SCT Spin Axis Module

The Spin Axis Attitude Determination Module (SAAD), for use with the Spacecraft Control Toolbox provides you with a complete, integrated set of tools needed to perform spin-axis attitude determination using horizon sensor and sun sensor measurements. Spin-axis attitude determination requires at least one horizon sensor and one single-axis sun sensor.

SAAD makes extensive use of the MATLAB® graphics capabilities, which makes analyzing your data an easy task. Plots of measurement data make evaluating data quality and effectiveness of data culling a snap. You can also see how well the measured data matches predictions before and after solutions, as in the plot below. Solutions are also presented numerically (as errors and residual statistics) for all of the solution methods.

The SAAD Package can process any combination of data that is available on your system. It accepts horizon sensor inputs as either leading and trailing edge times or as dihedral angles. Midscan, leading or trailing dihedral angles are handled with equal ease. The data can even be processed without dihedral angles or without chordwidths. This feature was useful on a recent mission when a temporary glitch made the leading edge times, and therefore the chordwidths, unavailable. We were able to continue attitude determination using only the sun angle and the trailing edge dihedral angles.

We’ve used this package on four missions for three different types of spacecraft with excellent results! On the most recent mission our predictions, from all of our algorithms, matched post apogee burn attitude predictions to within two tenths of a degree.