A sub-arcsecond Pointing stability fine stage for a high altitude balloon platform

High-altitude balloons (HABs) are platforms for
collecting astrophysical and planetary science data that offer
a number of advantages compared to conventional groundbased
or space-based systems. However, they also pose a set
of new environmental challenges that must be addressed in
order to offer a viable alternative to ground- or space- based
assets. In particular, maintaining science-quality pointing
stability is a critical challenge for HAB platforms. For these
missions, dynamic errors must be limited to a fraction of the
observation wavelength, so as the wavelength becomes
smaller, it becomes more difficult to meet the needed
performance. As a result, there are very few existing pointing
stabilization solutions that use visible-spectrum guide stars,
despite their relatively wide distribution across the sky. This
paper describes the results achieved with the STABLE (Subarcsecond
Telescope And BaLloon Experiment) project
whose goal is to provide the fine pointing stage for a balloonborne
platform observing in the visible wavelength.