The Wallops Arc Second Pointer (WASP) is a balloon-borne attitude control system capable of pointing a telescope or instrument with accuracy and stability down to the arc second, or 1/3600 of a degree of angular measurement. When a high-powered telescope is integrated with WASP, it provides a highly precise platform for conducting astronomical research. To date, the WASP system has been tested aboard five helium-filled scientific balloons at altitudes between 100,000 – 125,000 feet with flight durations up to 15 hours. During these pathfinder missions, the WASP controlled instrument structures with masses between 1,000 – 2,000 lbs.
WASP technology is well suited for future long-duration (month-long) exoplanetary studies. The benefits of such balloon-borne science include enabling experiments in a near-space environment, science collection above 99.5% of Earth’s atmosphere, and the high likelihood of instrument recovery. For pointing of instruments where milli-arcsecond stability is required, WASP provides arc-second level pointing for the primary mirrors along with a stable platform for the deployment of high-bandwidth control systems on secondary mirrors to achieve the tight pointing requirements.
The WASP control system uses the balloon flight train as a reaction torque source, allowing for continuous pointing by making use of the attachment of the gondola to the balloon to absorb the momentum reacted from the instrument payload. Consistent sub-arcsecond stability is achieved largely by the mechanical design of the WASP rotation axis hubs, which eliminate static friction between the pointed items and the rest of the gondola through the use of continually rotating inner shafts.