Stochastic performance analysis and staged controller designs for space interferometry systems

Abstract

During the preliminary design phase of space-based interferometer missions, observational requirements need to be translated into dynamical accuracy requirements on the optical components. The first part of this paper presents a methodology that specifies allowable statistical variances on the optical path difference in order to achieve a specified mean level of null depth for a nulling interferometer. These dynamical requirements can then be used as inputs to controller design processes which ensures that the closed-loop system satisfies the performance requirements.The second part of this paper describes a staging control design tool that optimally uses a suite of actuators to reject disturbances and analyzes the performance limitations as a function of actuator constraints. The particular actuator constraints considered here are saturation limit, resolution level, and the operational bandwidth of each actuator. As an example, the control design tool is applied to an example optical delay line problem yielding a feedback control law which ensures nanometer level stabilization of optical path difference for the interferometer. This benchmark problem allows the control design tool to demonstrate its capabilities on a system with stringent dynamical requirements.

Integrated modeling of optical performance for the Terrestrial Planet Finder structurally connected interferometer

“…The analysis used to generate this plot set the null depth requirement at 106. A minimum of three apertures would be needed to meet this requirement [22]. These performance metrics must meet very stringent requirements under the influence of disturbances from sources such as reaction wheel imbalance and sensor noise.…”

“…It can be lanet c. Figure 1-4: Normalized intensity of two rectangular apertures (left). Normalized nulling interferometer response for a family of apertures [22].…”

“…tures with null depth requirement [22].. Scientists and engineers are still involved in early trade studies to determine which architecture will best serve the needs of TPF.…”