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/* Copyright (C) 2018, Project Pluto
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA. */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>
#include <stdint.h>
/* Very Guide-specific code to convert an ephemeris gathered from JPL's
_Horizons_ system into the .b32 ("binary 32-bit fixed-point integer")
format used in Guide. Probably of no interest to anyone except me.
See comments below on how to get the _Horizons_ ephemerides in the
first place. */
int main( const int argc, const char **argv)
{
time_t t0 = time( NULL);
FILE *ifile = (argc > 1 ? fopen( argv[1], "rb") : NULL);
FILE *ofile = NULL;
char buff[200];
int n_written = 0, pass;
const int sat_id = (argc > 1 ? atoi( argv[1]) : 0);
double jd0 = 0., step_size = 0., jd, max_ordinate = 0;
if( argc > 1 && !ifile)
printf( "\nCouldn't open the JPL file '%s'\n", argv[1]);
if( argc < 2 || !ifile)
{
printf( "\nJPL2B32 takes input ephemeri(de)s generated by HORIZONS,\n");
printf( "and produces .B32 file(s) suitable for use in Guide. The\n");
printf( "name of the input ephemeris must be provided as a command-line\n");
printf( "argument. For example:\n");
printf( "\njpl2b32 9002.txt\n\n");
printf( "The JPL ephemeris must be in text form (can use the 'download/save'\n");
printf( "option for this), with vectors in units of AU. Also, the data\n");
printf( "should be equatorial (not the default ecliptic!) coordinates.\n");
printf( "You can also select position (xyz) output only, if you wish, but\n");
printf( "you don't have to; velocities and range/rate/light time will\n");
printf( "simply be ignored if present.\n");
exit( -1);
}
sprintf( buff, "%d.b32", sat_id);
ofile = fopen( buff, "wb");
fwrite( buff, 128, 1, ofile); /* output dummy 'placeholder' buffer */
for( pass = 0; pass < 2; pass++)
{
n_written = 0;
fseek( ifile, 0L, SEEK_SET);
while( fgets( buff, sizeof( buff), ifile))
if( (jd = atof( buff)) > 2000000. && jd < 3000000. &&
strlen( buff) > 54 && !memcmp( buff + 17, " = A.D.", 7)
&& !memcmp( buff + 37, "00:00:00.0000 (CT)", 18))
{
int i;
if( !fgets( buff, sizeof( buff), ifile))
{
printf( "Failed to get data from input file\n");
return( -2);
}
if( !n_written)
jd0 = jd;
else if( n_written == 1)
step_size = jd - jd0;
for( i = 0; i < 3; i++)
{
const double ordinate = atof( buff + i * 23 + 1);
if( !pass)
{
if( max_ordinate < fabs( ordinate))
max_ordinate = fabs( ordinate);
}
else
{
const int32_t oval =
(int32_t)( ordinate * 1.5e+9 / max_ordinate);
fwrite( &oval, sizeof( int32_t), 1, ofile);
}
}
n_written++;
}
}
fclose( ifile);
fprintf( ofile, "Ephemeris from JPL Horizons output\n");
fprintf( ofile, "Created using 'jpl2b32', version %s\n", __DATE__);
fprintf( ofile, "Ephemeris converted %s", ctime( &t0));
printf( "JD0: %f Step size: %f %ld steps\n",
jd0, step_size, (long)n_written);
/* Seek back to start of file & write corrected hdr: */
fseek( ofile, 0L, SEEK_SET);
memset( buff, 0, 128);
sprintf( buff, "%d %d %10.1f %f %ld %d %g %d %d ",
128, sat_id, /* JPL ID */
jd0, step_size, (long)n_written, 6,
max_ordinate / 1.5e+9, 32, 0);
fwrite( buff, 128, 1, ofile);
fclose( ofile);
return( 0);
}
/* Following is an example e-mail request to the Horizons server for a
suitable text ephemeris for 2011P1, a satellite known to Horizons as
major body 904. For other objects, you would modify the COMMAND and
CENTER lines, as well as the START_TIME, STOP_TIME, and STEP_SIZE.
And, of course, the EMAIL_ADDR.
Aside from that, all is as it should be: vectors are requested
with positions only, with no light-time corrections, in equatorial
J2000 coordinates, in AU (not kilometers).
After making those modifications, you would send the result to
horizons@ssd.jpl.nasa.gov, subject line JOB.
!$$SOF (ssd) JPL/Horizons Execution Control VARLIST
! Full directions are at
! ftp://ssd.jpl.nasa.gov/pub/ssd/horizons_batch_example.long
! EMAIL_ADDR sets e-mail address output is sent to. Enclose
! in quotes. Null assignment uses mailer return address.
EMAIL_ADDR = 'pluto@projectpluto.com'
COMMAND = '904'
! MAKE_EPHEM toggles generation of ephemeris, if possible.
! Values: YES or NO
MAKE_EPHEM = 'YES'
! TABLE_TYPE selects type of table to generate, if possible.
! Values: OBSERVER, ELEMENTS, VECTORS
! (or unique abbreviation of those values).
TABLE_TYPE = 'VECTORS'
CENTER = '500@999'
REF_PLANE = 'FRAME'
! START_TIME specifies ephemeris start time
! (i.e. YYYY-MMM-DD {HH:MM} {UT/TT}) ... where braces "{}"
! denote optional inputs. See program user's guide for
! lists of the numerous ways to specify times. Time zone
! offsets can be set. For example, '1998-JAN-1 10:00 UT-8'
! would produce a table in Pacific Standard Time. 'UT+00:00'
! is the same as 'UT'. Offsets are not applied to TT
! (Terrestrial Time) tables. See TIME_ZONE variable also.
START_TIME = '2009-JAN-27 00:00 TDB'
! STOP_TIME specifies ephemeris stop time
! (i.e. YYYY-MMM-DD {HH:MM}).
STOP_TIME = '2015-JAN-01'
STEP_SIZE = '2 day'
QUANTITIES = '
REF_SYSTEM = 'J2000'
OUT_UNITS = 'AU-D'
! VECT_TABLE = 1 means XYZ only, no velocity, light-time,
! range, or range-rate.
VECT_TABLE = '1'
! VECT_CORR selects level of correction: NONE=geometric states
! (which we happen to want); 'LT' = astrometric states, 'LT+S'
! = same with stellar aberration included.
VECT_CORR = 'NONE'
CAL_FORMAT = 'CAL'
!$$EOF++++++++++++++++++++++++++++++++++++++++++++++++++++++
*/
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