Chapter 5 Robust Performance Tailoring with Tuning - SSL - MIT

Chapter 1
Introduction
Next-generation precision telescopes, such as space-based interferometers, push the
boundaries of existing design methodologies. In order to achieve science goals, nanome-
ter level pointing stability and precise wavefront control are necessary. These require-
ments place a large burden on the structural dynamics and control systems. In ad-
dition, fully-integrated system tests on interferometers are cost-prohibitive, placing a
heavy dependence on models and simulation for pre-launch performance assessment.
In effect, inherently uncertain models and approximations are relied upon to pro-
vide precise performance predictions. Traditional robust design techniques are not
adequate to guarantee success under such conditions.
To address this problem, a two-stage design methodology called Robust Perfor-
mance Tailoring for Tuning (RPTT) is developed. It is an extension to robust design
that includes, in the cost function, the concept of tunability . Uncertainty compen-
sation is shared between robust design and hardware tuning. RPTT is employed
during the design stage when uncertainty is high but the design parameter space is
large. Hardware tuning is used after the components are built, when the performance
is known, but only limited adjustments are possible. The methodology is developed
in the context of structurally-connected space-based interferometers such as NASA’s
Space Interferometry Mission (SIM) and Terrestrial Planet Finder (TPF), but is also
applicable to other precision optical systems such as the James Webb Space Telescope
(JWST) and coronographs.
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