I. Introduction
After 60 years of near oblivion, the use of airships seems to have been rediscovered. Nowadays, airships are being used both for heavy freight aerial transport and for small indoor or outdoor advertising or surveillance tasks. The work presented in this paper, developed in the frame of the Portuguese DIVA project, is based on the dynamic model of the AURORA airship and is part of the effort applied to mature and propose solutions for small autonomous airships to be used in aerial monitoring and surveillance [1].