sentences:  The GC3 unit enabled the flight control system to interface with computers on the ground.The flight test vehicle flew autonomously and was controlled by the FTINU, located on the underside of the lower ballast plates of the upper-stage simulator (USS).The avionics were developed by Lockheed-Martin of Denver, Colorado, a subcontractor to Jacobs Engineering of Huntsville, Alabama, and is managed by Marshall Space Flight Center in Huntsville, Alabama.