I've finally figured out how to reset the Orbit Stepper once Orbit is reached (which lights centre target and outlanes for special)

Now, you reach Orbit, light specs, collect 300,000 points and Orbit stepper resets , so you can try to reach Orbit again within the same game.
It all came down to a lot of schematic reading to eventually find a suitable normally open switch, that closes to earth once Orbit is reached  and wire the output of that to the earth lug on the Orbit stepper reset coil