How to get a column vector for all the considered time instants?

Hi everyone. I have a problem with this code. At the end I would like to obtain the r_ORF column vector for all the time instants (41) but I don't understand why this does not happen in this code. Thanks in advance.

        clc;clear all; close all;
        % Components determination in ORF
        
        % ECI (GEOC) to ORF matrix determination
        A = load('DatiCosmoSkymed.txt');
        times = A(:,1);

        for i = 1: length(times)
        r_inertial(1,i)= A(i,8);
        r_inertial(2,i)= A(i,9);
        r_inertial(3,i)= A(i,10);
        
        v_inertial(1,i)= A(i,11);
        v_inertial(2,i)= A(i,12);
        v_inertial(3,i)= A(i,13);
               
        kORF_ECI=-r_inertial/norm(r_inertial);
        jORF_ECI=-cross(r_inertial,v_inertial)/norm(cross(r_inertial,v_inertial));
        iORF_ECI=cross(jORF_ECI,kORF_ECI);
        
        M_ECItoORF(1,1)=iORF_ECI(1,1);
        M_ECItoORF(1,2)=iORF_ECI(2,1);
        M_ECItoORF(1,3)=iORF_ECI(3,1);
        
        M_ECItoORF(2,1)=jORF_ECI(1,1);
        M_ECItoORF(2,2)=jORF_ECI(2,1);
        M_ECItoORF(2,3)=jORF_ECI(3,1);
        
        M_ECItoORF(3,1)=kORF_ECI(1,1);
        M_ECItoORF(3,2)=kORF_ECI(2,1);
        M_ECItoORF(3,3)=kORF_ECI(3,1);
        
        r_ECI = r_inertial;
        r_ORF = M_ECItoORF*r_ECI;
        display(r_ORF)

end

        
           

Answer 1

[Walter Roberson]

    % Components determination in ORF
    
    % ECI (GEOC) to ORF matrix determination
    A = load('DatiCosmoSkymed.txt');
    times = A(:,1);
    num_times = size(times,1);
    r_ORDF = cell(num_times,1);
    
    for i = 1: num_times
        r_inertial(1,i)= A(i,8);
        r_inertial(2,i)= A(i,9);
        r_inertial(3,i)= A(i,10);
        
        v_inertial(1,i)= A(i,11);
        v_inertial(2,i)= A(i,12);
        v_inertial(3,i)= A(i,13);
               
        kORF_ECI=-r_inertial/norm(r_inertial);
        jORF_ECI=-cross(r_inertial,v_inertial)/norm(cross(r_inertial,v_inertial));
        iORF_ECI=cross(jORF_ECI,kORF_ECI);
        
        M_ECItoORF(1,1)=iORF_ECI(1,1);
        M_ECItoORF(1,2)=iORF_ECI(2,1);
        M_ECItoORF(1,3)=iORF_ECI(3,1);
        
        M_ECItoORF(2,1)=jORF_ECI(1,1);
        M_ECItoORF(2,2)=jORF_ECI(2,1);
        M_ECItoORF(2,3)=jORF_ECI(3,1);
        
        M_ECItoORF(3,1)=kORF_ECI(1,1);
        M_ECItoORF(3,2)=kORF_ECI(2,1);
        M_ECItoORF(3,3)=kORF_ECI(3,1);
        
        r_ECI = r_inertial;
        r_ORF{i} = M_ECItoORF*r_ECI;
    end

I think you should reconsider your code a bit.

The first iteration, you write to the first column of r_inertial, so r_intertial is 3 x 1. M_ECItoORF is 3 x 3. In the calculation of r_ORF you use the * operator between the 3 x 3 M_ECItoORF and the 3 x 1 R_ECI to get a 3 x 1 result the first iteration.

The second iteration, you write to the second column of r_interial, so r_inertial is 3 x 2. And for kORF_ECI and jORF_ECI you use that entire 3 x 2 r_intertial . Are you certain that you want to be using the cumulative r_intertial in the calculation, not just the "current" column of r_intertial ?

Then you get down to the r_ORF, M_ECI is still 3 x 3, r_ECI is now 3 x 2 because it is is the 3 x 2 r_inertial, so r_ORF becomes 3 x 2, not 3 x 1.

And so on, until you get to the end, and the last r_ORF is 3 x number_of_times .

Does this make sense to do ???

[Loren99]

the problem is that in the second iteration, I would like to use only the current value of r_inertial, ie only the second column of r_inertial; then get r_ECI coincident with the current value of r_inertial and finally get r_ORF as a 3x1 column vector. Can you help me modify the code to achieve this? Please

[Loren99]

At the end I would like to diplay on the command window r_ORF as 3x1 column vectors for each time instant analyzed

[Walter Roberson]

    % Components determination in ORF
    
    % ECI (GEOC) to ORF matrix determination
    A = load('DatiCosmoSkymed.txt');
    times = A(:,1);
    num_times = size(times,1);
    r_ORDF = zeros(3, num_times);
    
    for i = 1: num_times
        r_inertial(1,1)= A(i,8);
        r_inertial(2,1)= A(i,9);
        r_inertial(3,1)= A(i,10);
        
        v_inertial(1,1)= A(i,11);
        v_inertial(2,1)= A(i,12);
        v_inertial(3,1)= A(i,13);
               
        kORF_ECI=-r_inertial/norm(r_inertial);
        jORF_ECI=-cross(r_inertial,v_inertial)/norm(cross(r_inertial,v_inertial));
        iORF_ECI=cross(jORF_ECI,kORF_ECI);
        
        M_ECItoORF(1,1)=iORF_ECI(1,1);
        M_ECItoORF(1,2)=iORF_ECI(2,1);
        M_ECItoORF(1,3)=iORF_ECI(3,1);
        
        M_ECItoORF(2,1)=jORF_ECI(1,1);
        M_ECItoORF(2,2)=jORF_ECI(2,1);
        M_ECItoORF(2,3)=jORF_ECI(3,1);
        
        M_ECItoORF(3,1)=kORF_ECI(1,1);
        M_ECItoORF(3,2)=kORF_ECI(2,1);
        M_ECItoORF(3,3)=kORF_ECI(3,1);
        
        r_ECI = r_inertial;
        r_ORF(:,i) = M_ECItoORF*r_ECI;
    end

I believe that should give you a 3 x (number of times) array