built SGP4 from scratch (the actual math real orbit trackers use, not a library). got it working fast and it looked fine but then i found the official test case with known correct answers and mine was 370km off after a day lol. turned out i swapped a constant, a problem small enough that it looked right but over time it turned into a problem. fixed it and now it matches the reference to under 10 meters over 24 hours. next up: figuring out when satellites actually fly over your house