Season 1 - An incredible (almost) historical drama in stunning detail of the 70’s Moon landings with a twist.
Season 2 - Moves away from Historical and towards political and action.
Season 3 - Pushes into Sci Fi territory and slowly gets weaker as a show.
Season 4 - Plods along pretty much like the Stargate Series did near the end, before a twist brings the final 3 episodes back to dramatic tension.
Overall, the first two seasons were the best, but while the drama and acting has weakened more recently it is still a very enjoyable show and can potentially continue for many more seasons with a strong set of writers.