help me fix the Error

% Physical constants
mu = 398600.4418; % km^3/s^2
R_E = 6378.137; % km
omega_E = 7.2921158553e-5; % rad/s
% Satellite parameters
e = 0; % Eccentricity
i = 30; % Inclination [deg]
RAAN = 20; % RAAN [deg]
n = sqrt(mu/R_E^3); % Mean motion [rad/s]
h = R_E*sqrt(1-e^2); % Specific angular momentum
a = h^2/mu; % Semi-major axis
% Sensor parameters
nadir_angle = 4; % [deg]
nadir_angle_rad = deg2rad(nadir_angle);
distance_to_earth = R_E + (a*sin(nadir_angle_rad)); % Distance to the point where the sensor line of sight intersects the earth
% NMW Inertial coordinate system
x_NMW = [cosd(RAAN), sind(RAAN), 0]; % x-axis
z_NMW = [0, 0, 1]; % z-axis
y_NMW = cross(z_NMW, x_NMW); % y-axis
% Line-of-sight point of intersection with the Earth as the satellite makes one orbit revolution
theta = linspace(0, 2*pi, 1000);
x = distance_to_earthcos(theta);
y = (acosd(i) + distance_to_earthsin(nadir_angle_rad))*sin(theta);
z = (asind(i))*sin(theta);
% Earth Centered Inertial (ECI) frame
t = linspace(0, 2*pi/n, 1000);
r = [x', y', z'];
v = cross([0, 0, n], r);
eci_states = [r, v];
ECI_path = eci_states(:, 1:3);
plot3(ECI_path(:, 1), ECI_path(:, 2), ECI_path(:, 3))
xlabel('x (km)')
ylabel('y (km)')
zlabel('z (km)')
title('Path of the satellite in ECI frame')
grid on
% Argument of Latitude
lat_30 = 30;
u = atan2d(tand(lat_30), cosd(RAAN));
fprintf('Argument of latitude: %.2f degrees\n', u);
% Earth Centered Earth Fixed (ECEF) frame
GMST = @(t) mod(omega_Et, 2*pi);
ecef_states = zeros(size(eci_states));
for i = 1:size(eci_states, 1)
    T = [cos(GMST(t(i))), sin(GMST(t(i))), 0;
        -sin(GMST(t(i))), cos(GMST(t(i))), 0;
        0, 0, 1];
    ecef_states(i, :) = Teci_states(i, :)';
end
ECEF_path = ecef_states(:, 1:3);
figure
plot(ECEF_path(:, 2), ECEF_path(:, 1))
xlabel('Longitude (deg)')
ylabel('Latitude (deg)')
title('Ground track of the satellite in ECEF frame')
hold on
plot(u, lat_30, 'r')
hold off
legend('Ground track', 'Spot beam')
grid on
% Part of the world where the spot beam is hitting
fprintf('The spot beam is hitting the part of the world near %.2f degrees N, %.2f degrees E.\n', lat_30, u);

[John D'Errico]

Fix what error? When you have an error in your code, then report the ENTIRE error, so everything in red. That makes it often possible for someone to answer your question without even running your code.

If the code is returning a result that you think to be inorrect, then tell people what you think is wrong, and what the corrrect result should be.

Is there a good reason why you want to make it more difficult for someone to help you?

[Jagrut Alpeshbhai]

Undefined function 'distance_to_earthcos' for input arguments of type

'double'. I'm getting this error

[Walter Roberson]

distance_to_earthcos and distance_to_earthsin are not function provided by MATLAB. Indeed, I cannot find them anywhere on the internet.

Conversion formulas are discussed at https://space.stackexchange.com/questions/1904/how-to-programmatically-calculate-orbital-elements-using-position-velocity-vecto/1919#1919

Answer 1

[John D'Errico]

which distance_to_earthcos -all

'distance_to_earthcos' not found.

This function is not a MATLAB function. It is not found in any toolbox either. For that matter, distance_to_earthsin is also not a function in MATLAB.

These functions may have been written by you, or perhaps by someone you know.