Pointing and jitter control for the Eclipse mission

Abstract

The <i>ECLIPSE</i> mission will carry out the first sensitive imaging survey of nearby planetary systems, including the detection and characterization of Jovian planets, exozodiacal dust disks and cool brown dwarfs in the solar neighborhood. This survey will be performed with a 1.8 meter optical telescope and a coronagraphic camera, with active wavefront control, designed to achieve contrast levels of 10^-9 for bright objects centered on the coronagraph's occulting spot with an accuracy of 2 arcseconds (1&#963;) and a stability of 0.01 arcseconds (1&#963;). These requirements impose a number of significant challenges, including the need to: (1) Sense pointing errors to the 1 milli-arcsecond (mas) accuracy level, (2) Keep satellite jitter below 3 mas, (3) Design an attitude control system to meet the stringent pointing and pointing stability requirements, and (4) Avoid exciting satellite vibrational modes. Drawing on our experience with large space telescopes such as the Chandra X-ray Observatory, the Space Interferometry Mission and the Next Generation Space Telescope, we have designed an attitude control system for <i>ECLIPSE</i> that successfully meets these challenging requirements. This paper describes the trades and analyses that led up to our design, and its predicted performance.