Astrogator Technical Notes

This section contains topics that describe constants and equations related to Astrogator calculations.

Eigenvalue and Eigenvector sorting

After you run a mission control sequence, when applicable Astrogator sorts the STM eigenvalues and eigenvectors to maintain consistency of the eigenvalues with the previous ephemeris point. This is done by comparing of the result of linear interpolation using the previous two points with the true value at each ephemeris point. Additionally, Astrogator adjusts the sign of the eigenvectors so that the largest element of each eigenvector is positive for the first three ephemeris points and the signs are consistent with the previous time for the rest of the ephemeris points. It uses a similar method as the eigenvalue sorting.

When accessing eigenvalues and eigenvectors, Astrogator does not do sorting while the MCS is running, such as through calculation graphs. Instead, Astrogator sorts the eigenvalues by the absolute value of their real parts in ascending order, and it does not modify the signs of the eigenvectors from the output of the eigenvalue algorithm. Therefore, there will likely be large jumps for individual eigenvalues and eigenvector elements if Astrogator is reporting on them while the MCS is running.