STEX (NROL-8) (USA-140) (USA-141)

The STEX (Space Technology Experiments) satellite carried 29 new technologies intended to result in lower cost and higher performance spacecraft for future missions.

The ATEx (Advanced Tether Experiment), designed and built by the Naval Center for Space Technology (NCST), was a mission to extend the knowledge of control and survivability of tethered space systems. ATEx consisted of two parts: ATEx-LEB (Advanced Tether Experiment - Lower End Body) and ATEx-UEB (Advanced Tether Experiment - Upper End Body). Experiments in active control were to study deployment dynamics via a constant-speed motor and utilization of both in-plane and cross-plane thrusters to excite and arrest librations. Additionally, ATEx was to investigate the survivability of long-life tether materials.