The Z1 truss was the first exterior framework installed on the ISS and allowed the first U.S. solar arrays to be temporarily installed on Unity for early power during flight 4A. The Ku-band communication system supported early science capabilities and U.S. television on flight 6A. The CMGs (Control Moment Gyros) weigh about 27 kilograms and provide non-propulsive (electrically powered) attitude control when activated on flight 5A, and PMA-3 provides shuttle docking port for solar array installation on flight 4A and Destiny Lab installation on flight 5A.