ATEx

ATEx-UEB & ATEx-LEB [USAF]

The ATEx (Advanced Tether Experiment) was designed to extend the knowledge of control and survivability of tethered space systems. 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. The objectives of ATEx were to:

• demonstrate tether system stability and control;
• demonstrate end-body attitude determination and control; and,
• fly a tether designed for survivability.

The tether's lower end-body was placed on top of an active spacecraft (STEX), permiting the opportunity to perform libration control experiments. Such control was deemed necessary prior to developing more sophisticated tethered space systems.

The upper end-body (UEB) was 0.62 × 0.52 × 0.07 m in dimension and 11.8 kg. The lower end-body (LEB) was 0.53 × 0.43 × 0.60 m and 27.6 kg. The tether was 13.4 kg. When fully deployed, the two masses were to be over 6 km apart.

ATEx was released from the STEX spacecraft on 16 January 1999 after deploying only 22 m. The jettison was triggered by an automatic protection system designed to save STEX if the tether strayed from its expected departure angle. As a result, none of the desired goals were achieved.