function isSatVis = isSatelliteVisiable(UserPosition,Satellite,t)
%　驗證在某一時刻，某一位置，某一顆衛(wèi)星的可見性，衛(wèi)星可見則返回1,否則返回0
%　UserPosition = [latitude longitude];
%    其中-180 < longitude < 180 東經(jīng)為正，西經(jīng)為負(fù)；-90< latitude <90, 北緯為正，南緯為負(fù)
%  Satellite = [ i Omiga a e w M ]; 　　　　其中6個分量為初始時刻t0時的初始值
%　　6個分量分別是軌道面傾角，升交點(diǎn)赤經(jīng)，長半軸，軌道偏心率，近地點(diǎn)角中，平近地角
%　求出t時刻衛(wèi)星位置，將t時刻用戶地理坐標(biāo)轉(zhuǎn)換成空間坐標(biāo)，驗證衛(wèi)星的可見性

DtoR = 2*pi/360;
CommandAngle = 90 * 2*pi/360; % 地心－用戶－衛(wèi)星　間夾角大于該角度時，衛(wèi)星可見
                              %　如果要求10度仰角，則最夾角最低為100度
%%%%%%%%%%%%%%%%%%%%% 求解衛(wèi)星位置
%  GASTw : 星期六午夜至星期天子夜的交換時刻格林尼治視恒星時
% SatPos = [Xk Xk Xk]';
GASTw = pi/3;
SatPos = SatellitePos(Satellite,GASTw,t);

%%%%%%%%%%%%%%%%%%%%%　用戶坐標(biāo)轉(zhuǎn)換
Re = 6366707;   % 地球圓體半徑
long = UserPosition(2) * DtoR;
lat = UserPosition(1) * DtoR;
% 用戶的地心直角坐標(biāo)
Xu = Re * cos(long);
Yu = Re * sin(long);
Zu = Re * sin(lat);
UserPos = [Xu Yu Zu]';

Delta_Pos = SatPos - UserPos;
RR = [-sin(lat)*cos(long)  -sin(lat)*sin(long)  cos(lat);
      -sin(long)           cos(long)            0;
      cos(lat)*cos(long)   cos(lat)*sin(long)   sin(lat);];  % 轉(zhuǎn)換距陣
PosUser = RR *  Delta_Pos;  %　衛(wèi)星在觀測站的站心直角坐標(biāo)系坐標(biāo)
Xps = PosUser(1);
Yps = PosUser(2);
Zps = PosUser(3);
%%%%%%%%%%%%%%%%%%%% 　驗證衛(wèi)星是否可見
% 用站心極坐標(biāo)表示衛(wèi)星位置
% Rp - 測者到衛(wèi)星間的距離；Ap - 衛(wèi)星方位角；Ep - 衛(wèi)星高度角
Rp = sqrt(Xps^2+Yps^2+Zps^2);
Ap = atan(Yps/Xps);
Ep = atan(Zps/sqrt(Xps^2+Yps^2));
if Ep>0
    isSatVis = 1;
else
    isSatVis=0;
end