It's calculated using historical data (the most recent observation) using the Simplified General Perturbations model: https://en.wikipedia.org/wiki/Simplified_p

It's calculated using historical data (the most recent observation) using the Simplified General Perturbations model: https://en.wikipedia.org/wiki/Simplified_perturbations_models https://en.wikipedia.org/wiki/Simplified_perturbations_model... This is why it's a beast to run. It's looping through some hefty calculations for each satellite every second.