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dpper.m
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dpper.m
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% -----------------------------------------------------------------------------
%
% 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:
% Jeff Beck
% 1.0 (aug 7, 2006) - update for paper dav
% original comments from Vallado C++ version:
% 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
% ----------------------------------------------------------------------------*/
function [ ep, inclp, nodep, argpp, mp]...
= 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, inclo, init, ep, inclp, nodep, argpp, mp)
% /* --------------------- local variables ------------------------ */
twopi = 2.0 * pi;
% /* ---------------------- 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 * sin(zm);
sinzf = sin(zf);
f2 = 0.5 * sinzf * sinzf - 0.25;
f3 = -0.5 * sinzf * 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 * sin(zm);
sinzf = sin(zf);
f2 = 0.5 * sinzf * sinzf - 0.25;
f3 = -0.5 * sinzf * 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')
% // 0.2 rad = 11.45916 deg
% // sgp4fix for lyddane choice
% // add next four lines to set up use of original inclination per strn3 ver
ildm = 'y';
if (inclo >= 0.2)
ildm = 'n';
end
pe = pe - peo;
pinc = pinc - pinco;
pl = pl - plo;
pgh = pgh - pgho;
ph = ph - pho;
inclp = inclp + pinc;
ep = ep + pe;
sinip = sin(inclp);
cosip = 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
% // 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 = ph / sinip;
pgh = pgh - cosip * ph;
argpp = argpp + pgh;
nodep = nodep + ph;
mp = mp + pl;
else
% /* ---- apply periodics with lyddane modification ---- */
sinop = sin(nodep);
cosop = cos(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;
nodep = rem(nodep, twopi);
xls = mp + argpp + cosip * nodep;
dls = pl + pgh - pinc * nodep * sinip;
xls = xls + dls;
xnoh = nodep;
nodep = atan2(alfdp, betdp);
if (abs(xnoh - nodep) > pi)
if (nodep < xnoh)
nodep = nodep + twopi;
else
nodep = nodep - twopi;
end
end
mp = mp + pl;
argpp = xls - mp - cosip * nodep;
end
end % // if init == 'n'
global idebug dbgfile
if idebug
debug1;
end
return;