The Viking orbiters were larger and heavier than their Mariner predecessors. Consequently they needed more propellant: two tanks containing a total of 1,600 kg. Each tank measured 140 by 90 cm.
Viking 1 was placed into orbit on 19 JUN 1976, with a 38-minute engine burn. This was the longest burn ever to take place in deep space, and 1,063 kg of propellant were expended. Two days later a 'trim maneuver' was used to fine-tune the orbit into one that was highly elongated and synchronous (meaning that the orbiter had an identical rotation period to Mars itself). This orbit had a periapsis of 1,500 km when it was above the lander site and an apoapsis of 32,800 km.
