Terrestrial Planet Finder coronagraph pointing control system design and evaluation for flight baseline 1.

The Terrestrial Planet Finder mission will search for Earth-like, extrasolar planets. The Coronagraph architecture option (TPF-C) will use contrast imaging to suppress the bright starlight in order to detect reflected visible light from the planet. To achieve the required contrast ratio stability of 2e-11, the payload pointing stability must be maintained to better than 4 milli-asec (1σ). The passive TPF-C pointing architecture uses a 3-stage control system combined with a 2- stage passive isolation system to achieve the required pointing accuracy. The active pointing stage includes reaction wheels used for coarse pointing of the spacecraft, a position controlled secondary mirror that provides intermediate alignment, and a Fine Guidance Mirror that provides fine steering control.