Class: Korba::SGP4

Inherits:

Object

Object
Korba::SGP4

show all

Defined in:: lib/korba/sgp4/sgp4.rb

Constant Summary collapse

PI = copied from github.com/aholinch/sgp4 ---------------------------------------------------------------- sgp4unit.cpp this file contains the sgp4 procedures for analytical propagation of a satellite. the code was originally released in the 1980 and 1986 spacetrack papers. a detailed discussion of the theory and history may be found in the 2006 aiaa paper by vallado, crawford, hujsak, and kelso.

Math::PI

TWOPI =

2.0 * Math::PI

DEG2RAD =

PI / 180.0

WGS72old =

WGS72 =

WGS84 =

Class Method Summary collapse

.dpper(e3, ee2, peo, pgho, pho, pinco, plo, se2, se3, sgh2, sgh3, sgh4, sh2, sh3, si2, si3, sl2, sl3, sl4, t, xgh2, xgh3, xgh4, xh2, xh3, xi2, xi3, xl2, xl3, xl4, zmol, zmos, init, rec, opsmode) ⇒ Object

—————————————————————————–.
.dscom(epoch, ep, argpp, tc, inclp, nodep, np, rec) ⇒ Object

/*—————————————————————————– * * procedure dscom * * this procedure provides deep space common items used by both the secular * and periodics subroutines.
.dsinit(tc, xpidot, rec) ⇒ Object

/*—————————————————————————– * * procedure dsinit * * this procedure provides deep space contributions to mean motion dot due * to geopotential resonance with half day and one day orbits.
.dspace(tc, rec) ⇒ Object

/*—————————————————————————– * * procedure dspace * * this procedure provides deep space contributions to mean elements for * perturbing third body.
.fmod(numer, denom) ⇒ Object

} // getgravconst.
.getgravconst(whichconst, rec) ⇒ Object

/* —————————————————————————– * * function getgravconst * * this function gets constants for the propagator.
.gstime(jdut1) ⇒ Object

/* —————————————————————————– * * function gstime * * this function finds the greenwich sidereal time.
.initl(epoch, rec) ⇒ Object

/*—————————————————————————– * * procedure initl * * this procedure initializes the spg4 propagator.
.jday(year, mon, day, hr, minute, sec) ⇒ Object

/* —————————————————————————– * * procedure jday * * this procedure finds the julian date given the year, month, day, and time.
.sgp4(satrec, tsince, r, v) ⇒ Object

/*—————————————————————————– * * procedure sgp4 * * this procedure is the sgp4 prediction model from space command.
.sgp4init(opsmode, satrec) ⇒ Object

/*—————————————————————————– * * procedure sgp4init * * this procedure initializes variables for sgp4.

Class Method Details

.dpper(e3, ee2, peo, pgho, pho, pinco, plo, se2, se3, sgh2, sgh3, sgh4, sh2, sh3, si2, si3, sl2, sl3, sl4, t, xgh2, xgh3, xgh4, xh2, xh3, xi2, xi3, xl2, xl3, xl4, zmol, zmos, init, rec, opsmode) ⇒ `Object`

                         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.
この手順は、平均要素に対する深宇宙の長周期の周期的寄与を提供します。
 設計上、これらの周期的寄与はエポック時にゼロです。
 以前は初期化を含む dscom でしたが、実際には再帰的な関数です。

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

—————————————————————————*/

# File 'lib/korba/sgp4/sgp4.rb', line 141

def self.dpper(e3, ee2, peo, pgho, pho, pinco, plo, se2, se3, sgh2,
               sgh3, sgh4, sh2, sh3, si2, si3, sl2, sl3, sl4, t,
               xgh2, xgh3, xgh4, xh2, xh3, xi2, xi3, xl2, xl3, xl4,
               zmol, zmos, init, rec, opsmode)

  # --------------------- local variables ------------------------ */
  #double alfdp, betdp, cosip, cosop, dalf, dbet, dls,
  #  f2, f3, pe, pgh, ph, pinc, pl,
  #  sel, ses, sghl, sghs, shll, shs, sil,
  #  sinip, sinop, sinzf, sis, sll, sls, xls,
  #  xnoh, zf, zm, zel, zes, znl, zns

  #/* ---------------------- constants ----------------------------- */
  zns = 1.19459e-5
  zes = 0.01675
  znl = 1.5835218e-4
  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
  end

  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)
  ses = se2 * f2 + se3 * f3
  sis = si2 * f2 + si3 * f3
  sls = sl2 * f2 + sl3 * f3 + sl4 * sinzf
  sghs = sgh2 * f2 + sgh3 * f3 + sgh4 * sinzf
  shs = sh2 * f2 + sh3 * f3
  zm = zmol + znl * t
  if init == "y"
    zm = zmol
  end

  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)
  sel = ee2 * f2 + e3 * f3
  sil = xi2 * f2 + xi3 * f3
  sll = xl2 * f2 + xl3 * f3 + xl4 * sinzf
  sghl = xgh2 * f2 + xgh3 * f3 + xgh4 * sinzf
  shll = xh2 * f2 + xh3 * f3
  pe = ses + sel
  pinc = sis + sil
  pl = sls + sll
  pgh = sghs + sghl
  ph = shs + shll

  if init == "n"
    pe = pe - peo
    pinc = pinc - pinco
    pl = pl - plo
    pgh = pgh - pgho
    ph = ph - pho
    rec.inclp = rec.inclp + pinc
    rec.ep = rec.ep + pe
    sinip = Math.sin(rec.inclp)
    cosip = Math.cos(rec.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 rec.inclp >= 0.2
      ph = ph / sinip
      pgh = pgh - cosip * ph
      rec.argpp = rec.argpp + pgh
      rec.nodep = rec.nodep + ph
      rec.mp = rec.mp + pl
    else
      #/* ---- apply periodics with lyddane modification ---- */
      sinop = Math.sin(rec.nodep)
      cosop = Math.cos(rec.nodep)
      alfdp = sinip * sinop
      betdp = sinip * cosop
      dalf = ph * cosop + pinc * cosip * sinop
      dbet = -ph * sinop + pinc * cosip * cosop
      alfdp = alfdp + dalf
      betdp = betdp + dbet
      rec.nodep = fmod(rec.nodep, TWOPI)
      #//  sgp4fix for afspc written intrinsic functions
      #// nodep used without a trigonometric function ahead
      if (rec.nodep < 0.0) and (opsmode == "a")
        rec.nodep = rec.nodep + TWOPI
      end
      xls = rec.mp + rec.argpp + cosip * rec.nodep
      dls = pl + pgh - pinc * rec.nodep * sinip
      xls = xls + dls
      xls = fmod(xls, TWOPI)
      xnoh = rec.nodep
      rec.nodep = Math.atan2(alfdp, betdp)
      #//  sgp4fix for afspc written intrinsic functions
      #// nodep used without a trigonometric function ahead
      if (rec.nodep < 0.0) and (opsmode == "a")
        rec.nodep = rec.nodep + TWOPI
      end
      if (xnoh - rec.nodep).abs > PI
        if (rec.nodep < xnoh)
          rec.nodep = rec.nodep + TWOPI
        else
          rec.nodep = rec.nodep - TWOPI
        end
      end
      rec.mp = rec.mp + pl
      rec.argpp = xls - rec.mp - cosip * rec.nodep
    end
    #   // if init == 'n'
  end

  #// dpper
end

.dscom(epoch, ep, argpp, tc, inclp, nodep, np, rec) ⇒ `Object`

/*—————————————————————————– *

procedure dscom

this procedure provides deep space common items used by both the secular
and periodics subroutines. input is provided as shown. this routine
used to be called dpper, but the functions inside weren’t well organized.
この手順は、深宇宙の共通項目を提供し、世俗的および周期的なサブルーチンの両方で使用されます。
入力は以下のように提供されます。このルーチンは以前はdpperと呼ばれていましたが、
内部の関数がうまく整理されていませんでした。

author : david vallado 719-573-2600 28 jun 2005

inputs :
epoch -
ep - eccentricity
argpp - argument of perigee
tc -
inclp - inclination
nodep - right ascension of ascending node
np - mean motion

outputs :
sinim , cosim , sinomm , cosomm , snodm , cnodm
day -
e3 -
ee2 -
em - eccentricity
emsq - eccentricity squared
gam -
peo -
pgho -
pho -
pinco -
plo -
rtemsq -
se2, se3 -
sgh2, sgh3, sgh4 -
sh2, sh3, si2, si3, sl2, sl3, sl4 -
s1, s2, s3, s4, s5, s6, s7 -
ss1, ss2, ss3, ss4, ss5, ss6, ss7, sz1, sz2, sz3 -
sz11, sz12, sz13, sz21, sz22, sz23, sz31, sz32, sz33 -
xgh2, xgh3, xgh4, xh2, xh3, xi2, xi3, xl2, xl3, xl4 -
nm - mean motion
z1, z2, z3, z11, z12, z13, z21, z22, z23, z31, z32, z33 -
zmol -
zmos -

locals :
a1, a2, a3, a4, a5, a6, a7, a8, a9, a10 -
betasq -
cc -
ctem, stem -
x1, x2, x3, x4, x5, x6, x7, x8 -
xnodce -
xnoi -
zcosg , zsing , zcosgl , zsingl , zcosh , zsinh , zcoshl , zsinhl ,
zcosi , zsini , zcosil , zsinil ,
zx -
zy -

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

—————————————————————————-*/

# File 'lib/korba/sgp4/sgp4.rb', line 335

def self.dscom(epoch, ep, argpp, tc, inclp, nodep, np, rec)
  #/* -------------------------- constants ------------------------- */
  zes = 0.01675
  zel = 0.05490
  c1ss = 2.9864797e-6
  c1l = 4.7968065e-7
  zsinis = 0.39785416
  zcosis = 0.91744867
  zcosgs = 0.1945905
  zsings = -0.98088458

  #/* --------------------- local variables ------------------------ */
  #int lsflg
  #double a1, a2, a3, a4, a5, a6, a7,
  #  a8, a9, a10, betasq, cc, ctem, stem,
  #  x1, x2, x3, x4, x5, x6, x7,
  #  x8, xnodce, xnoi, zcosg, zcosgl, zcosh, zcoshl,
  #  zcosi, zcosil, zsing, zsingl, zsinh, zsinhl, zsini,
  #  zsinil, zx, zy

  rec.nm = np
  rec.em = ep
  rec.snodm = Math.sin(nodep)
  rec.cnodm = Math.cos(nodep)
  rec.sinomm = Math.sin(argpp)
  rec.cosomm = Math.cos(argpp)
  rec.sinim = Math.sin(inclp)
  rec.cosim = Math.cos(inclp)
  rec.emsq = rec.em * rec.em
  betasq = 1.0 - rec.emsq
  rec.rtemsq = Math.sqrt(betasq)

  #/* ----------------- initialize lunar solar terms --------------- */
  rec.peo = 0.0
  rec.pinco = 0.0
  rec.plo = 0.0
  rec.pgho = 0.0
  rec.pho = 0.0
  rec.day = epoch + 18261.5 + tc / 1440.0
  xnodce = fmod(4.5236020 - 9.2422029e-4 * rec.day, TWOPI)
  stem = Math.sin(xnodce)
  ctem = Math.cos(xnodce)
  zcosil = 0.91375164 - 0.03568096 * ctem
  zsinil = Math.sqrt(1.0 - zcosil * zcosil)
  zsinhl = 0.089683511 * stem / zsinil
  zcoshl = Math.sqrt(1.0 - zsinhl * zsinhl)
  rec.gam = 5.8351514 + 0.0019443680 * rec.day
  zx = 0.39785416 * stem / zsinil
  zy = zcoshl * ctem + 0.91744867 * zsinhl * stem
  zx = Math.atan2(zx, zy)
  zx = rec.gam + zx - xnodce
  zcosgl = Math.cos(zx)
  zsingl = Math.sin(zx)

  #/* ------------------------- do solar terms --------------------- */
  zcosg = zcosgs
  zsing = zsings
  zcosi = zcosis
  zsini = zsinis
  zcosh = rec.cnodm
  zsinh = rec.snodm
  cc = c1ss
  xnoi = 1.0 / rec.nm

  for lsflg in 1..3
    a1 = zcosg * zcosh + zsing * zcosi * zsinh
    a3 = -zsing * zcosh + zcosg * zcosi * zsinh
    a7 = -zcosg * zsinh + zsing * zcosi * zcosh
    a8 = zsing * zsini
    a9 = zsing * zsinh + zcosg * zcosi * zcosh
    a10 = zcosg * zsini
    a2 = rec.cosim * a7 + rec.sinim * a8
    a4 = rec.cosim * a9 + rec.sinim * a10
    a5 = -rec.sinim * a7 + rec.cosim * a8
    a6 = -rec.sinim * a9 + rec.cosim * a10

    x1 = a1 * rec.cosomm + a2 * rec.sinomm
    x2 = a3 * rec.cosomm + a4 * rec.sinomm
    x3 = -a1 * rec.sinomm + a2 * rec.cosomm
    x4 = -a3 * rec.sinomm + a4 * rec.cosomm
    x5 = a5 * rec.sinomm
    x6 = a6 * rec.sinomm
    x7 = a5 * rec.cosomm
    x8 = a6 * rec.cosomm

    rec.z31 = 12.0 * x1 * x1 - 3.0 * x3 * x3
    rec.z32 = 24.0 * x1 * x2 - 6.0 * x3 * x4
    rec.z33 = 12.0 * x2 * x2 - 3.0 * x4 * x4
    rec.z1 = 3.0 * (a1 * a1 + a2 * a2) + rec.z31 * rec.emsq
    rec.z2 = 6.0 * (a1 * a3 + a2 * a4) + rec.z32 * rec.emsq
    rec.z3 = 3.0 * (a3 * a3 + a4 * a4) + rec.z33 * rec.emsq
    rec.z11 = -6.0 * a1 * a5 + rec.emsq * (-24.0 * x1 * x7 - 6.0 * x3 * x5)
    rec.z12 = (-6.0 * (a1 * a6 + a3 * a5) + rec.emsq *
                                            (-24.0 * (x2 * x7 + x1 * x8) - 6.0 * (x3 * x6 + x4 * x5)))
    rec.z13 = -6.0 * a3 * a6 + rec.emsq * (-24.0 * x2 * x8 - 6.0 * x4 * x6)
    rec.z21 = 6.0 * a2 * a5 + rec.emsq * (24.0 * x1 * x5 - 6.0 * x3 * x7)
    rec.z22 = (6.0 * (a4 * a5 + a2 * a6) + rec.emsq *
                                           (24.0 * (x2 * x5 + x1 * x6) - 6.0 * (x4 * x7 + x3 * x8)))
    rec.z23 = 6.0 * a4 * a6 + rec.emsq * (24.0 * x2 * x6 - 6.0 * x4 * x8)
    rec.z1 = rec.z1 + rec.z1 + betasq * rec.z31
    rec.z2 = rec.z2 + rec.z2 + betasq * rec.z32
    rec.z3 = rec.z3 + rec.z3 + betasq * rec.z33
    rec.s3 = cc * xnoi
    rec.s2 = -0.5 * rec.s3 / rec.rtemsq
    rec.s4 = rec.s3 * rec.rtemsq
    rec.s1 = -15.0 * rec.em * rec.s4
    rec.s5 = x1 * x3 + x2 * x4
    rec.s6 = x2 * x3 + x1 * x4
    rec.s7 = x2 * x4 - x1 * x3

    #/* ----------------------- do lunar terms ------------------- */
    if lsflg == 1
      rec.ss1 = rec.s1
      rec.ss2 = rec.s2
      rec.ss3 = rec.s3
      rec.ss4 = rec.s4
      rec.ss5 = rec.s5
      rec.ss6 = rec.s6
      rec.ss7 = rec.s7
      rec.sz1 = rec.z1
      rec.sz2 = rec.z2
      rec.sz3 = rec.z3
      rec.sz11 = rec.z11
      rec.sz12 = rec.z12
      rec.sz13 = rec.z13
      rec.sz21 = rec.z21
      rec.sz22 = rec.z22
      rec.sz23 = rec.z23
      rec.sz31 = rec.z31
      rec.sz32 = rec.z32
      rec.sz33 = rec.z33
      zcosg = zcosgl
      zsing = zsingl
      zcosi = zcosil
      zsini = zsinil
      zcosh = zcoshl * rec.cnodm + zsinhl * rec.snodm
      zsinh = rec.snodm * zcoshl - rec.cnodm * zsinhl
      cc = c1l
    end
    #end lsflg == 1
  end
  # end for loop

  rec.zmol = fmod(4.7199672 + 0.22997150 * rec.day - rec.gam, TWOPI)
  rec.zmos = fmod(6.2565837 + 0.017201977 * rec.day, TWOPI)

  #/* ------------------------ do solar terms ---------------------- */
  rec.se2 = 2.0 * rec.ss1 * rec.ss6
  rec.se3 = 2.0 * rec.ss1 * rec.ss7
  rec.si2 = 2.0 * rec.ss2 * rec.sz12
  rec.si3 = 2.0 * rec.ss2 * (rec.sz13 - rec.sz11)
  rec.sl2 = -2.0 * rec.ss3 * rec.sz2
  rec.sl3 = -2.0 * rec.ss3 * (rec.sz3 - rec.sz1)
  rec.sl4 = -2.0 * rec.ss3 * (-21.0 - 9.0 * rec.emsq) * zes
  rec.sgh2 = 2.0 * rec.ss4 * rec.sz32
  rec.sgh3 = 2.0 * rec.ss4 * (rec.sz33 - rec.sz31)
  rec.sgh4 = -18.0 * rec.ss4 * zes
  rec.sh2 = -2.0 * rec.ss2 * rec.sz22
  rec.sh3 = -2.0 * rec.ss2 * (rec.sz23 - rec.sz21)

  #/* ------------------------ do lunar terms ---------------------- */
  rec.ee2 = 2.0 * rec.s1 * rec.s6
  rec.e3 = 2.0 * rec.s1 * rec.s7
  rec.xi2 = 2.0 * rec.s2 * rec.z12
  rec.xi3 = 2.0 * rec.s2 * (rec.z13 - rec.z11)
  rec.xl2 = -2.0 * rec.s3 * rec.z2
  rec.xl3 = -2.0 * rec.s3 * (rec.z3 - rec.z1)
  rec.xl4 = -2.0 * rec.s3 * (-21.0 - 9.0 * rec.emsq) * zel
  rec.xgh2 = 2.0 * rec.s4 * rec.z32
  rec.xgh3 = 2.0 * rec.s4 * (rec.z33 - rec.z31)
  rec.xgh4 = -18.0 * rec.s4 * zel
  rec.xh2 = -2.0 * rec.s2 * rec.z22
  rec.xh3 = -2.0 * rec.s2 * (rec.z23 - rec.z21)

  #}  // dscom
end

.dsinit(tc, xpidot, rec) ⇒ `Object`

/*—————————————————————————– *

procedure dsinit

this procedure provides deep space contributions to mean motion dot due
to geopotential resonance with half day and one day orbits.
この手順は、半日および一日の軌道との重力共鳴による平均運動ドットへの深宇宙寄与を提供します。

author : david vallado 719-573-2600 28 jun 2005

inputs :
xke - reciprocal of tumin
cosim, sinim-
emsq - eccentricity squared
argpo - argument of perigee
s1, s2, s3, s4, s5 -
ss1, ss2, ss3, ss4, ss5 -
sz1, sz3, sz11, sz13, sz21, sz23, sz31, sz33 -
t - time
tc -
gsto - greenwich sidereal time rad
mo - mean anomaly
mdot - mean anomaly dot (rate)
no - mean motion
nodeo - right ascension of ascending node
nodedot - right ascension of ascending node dot (rate)
xpidot -
z1, z3, z11, z13, z21, z23, z31, z33 -
eccm - eccentricity
argpm - argument of perigee
inclm - inclination
mm - mean anomaly
xn - mean motion
nodem - right ascension of ascending node

outputs :
em - eccentricity
argpm - argument of perigee
inclm - inclination
mm - mean anomaly
nm - mean motion
nodem - right ascension of ascending node
irez - flag for resonance 0-none, 1-one day, 2-half day
atime -
d2201, d2211, d3210, d3222, d4410, d4422, d5220, d5232, d5421, d5433 -
dedt -
didt -
dmdt -
dndt -
dnodt -
domdt -
del1, del2, del3 -
ses , sghl , sghs , sgs , shl , shs , sis , sls
theta -
xfact -
xlamo -
xli -
xni

locals :
ainv2 -
aonv -
cosisq -
eoc -
f220, f221, f311, f321, f322, f330, f441, f442, f522, f523, f542, f543 -
g200, g201, g211, g300, g310, g322, g410, g422, g520, g521, g532, g533 -
sini2 -
temp -
temp1 -
theta -
xno2 -

coupling :
getgravconst- no longer used

references :
hoots, roehrich, norad spacetrack report #3 1980
hoots, norad spacetrack report #6 1986
hoots, schumacher and glover 2004
vallado, crawford, hujsak, kelso 2006

—————————————————————————-*/

# File 'lib/korba/sgp4/sgp4.rb', line 593

def self.dsinit(tc, xpidot, rec)
  #/* --------------------- local variables ------------------------ */

  #double ainv2, aonv = 0.0, cosisq, eoc, f220, f221, f311,
  #  f321, f322, f330, f441, f442, f522, f523,
  #  f542, f543, g200, g201, g211, g300, g310,
  #  g322, g410, g422, g520, g521, g532, g533,
  #  ses, sgs, sghl, sghs, shs, shll, sis,
  #  sini2, sls, temp, temp1, theta, xno2, q22,
  #  q31, q33, root22, root44, root54, rptim, root32,
  #  root52, x2o3, znl, emo, zns, emsqo

  q22 = 1.7891679e-6
  q31 = 2.1460748e-6
  q33 = 2.2123015e-7
  root22 = 1.7891679e-6
  root44 = 7.3636953e-9
  root54 = 2.1765803e-9
  rptim = 4.37526908801129966e-3 #// this equates to 7.29211514668855e-5 rad/sec
  root32 = 3.7393792e-7
  root52 = 1.1428639e-7
  x2o3 = 2.0 / 3.0
  znl = 1.5835218e-4
  zns = 1.19459e-5

  #// sgp4fix identify constants and allow alternate values
  #// just xke is used here so pass it in rather than have multiple calls
  #// getgravconst( whichconst, tumin, mu, radiusearthkm, xke, j2, j3, j4, j3oj2 )

  #/* -------------------- deep space initialization ------------ */
  rec.irez = 0
  if ((rec.nm < 0.0052359877) and (rec.nm > 0.0034906585))
    rec.irez = 1
  end
  if ((rec.nm >= 8.26e-3) and (rec.nm <= 9.24e-3) and (rec.em >= 0.5))
    rec.irez = 2
  end

  #/* ------------------------ do solar terms ------------------- */
  ses = rec.ss1 * zns * rec.ss5
  sis = rec.ss2 * zns * (rec.sz11 + rec.sz13)
  sls = -zns * rec.ss3 * (rec.sz1 + rec.sz3 - 14.0 - 6.0 * rec.emsq)
  sghs = rec.ss4 * zns * (rec.sz31 + rec.sz33 - 6.0)
  shs = -zns * rec.ss2 * (rec.sz21 + rec.sz23)
  #// sgp4fix for 180 deg incl
  if ((rec.inclm < 5.2359877e-2) or (rec.inclm > PI - 5.2359877e-2))
    shs = 0.0
  end
  if (rec.sinim != 0.0)
    shs = shs / rec.sinim
  end
  sgs = sghs - rec.cosim * shs

  #/* ------------------------- do lunar terms ------------------ */
  rec.dedt = ses + rec.s1 * znl * rec.s5
  rec.didt = sis + rec.s2 * znl * (rec.z11 + rec.z13)
  rec.dmdt = sls - znl * rec.s3 * (rec.z1 + rec.z3 - 14.0 - 6.0 * rec.emsq)
  sghl = rec.s4 * znl * (rec.z31 + rec.z33 - 6.0)
  shll = -znl * rec.s2 * (rec.z21 + rec.z23)
  #// sgp4fix for 180 deg incl
  if ((rec.inclm < 5.2359877e-2) or (rec.inclm > PI - 5.2359877e-2))
    shll = 0.0
  end
  rec.domdt = sgs + sghl
  rec.dnodt = shs
  if (rec.sinim != 0.0)
    rec.domdt = rec.domdt - rec.cosim / rec.sinim * shll
    rec.dnodt = rec.dnodt + shll / rec.sinim
  end

  #/* ----------- calculate deep space resonance effects -------- */
  rec.dndt = 0.0
  theta = fmod(rec.gsto + tc * rptim, TWOPI)
  rec.em = rec.em + rec.dedt * rec.t
  rec.inclm = rec.inclm + rec.didt * rec.t
  rec.argpm = rec.argpm + rec.domdt * rec.t
  rec.nodem = rec.nodem + rec.dnodt * rec.t
  rec.mm = rec.mm + rec.dmdt * rec.t
  #//   sgp4fix for negative inclinations
  #//   the following if statement should be commented out
  #//if (inclm < 0.0)
  #//  {
  #//    inclm  = -inclm
  #//    argpm  = argpm - pi
  #//    nodem = nodem + pi
  #//  }

  #/* -------------- initialize the resonance terms ------------- */
  if (rec.irez != 0)
    aonv = (rec.nm / rec.xke) ** x2o3

    #/* ---------- geopotential resonance for 12 hour orbits ------ */
    if (rec.irez == 2)
      cosisq = rec.cosim * rec.cosim
      emo = rec.em
      rec.em = rec.ecco
      emsqo = rec.emsq
      rec.emsq = rec.eccsq
      eoc = rec.em * rec.emsq
      g201 = -0.306 - (rec.em - 0.64) * 0.440

      if (rec.em <= 0.65)
        g211 = 3.616 - 13.2470 * rec.em + 16.2900 * rec.emsq
        g310 = -19.302 + 117.3900 * rec.em - 228.4190 * rec.emsq + 156.5910 * eoc
        g322 = -18.9068 + 109.7927 * rec.em - 214.6334 * rec.emsq + 146.5816 * eoc
        g410 = -41.122 + 242.6940 * rec.em - 471.0940 * rec.emsq + 313.9530 * eoc
        g422 = -146.407 + 841.8800 * rec.em - 1629.014 * rec.emsq + 1083.4350 * eoc
        g520 = -532.114 + 3017.977 * rec.em - 5740.032 * rec.emsq + 3708.2760 * eoc
      else
        g211 = -72.099 + 331.819 * rec.em - 508.738 * rec.emsq + 266.724 * eoc
        g310 = -346.844 + 1582.851 * rec.em - 2415.925 * rec.emsq + 1246.113 * eoc
        g322 = -342.585 + 1554.908 * rec.em - 2366.899 * rec.emsq + 1215.972 * eoc
        g410 = -1052.797 + 4758.686 * rec.em - 7193.992 * rec.emsq + 3651.957 * eoc
        g422 = -3581.690 + 16178.110 * rec.em - 24462.770 * rec.emsq + 12422.520 * eoc
        if (rec.em > 0.715)
          g520 = -5149.66 + 29936.92 * rec.em - 54087.36 * rec.emsq + 31324.56 * eoc
        else
          g520 = 1464.74 - 4664.75 * rec.em + 3763.64 * rec.emsq
        end
      end

      if (rec.em < 0.7)
        g533 = -919.22770 + 4988.6100 * rec.em - 9064.7700 * rec.emsq + 5542.21 * eoc
        g521 = -822.71072 + 4568.6173 * rec.em - 8491.4146 * rec.emsq + 5337.524 * eoc
        g532 = -853.66600 + 4690.2500 * rec.em - 8624.7700 * rec.emsq + 5341.4 * eoc
      else
        g533 = -37995.780 + 161616.52 * rec.em - 229838.20 * rec.emsq + 109377.94 * eoc
        g521 = -51752.104 + 218913.95 * rec.em - 309468.16 * rec.emsq + 146349.42 * eoc
        g532 = -40023.880 + 170470.89 * rec.em - 242699.48 * rec.emsq + 115605.82 * eoc
      end

      sini2 = rec.sinim * rec.sinim
      f220 = 0.75 * (1.0 + 2.0 * rec.cosim + cosisq)
      f221 = 1.5 * sini2
      f321 = 1.875 * rec.sinim * (1.0 - 2.0 * rec.cosim - 3.0 * cosisq)
      f322 = -1.875 * rec.sinim * (1.0 + 2.0 * rec.cosim - 3.0 * cosisq)
      f441 = 35.0 * sini2 * f220
      f442 = 39.3750 * sini2 * sini2
      f522 = (9.84375 * rec.sinim * (sini2 * (1.0 - 2.0 * rec.cosim - 5.0 * cosisq) +
                                     0.33333333 * (-2.0 + 4.0 * rec.cosim + 6.0 * cosisq)))
      f523 = (rec.sinim * (4.92187512 * sini2 * (-2.0 - 4.0 * rec.cosim +
                                                 10.0 * cosisq) + 6.56250012 * (1.0 + 2.0 * rec.cosim - 3.0 * cosisq)))
      f542 = (29.53125 * rec.sinim * (2.0 - 8.0 * rec.cosim + cosisq *
                                                              (-12.0 + 8.0 * rec.cosim + 10.0 * cosisq)))
      f543 = (29.53125 * rec.sinim * (-2.0 - 8.0 * rec.cosim + cosisq *
                                                               (12.0 + 8.0 * rec.cosim - 10.0 * cosisq)))
      xno2 = rec.nm * rec.nm
      ainv2 = aonv * aonv
      temp1 = 3.0 * xno2 * ainv2
      temp = temp1 * root22
      rec.d2201 = temp * f220 * g201
      rec.d2211 = temp * f221 * g211
      temp1 = temp1 * aonv
      temp = temp1 * root32
      rec.d3210 = temp * f321 * g310
      rec.d3222 = temp * f322 * g322
      temp1 = temp1 * aonv
      temp = 2.0 * temp1 * root44
      rec.d4410 = temp * f441 * g410
      rec.d4422 = temp * f442 * g422
      temp1 = temp1 * aonv
      temp = temp1 * root52
      rec.d5220 = temp * f522 * g520
      rec.d5232 = temp * f523 * g532
      temp = 2.0 * temp1 * root54
      rec.d5421 = temp * f542 * g521
      rec.d5433 = temp * f543 * g533
      rec.xlamo = fmod(rec.mo + rec.nodeo + rec.nodeo - theta - theta, TWOPI)
      rec.xfact = rec.mdot + rec.dmdt + 2.0 * (rec.nodedot + rec.dnodt - rptim) - rec.no_unkozai
      rec.em = emo
      rec.emsq = emsqo
    end
    #}

    #/* ---------------- synchronous resonance terms -------------- */
    if (rec.irez == 1)
      g200 = 1.0 + rec.emsq * (-2.5 + 0.8125 * rec.emsq)
      g310 = 1.0 + 2.0 * rec.emsq
      g300 = 1.0 + rec.emsq * (-6.0 + 6.60937 * rec.emsq)
      f220 = 0.75 * (1.0 + rec.cosim) * (1.0 + rec.cosim)
      f311 = 0.9375 * rec.sinim * rec.sinim * (1.0 + 3.0 * rec.cosim) - 0.75 * (1.0 + rec.cosim)
      f330 = 1.0 + rec.cosim
      f330 = 1.875 * f330 * f330 * f330
      rec.del1 = 3.0 * rec.nm * rec.nm * aonv * aonv
      rec.del2 = 2.0 * rec.del1 * f220 * g200 * q22
      rec.del3 = 3.0 * rec.del1 * f330 * g300 * q33 * aonv
      rec.del1 = rec.del1 * f311 * g310 * q31 * aonv
      rec.xlamo = fmod(rec.mo + rec.nodeo + rec.argpo - theta, TWOPI)
      rec.xfact = rec.mdot + xpidot - rptim + rec.dmdt + rec.domdt + rec.dnodt - rec.no_unkozai
    end

    #/* ------------ for sgp4, initialize the integrator ---------- */
    rec.xli = rec.xlamo
    rec.xni = rec.no_unkozai
    rec.atime = 0.0
    rec.nm = rec.no_unkozai + rec.dndt
  end
end

.dspace(tc, rec) ⇒ `Object`

/*—————————————————————————– *

procedure dspace

this procedure provides deep space contributions to mean elements for
perturbing third body. these effects have been averaged over one
revolution of the sun and moon. for earth resonance effects, the
effects have been averaged over no revolutions of the satellite.
(mean motion)
この手順は、摂動する第三体の平均要素に対する深宇宙寄与を提供します。
これらの効果は、太陽と月の1回の公転にわたって平均化されています。
地球の共鳴効果については、衛星の公転数にわたって効果が平均化されています。
（平均運動）

author : david vallado 719-573-2600 28 jun 2005

inputs :
d2201, d2211, d3210, d3222, d4410, d4422, d5220, d5232, d5421, d5433 -
dedt -
del1, del2, del3 -
didt -
dmdt -
dnodt -
domdt -
irez - flag for resonance 0-none, 1-one day, 2-half day
argpo - argument of perigee
argpdot - argument of perigee dot (rate)
t - time
tc -
gsto - gst
xfact -
xlamo -
no - mean motion
atime -
em - eccentricity
ft -
argpm - argument of perigee
inclm - inclination
xli -
mm - mean anomaly
xni - mean motion
nodem - right ascension of ascending node

outputs :
atime -
em - eccentricity
argpm - argument of perigee
inclm - inclination
xli -
mm - mean anomaly
xni -
nodem - right ascension of ascending node
dndt -
nm - mean motion

locals :
delt -
ft -
theta -
x2li -
x2omi -
xl -
xldot -
xnddt -
xndt -
xomi -

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

—————————————————————————-*/

# File 'lib/korba/sgp4/sgp4.rb', line 870

def self.dspace(tc, rec)
  #int iretn
  #double delt, ft, theta, x2li, x2omi, xl, xldot, xnddt, xndt, xomi, g22, g32,
  #  g44, g52, g54, fasx2, fasx4, fasx6, rptim, step2, stepn, stepp

  xndt = 0
  xnddt = 0
  xldot = 0

  fasx2 = 0.13130908
  fasx4 = 2.8843198
  fasx6 = 0.37448087
  g22 = 5.7686396
  g32 = 0.95240898
  g44 = 1.8014998
  g52 = 1.0508330
  g54 = 4.4108898
  rptim = 4.37526908801129966e-3 #// this equates to 7.29211514668855e-5 rad/sec
  stepp = 720.0
  stepn = -720.0
  step2 = 259200.0

  #/* ----------- calculate deep space resonance effects ----------- */
  rec.dndt = 0.0
  theta = fmod(rec.gsto + tc * rptim, TWOPI)
  rec.em = rec.em + rec.dedt * rec.t

  rec.inclm = rec.inclm + rec.didt * rec.t
  rec.argpm = rec.argpm + rec.domdt * rec.t
  rec.nodem = rec.nodem + rec.dnodt * rec.t
  rec.mm = rec.mm + rec.dmdt * rec.t

  #//   sgp4fix for negative inclinations
  #//   the following if statement should be commented out
  #//  if (inclm < 0.0)
  #// {
  #//    inclm = -inclm
  #//    argpm = argpm - pi
  #//    nodem = nodem + pi
  #//  }

  #/* - update resonances : numerical (euler-maclaurin) integration - */
  #/* ------------------------- epoch restart ----------------------  */
  #//   sgp4fix for propagator problems
  #//   the following integration works for negative time steps and periods
  #//   the specific changes are unknown because the original code was so convoluted

  #// sgp4fix take out atime = 0.0 and fix for faster operation
  ft = 0.0
  if (rec.irez != 0)
    #// sgp4fix streamline check
    if ((rec.atime == 0.0) or (rec.t * rec.atime <= 0.0) or ((rec.t).abs < (rec.atime).abs))
      rec.atime = 0.0
      rec.xni = rec.no_unkozai
      rec.xli = rec.xlamo
    end
    #// sgp4fix move check outside loop
    if (rec.t > 0.0)
      delt = stepp
    else
      delt = stepn
    end

    iretn = 381 #// added for do loop
    while (iretn == 381)
      #/* ------------------- dot terms calculated ------------- */
      #/* ----------- near - synchronous resonance terms ------- */
      if (rec.irez != 2)
        xndt = (rec.del1 * Math.sin(rec.xli - fasx2) + rec.del2 * Math.sin(2.0 * (rec.xli - fasx4)) +
                rec.del3 * Math.sin(3.0 * (rec.xli - fasx6)))
        xldot = rec.xni + rec.xfact
        xnddt = (rec.del1 * Math.cos(rec.xli - fasx2) +
                 2.0 * rec.del2 * Math.cos(2.0 * (rec.xli - fasx4)) +
                 3.0 * rec.del3 * Math.cos(3.0 * (rec.xli - fasx6)))
        xnddt = xnddt * xldot
      else
        #/* --------- near - half-day resonance terms -------- */
        xomi = rec.argpo + rec.argpdot * rec.atime
        x2omi = xomi + xomi
        x2li = rec.xli + rec.xli
        xndt = (rec.d2201 * Math.sin(x2omi + rec.xli - g22) + rec.d2211 * Math.sin(rec.xli - g22) +
                rec.d3210 * Math.sin(xomi + rec.xli - g32) + rec.d3222 * Math.sin(-xomi + rec.xli - g32) +
                rec.d4410 * Math.sin(x2omi + x2li - g44) + rec.d4422 * Math.sin(x2li - g44) +
                rec.d5220 * Math.sin(xomi + rec.xli - g52) + rec.d5232 * Math.sin(-xomi + rec.xli - g52) +
                rec.d5421 * Math.sin(xomi + x2li - g54) + rec.d5433 * Math.sin(-xomi + x2li - g54))
        xldot = rec.xni + rec.xfact
        xnddt = (rec.d2201 * Math.cos(x2omi + rec.xli - g22) + rec.d2211 * Math.cos(rec.xli - g22) +
                 rec.d3210 * Math.cos(xomi + rec.xli - g32) + rec.d3222 * Math.cos(-xomi + rec.xli - g32) +
                 rec.d5220 * Math.cos(xomi + rec.xli - g52) + rec.d5232 * Math.cos(-xomi + rec.xli - g52) +
                 2.0 * (rec.d4410 * Math.cos(x2omi + x2li - g44) +
                        rec.d4422 * Math.cos(x2li - g44) + rec.d5421 * Math.cos(xomi + x2li - g54) +
                        rec.d5433 * Math.cos(-xomi + x2li - g54)))
        xnddt = xnddt * xldot
      end

      #/* ----------------------- integrator ------------------- */
      #// sgp4fix move end checks to end of routine
      if ((rec.t - rec.atime).abs >= stepp)
        iretn = 381
      else #// exit here
        ft = rec.t - rec.atime
        iretn = 0
      end

      if (iretn == 381)
        rec.xli = rec.xli + xldot * delt + xndt * step2
        rec.xni = rec.xni + xndt * delt + xnddt * step2
        rec.atime = rec.atime + delt
      end
    end
    #}  #// while iretn = 381

    rec.nm = rec.xni + xndt * ft + xnddt * ft * ft * 0.5
    xl = rec.xli + xldot * ft + xndt * ft * ft * 0.5
    if (rec.irez != 1)
      rec.mm = xl - 2.0 * rec.nodem + 2.0 * theta
      rec.dndt = rec.nm - rec.no_unkozai
    else
      rec.mm = xl - rec.nodem - rec.argpm + theta
      rec.dndt = rec.nm - rec.no_unkozai
    end
    rec.nm = rec.no_unkozai + rec.dndt
  end
end

.fmod(numer, denom) ⇒ `Object`

} // getgravconst

# File 'lib/korba/sgp4/sgp4.rb', line 1926

def self.fmod(numer, denom)
  #return numer%denom
  tquot = (numer / denom).floor
  return numer - tquot * denom
end

.getgravconst(whichconst, rec) ⇒ `Object`

/* —————————————————————————– *

function getgravconst

this function gets constants for the propagator. note that mu is identified to
facilitiate comparisons with newer models. the common useage is WGS72.
この関数はプロパゲータのための定数を取得します。muは新しいモデルとの比較を容易にするために識別されています。
一般的な使用法はWGS72です。

author : david vallado 719-573-2600 21 jul 2006

inputs :
whichconst - which set of constants to use wgs72old, wgs72, wgs84

outputs :
tumin - minutes in one time unit
mu - earth gravitational parameter
radiusearthkm - radius of the earth in km
xke - reciprocal of tumin
j2, j3, j4 - un-normalized zonal harmonic values
j3oj2 - j3 divided by j2

locals :

coupling :
none

references :
norad spacetrack report #3
vallado, crawford, hujsak, kelso 2006

————————————————————————— */

# File 'lib/korba/sgp4/sgp4.rb', line 1889

def self.getgravconst(whichconst, rec)
  rec.whichconst = whichconst

  #// -- wgs-72 low precision str#3 constants --
  if whichconst == WGS72old
    rec.mu = 398600.79964        #// in km3 / s2
    rec.radiusearthkm = 6378.135    # // km
    rec.xke = 0.0743669161       # // reciprocal of tumin
    rec.tumin = 1.0 / rec.xke
    rec.j2 = 0.001082616
    rec.j3 = -0.00000253881
    rec.j4 = -0.00000165597
    rec.j3oj2 = rec.j3 / rec.j2
    #// ------------ WGS-72 constants ------------
  elsif whichconst == WGS72
    rec.mu = 398600.8            #// in km3 / s2
    rec.radiusearthkm = 6378.135    # // km
    rec.xke = 60.0 / Math.sqrt(rec.radiusearthkm * rec.radiusearthkm * rec.radiusearthkm / rec.mu)
    rec.tumin = 1.0 / rec.xke
    rec.j2 = 0.001082616
    rec.j3 = -0.00000253881
    rec.j4 = -0.00000165597
    rec.j3oj2 = rec.j3 / rec.j2
  else # WGS84
    #// ------------ WGS-84 constants ------------
    rec.mu = 398600.44188          #  // in km3 / s2
    rec.radiusearthkm = 6378.137  #   // km
    rec.xke = 60.0 / Math.sqrt(rec.radiusearthkm * rec.radiusearthkm * rec.radiusearthkm / rec.mu)
    rec.tumin = 1.0 / rec.xke
    rec.j2 = 0.00108262998905
    rec.j3 = -0.00000253215306
    rec.j4 = -0.00000161098761
    rec.j3oj2 = rec.j3 / rec.j2
  end
end

.gstime(jdut1) ⇒ `Object`

/* —————————————————————————– *

function gstime

this function finds the greenwich sidereal time.

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units
jdut1 - julian date in ut1 days from 4713 bc

outputs :
gstime - greenwich sidereal time 0 to 2pi rad

locals :
temp - temporary variable for doubles rad
tut1 - julian centuries from the
jan 1, 2000 12 h epoch (ut1)

coupling :
none

references :
vallado 2013, 187, eq 3-45
————————————————————————— */

# File 'lib/korba/sgp4/sgp4.rb', line 1958

def self.gstime(jdut1)
  tut1 = (jdut1 - 2451545.0) / 36525.0
  temp = (-6.2e-6 * tut1 * tut1 * tut1 + 0.093104 * tut1 * tut1 +
          (876600.0 * 3600 + 8640184.812866) * tut1 + 67310.54841)  #// sec
  temp = fmod(temp * DEG2RAD / 240.0, TWOPI) #//360/86400 = 1/240, to deg, to rad

  #// ------------------------ check quadrants ---------------------
  if temp < 0.0
    temp += TWOPI
  end

  return temp
end

.initl(epoch, rec) ⇒ `Object`

/*—————————————————————————– *

procedure initl

this procedure initializes the spg4 propagator. all the initialization is
consolidated here instead of having multiple loops inside other routines.
この手順はspg4プロパゲータを初期化します。すべての初期化は他のルーチン内に複数のループを持つ代わりにここに統合されています。

author : david vallado 719-573-2600 28 jun 2005

inputs :
satn - satellite number - not needed, placed in satrec
xke - reciprocal of tumin
j2 - j2 zonal harmonic
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

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- no longer used
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

—————————————————————————-*/

# File 'lib/korba/sgp4/sgp4.rb', line 1050

def self.initl(epoch, rec)
  #/* --------------------- local variables ------------------------ */
  #double ak, d1, del, adel, po, x2o3

  #// sgp4fix use old way of finding gst
  #double ds70
  #double ts70, tfrac, c1, thgr70, fk5r, c1p2p

  #/* ----------------------- earth constants ---------------------- */
  #// sgp4fix identify constants and allow alternate values
  #// only xke and j2 are used here so pass them in directly
  #// getgravconst( whichconst, tumin, mu, radiusearthkm, xke, j2, j3, j4, j3oj2 )
  x2o3 = 2.0 / 3.0

  #/* ------------- calculate auxillary epoch quantities ---------- */
  rec.eccsq = rec.ecco * rec.ecco
  rec.omeosq = 1.0 - rec.eccsq
  rec.rteosq = Math.sqrt(rec.omeosq)
  rec.cosio = Math.cos(rec.inclo)
  rec.cosio2 = rec.cosio * rec.cosio

  #/* ------------------ un-kozai the mean motion ----------------- */
  ak = (rec.xke / rec.no_kozai) ** x2o3
  d1 = 0.75 * rec.j2 * (3.0 * rec.cosio2 - 1.0) / (rec.rteosq * rec.omeosq)
  ddel = d1 / (ak * ak)
  # del is a keyword in python
  adel = ak * (1.0 - ddel * ddel - ddel * (1.0 / 3.0 + 134.0 * ddel * ddel / 81.0))
  ddel = d1 / (adel * adel)
  rec.no_unkozai = rec.no_kozai / (1.0 + ddel)

  #puts "koz = #{rec.no_kozai}"
  #puts "unkoz = #{rec.no_unkozai}"

  rec.ao = (rec.xke / (rec.no_unkozai)) ** x2o3
  rec.sinio = Math.sin(rec.inclo)
  po = rec.ao * rec.omeosq
  rec.con42 = 1.0 - 5.0 * rec.cosio2
  rec.con41 = -rec.con42 - rec.cosio2 - rec.cosio2
  rec.ainv = 1.0 / rec.ao
  rec.posq = po * po
  rec.rp = rec.ao * (1.0 - rec.ecco)
  rec.method = "n"

  #// sgp4fix modern approach to finding sidereal time
  #//   if (opsmode == 'a')
  #//      {
  #// sgp4fix use old way of finding gst
  #// count integer number of days from 0 jan 1970
  ts70 = epoch - 7305.0
  ds70 = (ts70 + 1.0e-8).floor
  tfrac = ts70 - ds70
  #// find greenwich location at epoch
  c1 = 1.72027916940703639e-2
  thgr70 = 1.7321343856509374
  fk5r = 5.07551419432269442e-15
  c1p2p = c1 + TWOPI
  gsto1 = fmod(thgr70 + c1 * ds70 + c1p2p * tfrac + ts70 * ts70 * fk5r, TWOPI)
  if (gsto1 < 0.0)
    gsto1 = gsto1 + TWOPI
  end
  #//    }
  #//    else
  rec.gsto = gstime(epoch + 2433281.5)
end

.jday(year, mon, day, hr, minute, sec) ⇒ `Object`

/* —————————————————————————– *

procedure jday

this procedure finds the julian date given the year, month, day, and time.
the julian date is defined by each elapsed day since noon, jan 1, 4713 bc.

algorithm : calculate the answer in one step for efficiency

author : david vallado 719-573-2600 1 mar 2001

inputs description range / units
year - year 1900 .. 2100
mon - month 1 .. 12
day - day 1 .. 28,29,30,31
hr - universal time hour 0 .. 23
min - universal time min 0 .. 59
sec - universal time sec 0.0 .. 59.999

outputs :
jd - julian date days from 4713 bc
jdfrac - julian date fraction into day days from 4713 bc

locals :
none.

coupling :
none.

references :
vallado 2013, 183, alg 14, ex 3-4
————————————————————————— */

# File 'lib/korba/sgp4/sgp4.rb', line 2006

def self.jday(year, mon, day, hr, minute, sec)
  jd = 0
  jdFrac = 0

  t1 = ((7 * (year + ((mon + 9) / 12.0).floor)) * 0.25).floor
  t2 = (275 * mon / 9.0).floor

  jd = (367.0 * year - t1 + t2 + day + 1721013.5) # // use - 678987.0 to go to mjd directly

  jdFrac = (sec + minute * 60.0 + hr * 3600.0) / 86400.0

  #// check that the day and fractional day are correct
  if (jdFrac.abs > 1.0)
    dtt = jdFrac.floor
    jd = jd + dtt
    jdFrac = jdFrac - dtt
  end

  return [jd, jdFrac]
end

.sgp4(satrec, tsince, r, v) ⇒ `Object`

/*—————————————————————————– *

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.
この手順は、スペースコマンドからのsgp4予測モデルです。これは、元々
spacetrack report #3で別々に公開されたsgp4とsdp4の更新および統合バージョンです。
このバージョンは、コードの歴史と開発を説明するaiaa論文（2006）の方法論に従っています。

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 -c
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- no longer used. Variables are conatined within satrec
dpper
dpspace

references :
hoots, roehrich, norad spacetrack report #3 1980
hoots, norad spacetrack report #6 1986
hoots, schumacher and glover 2004
vallado, crawford, hujsak, kelso 2006

—————————————————————————-*/

# File 'lib/korba/sgp4/sgp4.rb', line 1587

def self.sgp4(satrec, tsince, r, v)

  #double axnl, aynl, betal, cnod,
  #  cos2u, coseo1, cosi, cosip, cosisq, cossu, cosu,
  #  delm, delomg, ecose, el2, eo1,
  #  esine, argpdf, pl, mrt = 0.0,
  #  mvt, rdotl, rl, rvdot, rvdotl,
  #  sin2u, sineo1, sini, sinip, sinsu, sinu,
  #  snod, su, t2, t3, t4, tem5, temp,
  #  temp1, temp2, tempa, tempe, templ, u, ux,
  #  uy, uz, vx, vy, vz,
  #  xinc, xincp, xl, xlm,
  #  xmdf, xmx, xmy, nodedf, xnode, tc,
  #  x2o3, vkmpersec, delmtemp

  #int ktr

  #/* ------------------ 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
  temp4 = 1.5e-12
  x2o3 = 2.0 / 3.0
  #// sgp4fix identify constants and allow alternate values
  #// getgravconst( whichconst, tumin, mu, radiusearthkm, xke, j2, j3, j4, j3oj2 )
  vkmpersec = satrec.radiusearthkm * satrec.xke / 60.0

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

  #/* ------- update for secular gravity and atmospheric drag ----- */
  xmdf = satrec.mo + satrec.mdot * satrec.t
  argpdf = satrec.argpo + satrec.argpdot * satrec.t
  nodedf = satrec.nodeo + satrec.nodedot * satrec.t
  satrec.argpm = argpdf
  satrec.mm = xmdf
  t2 = satrec.t * satrec.t
  satrec.nodem = nodedf + satrec.nodecf * t2
  tempa = 1.0 - satrec.cc1 * satrec.t
  tempe = satrec.bstar * satrec.cc4 * satrec.t
  templ = satrec.t2cof * t2

  delomg = 0
  delmtemp = 0
  delm = 0
  temp = 0
  t3 = 0
  t4 = 0
  mrt = 0

  if (satrec.isimp != 1)
    delomg = satrec.omgcof * satrec.t
    delmtemp = 1.0 + satrec.eta * Math.cos(xmdf)
    delm = satrec.xmcof * (delmtemp * delmtemp * delmtemp - satrec.delmo)
    temp = delomg + delm
    satrec.mm = xmdf + temp
    satrec.argpm = argpdf - temp
    t3 = t2 * satrec.t
    t4 = t3 * satrec.t
    tempa = tempa - satrec.d2 * t2 - satrec.d3 * t3 - satrec.d4 * t4
    tempe = tempe + satrec.bstar * satrec.cc5 * (Math.sin(satrec.mm) - satrec.sinmao)
    templ = templ + satrec.t3cof * t3 + t4 * (satrec.t4cof + satrec.t * satrec.t5cof)
  end

  tc = 0
  satrec.nm = satrec.no_unkozai
  satrec.em = satrec.ecco
  satrec.inclm = satrec.inclo
  if (satrec.method == "d")
    tc = satrec.t
    dspace(tc, satrec)
  end

  if (satrec.nm <= 0.0)
    satrec.error = 2
    return false
  end

  #puts "nm,xke,tempa = #{satrec.nm}  #{satrec.xke}  #{tempa}"
  satrec.am = ((satrec.xke / satrec.nm) ** x2o3) * tempa * tempa
  satrec.nm = satrec.xke / (satrec.am ** 1.5)
  satrec.em = satrec.em - tempe
  #puts "am,nm,em = #{satrec.am}  #{satrec.nm}  #{satrec.em}"
  if ((satrec.em >= 1.0) or (satrec.em < -0.001))
    satrec.error = 1
    return false
  end

  if (satrec.em < 1.0e-6)
    satrec.em = 1.0e-6
  end

  satrec.mm = satrec.mm + satrec.no_unkozai * templ
  xlm = satrec.mm + satrec.argpm + satrec.nodem
  satrec.emsq = satrec.em * satrec.em
  temp = 1.0 - satrec.emsq

  satrec.nodem = fmod(satrec.nodem, TWOPI)
  satrec.argpm = fmod(satrec.argpm, TWOPI)
  xlm = fmod(xlm, TWOPI)
  satrec.mm = fmod(xlm - satrec.argpm - satrec.nodem, TWOPI)

  satrec.am = satrec.am
  satrec.em = satrec.em
  satrec.im = satrec.inclm
  satrec.Om = satrec.nodem
  satrec.om = satrec.argpm
  satrec.mm = satrec.mm
  satrec.nm = satrec.nm

  # ----------------- compute extra mean quantities -------------
  satrec.sinim = Math.sin(satrec.inclm)
  satrec.cosim = Math.cos(satrec.inclm)

  # -------------------- add lunar-solar periodics --------------
  satrec.ep = satrec.em
  xincp = satrec.inclm
  satrec.inclp = satrec.inclm
  satrec.argpp = satrec.argpm
  satrec.nodep = satrec.nodem
  satrec.mp = satrec.mm
  sinip = satrec.sinim
  cosip = satrec.cosim

  if (satrec.method == "d")
    dpper(satrec.e3, satrec.ee2, satrec.peo, satrec.pgho,
          satrec.pho, satrec.pinco, satrec.plo, satrec.se2,
          satrec.se3, satrec.sgh2, satrec.sgh3, satrec.sgh4,
          satrec.sh2, satrec.sh3, satrec.si2, satrec.si3,
          satrec.sl2, satrec.sl3, satrec.sl4, satrec.t,
          satrec.xgh2, satrec.xgh3, satrec.xgh4, satrec.xh2,
          satrec.xh3, satrec.xi2, satrec.xi3, satrec.xl2,
          satrec.xl3, satrec.xl4, satrec.zmol, satrec.zmos,
          "n", satrec, satrec.operationmode)

    xincp = satrec.inclp
    if (xincp < 0.0)
      xincp = -xincp
      satrec.nodep = satrec.nodep + PI
      satrec.argpp = satrec.argpp - PI
    end

    if ((satrec.ep < 0.0) or (satrec.ep > 1.0))
      satrec.error = 3
      #// sgp4fix add return
      return false
    end
  end
  #} // if method = d

  #/* -------------------- long period periodics ------------------ */
  if (satrec.method == "d")
    sinip = Math.sin(xincp)
    cosip = Math.cos(xincp)
    satrec.aycof = -0.5 * satrec.j3oj2 * sinip
    #// sgp4fix for divide by zero for xincp = 180 deg
    if ((cosip + 1.0).abs > 1.5e-12)
      satrec.xlcof = -0.25 * satrec.j3oj2 * sinip * (3.0 + 5.0 * cosip) / (1.0 + cosip)
    else
      satrec.xlcof = -0.25 * satrec.j3oj2 * sinip * (3.0 + 5.0 * cosip) / temp4
    end
  end

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

  #/* --------------------- solve kepler's equation --------------- */
  u = fmod(xl - satrec.nodep, TWOPI)
  eo1 = u
  tem5 = 9999.9
  ktr = 1
  sineo1 = 0
  coseo1 = 0
  #//   sgp4fix for kepler iteration
  #//   the following iteration needs better limits on corrections
  while ((tem5.abs >= 1.0e-12) and (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 (tem5.abs >= 0.95)
      if (tem5 > 0)
        tem5 = 0.95
      else
        tem5 = -0.95
      end
      #tem5 = tem5 > 0.0 ? 0.95 : -0.95
    end
    eo1 = eo1 + tem5
    ktr = ktr + 1
  end

  #/* ------------- short period preliminary quantities ----------- */
  ecose = axnl * coseo1 + aynl * sineo1
  esine = axnl * sineo1 - aynl * coseo1
  el2 = axnl * axnl + aynl * aynl
  pl = satrec.am * (1.0 - el2)
  if (pl < 0.0)
    satrec.error = 4
    #// sgp4fix add return
    return false
  else
    rl = satrec.am * (1.0 - ecose)
    rdotl = Math.sqrt(satrec.am) * esine / rl
    rvdotl = Math.sqrt(pl) / rl
    betal = Math.sqrt(1.0 - el2)
    temp = esine / (1.0 + betal)
    sinu = satrec.am / rl * (sineo1 - aynl - axnl * temp)
    cosu = satrec.am / rl * (coseo1 - axnl + aynl * temp)
    su = Math.atan2(sinu, cosu)
    sin2u = (cosu + cosu) * sinu
    cos2u = 1.0 - 2.0 * sinu * sinu
    temp = 1.0 / pl
    temp1 = 0.5 * satrec.j2 * temp
    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
    end

    mrt = rl * (1.0 - 1.5 * temp2 * betal * satrec.con41) + 0.5 * temp1 * satrec.x1mth2 * cos2u
    su = su - 0.25 * temp2 * satrec.x7thm1 * sin2u
    xnode = satrec.nodep + 1.5 * temp2 * cosip * sin2u
    xinc = xincp + 1.5 * temp2 * cosip * sinip * cos2u
    mvt = rdotl - satrec.nm * temp1 * satrec.x1mth2 * sin2u / satrec.xke
    rvdot = rvdotl + satrec.nm * temp1 * (satrec.x1mth2 * cos2u + 1.5 * satrec.con41) / satrec.xke

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

    #/* --------- position and velocity (in km and km/sec) ---------- */
    r[0] = (mrt * ux) * satrec.radiusearthkm
    r[1] = (mrt * uy) * satrec.radiusearthkm
    r[2] = (mrt * uz) * satrec.radiusearthkm
    v[0] = (mvt * ux + rvdot * vx) * vkmpersec
    v[1] = (mvt * uy + rvdot * vy) * vkmpersec
    v[2] = (mvt * uz + rvdot * vz) * vkmpersec
  end
  #}  // if pl > 0

  #// sgp4fix for decaying satellites
  if (mrt < 1.0)
    satrec.error = 6
    return false
  end

  return true
end

.sgp4init(opsmode, satrec) ⇒ `Object`

/*—————————————————————————– *

procedure sgp4init

this procedure initializes variables for sgp4.

author : david vallado 719-573-2600 28 jun 2005

inputs :
opsmode - mode of operation afspc or improved ‘a’, ‘i’
whichconst - which set of constants to use 72, 84
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 :
satrec - 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

—————————————————————————-*/

# File 'lib/korba/sgp4/sgp4.rb', line 1198

def self.sgp4init(opsmode, satrec)
  #/* --------------------- local variables ------------------------ */

  #double cc1sq,
  #  cc2, cc3, coef, coef1, cosio4,
  #  eeta, etasq, perige, pinvsq, psisq, qzms24,
  #        sfour,tc, temp, temp1, temp2, temp3, tsi, xpidot,
  #  xhdot1,qzms2t, ss, x2o3, r[], v[],
  #  delmotemp, qzms2ttemp, qzms24temp

  epoch = (satrec.jdsatepoch + satrec.jdsatepochF) - 2433281.5

  #/* ------------------------ initialization --------------------- */
  #// 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
  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

  #/* ------------------------ earth constants ----------------------- */
  #// sgp4fix identify constants and allow alternate values
  #// this is now the only call for the constants
  getgravconst(satrec.whichconst, satrec)

  #//-------------------------------------------------------------------------

  satrec.error = 0
  satrec.operationmode = opsmode

  #// single averaged mean elements
  satrec.am = satrec.em = satrec.im = satrec.Om = satrec.mm = satrec.nm = 0.0

  #/* ------------------------ earth constants ----------------------- */
  #// sgp4fix identify constants and allow alternate values no longer needed
  #// getgravconst( whichconst, tumin, mu, radiusearthkm, xke, j2, j3, j4, j3oj2 )
  ss = 78.0 / satrec.radiusearthkm + 1.0
  #// sgp4fix use multiply for speed instead of pow
  qzms2ttemp = (120.0 - 78.0) / satrec.radiusearthkm
  qzms2t = qzms2ttemp * qzms2ttemp * qzms2ttemp * qzms2ttemp
  x2o3 = 2.0 / 3.0

  satrec.init = "y"
  satrec.t = 0.0

  #// sgp4fix remove satn as it is not needed in initl

  initl(epoch, satrec)

  satrec.a = (satrec.no_unkozai * satrec.tumin) ** (-2.0 / 3.0)
  satrec.alta = satrec.a * (1.0 + satrec.ecco) - 1.0
  satrec.altp = satrec.a * (1.0 - satrec.ecco) - 1.0
  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)
  #//       {
  #//         satrec.error = 5
  #//       }

  if ((satrec.omeosq >= 0.0) or (satrec.no_unkozai >= 0.0))
    satrec.isimp = 0
    if (satrec.rp < (220.0 / satrec.radiusearthkm + 1.0))
      satrec.isimp = 1
    end
    sfour = ss
    qzms24 = qzms2t
    perige = (satrec.rp - 1.0) * satrec.radiusearthkm

    #/* - 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
      end
      #// sgp4fix use multiply for speed instead of pow
      qzms24temp = (120.0 - sfour) / satrec.radiusearthkm
      qzms24 = qzms24temp * qzms24temp * qzms24temp * qzms24temp
      sfour = sfour / satrec.radiusearthkm + 1.0
    end

    pinvsq = 1.0 / satrec.posq

    tsi = 1.0 / (satrec.ao - sfour)
    satrec.eta = satrec.ao * satrec.ecco * tsi
    etasq = satrec.eta * satrec.eta
    eeta = satrec.ecco * satrec.eta
    psisq = (1.0 - etasq).abs
    coef = qzms24 * (tsi ** 4.0)
    coef1 = coef / (psisq ** 3.5)
    cc2 = (coef1 * satrec.no_unkozai * (satrec.ao * (1.0 + 1.5 * etasq + eeta *
                                                                         (4.0 + etasq)) + 0.375 * satrec.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 * satrec.j3oj2 * satrec.no_unkozai * satrec.sinio / satrec.ecco
    end
    satrec.x1mth2 = 1.0 - satrec.cosio2
    satrec.cc4 = (2.0 * satrec.no_unkozai * coef1 * satrec.ao * satrec.omeosq *
                  (satrec.eta * (2.0 + 0.5 * etasq) + satrec.ecco *
                                                      (0.5 + 2.0 * etasq) - satrec.j2 * tsi / (satrec.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 * satrec.ao * satrec.omeosq * (1.0 + 2.75 *
                                                                   (etasq + eeta) + eeta * etasq))
    cosio4 = satrec.cosio2 * satrec.cosio2
    temp1 = 1.5 * satrec.j2 * pinvsq * satrec.no_unkozai
    temp2 = 0.5 * temp1 * satrec.j2 * pinvsq
    temp3 = -0.46875 * satrec.j4 * pinvsq * pinvsq * satrec.no_unkozai
    satrec.mdot = (satrec.no_unkozai + 0.5 * temp1 * satrec.rteosq * satrec.con41 + 0.0625 *
                                                                                    temp2 * satrec.rteosq * (13.0 - 78.0 * satrec.cosio2 + 137.0 * cosio4))
    satrec.argpdot = (-0.5 * temp1 * satrec.con42 + 0.0625 * temp2 *
                                                    (7.0 - 114.0 * satrec.cosio2 + 395.0 * cosio4) +
                      temp3 * (3.0 - 36.0 * satrec.cosio2 + 49.0 * cosio4))
    xhdot1 = -temp1 * satrec.cosio
    satrec.nodedot = (xhdot1 + (0.5 * temp2 * (4.0 - 19.0 * satrec.cosio2) +
                                2.0 * temp3 * (3.0 - 7.0 * satrec.cosio2)) * satrec.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
    end
    satrec.nodecf = 3.5 * satrec.omeosq * xhdot1 * satrec.cc1
    satrec.t2cof = 1.5 * satrec.cc1
    #// sgp4fix for divide by zero with xinco = 180 deg
    if ((satrec.cosio + 1.0).abs > 1.5e-12)
      satrec.xlcof = -0.25 * satrec.j3oj2 * satrec.sinio * (3.0 + 5.0 * satrec.cosio) / (1.0 + satrec.cosio)
    else
      satrec.xlcof = -0.25 * satrec.j3oj2 * satrec.sinio * (3.0 + 5.0 * satrec.cosio) / temp4
    end
    satrec.aycof = -0.5 * satrec.j3oj2 * satrec.sinio
    #// sgp4fix use multiply for speed instead of pow
    delmotemp = 1.0 + satrec.eta * Math.cos(satrec.mo)
    satrec.delmo = delmotemp * delmotemp * delmotemp
    satrec.sinmao = Math.sin(satrec.mo)
    satrec.x7thm1 = 7.0 * satrec.cosio2 - 1.0

    #/* --------------- deep space initialization ------------- */
    if ((2 * PI / satrec.no_unkozai) >= 225.0)
      satrec.method = "d"
      satrec.isimp = 1
      tc = 0.0
      satrec.inclm = satrec.inclo

      dscom(epoch, satrec.ecco, satrec.argpo, tc, satrec.inclo, satrec.nodeo, satrec.no_unkozai, satrec)

      satrec.ep = satrec.ecco
      satrec.inclp = satrec.inclo
      satrec.nodep = satrec.nodeo
      satrec.argpp = satrec.argpo
      satrec.mp = satrec.mo

      dpper(satrec.e3, satrec.ee2, satrec.peo, satrec.pgho,
            satrec.pho, satrec.pinco, satrec.plo, satrec.se2,
            satrec.se3, satrec.sgh2, satrec.sgh3, satrec.sgh4,
            satrec.sh2, satrec.sh3, satrec.si2, satrec.si3,
            satrec.sl2, satrec.sl3, satrec.sl4, satrec.t,
            satrec.xgh2, satrec.xgh3, satrec.xgh4, satrec.xh2,
            satrec.xh3, satrec.xi2, satrec.xi3, satrec.xl2,
            satrec.xl3, satrec.xl4, satrec.zmol, satrec.zmos, satrec.init, satrec,
            satrec.operationmode)

      satrec.ecco = satrec.ep
      satrec.inclo = satrec.inclp
      satrec.nodeo = satrec.nodep
      satrec.argpo = satrec.argpp
      satrec.mo = satrec.mp

      satrec.argpm = 0.0
      satrec.nodem = 0.0
      satrec.mm = 0.0

      dsinit(tc, xpidot, satrec)
    end
    #}

    #/* ----------- set variables if not deep space ----------- */
    if (satrec.isimp != 1)
      cc1sq = satrec.cc1 * satrec.cc1
      satrec.d2 = 4.0 * satrec.ao * tsi * cc1sq
      temp = satrec.d2 * tsi * satrec.cc1 / 3.0
      satrec.d3 = (17.0 * satrec.ao + sfour) * temp
      satrec.d4 = 0.5 * temp * satrec.ao * tsi * (221.0 * satrec.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)))
    end
  end
  #} // if omeosq = 0 ...

  #/* 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)

  r = [0, 0, 0]
  v = [0, 0, 0]

  sgp4(satrec, 0.0, r, v)

  satrec.init = "n"

  #/sgp4fix return boolean. satrec.error contains any error codes
  return true
end

Class: Korba::SGP4

Constant Summary collapse

Class Method Summary collapse

Class Method Details

.dpper(e3, ee2, peo, pgho, pho, pinco, plo, se2, se3, sgh2, sgh3, sgh4, sh2, sh3, si2, si3, sl2, sl3, sl4, t, xgh2, xgh3, xgh4, xh2, xh3, xi2, xi3, xl2, xl3, xl4, zmol, zmos, init, rec, opsmode) ⇒ Object

.dscom(epoch, ep, argpp, tc, inclp, nodep, np, rec) ⇒ Object

.dsinit(tc, xpidot, rec) ⇒ Object

.dspace(tc, rec) ⇒ Object

.fmod(numer, denom) ⇒ Object

.getgravconst(whichconst, rec) ⇒ Object

.gstime(jdut1) ⇒ Object

.initl(epoch, rec) ⇒ Object

.jday(year, mon, day, hr, minute, sec) ⇒ Object

.sgp4(satrec, tsince, r, v) ⇒ Object

.sgp4init(opsmode, satrec) ⇒ Object

.dpper(e3, ee2, peo, pgho, pho, pinco, plo, se2, se3, sgh2, sgh3, sgh4, sh2, sh3, si2, si3, sl2, sl3, sl4, t, xgh2, xgh3, xgh4, xh2, xh3, xi2, xi3, xl2, xl3, xl4, zmol, zmos, init, rec, opsmode) ⇒ `Object`

.dscom(epoch, ep, argpp, tc, inclp, nodep, np, rec) ⇒ `Object`

.dsinit(tc, xpidot, rec) ⇒ `Object`

.dspace(tc, rec) ⇒ `Object`

.fmod(numer, denom) ⇒ `Object`

.getgravconst(whichconst, rec) ⇒ `Object`

.gstime(jdut1) ⇒ `Object`

.initl(epoch, rec) ⇒ `Object`

.jday(year, mon, day, hr, minute, sec) ⇒ `Object`

.sgp4(satrec, tsince, r, v) ⇒ `Object`

.sgp4init(opsmode, satrec) ⇒ `Object`