Precision telescope pointing and spacecraft vibration isolation for the Terrestrial Planet Finder Coronagraph

Abstract

The Terrestrial Planet Finder Coronagraph is a visible-light coronagraph to detect planets that are orbiting within the Habitable Zone of stars. The coronagraph instrument must achieve a contrast ratio stability of 2e-11 in order to achieve planet detection. This places stringent requirements on several spacecraft subsystems, such as pointing stability and structural vibration of the instrument in the presence of mechanical disturbance: for example, telescope pointing must be accurate to within 4 milli-arcseconds, and the jitter of optics must be less than 5 nm. This paper communicates the architecture and predicted performance of a precision pointing and vibration isolation approach for TPF-C called Disturbance Free Payload (DFP) * . In this architecture, the spacecraft and payload fly in close-proximity, and interact with forces and torques through a set of non-contact interface sensors and actuators. In contrast to other active vibration isolation approaches, this architecture allows for isolation down to zero frequency, and the performance of the isolation system is not limited by sensor characteristics. This paper describes the DFP architecture, interface hardware and technical maturity of the technology. In addition, an integrated model of TPF-C Flight Baseline 1 (FB1) is described that allows for explicit computation of performance metrics from system disturbance sources. Using this model, it is shown that the DFP pointing and isolation architecture meets all pointing and jitter stability requirements with substantial margin. This performance relative to requirements is presented, and several fruitful avenues for utilizing performance margin for system design simplification are identified.

Modeling and robust H-infinite control of a novel non-contact ultra-quiet Stewart spacecraft

“…The performance weighting function is reduced to 10%. By using D-K iterations, the robust H ∞ controller of the PM is given by 11 …”

“…The vibration isolation systems have attracted considerable attentions by various researchers and engineers, (see, e.g., [1]- [11], [14]- [18]). The general methods usually contain passive vibration isolation system, active vibration isolation system and the mixed vibration isolation system, but currently these vibration isolation systems have limited performance to isolate and compensate jitters over a broad band rage of frequencies.…”

Design and experiments of an active isolator for satellite micro-vibration

“…Refs. [29]- [30] demonstrated the concept of a disturbance-free payload architecture for active isolation as well as precision steering of a payload, which was controlled by non-contact voice coil motor SAIs. Ref.…”

Collision modeling and two-echelon collaborative control of non-contact ultra-quiet Stewart spacecraft

“…In contrast to other Stewart platforms, this king of non-contact architecture can suppress isolation down to 0 Hz. 21,22 One of the important problems of non-contact ultraquiet Stewart spacecraft in space application is the collision of non-contact voice coil actuators induced by the release of electromagnetic locking device after capturing the Earth. In this article, the equivalent collision modeling with a small releasing velocity and control algorithm to guarantee the collision rejection and the stability performance of non-contact ultra-quiet Stewart spacecraft were studied.…”