Spherical Trigonometry

Thank you for all you have done! If possible, could there be a few videos on Spherical Trigonometry? I was taking a class not too long ago on orbital mechanics and we went over footprints and viewing angles on a sphere with respect to a body in orbit. Needless to say, I was overwhelmed for that particular topic. I passed the course but I still never learned how to do this. There was an entire section in the textbook "Space Mission Engineering: The New SMAD" Dedicated to space mission geometry and it wasn't very helpful since it did not take a math based approach. I was hoping that you could dedicate a few videos on this topic. Thanks again, I love the site and have used it for the last 6 years.