mdl_principle

Another option for those who don't want to download the app: https://www.heavens-above.com (also works for many other satellites).

Set your location in the upper-right corner, then select the ACS3 on the main page.

Cool - looks like we both walked similar paths: Using a stack-based language, pruning invalid programs, even having similar bugs (I too had one related to excluded prefixes).

It's sad that things like this are nearly impossible to find on Google unless you already know the exact title.