Complex sentence: The station could have been moved to within 1,000 m of the craft, at which point Soyuz 33 could be docked using its thrusters, but the two craft were drifting apart at 28 metres per second, and time was needed to calculate the maneuvers.
Split into simpler sentences: The station could have been moved to within 1,000 m of the craft, at which point Soyuz 33 could be docked using its thrusters. But the two crafts were drifting apart at 28 metres per second, and time was needed to calculate the maneuvers.