PQR=gaussvec(lan,inc,aop)

function PQR=gaussvec(lan,inc,aop)

% function PQR=gaussvec(lan,inc,aop)
%
% computation of the 3 Gaussian vectors
% from ecliptical orbit elements
% algorithms by Montenbruck/Pfleger: "Astronomy with the Personal Computer"
%
% 05.05.04 M.Penzkofer

% constants
rho = pi/180;

C1=cos(aop*rho);  C2=cos(inc*rho);  C3=cos(lan*rho);
S1=sin(aop*rho);  S2=sin(inc*rho);  S3=sin(lan*rho);
PQR(1,1)=+C1*C3-S1*C2*S3; PQR(1,2)=-S1*C3-C1*C2*S3; PQR(1,3)=+S2*S3;
PQR(2,1)=+C1*S3+S1*C2*C3; PQR(2,2)=-S1*S3+C1*C2*C3; PQR(2,3)=-S2*C3;
PQR(3,1)=+S1*S2;          PQR(3,2)=+C1*S2;          PQR(3,3)=+C2;