Exemplo n.º 1
0
/*-----------------------------------------------------------------------------
 *
 *                             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 */
        }
Exemplo n.º 2
0
        /* -----------------------------------------------------------------------------
         *
         *                           procedure dpper
         *
         *  this procedure provides deep space long period periodic contributions
         *    to the mean elements.  by design, these periodics are zero at epoch.
         *    this used to be dscom which included initialization, but it's really a
         *    recurring function.
         *
         *  author        : david vallado                  719-573-2600   28 jun 2005
         *
         *  inputs        :
         *    e3          -
         *    ee2         -
         *    peo         -
         *    pgho        -
         *    pho         -
         *    pinco       -
         *    plo         -
         *    se2 , se3 , sgh2, sgh3, sgh4, sh2, sh3, si2, si3, sl2, sl3, sl4 -
         *    t           -
         *    xh2, xh3, xi2, xi3, xl2, xl3, xl4 -
         *    zmol        -
         *    zmos        -
         *    ep          - eccentricity                           0.0 - 1.0
         *    inclo       - inclination - needed for lyddane modification
         *    nodep       - right ascension of ascending node
         *    argpp       - argument of perigee
         *    mp          - mean anomaly
         *
         *  outputs       :
         *    ep          - eccentricity                           0.0 - 1.0
         *    inclp       - inclination
         *    nodep        - right ascension of ascending node
         *    argpp       - argument of perigee
         *    mp          - mean anomaly
         *
         *  locals        :
         *    alfdp       -
         *    betdp       -
         *    cosip  , sinip  , cosop  , sinop  ,
         *    dalf        -
         *    dbet        -
         *    dls         -
         *    f2, f3      -
         *    pe          -
         *    pgh         -
         *    ph          -
         *    pinc        -
         *    pl          -
         *    sel   , ses   , sghl  , sghs  , shl   , shs   , sil   , sinzf , sis   ,
         *    sll   , sls
         *    xls         -
         *    xnoh        -
         *    zf          -
         *    zm          -
         *
         *  coupling      :
         *    none.
         *
         *  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 DpperResult dpper(Satrec satrec, DpperOptions dpperOptions)
        {
            Globals globals = new Globals();
            double  pi      = globals.pi;
            double  twoPi   = globals.twoPi;

            double e3    = satrec.e3;
            double ee2   = satrec.ee2;
            double peo   = satrec.peo;
            double pgho  = satrec.pgho;
            double pho   = satrec.pho;
            double pinco = satrec.pinco;
            double plo   = satrec.plo;
            double se2   = satrec.se2;
            double se3   = satrec.se3;
            double sgh2  = satrec.sgh2;
            double sgh3  = satrec.sgh3;
            double sgh4  = satrec.sgh4;
            double sh2   = satrec.sh2;
            double sh3   = satrec.sh3;
            double si2   = satrec.si2;
            double si3   = satrec.si3;
            double sl2   = satrec.sl2;
            double sl3   = satrec.sl3;
            double sl4   = satrec.sl4;
            double t     = satrec.t;
            double xgh2  = satrec.xgh2;
            double xgh3  = satrec.xgh3;
            double xgh4  = satrec.xgh4;
            double xh2   = satrec.xh2;
            double xh3   = satrec.xh3;
            double xi2   = satrec.xi2;
            double xi3   = satrec.xi3;
            double xl2   = satrec.xl2;
            double xl3   = satrec.xl3;
            double xl4   = satrec.xl4;
            double zmol  = satrec.zmol;
            double zmos  = satrec.zmos;

            double init    = dpperOptions.init;
            double opsmode = dpperOptions.opsmode;

            double ep    = dpperOptions.ep;
            double inclp = dpperOptions.inclp;
            double nodep = dpperOptions.nodep;
            double argpp = dpperOptions.argpp;
            double mp    = dpperOptions.mp;

            // Copy satellite attributes into local variables for convenience
            // and symmetry in writing formulae.

            double alfdp = 0.0;
            double betdp = 0.0;
            double cosip = 0.0;
            double sinip = 0.0;
            double cosop = 0.0;
            double sinop = 0.0;
            double dalf  = 0.0;
            double dbet  = 0.0;
            double dls   = 0.0;
            double f2    = 0.0;
            double f3    = 0.0;
            double pe    = 0.0;
            double pgh   = 0.0;
            double ph    = 0.0;
            double pinc  = 0.0;
            double pl    = 0.0;
            double sinzf = 0.0;
            double xls   = 0.0;
            double xnoh  = 0.0;
            double zf    = 0.0;
            double zm    = 0.0;

            //  ---------------------- constants -----------------------------
            double zns = 1.19459e-5;
            double zes = 0.01675;
            double znl = 1.5835218e-4;
            double zel = 0.05490;

            //  --------------- calculate time varying periodics -----------
            zm = zmos + (zns * t);

            // be sure that the initial call has time set to zero
            if (init == 'y')
            {
                zm = zmos;
            }
            zf    = zm + (2.0 * zes * Math.Sin(zm));
            sinzf = Math.Sin(zf);
            f2    = (0.5 * sinzf * sinzf) - 0.25;
            f3    = -0.5 * sinzf * Math.Cos(zf);

            double ses  = (se2 * f2) + (se3 * f3);
            double sis  = (si2 * f2) + (si3 * f3);
            double sls  = (sl2 * f2) + (sl3 * f3) + (sl4 * sinzf);
            double sghs = (sgh2 * f2) + (sgh3 * f3) + (sgh4 * sinzf);
            double shs  = (sh2 * f2) + (sh3 * f3);

            zm = zmol + (znl * t);
            if (init == 'y')
            {
                zm = zmol;
            }

            zf    = zm + (2.0 * zel * Math.Sin(zm));
            sinzf = Math.Sin(zf);
            f2    = (0.5 * sinzf * sinzf) - 0.25;
            f3    = -0.5 * sinzf * Math.Cos(zf);

            double sel  = (ee2 * f2) + (e3 * f3);
            double sil  = (xi2 * f2) + (xi3 * f3);
            double sll  = (xl2 * f2) + (xl3 * f3) + (xl4 * sinzf);
            double sghl = (xgh2 * f2) + (xgh3 * f3) + (xgh4 * sinzf);
            double shll = (xh2 * f2) + (xh3 * f3);

            pe   = ses + sel;
            pinc = sis + sil;
            pl   = sls + sll;
            pgh  = sghs + sghl;
            ph   = shs + shll;

            if (init == 'n')
            {
                pe    -= peo;
                pinc  -= pinco;
                pl    -= plo;
                pgh   -= pgho;
                ph    -= pho;
                inclp += pinc;
                ep    += pe;
                sinip  = Math.Sin(inclp);
                cosip  = Math.Cos(inclp);

                /* ----------------- apply periodics directly ------------ */
                // sgp4fix for lyddane choice
                // strn3 used original inclination - this is technically feasible
                // gsfc used perturbed inclination - also technically feasible
                // probably best to readjust the 0.2 limit value and limit discontinuity
                // 0.2 rad = 11.45916 deg
                // use next line for original strn3 approach and original inclination
                // if (inclo >= 0.2)
                // use next line for gsfc version and perturbed inclination

                if (inclp >= 0.2)
                {
                    ph    /= sinip;
                    pgh   -= cosip * ph;
                    argpp += pgh;
                    nodep += ph;
                    mp    += pl;
                }
                else
                {
                    //  ---- apply periodics with lyddane modification ----
                    sinop  = Math.Sin(nodep);
                    cosop  = Math.Cos(nodep);
                    alfdp  = sinip * sinop;
                    betdp  = sinip * cosop;
                    dalf   = (ph * cosop) + (pinc * cosip * sinop);
                    dbet   = (-ph * sinop) + (pinc * cosip * cosop);
                    alfdp += dalf;
                    betdp += dbet;
                    nodep %= twoPi;

                    //  sgp4fix for afspc written intrinsic functions
                    //  nodep used without a trigonometric function ahead
                    if (nodep < 0.0 && opsmode == 'a')
                    {
                        nodep += twoPi;
                    }
                    xls   = mp + argpp + (cosip * nodep);
                    dls   = (pl + pgh) - (pinc * nodep * sinip);
                    xls  += dls;
                    xnoh  = nodep;
                    nodep = Math.Atan2(alfdp, betdp);

                    //  sgp4fix for afspc written intrinsic functions
                    //  nodep used without a trigonometric function ahead
                    if (nodep < 0.0 && opsmode == 'a')
                    {
                        nodep += twoPi;
                    }
                    if (Math.Abs(xnoh - nodep) > pi)
                    {
                        if (nodep < xnoh)
                        {
                            nodep += twoPi;
                        }
                        else
                        {
                            nodep -= twoPi;
                        }
                    }
                    mp   += pl;
                    argpp = xls - mp - (cosip * nodep);
                }
            }


            DpperResult dpperResult = new DpperResult();

            dpperResult.ep    = ep;
            dpperResult.inclp = inclp;
            dpperResult.nodep = nodep;
            dpperResult.argpp = argpp;
            dpperResult.mp    = mp;

            return(dpperResult);
        }
Exemplo n.º 3
0
/*----------------------------------------------------------------------------
*
*                             procedure sgp4
*
*  this procedure is the sgp4 prediction model from space command. this is an
*    updated and combined version of sgp4 and sdp4, which were originally
*    published separately in spacetrack report //3. this version follows the
*    methodology from the aiaa paper (2006) describing the history and
*    development of the code.
*
*  author        : david vallado                  719-573-2600   28 jun 2005
*
*  inputs        :
*    satrec  - initialised structure from sgp4init() call.
*    tsince  - time since epoch (minutes)
*
*  outputs       :
*    r           - position vector                     km
*    v           - velocity                            km/sec
*  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        :
*    am          -
*    axnl, aynl        -
*    betal       -
*    cosim   , sinim   , cosomm  , sinomm  , cnod    , snod    , cos2u   ,
*    sin2u   , coseo1  , sineo1  , cosi    , sini    , cosip   , sinip   ,
*    cosisq  , cossu   , sinsu   , cosu    , sinu
*    delm        -
*    delomg      -
*    dndt        -
*    eccm        -
*    emsq        -
*    ecose       -
*    el2         -
*    eo1         -
*    eccp        -
*    esine       -
*    argpm       -
*    argpp       -
*    omgadf      -
*    pl          -
*    r           -
*    rtemsq      -
*    rdotl       -
*    rl          -
*    rvdot       -
*    rvdotl      -
*    su          -
*    t2  , t3   , t4    , tc
*    tem5, temp , temp1 , temp2  , tempa  , tempe  , templ
*    u   , ux   , uy    , uz     , vx     , vy     , vz
*    inclm       - inclination
*    mm          - mean anomaly
*    nm          - mean motion
*    nodem       - right asc of ascending node
*    xinc        -
*    xincp       -
*    xl          -
*    xlm         -
*    mp          -
*    xmdf        -
*    xmx         -
*    xmy         -
*    nodedf      -
*    xnode       -
*    nodep       -
*    np          -
*
*  coupling      :
*    getgravconst-
*    dpper
*    dspace
*
*  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 PositionAndVelocity sgp4(Satrec satrec, double tsince)
        {
            Globals globals = new Globals();

            double pi          = globals.pi;
            double twoPi       = globals.twoPi;
            double earthRadius = globals.earthRadius;
            double xke         = globals.xke;
            double vkmpersec   = globals.vkmpersec;
            double j2          = globals.j2;
            double j3oj2       = globals.j3oj2;
            double x2o3        = globals.x2o3;

            double coseo1 = 0.0;
            double sineo1 = 0.0;
            double cosip  = 0.0;
            double sinip  = 0.0;
            double cosisq = 0.0;
            double delm   = 0.0;
            double delomg = 0.0;
            double eo1    = 0.0;
            double argpm  = 0.0;
            double argpp  = 0.0;
            double su     = 0.0;
            double t3     = 0.0;
            double t4     = 0.0;
            double tc     = 0.0;
            double tem5   = 0.0;
            double temp   = 0.0;
            double tempa  = 0.0;
            double tempe  = 0.0;
            double templ  = 0.0;
            double inclm  = 0.0;
            double mm     = 0.0;
            double nm     = 0.0;
            double nodem  = 0.0;
            double xincp  = 0.0;
            double xlm    = 0.0;
            double mp     = 0.0;
            double nodep  = 0.0;

            /* ------------------ set mathematical constants --------------- */
            // sgp4fix divisor for divide by zero check on inclination
            // the old check used 1.0 + 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;

            // --------------------- clear sgp4 error flag -----------------
            satrec.t     = tsince;
            satrec.error = 0;

            //  ------- update for secular gravity and atmospheric drag -----
            double xmdf   = satrec.mo + (satrec.mdot * satrec.t);
            double argpdf = satrec.argpo + (satrec.argpdot * satrec.t);
            double nodedf = satrec.nodeo + (satrec.nodedot * satrec.t);

            argpm = argpdf;
            mm    = xmdf;
            double t2 = satrec.t * satrec.t;

            nodem = nodedf + (satrec.nodecf * t2);
            tempa = 1.0 - (satrec.cc1 * satrec.t);
            tempe = satrec.bstar * satrec.cc4 * satrec.t;
            templ = satrec.t2cof * t2;

            if (satrec.isimp != 1)
            {
                delomg = satrec.omgcof * satrec.t;
                //  sgp4fix use mutliply for speed instead of pow
                double delmtemp = 1.0 + (satrec.eta * Math.Cos(xmdf));
                delm   = satrec.xmcof * ((delmtemp * delmtemp * delmtemp) - satrec.delmo);
                temp   = delomg + delm;
                mm     = xmdf + temp;
                argpm  = argpdf - temp;
                t3     = t2 * satrec.t;
                t4     = t3 * satrec.t;
                tempa  = tempa - (satrec.d2 * t2) - (satrec.d3 * t3) - (satrec.d4 * t4);
                tempe += satrec.bstar * satrec.cc5 * (Math.Sin(mm) - satrec.sinmao);
                templ  = templ + (satrec.t3cof * t3) + (t4 * (satrec.t4cof + (satrec.t * satrec.t5cof)));
            }

            nm = satrec.no;
            double em = satrec.ecco;

            inclm = satrec.inclo;

            if (satrec.method == 'd')
            {
                tc = satrec.t;

                DspaceOptions dspaceOptions = new DspaceOptions();

                dspaceOptions.irez    = satrec.irez;
                dspaceOptions.d2201   = satrec.d2201;
                dspaceOptions.d2211   = satrec.d2211;
                dspaceOptions.d3210   = satrec.d3210;
                dspaceOptions.d3222   = satrec.d3222;
                dspaceOptions.d4410   = satrec.d4410;
                dspaceOptions.d4422   = satrec.d4422;
                dspaceOptions.d5220   = satrec.d5220;
                dspaceOptions.d5232   = satrec.d5232;
                dspaceOptions.d5421   = satrec.d5421;
                dspaceOptions.d5433   = satrec.d5433;
                dspaceOptions.dedt    = satrec.dedt;
                dspaceOptions.del1    = satrec.del1;
                dspaceOptions.del2    = satrec.del2;
                dspaceOptions.del3    = satrec.del3;
                dspaceOptions.didt    = satrec.didt;
                dspaceOptions.dmdt    = satrec.dmdt;
                dspaceOptions.dnodt   = satrec.dnodt;
                dspaceOptions.domdt   = satrec.domdt;
                dspaceOptions.argpo   = satrec.argpo;
                dspaceOptions.argpdot = satrec.argpdot;
                dspaceOptions.t       = satrec.t;
                dspaceOptions.tc      = tc;
                dspaceOptions.gsto    = satrec.gsto;
                dspaceOptions.xfact   = satrec.xfact;
                dspaceOptions.xlamo   = satrec.xlamo;
                dspaceOptions.no      = satrec.no;
                dspaceOptions.atime   = satrec.atime;
                dspaceOptions.em      = em;
                dspaceOptions.argpm   = argpm;
                dspaceOptions.inclm   = inclm;
                dspaceOptions.xli     = satrec.xli;
                dspaceOptions.mm      = mm;
                dspaceOptions.xni     = satrec.xni;
                dspaceOptions.nodem   = nodem;
                dspaceOptions.nm      = nm;


                Dspace        dspace        = new Dspace();
                DspaceResults dspaceResults = new DspaceResults();
                dspaceResults = dspace.dspace(dspaceOptions);

                em    = dspaceResults.em;
                argpm = dspaceResults.argpm;
                inclm = dspaceResults.inclm;
                mm    = dspaceResults.mm;
                nodem = dspaceResults.nodem;
                nm    = dspaceResults.nm;
            }

            if (nm <= 0.0)
            {
                // printf("// error nm %f\n", nm);
                satrec.error = 2;
                // sgp4fix add return
                PositionAndVelocity noValue = new PositionAndVelocity();
                return(noValue); //TODO set this to 0
            }

            double am = (Math.Pow((xke / nm), x2o3)) * tempa * tempa;

            nm  = xke / (Math.Pow(am, 1.5));
            em -= tempe;

            // fix tolerance for error recognition
            // sgp4fix am is fixed from the previous nm check
            if (em >= 1.0 || em < -0.001) // || (am < 0.95)
            // printf("// error em %f\n", em);
            {
                satrec.error = 1;
                PositionAndVelocity noValue = new PositionAndVelocity();
                return(noValue); //TODO set this to 0
            }

            //  sgp4fix fix tolerance to avoid a divide by zero
            if (em < 1.0e-6)
            {
                em = 1.0e-6;
            }
            mm += satrec.no * templ;
            xlm = mm + argpm + nodem;

            nodem %= twoPi;
            argpm %= twoPi;
            xlm   %= twoPi;
            mm     = (xlm - argpm - nodem) % twoPi;

            // ----------------- compute extra mean quantities -------------
            double sinim = Math.Sin(inclm);
            double cosim = Math.Cos(inclm);

            // -------------------- add lunar-solar periodics --------------
            double ep = em;

            xincp = inclm;
            argpp = argpm;
            nodep = nodem;
            mp    = mm;
            sinip = sinim;
            cosip = cosim;
            if (satrec.method == 'd')
            {
                DpperOptions dpperParameters = new DpperOptions();
                dpperParameters.inclo   = satrec.inclo;
                dpperParameters.init    = 'n';
                dpperParameters.ep      = ep;
                dpperParameters.inclp   = xincp;
                dpperParameters.nodep   = nodep;
                dpperParameters.argpp   = argpp;
                dpperParameters.mp      = mp;
                dpperParameters.opsmode = satrec.operationmode;


                Dpper       dpper       = new Dpper();
                DpperResult dpperResult = new DpperResult();
                dpperResult = dpper.dpper(satrec, dpperParameters);
                ep          = dpperResult.ep;
                nodep       = dpperResult.nodep;
                argpp       = dpperResult.argpp;
                mp          = dpperResult.mp;

                xincp = dpperResult.inclp;

                if (xincp < 0.0)
                {
                    xincp  = -xincp;
                    nodep += pi;
                    argpp -= pi;
                }
                if (ep < 0.0 || ep > 1.0)
                {
                    //  printf("// error ep %f\n", ep);
                    satrec.error = 3;
                    //  sgp4fix add return
                    PositionAndVelocity noValue = new PositionAndVelocity();
                    return(noValue); //TODO set this to 0
                }
            }

            //  -------------------- long period periodics ------------------
            if (satrec.method == 'd')
            {
                sinip        = Math.Sin(xincp);
                cosip        = Math.Cos(xincp);
                satrec.aycof = -0.5 * j3oj2 * sinip;

                //  sgp4fix for divide by zero for xincp = 180 deg
                if (Math.Abs(cosip + 1.0) > 1.5e-12)
                {
                    satrec.xlcof = (-0.25 * j3oj2 * sinip * (3.0 + (5.0 * cosip))) / (1.0 + cosip);
                }
                else
                {
                    satrec.xlcof = (-0.25 * j3oj2 * sinip * (3.0 + (5.0 * cosip))) / temp4;
                }
            }

            double axnl = ep * Math.Cos(argpp);

            temp = 1.0 / (am * (1.0 - (ep * ep)));
            double aynl = (ep * Math.Sin(argpp)) + (temp * satrec.aycof);
            double xl   = mp + argpp + nodep + (temp * satrec.xlcof * axnl);

            // --------------------- solve kepler's equation ---------------
            double u = (xl - nodep) % twoPi;

            eo1  = u;
            tem5 = 9999.9;
            double ktr = 1;

            //    sgp4fix for kepler iteration
            //    the following iteration needs better limits on corrections
            while (Math.Abs(tem5) >= 1.0e-12 && ktr <= 10)
            {
                sineo1 = Math.Sin(eo1);
                coseo1 = Math.Cos(eo1);
                tem5   = 1.0 - (coseo1 * axnl) - (sineo1 * aynl);
                tem5   = (((u - (aynl * coseo1)) + (axnl * sineo1)) - eo1) / tem5;
                if (Math.Abs(tem5) >= 0.95)
                {
                    if (tem5 > 0.0)
                    {
                        tem5 = 0.95;
                    }
                    else
                    {
                        tem5 = -0.95;
                    }
                }
                eo1 += tem5;
                ktr += 1;
            }

            //  ------------- short period preliminary quantities -----------
            double ecose = (axnl * coseo1) + (aynl * sineo1);
            double esine = (axnl * sineo1) - (aynl * coseo1);
            double el2   = (axnl * axnl) + (aynl * aynl);
            double pl    = am * (1.0 - el2);

            if (pl < 0.0)
            {
                //  printf("// error pl %f\n", pl);
                satrec.error = 4;
                //  sgp4fix add return
                PositionAndVelocity noValue = new PositionAndVelocity();
                return(noValue); //TODO set this to 0
            }

            double rl     = am * (1.0 - ecose);
            double rdotl  = (Math.Sqrt(am) * esine) / rl;
            double rvdotl = Math.Sqrt(pl) / rl;
            double betal  = Math.Sqrt(1.0 - el2);

            temp = esine / (1.0 + betal);
            double sinu = (am / rl) * (sineo1 - aynl - (axnl * temp));
            double cosu = (am / rl) * ((coseo1 - axnl) + (aynl * temp));

            su = Math.Atan2(sinu, cosu);
            double sin2u = (cosu + cosu) * sinu;
            double cos2u = 1.0 - (2.0 * sinu * sinu);

            temp = 1.0 / pl;
            double temp1 = 0.5 * j2 * temp;
            double temp2 = temp1 * temp;

            // -------------- update for short period periodics ------------
            if (satrec.method == 'd')
            {
                cosisq        = cosip * cosip;
                satrec.con41  = (3.0 * cosisq) - 1.0;
                satrec.x1mth2 = 1.0 - cosisq;
                satrec.x7thm1 = (7.0 * cosisq) - 1.0;
            }

            double mrt = (rl * (1.0 - (1.5 * temp2 * betal * satrec.con41)))
                         + (0.5 * temp1 * satrec.x1mth2 * cos2u);

            // sgp4fix for decaying satellites
            if (mrt < 1.0)
            {
                // printf("// decay condition %11.6f \n",mrt);
                satrec.error = 6;
                // return {
                //   position: false,
                //   velocity: false,
                // };

                PositionAndVelocity noValue = new PositionAndVelocity();
                return(noValue); //TODO set this to 0
            }

            su -= 0.25 * temp2 * satrec.x7thm1 * sin2u;
            double xnode = nodep + (1.5 * temp2 * cosip * sin2u);
            double xinc  = xincp + (1.5 * temp2 * cosip * sinip * cos2u);
            double mvt   = rdotl - ((nm * temp1 * satrec.x1mth2 * sin2u) / xke);
            double rvdot = rvdotl + ((nm * temp1 * ((satrec.x1mth2 * cos2u) + (1.5 * satrec.con41))) / xke);


            // --------------------- orientation vectors -------------------
            double sinsu = Math.Sin(su);
            double cossu = Math.Cos(su);
            double snod  = Math.Sin(xnode);
            double cnod  = Math.Cos(xnode);
            double sini  = Math.Sin(xinc);
            double cosi  = Math.Cos(xinc);
            double xmx   = -snod * cosi;
            double xmy   = cnod * cosi;
            double ux    = (xmx * sinsu) + (cnod * cossu);
            double uy    = (xmy * sinsu) + (snod * cossu);
            double uz    = sini * sinsu;
            double vx    = (xmx * cossu) - (cnod * sinsu);
            double vy    = (xmy * cossu) - (snod * sinsu);
            double vz    = sini * cossu;

            // --------- position and velocity (in km and km/sec) ----------

            PositionAndVelocity positionAndVelocity = new PositionAndVelocity();

            positionAndVelocity.position_ECI.x = (mrt * ux) * earthRadius;
            positionAndVelocity.position_ECI.y = (mrt * uy) * earthRadius;
            positionAndVelocity.position_ECI.z = (mrt * uz) * earthRadius;

            // double r = {
            //   x: (mrt * ux) * earthRadius,
            //   y: (mrt * uy) * earthRadius,
            //   z: (mrt * uz) * earthRadius,
            // };

            positionAndVelocity.velocity_ECI.x = ((mvt * ux) + (rvdot * vx)) * vkmpersec;
            positionAndVelocity.velocity_ECI.y = ((mvt * uy) + (rvdot * vy)) * vkmpersec;
            positionAndVelocity.velocity_ECI.z = ((mvt * uz) + (rvdot * vz)) * vkmpersec;



            // double v = {
            //   x: ((mvt * ux) + (rvdot * vx)) * vkmpersec,
            //   y: ((mvt * uy) + (rvdot * vy)) * vkmpersec,
            //   z: ((mvt * uz) + (rvdot * vz)) * vkmpersec,
            // };

            // return {
            //   position: r,
            //   velocity: v,
            // };


            return(positionAndVelocity);
        }