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/* mpcorb.cpp: extracts orbital elements from 'mpcorb.dat' or 'astorb.dat'
Copyright (C) 2010, 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 <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "watdefs.h"
#include "comets.h"
#include "date.h"
/* Tools for extracting orbital elements from 'mpcorb.dat'-style files. */
#define PI 3.1415926535897932384626433832795028841971693993751058209749445923
#define GAUSS_K .01720209895
#define SOLAR_GM (GAUSS_K * GAUSS_K)
/* Many values in MPC files are stored in an 'extended hex' */
/* scheme: usual '0'-'9' = 0 to 9, 'A-F' = 10 to 15. But */
/* then 'G'-'Z' = 16 to 35 and 'a' to 'z' = 36 to 61. */
static int extended_hex_to_int( const char ichar)
{
int rval;
if( ichar >= '0' && ichar <= '9')
rval = ichar - '0';
else if( ichar >= 'A' && ichar <= 'Z')
rval = ichar - 'A' + 10;
else /* if( ichar >= 'a' && ichar <= 'z') */
rval = ichar - 'a' + 10 + 26;
return( rval);
}
static long extract_mpc_epoch( const char *epoch_buff)
{
const long year = 100 * extended_hex_to_int( epoch_buff[0])
+ 10 * extended_hex_to_int( epoch_buff[1])
+ extended_hex_to_int( epoch_buff[2]);
const int month = extended_hex_to_int( epoch_buff[3]);
const int day = extended_hex_to_int( epoch_buff[4]);
return( dmy_to_day( day, month, year, CALENDAR_GREGORIAN));
}
static void do_remaining_element_setup( ELEMENTS *elem)
{
double ma;
elem->mean_anomaly *= PI / 180.;
elem->arg_per *= PI / 180.;
elem->asc_node *= PI / 180.;
elem->incl *= PI / 180.;
elem->q = elem->major_axis * (1. - elem->ecc);
derive_quantities( elem, SOLAR_GM);
elem->angular_momentum = sqrt( SOLAR_GM * elem->q * (1. + elem->ecc));
ma = elem->mean_anomaly;
if( ma > PI) /* find _nearest_ perihelion time */
ma -= PI + PI;
elem->perih_time = elem->epoch - ma * elem->t0;
elem->is_asteroid = 1;
elem->central_obj = 0;
elem->gm = SOLAR_GM;
}
/* extract_mpcorb_dat( ) extracts the data from an 'mpcorb.dat'-formatted
buffer, putting the orbital elements into 'elem' if 'elem' is non-NULL.
The epoch of the elements is returned. (You can call the function with
elem=NULL to verify that the buffer is in the right format, or to find
out what the epoch is.)
Note that there's a very similar function for 'astorb'-formatted
data below. */
long extract_mpcorb_dat( ELEMENTS *elem, const char *buff)
{
long epoch_jd = 0;
if( strlen( buff) > 200 && buff[47] == ' ' && buff[82] == '.' &&
buff[25] == ' ' && buff[29] == '.' && buff[36] == ' ')
{
epoch_jd = extract_mpc_epoch( buff + 20);
if( elem) /* just doing a format check */
{
elem->epoch = (double)epoch_jd - .5;
elem->mean_anomaly = atof( buff + 26);
elem->arg_per = atof( buff + 37);
elem->asc_node = atof( buff + 48);
elem->incl = atof( buff + 59);
elem->ecc = atof( buff + 69);
elem->major_axis = atof( buff + 92);
do_remaining_element_setup( elem);
if( buff[10] == '.')
elem->abs_mag = atof( buff + 8);
else
elem->abs_mag = 0.;
if( buff[16] == '.')
elem->slope_param = atof( buff + 14);
else
elem->slope_param = 0.;
}
}
return( epoch_jd);
}
/* extract_astorb_dat( ) is essentially the same as the above
extract_mpcorb_dat( ) function, except using 'astorb.dat'-formatted
data. */
static long extract_long( const char *ibuff)
{
long rval = 0;
while( *ibuff == ' ') /* skip leading spaces */
ibuff++;
while( *ibuff != ' ')
{
if( *ibuff != '.')
rval = rval * 10 + (long)( *ibuff - '0');
ibuff++;
}
return( rval);
}
long extract_astorb_dat( ELEMENTS *elem, const char *buff)
{
long epoch_jd;
ELEMENTS telem;
if( strlen( buff) > 267
&& sscanf( buff + 41, "%lf %lf", &telem.abs_mag, &telem.slope_param) == 2)
{
epoch_jd = atoi( buff + 106);
telem.mean_anomaly = (double)extract_long( buff + 115) / 1.e+6;
telem.arg_per = (double)extract_long( buff + 126) / 1.e+6;
telem.asc_node = (double)extract_long( buff + 137) / 1.e+6;
telem.incl = (double)extract_long( buff + 148) / 1.e+6;
telem.ecc = (double)extract_long( buff + 160) / 1.e+8;
telem.major_axis = atof( buff + 169);
epoch_jd = dmy_to_day( epoch_jd % 100L, /* day */
(epoch_jd / 100L) % 100L, /* month */
epoch_jd / 10000L, /* year */
CALENDAR_GREGORIAN);
telem.epoch = (double)epoch_jd - .5;
do_remaining_element_setup( &telem);
if( elem)
*elem = telem;
}
else
epoch_jd = 0;
return( epoch_jd);
}
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