There are two common tools used to specify attitude. First and quite common one being [https://en.wikipedia.org/wiki/Euler_angles Euler angles]. Basically, you start with an initial frame and tell by what angle and about which axes you need to do the rotation. Repeat this two more times each time using the ‘newly’ obtained axes post rotation. The final frame achieved is your required frame.This set of three angles are specified in the same order. Euler angles tells you how to get from one frame to another and hence the attitude. <br \>

In the above gif, we are trying to reach to a final orientation of the globe. However, the order of axis about which these rotations are done are predefined (here, z-x-z) and this in turn fixes the euler angles. But the problem with euler angles, as you may have noticed,is that these angles are not very intuitive. The axes of rotation and their order are decided beforehand. Now, how do we decide the angles constraining ourselves to that specific order? Not easy, is it? <br \>

[[File:Quaternion1.png|thumb]]

There is an interesting story about Hamilton who had devised quaternions. So Hamilton was on his way to preside a meeting when the idea of quaternions dawned upon him. He had been struggling to extrapolate the idea of 2-D rotation which can be done using complex numbers to 3-D. And when he had his moment of epiphany, he got so excited that he couldn’t resist the urge to carve its formulae into the stone of Brougham Bridge as he paused on it. <br \>

To summarise, attitude of a satellite gives its orientation and finding it is the first step to controlling it. <br \>

If you are done reading this page, you can go back to [[Attitude Determination and Control Subsystem]].