENGTH, 1, EPHFILE))
{
ephem_close ();
return 1;
}
}
/*
Check and interpolate for requested body.
*/
interpolate (&BUFFER[IPT[0][target]-1],t,IPT[1][target],
IPT[2][target], target_pos,target_vel);
for (i = 0; i < 3; i++)
{
target_pos[i] *= aufac;
target_vel[i] *= aufac;
}
return 0;
}
/********interpolate */
void interpolate (double *buf, double *t, long int ncf, long int na,
double *position, double *velocity)
/*
------------------------------------------------------------------------
PURPOSE:
This function differentiates and interpolates a set of
Chebyshev coefficients to give position and velocity.
REFERENCES:
Standish, E.M. and Newhall, X X (1988). "The JPL Export
Planetary Ephemeris"; JPL document dated 17 June 1988.
INPUT
ARGUMENTS:
*buf (double)
Array of Chebyshev coefficients of position.
*t (double)
t[0] is fractional time interval covered by coefficients at
which interpolation is desired (0 <= t[0] <= 1).
t[1] is length of whole interval in input time units.
ncf (long int)
Number of coefficients per component.
na (long int)
Number of sets of coefficients in full array
(i.e., number of sub-intervals in full interval).
OUTPUT
ARGUMENTS:
*position (double)
Position array of requested object.
*velocity (double)
Velocity array of requested object.
RETURNED
VALUE:
None.
GLOBALS
USED:
NP eph_manager.h
NV eph_manager.h
PC eph_manager.h
VC eph_manager.h
TWOT eph_manager.h
FUNCTIONS
CALLED:
fmod math.h
VER./DATE/
PROGRAMMER:
V1.0/03-93/WTH (USNO/AA): Convert FORTRAN to C.
V1.1/07-93/WTH (USNO/AA): Update to C standards.
V1.2/07-98/WTH (USNO/AA): Modify to make position and velocity
two distinct vector arrays.
V1.3/11-07/WKP (USNO/AA): Updated prolog.
V1.4/12-07/WKP (USNO/AA): Changed ncf and na arguments from short
int to long int.
V1.5/10-10/WKP (USNO/AA): Renamed function to lowercase to
comply with coding standards.
NOTES:
None.
------------------------------------------------------------------------
*/
{
long int i, j, k, l;
double dna, dt1, temp, tc, vfac;
/*
Get correct sub-interval number for this set of coefficients and
then get normalized Chebyshev time within that subinterval.
*/
dna = (double) na;
dt1 = (double) ((long int) t[0]);
temp = dna * t[0];
l = (long int) (temp - dt1);
/*
'tc' is the normalized Chebyshev time (-1 <= tc <= 1).
*/
tc = 2.0 * (fmod (temp, 1.0) + dt1) - 1.0;
/*
Check to see whether Chebyshev time has changed, and compute new
polynomial values if it has. (The element PC[1] is the value of
t1[tc] and hence contains the value of 'tc' on the previous call.)
*/
if (tc != PC[1])
{
NP = 2;
NV = 3;
PC[1] = tc;
TWOT = tc + tc;
}
/*
Be sure that at least 'ncf' polynomials have been evaluated and
are stored in the array 'PC'.
*/
if (NP < ncf)
{
for (i = NP; i < ncf; i++)
PC[i] = TWOT * PC[i-1] - PC[i-2];
NP = ncf;
}
/*
Interpolate to get position for each component.
*/
for (i = 0; i < 3; i++)
{
position[i] = 0.0;
for (j = ncf-1; j >= 0; j--)
{
k = j + (i * ncf) + (l * (3 * ncf));
position[i] += PC[j] * buf[k];
}
}
/*
If velocity interpolation is desired, be sure enough derivative
polynomials have been generated and stored.
*/
vfac = (2.0 * dna) / t[1];
VC[2] = 2.0 * TWOT;
if (NV < ncf)
{
for (i = NV; i < ncf; i++)
VC[i] = TWOT * VC[i-1] + PC[i-1] + PC[i-1] - VC[i-2];
NV = ncf;
}
/*
Interpolate to get velocity for each component.
*/
for (i = 0; i < 3; i++)
{
velocity[i] = 0.0;
for (j = ncf-1; j > 0; j--)
{
k = j + (i * ncf) + (l * (3 * ncf));
velocity[i] += VC[j] * buf[k];
}
velocity[i] *= vfac;
}
return;
}
/********split */
void split (double tt,
double *fr)
/*
------------------------------------------------------------------------
PURPOSE:
This function breaks up a double number into a double integer
part and a fractional part.
REFERENCES:
Standish, E.M. and Newhall, X X (1988). "The JPL Export
Planetary Ephemeris"; JPL document dated 17 June 1988.
INPUT
ARGUMENTS:
tt (double)
Input number.
OUTPUT
ARGUMENTS:
*fr (double)
2-element output array;
fr[0] contains integer part,
fr[1] contains fractional part.
For negative input numbers,
fr[0] contains the next more negative integer;
fr[1] contains a positive fraction.
RETURNED
VALUE:
None.
GLOBALS
USED:
None.
FUNCTIONS
CALLED: