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sgp4io.cpp
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sgp4io.cpp
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/* ----------------------------------------------------------------
*
* sgp4io.cpp
*
* this file contains a function to read two line element sets. while
* not formerly part of the sgp4 mathematical theory, it is
* required for practical implemenation.
*
* companion code for
* fundamentals of astrodynamics and applications
* 2007
* by david vallado
*
* (w) 719-573-2600, email [email protected]
*
* current :
* 27 Aug 10 david vallado
* fix input format and delete unused variables in twoline2rv
* changes :
* 3 sep 08 david vallado
* add operationmode for afspc (a) or improved (i)
* 9 may 07 david vallado
* fix year correction to 57
* 27 mar 07 david vallado
* misc fixes to manual inputs
* 14 aug 06 david vallado
* original baseline
* ---------------------------------------------------------------- */
#include "sgp4io.h"
/* -----------------------------------------------------------------------------
*
* function twoline2rv
*
* this function converts the two line element set character string data to
* variables and initializes the sgp4 variables. several intermediate varaibles
* and quantities are determined. note that the result is a structure so multiple
* satellites can be processed simultaneously without having to reinitialize. the
* verification mode is an important option that permits quick checks of any
* changes to the underlying technical theory. this option works using a
* modified tle file in which the start, stop, and delta time values are
* included at the end of the second line of data. this only works with the
* verification mode. the catalog mode simply propagates from -1440 to 1440 min
* from epoch and is useful when performing entire catalog runs.
*
* author : david vallado 719-573-2600 1 mar 2001
*
* inputs :
* longstr1 - first line of the tle
* longstr2 - second line of the tle
* typerun - type of run verification 'v', catalog 'c',
* manual 'm'
* typeinput - type of manual input mfe 'm', epoch 'e', dayofyr 'd'
* opsmode - mode of operation afspc or improved 'a', 'i'
* whichconst - which set of constants to use 72, 84
*
* outputs :
* satrec - structure containing all the sgp4 satellite information
*
* coupling :
* getgravconst-
* days2mdhms - conversion of days to month, day, hour, minute, second
* jday - convert day month year hour minute second into julian date
* sgp4init - initialize the sgp4 variables
*
* references :
* norad spacetrack report #3
* vallado, crawford, hujsak, kelso 2006
--------------------------------------------------------------------------- */
void twoline2rv
(
char longstr1[130], char longstr2[130],
char typerun, char typeinput, char opsmode,
gravconsttype whichconst,
double& startmfe, double& stopmfe, double& deltamin,
elsetrec& satrec
)
{
const double deg2rad = pi / 180.0; // 0.0174532925199433
const double xpdotp = 1440.0 / (2.0 *pi); // 229.1831180523293
double sec, mu, radiusearthkm, tumin, xke, j2, j3, j4, j3oj2;
double startsec, stopsec, startdayofyr, stopdayofyr, jdstart, jdstop;
int startyear, stopyear, startmon, stopmon, startday, stopday,
starthr, stophr, startmin, stopmin;
int cardnumb, numb, j;
long revnum = 0, elnum = 0;
char classification, intldesg[11];
int year = 0;
int mon, day, hr, minute, nexp, ibexp;
getgravconst( whichconst, tumin, mu, radiusearthkm, xke, j2, j3, j4, j3oj2 );
satrec.error = 0;
// set the implied decimal points since doing a formated read
// fixes for bad input data values (missing, ...)
for (j = 10; j <= 15; j++)
if (longstr1[j] == ' ')
longstr1[j] = '_';
if (longstr1[44] != ' ')
longstr1[43] = longstr1[44];
longstr1[44] = '.';
if (longstr1[7] == ' ')
longstr1[7] = 'U';
if (longstr1[9] == ' ')
longstr1[9] = '.';
for (j = 45; j <= 49; j++)
if (longstr1[j] == ' ')
longstr1[j] = '0';
if (longstr1[51] == ' ')
longstr1[51] = '0';
if (longstr1[53] != ' ')
longstr1[52] = longstr1[53];
longstr1[53] = '.';
longstr2[25] = '.';
for (j = 26; j <= 32; j++)
if (longstr2[j] == ' ')
longstr2[j] = '0';
if (longstr1[62] == ' ')
longstr1[62] = '0';
if (longstr1[68] == ' ')
longstr1[68] = '0';
sscanf(longstr1,"%2d %5ld %1c %10s %2d %12lf %11lf %7lf %2d %7lf %2d %2d %6ld ",
&cardnumb,&satrec.satnum,&classification, intldesg, &satrec.epochyr,
&satrec.epochdays,&satrec.ndot, &satrec.nddot, &nexp, &satrec.bstar,
&ibexp, &numb, &elnum );
if (typerun == 'v') // run for specified times from the file
{
if (longstr2[52] == ' ')
sscanf(longstr2,"%2d %5ld %9lf %9lf %8lf %9lf %9lf %10lf %6ld %lf %lf %lf \n",
&cardnumb,&satrec.satnum, &satrec.inclo,
&satrec.nodeo,&satrec.ecco, &satrec.argpo, &satrec.mo, &satrec.no,
&revnum, &startmfe, &stopmfe, &deltamin );
else
sscanf(longstr2,"%2d %5ld %9lf %9lf %8lf %9lf %9lf %11lf %6ld %lf %lf %lf \n",
&cardnumb,&satrec.satnum, &satrec.inclo,
&satrec.nodeo,&satrec.ecco, &satrec.argpo, &satrec.mo, &satrec.no,
&revnum, &startmfe, &stopmfe, &deltamin );
}
else // simply run -1 day to +1 day or user input times
{
if (longstr2[52] == ' ')
sscanf(longstr2,"%2d %5ld %9lf %9lf %8lf %9lf %9lf %10lf %6ld \n",
&cardnumb,&satrec.satnum, &satrec.inclo,
&satrec.nodeo,&satrec.ecco, &satrec.argpo, &satrec.mo, &satrec.no,
&revnum );
else
sscanf(longstr2,"%2d %5ld %9lf %9lf %8lf %9lf %9lf %11lf %6ld \n",
&cardnumb,&satrec.satnum, &satrec.inclo,
&satrec.nodeo,&satrec.ecco, &satrec.argpo, &satrec.mo, &satrec.no,
&revnum );
}
// ---- find no, ndot, nddot ----
satrec.no = satrec.no / xpdotp; //* rad/min
satrec.nddot= satrec.nddot * pow(10.0, nexp);
satrec.bstar= satrec.bstar * pow(10.0, ibexp);
// ---- convert to sgp4 units ----
satrec.a = pow( satrec.no*tumin , (-2.0/3.0) );
satrec.ndot = satrec.ndot / (xpdotp*1440.0); //* ? * minperday
satrec.nddot= satrec.nddot / (xpdotp*1440.0*1440);
// ---- find standard orbital elements ----
satrec.inclo = satrec.inclo * deg2rad;
satrec.nodeo = satrec.nodeo * deg2rad;
satrec.argpo = satrec.argpo * deg2rad;
satrec.mo = satrec.mo * deg2rad;
satrec.alta = satrec.a*(1.0 + satrec.ecco) - 1.0;
satrec.altp = satrec.a*(1.0 - satrec.ecco) - 1.0;
// ----------------------------------------------------------------
// find sgp4epoch time of element set
// remember that sgp4 uses units of days from 0 jan 1950 (sgp4epoch)
// and minutes from the epoch (time)
// ----------------------------------------------------------------
// ---------------- temp fix for years from 1957-2056 -------------------
// --------- correct fix will occur when year is 4-digit in tle ---------
if (satrec.epochyr < 57)
year= satrec.epochyr + 2000;
else
year= satrec.epochyr + 1900;
days2mdhms ( year,satrec.epochdays, mon,day,hr,minute,sec );
jday( year,mon,day,hr,minute,sec, satrec.jdsatepoch );
// ---- input start stop times manually
if ((typerun != 'v') && (typerun != 'c'))
{
// ------------- enter start/stop ymd hms values --------------------
if (typeinput == 'e')
{
printf("input start prop year mon day hr min sec \n");
// make sure there is no space at the end of the format specifiers in scanf!
scanf( "%i %i %i %i %i %lf",&startyear, &startmon, &startday, &starthr, &startmin, &startsec);
fflush(stdin);
jday( startyear,startmon,startday,starthr,startmin,startsec, jdstart );
printf("input stop prop year mon day hr min sec \n");
scanf( "%i %i %i %i %i %lf",&stopyear, &stopmon, &stopday, &stophr, &stopmin, &stopsec);
fflush(stdin);
jday( stopyear,stopmon,stopday,stophr,stopmin,stopsec, jdstop );
startmfe = (jdstart - satrec.jdsatepoch) * 1440.0;
stopmfe = (jdstop - satrec.jdsatepoch) * 1440.0;
printf("input time step in minutes \n");
scanf( "%lf",&deltamin );
}
// -------- enter start/stop year and days of year values -----------
if (typeinput == 'd')
{
printf("input start year dayofyr \n");
scanf( "%i %lf",&startyear, &startdayofyr );
printf("input stop year dayofyr \n");
scanf( "%i %lf",&stopyear, &stopdayofyr );
days2mdhms ( startyear,startdayofyr, mon,day,hr,minute,sec );
jday( startyear,mon,day,hr,minute,sec, jdstart );
days2mdhms ( stopyear,stopdayofyr, mon,day,hr,minute,sec );
jday( stopyear,mon,day,hr,minute,sec, jdstop );
startmfe = (jdstart - satrec.jdsatepoch) * 1440.0;
stopmfe = (jdstop - satrec.jdsatepoch) * 1440.0;
printf("input time step in minutes \n");
scanf( "%lf",&deltamin );
}
// ------------------ enter start/stop mfe values -------------------
if (typeinput == 'm')
{
printf("input start min from epoch \n");
scanf( "%lf",&startmfe );
printf("input stop min from epoch \n");
scanf( "%lf",&stopmfe );
printf("input time step in minutes \n");
scanf( "%lf",&deltamin );
}
}
// ------------ perform complete catalog evaluation, -+ 1 day -----------
if (typerun == 'c')
{
startmfe = -1440.0;
stopmfe = 1440.0;
deltamin = 10.0;
}
// ---------------- initialize the orbit at sgp4epoch -------------------
sgp4init( whichconst, opsmode, satrec.satnum, satrec.jdsatepoch-2433281.5, satrec.bstar,
satrec.ecco, satrec.argpo, satrec.inclo, satrec.mo, satrec.no,
satrec.nodeo, satrec);
} // end twoline2rv