I did one of these balloon launches myself several years ago, and attempted to build a flight computer myself with Arduino and multiple sensors. I could not find an efficient way to read all of the data from the selection of sensors in the limited memory, so I wound up using a Mega. Nobody involved was a licensed radio operator, so our live tracking was very primitive. It wasn't until after 45k' that we realized our GPS tracking stopped tracking at that altitude because why would a civilian be at that altitude. Of course we didn't know that until researching it after recovery, but we were very relieved when it started to updating once it came back under 45k'. Unfortunately, something happened (my coding to be sure) that caused the log to not be written as expected. Was hoping to be able to compare the GPS of the actual flight against the forecast model we used. This is the very thing I would have loved to have for future launches. I even made friends with a licensed operator to make it legit. (couldn't be bothered to take the test myself)

One thing to keep in mind for anyone wanting to do their first one. If you go to the trouble of printing up contact info for an "If Found", don't forget to attach it before lift off like I did.