The impact of Roland Shack's wavefront sensor on the development of modern active optics

This paper discusses the impact that Roland Shack and his eponymous wavefront sensor have had on the development of active optics in astronomy. There are a number of interesting threads to this story, from the early concept development and its drivers, to the uptake and realization by the broader astronomical community of the advantages offered by this system. Shack’s innovation not only directly benefited numerous large-scale astronomical projects, but it can be shown to have further inspired innovation, proving yet again that the “intangible benefits” of technical innovation are often themselves significant considerations. Another interesting aspect of this story is that via a quite distinct line of investigation initiated by Shack in the 1970’s, an important conceptual omission in the application of the wavefront sensor to the first generation of active telescopes was recognized, and resultant improvements have further enabled a new generation of active telescopes and in particular wide-field survey telescopes.