Could anyone tell me what the names of the Greek letters in the screenshot are? Is the first one alpha? They are used in calculating ICRF rotations. Wikipedia uses a different font for their list of characters, so it's hard to tell.
The first one is alpha (α); the second one is delta (δ). You can study the shapes of the letters here:
Here's what they mean (information from a comment to your question):
Orientation models use three Euler angles to describe body orientation. The first two angles are the right ascension and declination of the north pole of a body as a function of time. The third angle is the prime meridian location (represented by "W"), which is expressed as a rotation about the north pole, and is also a function of time.