/*-----------------------------------------------------------------------------
*
* procedure sgp4init
*
* this procedure initializes variables for sgp4.
*
* author : david vallado 719-573-2600 28 jun 2005
* author : david vallado 719-573-2600 28 jun 2005
*
* inputs :
* opsmode - mode of operation afspc or improved 'a', 'i'
* satn - satellite number
* bstar - sgp4 type drag coefficient kg/m2er
* ecco - eccentricity
* epoch - epoch time in days from jan 0, 1950. 0 hr
* argpo - argument of perigee (output if ds)
* inclo - inclination
* mo - mean anomaly (output if ds)
* no - mean motion
* nodeo - right ascension of ascending node
*
* outputs :
* rec - common values for subsequent calls
* return code - non-zero on error.
* 1 - mean elements, ecc >= 1.0 or ecc < -0.001 or a < 0.95 er
* 2 - mean motion less than 0.0
* 3 - pert elements, ecc < 0.0 or ecc > 1.0
* 4 - semi-latus rectum < 0.0
* 5 - epoch elements are sub-orbital
* 6 - satellite has decayed
*
* locals :
* cnodm , snodm , cosim , sinim , cosomm , sinomm
* cc1sq , cc2 , cc3
* coef , coef1
* cosio4 -
* day -
* dndt -
* em - eccentricity
* emsq - eccentricity squared
* eeta -
* etasq -
* gam -
* argpm - argument of perigee
* nodem -
* inclm - inclination
* mm - mean anomaly
* nm - mean motion
* perige - perigee
* pinvsq -
* psisq -
* qzms24 -
* rtemsq -
* s1, s2, s3, s4, s5, s6, s7 -
* sfour -
* ss1, ss2, ss3, ss4, ss5, ss6, ss7 -
* sz1, sz2, sz3
* sz11, sz12, sz13, sz21, sz22, sz23, sz31, sz32, sz33 -
* tc -
* temp -
* temp1, temp2, temp3 -
* tsi -
* xpidot -
* xhdot1 -
* z1, z2, z3 -
* z11, z12, z13, z21, z22, z23, z31, z32, z33 -
*
* coupling :
* getgravconst-
* initl -
* dscom -
* dpper -
* dsinit -
* sgp4 -
*
* references :
* hoots, roehrich, norad spacetrack report #3 1980
* hoots, norad spacetrack report #6 1986
* hoots, schumacher and glover 2004
* vallado, crawford, hujsak, kelso 2006
* ----------------------------------------------------------------------------*/
public void sgp4init(Satrec satrec, Sgp4initOptions options)
{
Globals globals = new Globals();
double pi = globals.pi;
double earthRadius = globals.earthRadius;
double j2 = globals.j2;
double j4 = globals.j4;
double j3oj2 = globals.j3oj2;
double x2o3 = globals.x2o3;
char opsmode = options.opsmode;
string satn = options.satn;
double epoch = options.epoch;
double xbstar = options.xbstar;
double xecco = options.xecco;
double xargpo = options.xargpo;
double xinclo = options.xinclo;
double xmo = options.xmo;
double xno = options.xno;
double xnodeo = options.xnodeo;
double cosim;
double sinim;
double cc1sq;
double cc2;
double cc3;
double coef;
double coef1;
double cosio4;
double em;
double emsq;
double eeta;
double etasq;
double argpm;
double nodem;
double inclm;
double mm;
double nm;
double perige;
double pinvsq;
double psisq;
double qzms24;
double s1;
double s2;
double s3;
double s4;
double s5;
double sfour;
double ss1;
double ss2;
double ss3;
double ss4;
double ss5;
double sz1;
double sz3;
double sz11;
double sz13;
double sz21;
double sz23;
double sz31;
double sz33;
double tc;
double temp;
double temp1;
double temp2;
double temp3;
double tsi;
double xpidot;
double xhdot1;
double z1;
double z3;
double z11;
double z13;
double z21;
double z23;
double z31;
double z33;
/* ------------------------ initialization --------------------- */
// sgp4fix divisor for divide by zero check on inclination
// the old check used 1.0 + Math.cos(pi-1.0e-9), but then compared it to
// 1.5 e-12, so the threshold was changed to 1.5e-12 for consistency
double temp4 = 1.5e-12;
// ----------- set all near earth variables to zero ------------
satrec.isimp = 0; satrec.method = 'n'; satrec.aycof = 0.0;
satrec.con41 = 0.0; satrec.cc1 = 0.0; satrec.cc4 = 0.0;
satrec.cc5 = 0.0; satrec.d2 = 0.0; satrec.d3 = 0.0;
satrec.d4 = 0.0; satrec.delmo = 0.0; satrec.eta = 0.0;
satrec.argpdot = 0.0; satrec.omgcof = 0.0; satrec.sinmao = 0.0;
satrec.t = 0.0; satrec.t2cof = 0.0; satrec.t3cof = 0.0;
satrec.t4cof = 0.0; satrec.t5cof = 0.0; satrec.x1mth2 = 0.0;
satrec.x7thm1 = 0.0; satrec.mdot = 0.0; satrec.nodedot = 0.0;
satrec.xlcof = 0.0; satrec.xmcof = 0.0; satrec.nodecf = 0.0;
// ----------- set all deep space variables to zero ------------
satrec.irez = 0; satrec.d2201 = 0.0; satrec.d2211 = 0.0;
satrec.d3210 = 0.0; satrec.d3222 = 0.0; satrec.d4410 = 0.0;
satrec.d4422 = 0.0; satrec.d5220 = 0.0; satrec.d5232 = 0.0;
satrec.d5421 = 0.0; satrec.d5433 = 0.0; satrec.dedt = 0.0;
satrec.del1 = 0.0; satrec.del2 = 0.0; satrec.del3 = 0.0;
satrec.didt = 0.0; satrec.dmdt = 0.0; satrec.dnodt = 0.0;
satrec.domdt = 0.0; satrec.e3 = 0.0; satrec.ee2 = 0.0;
satrec.peo = 0.0; satrec.pgho = 0.0; satrec.pho = 0.0;
satrec.pinco = 0.0; satrec.plo = 0.0; satrec.se2 = 0.0;
satrec.se3 = 0.0; satrec.sgh2 = 0.0; satrec.sgh3 = 0.0;
satrec.sgh4 = 0.0; satrec.sh2 = 0.0; satrec.sh3 = 0.0;
satrec.si2 = 0.0; satrec.si3 = 0.0; satrec.sl2 = 0.0;
satrec.sl3 = 0.0; satrec.sl4 = 0.0; satrec.gsto = 0.0;
satrec.xfact = 0.0; satrec.xgh2 = 0.0; satrec.xgh3 = 0.0;
satrec.xgh4 = 0.0; satrec.xh2 = 0.0; satrec.xh3 = 0.0;
satrec.xi2 = 0.0; satrec.xi3 = 0.0; satrec.xl2 = 0.0;
satrec.xl3 = 0.0; satrec.xl4 = 0.0; satrec.xlamo = 0.0;
satrec.zmol = 0.0; satrec.zmos = 0.0; satrec.atime = 0.0;
satrec.xli = 0.0; satrec.xni = 0.0;
// sgp4fix - note the following variables are also passed directly via satrec.
// it is possible to streamline the sgp4init call by deleting the "x"
// variables, but the user would need to set the satrec.* values first. we
// include the additional assignments in case twoline2rv is not used.
satrec.bstar = xbstar;
satrec.ecco = xecco;
satrec.argpo = xargpo;
satrec.inclo = xinclo;
satrec.mo = xmo;
satrec.no = xno;
satrec.nodeo = xnodeo;
// sgp4fix add opsmode
satrec.operationmode = opsmode;
// ------------------------ earth constants -----------------------
// sgp4fix identify constants and allow alternate values
double ss = (78.0 / earthRadius) + 1.0;
// sgp4fix use multiply for speed instead of pow
double qzms2ttemp = (120.0 - 78.0) / earthRadius;
double qzms2t = qzms2ttemp * qzms2ttemp * qzms2ttemp * qzms2ttemp;
satrec.init = 'y';
satrec.t = 0.0;
InitlOptions initlOptions = new InitlOptions();
initlOptions.satn = satn;
initlOptions.ecco = satrec.ecco;
initlOptions.epoch = epoch;
initlOptions.inlco = satrec.inclo;
initlOptions.no = satrec.no;
initlOptions.method = satrec.method;
initlOptions.opsmode = satrec.operationmode;
Initl initl = new Initl();
InitlResult initlResult = new InitlResult();
initlResult = initl.initl(initlOptions); //TODO: Finish impl
double ao = initlResult.ao;
double con42 = initlResult.con42;
double cosio = initlResult.cosio;
double cosio2 = initlResult.cosio2;
double eccsq = initlResult.eccsq;
double omeosq = initlResult.omeosq;
double posq = initlResult.posq;
double rp = initlResult.rp;
double rteosq = initlResult.rteosq;
double sinio = initlResult.sinio;
satrec.no = initlResult.no;
satrec.con41 = initlResult.con41;
satrec.gsto = initlResult.gsto;
satrec.error = 0;
// sgp4fix remove this check as it is unnecessary
// the mrt check in sgp4 handles decaying satellite cases even if the starting
// condition is below the surface of te earth
// if (rp < 1.0)
// {
// printf("// *** satn%d epoch elts sub-orbital ***\n", satn);
// satrec.error = 5;
// }
if (omeosq >= 0.0 || satrec.no >= 0.0)
{
satrec.isimp = 0;
if (rp < (220.0 / earthRadius + 1.0))
{
satrec.isimp = 1;
}
sfour = ss;
qzms24 = qzms2t;
perige = (rp - 1.0) * earthRadius;
// - for perigees below 156 km, s and qoms2t are altered -
if (perige < 156.0)
{
sfour = perige - 78.0;
if (perige < 98.0)
{
sfour = 20.0;
}
// sgp4fix use multiply for speed instead of pow
double qzms24temp = (120.0 - sfour) / earthRadius;
qzms24 = qzms24temp * qzms24temp * qzms24temp * qzms24temp;
sfour = (sfour / earthRadius) + 1.0;
}
pinvsq = 1.0 / posq;
tsi = 1.0 / (ao - sfour);
satrec.eta = ao * satrec.ecco * tsi;
etasq = satrec.eta * satrec.eta;
eeta = satrec.ecco * satrec.eta;
psisq = Math.Abs(1.0 - etasq);
coef = qzms24 * Math.Pow(tsi, 4.0);
coef1 = coef / (Math.Pow(psisq, 3.5));
cc2 = coef1 * satrec.no * ((ao * (1.0 + (1.5 * etasq) + (eeta * (4.0 + etasq))))
+ (((0.375 * j2 * tsi) / psisq) * satrec.con41
* (8.0 + (3.0 * etasq * (8.0 + etasq)))));
satrec.cc1 = satrec.bstar * cc2;
cc3 = 0.0;
if (satrec.ecco > 1.0e-4)
{
cc3 = (-2.0 * coef * tsi * j3oj2 * satrec.no * sinio) / satrec.ecco;
}
satrec.x1mth2 = 1.0 - cosio2;
satrec.cc4 = 2.0 * satrec.no * coef1 * ao * omeosq * (
((satrec.eta * (2.0 + (0.5 * etasq)))
+ (satrec.ecco * (0.5 + (2.0 * etasq))))
- (((j2 * tsi) / (ao * psisq))
* ((-3.0 * satrec.con41 * ((1.0 - (2.0 * eeta)) + (etasq * (1.5 - (0.5 * eeta)))))
+ (0.75 * satrec.x1mth2
* ((2.0 * etasq) - (eeta * (1.0 + etasq)))
* Math.Cos(2.0 * satrec.argpo))))
);
satrec.cc5 = 2.0 * coef1 * ao * omeosq * (1.0 + (2.75 * (etasq + eeta)) + (eeta * etasq));
cosio4 = cosio2 * cosio2;
temp1 = 1.5 * j2 * pinvsq * satrec.no;
temp2 = 0.5 * temp1 * j2 * pinvsq;
temp3 = -0.46875 * j4 * pinvsq * pinvsq * satrec.no;
satrec.mdot = satrec.no + (0.5 * temp1 * rteosq * satrec.con41)
+ (0.0625 * temp2 * rteosq * ((13.0 - (78.0 * cosio2)) + (137.0 * cosio4)));
satrec.argpdot = (-0.5 * temp1 * con42)
+ (0.0625 * temp2 * ((7.0 - (114.0 * cosio2)) + (395.0 * cosio4)))
+ (temp3 * ((3.0 - (36.0 * cosio2)) + (49.0 * cosio4)));
xhdot1 = -temp1 * cosio;
satrec.nodedot = xhdot1 + (((0.5 * temp2 * (4.0 - (19.0 * cosio2)))
+ (2.0 * temp3 * (3.0 - (7.0 * cosio2)))) * cosio);
xpidot = satrec.argpdot + satrec.nodedot;
satrec.omgcof = satrec.bstar * cc3 * Math.Cos(satrec.argpo);
satrec.xmcof = 0.0;
if (satrec.ecco > 1.0e-4)
{
satrec.xmcof = (-x2o3 * coef * satrec.bstar) / eeta;
}
satrec.nodecf = 3.5 * omeosq * xhdot1 * satrec.cc1;
satrec.t2cof = 1.5 * satrec.cc1;
// sgp4fix for divide by zero with xinco = 180 deg
if (Math.Abs(cosio + 1.0) > 1.5e-12)
{
satrec.xlcof = (-0.25 * j3oj2 * sinio * (3.0 + (5.0 * cosio))) / (1.0 + cosio);
}
else
{
satrec.xlcof = (-0.25 * j3oj2 * sinio * (3.0 + (5.0 * cosio))) / temp4;
}
satrec.aycof = -0.5 * j3oj2 * sinio;
// sgp4fix use multiply for speed instead of pow
double delmotemp = 1.0 + (satrec.eta * Math.Cos(satrec.mo));
satrec.delmo = delmotemp * delmotemp * delmotemp;
satrec.sinmao = Math.Sin(satrec.mo);
satrec.x7thm1 = (7.0 * cosio2) - 1.0;
// --------------- deep space initialization -------------
if ((2 * pi) / satrec.no >= 225.0)
{
satrec.method = 'd';
satrec.isimp = 1;
tc = 0.0;
inclm = satrec.inclo;
DscomOptions dscomOptions = new DscomOptions();
dscomOptions.epoch = epoch;
dscomOptions.ep = satrec.ecco;
dscomOptions.argpp = satrec.argpo;
dscomOptions.tc = tc;
dscomOptions.inclp = satrec.inclo;
dscomOptions.nodep = satrec.nodeo;
dscomOptions.np = satrec.no;
dscomOptions.e3 = satrec.e3;
dscomOptions.ee2 = satrec.ee2;
dscomOptions.peo = satrec.peo;
dscomOptions.pgho = satrec.pgho;
dscomOptions.pho = satrec.pho;
dscomOptions.pinco = satrec.pinco;
dscomOptions.plo = satrec.plo;
dscomOptions.se2 = satrec.se2;
dscomOptions.se3 = satrec.se3;
dscomOptions.sgh2 = satrec.sgh2;
dscomOptions.sgh3 = satrec.sgh3;
dscomOptions.sgh4 = satrec.sgh4;
dscomOptions.sh2 = satrec.sh2;
dscomOptions.sh3 = satrec.sh3;
dscomOptions.si2 = satrec.si2;
dscomOptions.si3 = satrec.si3;
dscomOptions.sl2 = satrec.sl2;
dscomOptions.sl3 = satrec.sl3;
dscomOptions.sl4 = satrec.sl4;
dscomOptions.xgh2 = satrec.xgh2;
dscomOptions.xgh3 = satrec.xgh3;
dscomOptions.xgh4 = satrec.xgh4;
dscomOptions.xh2 = satrec.xh2;
dscomOptions.xh3 = satrec.xh3;
dscomOptions.xi2 = satrec.xi2;
dscomOptions.xi3 = satrec.xi3;
dscomOptions.xl2 = satrec.xl2;
dscomOptions.xl3 = satrec.xl3;
dscomOptions.xl4 = satrec.xl4;
dscomOptions.zmol = satrec.zmol;
dscomOptions.zmos = satrec.zmos;
Dscom dscom = new Dscom();
DscomResult dscomResult = new DscomResult();
dscomResult = dscom.dscom(dscomOptions);
satrec.e3 = dscomResult.e3;
satrec.ee2 = dscomResult.ee2;
satrec.peo = dscomResult.peo;
satrec.pgho = dscomResult.pgho;
satrec.pho = dscomResult.pho;
satrec.pinco = dscomResult.pinco;
satrec.plo = dscomResult.plo;
satrec.se2 = dscomResult.se2;
satrec.se3 = dscomResult.se3;
satrec.sgh2 = dscomResult.sgh2;
satrec.sgh3 = dscomResult.sgh3;
satrec.sgh4 = dscomResult.sgh4;
satrec.sh2 = dscomResult.sh2;
satrec.sh3 = dscomResult.sh3;
satrec.si2 = dscomResult.si2;
satrec.si3 = dscomResult.si3;
satrec.sl2 = dscomResult.sl2;
satrec.sl3 = dscomResult.sl3;
satrec.sl4 = dscomResult.sl4;
sinim = dscomResult.sinim;
cosim = dscomResult.cosim;
em = dscomResult.em;
emsq = dscomResult.emsq;
s1 = dscomResult.s1;
s2 = dscomResult.s2;
s3 = dscomResult.s3;
s4 = dscomResult.s4;
s5 = dscomResult.s5;
ss1 = dscomResult.ss1;
ss2 = dscomResult.ss2;
ss3 = dscomResult.ss3;
ss4 = dscomResult.ss4;
ss5 = dscomResult.ss5;
sz1 = dscomResult.sz1;
sz3 = dscomResult.sz3;
sz11 = dscomResult.sz11;
sz13 = dscomResult.sz13;
sz21 = dscomResult.sz21;
sz23 = dscomResult.sz23;
sz31 = dscomResult.sz31;
sz33 = dscomResult.sz33;
satrec.xgh2 = dscomResult.xgh2;
satrec.xgh3 = dscomResult.xgh3;
satrec.xgh4 = dscomResult.xgh4;
satrec.xh2 = dscomResult.xh2;
satrec.xh3 = dscomResult.xh3;
satrec.xi2 = dscomResult.xi2;
satrec.xi3 = dscomResult.xi3;
satrec.xl2 = dscomResult.xl2;
satrec.xl3 = dscomResult.xl3;
satrec.xl4 = dscomResult.xl4;
satrec.zmol = dscomResult.zmol;
satrec.zmos = dscomResult.zmos;
nm = dscomResult.nm;
z1 = dscomResult.z1;
z3 = dscomResult.z3;
z11 = dscomResult.z11;
z13 = dscomResult.z13;
z21 = dscomResult.z21;
z23 = dscomResult.z23;
z31 = dscomResult.z31;
z33 = dscomResult.z33;
DpperOptions dpperOptions = new DpperOptions();
dpperOptions.inclo = inclm;
dpperOptions.init = satrec.init;
dpperOptions.ep = satrec.ecco;
dpperOptions.inclp = satrec.inclo;
dpperOptions.nodep = satrec.nodeo;
dpperOptions.argpp = satrec.argpo;
dpperOptions.mp = satrec.mo;
dpperOptions.opsmode = satrec.operationmode;
Dpper dpper = new Dpper();
DpperResult dpperResult = new DpperResult();
dpperResult = dpper.dpper(satrec, dpperOptions);
satrec.ecco = dpperResult.ep;
satrec.inclo = dpperResult.inclp;
satrec.nodeo = dpperResult.nodep;
satrec.argpo = dpperResult.argpp;
satrec.mo = dpperResult.mp;
argpm = 0.0;
nodem = 0.0;
mm = 0.0;
DsinitOptions dsinitOptions = new DsinitOptions();
dsinitOptions.cosim = cosim;
dsinitOptions.emsq = emsq;
dsinitOptions.argpo = satrec.argpo;
dsinitOptions.s1 = s1;
dsinitOptions.s2 = s2;
dsinitOptions.s3 = s3;
dsinitOptions.s4 = s4;
dsinitOptions.s5 = s5;
dsinitOptions.sinim = sinim;
dsinitOptions.ss1 = ss1;
dsinitOptions.ss2 = ss2;
dsinitOptions.ss3 = ss3;
dsinitOptions.ss4 = ss4;
dsinitOptions.ss5 = ss5;
dsinitOptions.sz1 = sz1;
dsinitOptions.sz3 = sz3;
dsinitOptions.sz11 = sz11;
dsinitOptions.sz13 = sz13;
dsinitOptions.sz21 = sz21;
dsinitOptions.sz23 = sz23;
dsinitOptions.sz31 = sz31;
dsinitOptions.sz33 = sz33;
dsinitOptions.t = satrec.t;
dsinitOptions.tc = tc;
dsinitOptions.gsto = satrec.gsto;
dsinitOptions.mo = satrec.mo;
dsinitOptions.mdot = satrec.mdot;
dsinitOptions.no = satrec.no;
dsinitOptions.nodeo = satrec.nodeo;
dsinitOptions.nodedot = satrec.nodedot;
dsinitOptions.xpidot = xpidot;
dsinitOptions.z1 = z1;
dsinitOptions.z3 = z3;
dsinitOptions.z11 = z11;
dsinitOptions.z13 = z13;
dsinitOptions.z21 = z21;
dsinitOptions.z23 = z23;
dsinitOptions.z31 = z31;
dsinitOptions.z33 = z33;
dsinitOptions.ecco = satrec.ecco;
dsinitOptions.eccsq = eccsq;
dsinitOptions.em = em;
dsinitOptions.argpm = argpm;
dsinitOptions.inclm = inclm;
dsinitOptions.mm = mm;
dsinitOptions.nm = nm;
dsinitOptions.nodem = nodem;
dsinitOptions.irez = satrec.irez;
dsinitOptions.atime = satrec.atime;
dsinitOptions.d2201 = satrec.d2201;
dsinitOptions.d2211 = satrec.d2211;
dsinitOptions.d3210 = satrec.d3210;
dsinitOptions.d3222 = satrec.d3222;
dsinitOptions.d4410 = satrec.d4410;
dsinitOptions.d4422 = satrec.d4422;
dsinitOptions.d5220 = satrec.d5220;
dsinitOptions.d5232 = satrec.d5232;
dsinitOptions.d5421 = satrec.d5421;
dsinitOptions.d5433 = satrec.d5433;
dsinitOptions.dedt = satrec.dedt;
dsinitOptions.didt = satrec.didt;
dsinitOptions.dmdt = satrec.dmdt;
dsinitOptions.dnodt = satrec.dnodt;
dsinitOptions.domdt = satrec.domdt;
dsinitOptions.del1 = satrec.del1;
dsinitOptions.del2 = satrec.del2;
dsinitOptions.del3 = satrec.del3;
dsinitOptions.xfact = satrec.xfact;
dsinitOptions.xlamo = satrec.xlamo;
dsinitOptions.xli = satrec.xli;
dsinitOptions.xni = satrec.xni;
Dsinit dsinit = new Dsinit();
DsinitResult dsinitResult = new DsinitResult();
dsinitResult = dsinit.dsinit(dsinitOptions);
satrec.irez = dsinitResult.irez;
satrec.atime = dsinitResult.atime;
satrec.d2201 = dsinitResult.d2201;
satrec.d2211 = dsinitResult.d2211;
satrec.d3210 = dsinitResult.d3210;
satrec.d3222 = dsinitResult.d3222;
satrec.d4410 = dsinitResult.d4410;
satrec.d4422 = dsinitResult.d4422;
satrec.d5220 = dsinitResult.d5220;
satrec.d5232 = dsinitResult.d5232;
satrec.d5421 = dsinitResult.d5421;
satrec.d5433 = dsinitResult.d5433;
satrec.dedt = dsinitResult.dedt;
satrec.didt = dsinitResult.didt;
satrec.dmdt = dsinitResult.dmdt;
satrec.dnodt = dsinitResult.dnodt;
satrec.domdt = dsinitResult.domdt;
satrec.del1 = dsinitResult.del1;
satrec.del2 = dsinitResult.del2;
satrec.del3 = dsinitResult.del3;
satrec.xfact = dsinitResult.xfact;
satrec.xlamo = dsinitResult.xlamo;
satrec.xli = dsinitResult.xli;
satrec.xni = dsinitResult.xni;
}
// ----------- set variables if not deep space -----------
if (satrec.isimp != 1)
{
cc1sq = satrec.cc1 * satrec.cc1;
satrec.d2 = 4.0 * ao * tsi * cc1sq;
temp = (satrec.d2 * tsi * satrec.cc1) / 3.0;
satrec.d3 = ((17.0 * ao) + sfour) * temp;
satrec.d4 = 0.5 * temp * ao * tsi * ((221.0 * ao) + (31.0 * sfour)) * satrec.cc1;
satrec.t3cof = satrec.d2 + (2.0 * cc1sq);
satrec.t4cof = 0.25 * ((3.0 * satrec.d3)
+ (satrec.cc1 * ((12.0 * satrec.d2) + (10.0 * cc1sq))));
satrec.t5cof = 0.2 * (
(3.0 * satrec.d4)
+ (12.0 * satrec.cc1 * satrec.d3)
+ (6.0 * satrec.d2 * satrec.d2)
+ (15.0 * cc1sq * ((2.0 * satrec.d2) + cc1sq))
);
}
/* finally propogate to zero epoch to initialize all others. */
// sgp4fix take out check to let satellites process until they are actually below earth surface
// if(satrec.error == 0)
}
Sgp4 sgp4 = new Sgp4();
sgp4.sgp4(satrec, 0);
satrec.init = 'n';
/* eslint-enable no-param-reassign */
}
/*-----------------------------------------------------------------------------
*
* procedure initl
*
* this procedure initializes the sgp4 propagator. all the initialization is
* consolidated here instead of having multiple loops inside other routines.
*
* author : david vallado 719-573-2600 28 jun 2005
*
* inputs :
* ecco - eccentricity 0.0 - 1.0
* epoch - epoch time in days from jan 0, 1950. 0 hr
* inclo - inclination of satellite
* no - mean motion of satellite
* satn - satellite number
*
* outputs :
* ainv - 1.0 / a
* ao - semi major axis
* con41 -
* con42 - 1.0 - 5.0 cos(i)
* cosio - cosine of inclination
* cosio2 - cosio squared
* eccsq - eccentricity squared
* method - flag for deep space 'd', 'n'
* omeosq - 1.0 - ecco * ecco
* posq - semi-parameter squared
* rp - radius of perigee
* rteosq - square root of (1.0 - ecco*ecco)
* sinio - sine of inclination
* gsto - gst at time of observation rad
* no - mean motion of satellite
*
* locals :
* ak -
* d1 -
* del -
* adel -
* po -
*
* coupling :
* getgravconst
* gstime - find greenwich sidereal time from the julian date
*
* references :
* hoots, roehrich, norad spacetrack report #3 1980
* hoots, norad spacetrack report #6 1986
* hoots, schumacher and glover 2004
* vallado, crawford, hujsak, kelso 2006
* ----------------------------------------------------------------------------*/
public InitlResult initl(InitlOptions initlOptions)
{
Globals globals = new Globals();
double twoPi = globals.twoPi;
double xke = globals.xke;
double j2 = globals.j2;
double x2o3 = globals.x2o3;
double ecco = initlOptions.ecco;
double epoch = initlOptions.epoch;
double inclo = initlOptions.inlco;
double opsmode = initlOptions.opsmode;
// let {
// no,
// } = options;
double no = initlOptions.no;
// sgp4fix use old way of finding gst
// ----------------------- earth constants ---------------------
// sgp4fix identify constants and allow alternate values
// ------------- calculate auxillary epoch quantities ----------
double eccsq = ecco * ecco;
double omeosq = 1.0 - eccsq;
double rteosq = Math.Sqrt(omeosq);
double cosio = Math.Cos(inclo);
double cosio2 = cosio * cosio;
// ------------------ un-kozai the mean motion -----------------
// double ak = ((xke / no) ** x2o3);
double ak = Math.Pow((xke / no), x2o3);
double d1 = (0.75 * j2 * ((3.0 * cosio2) - 1.0)) / (rteosq * omeosq);
double delPrime = d1 / (ak * ak);
double adel = ak * (1.0 - (delPrime * delPrime)
- (delPrime * ((1.0 / 3.0) + ((134.0 * delPrime * delPrime) / 81.0))));
delPrime = d1 / (adel * adel);
no /= (1.0 + delPrime);
// double ao = ((xke / no) ** x2o3);
double ao = Math.Pow((xke / no), x2o3);
double sinio = Math.Sin(inclo);
double po = ao * omeosq;
double con42 = 1.0 - (5.0 * cosio2);
double con41 = -con42 - cosio2 - cosio2;
double ainv = 1.0 / ao;
double posq = po * po;
double rp = ao * (1.0 - ecco);
double method = 'n';
// sgp4fix modern approach to finding sidereal time
double gsto;
if (opsmode == 'a')
{
// sgp4fix use old way of finding gst
// count integer number of days from 0 jan 1970
double ts70 = epoch - 7305.0;
double ds70 = Math.Floor(ts70 + 1.0e-8);
double tfrac = ts70 - ds70;
// find greenwich location at epoch
double c1 = 1.72027916940703639e-2;
double thgr70 = 1.7321343856509374;
double fk5r = 5.07551419432269442e-15;
double c1p2p = c1 + twoPi;
gsto = (thgr70 + (c1 * ds70) + (c1p2p * tfrac) + (ts70 * ts70 * fk5r)) % twoPi;
if (gsto < 0.0)
{
gsto += twoPi;
}
}
else
{
gsto = 0; //placeholder until gstime implemented;
//TODO: impl gstime
// gsto = gstime(epoch + 2433281.5);
}
// set variables and return object
InitlResult initlResult = new InitlResult();
initlResult.no = no;
initlResult.method = method;
initlResult.ainv = ainv;
initlResult.ao = ao;
initlResult.con41 = con41;
initlResult.con42 = con42;
initlResult.cosio = cosio;
initlResult.cosio2 = cosio2;
initlResult.eccsq = eccsq;
initlResult.omeosq = omeosq;
initlResult.posq = posq;
initlResult.rp = rp;
initlResult.rteosq = rteosq;
initlResult.sinio = sinio;
initlResult.gsto = gsto;
return(initlResult);
}
