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18 August 2005 Terrestrial Planet Finder Coronagraph pointing control system design and evaluation for flight baseline 1
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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. Each stage of the Pointing Control System (PCS) introduces some pointing inaccuracy due to actuator non-idealities that cause the physical commands to deviate by some amount from the ideal command, by sensor noises that are fed back through that stage's actuators to produce physical motions, and by modeling errors that arise because of imprecise knowledge of the dynamics of the system. The PCS must demonstrate the required accuracy of pointing performance in the presence of all of these effects. This paper presents the baseline PCS design and preliminary performance results. These results are compared to the TPF-C error requirements in order to assess the viability of the flight baseline design.
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Kuo-Chia Liu, Carl Blaurock, James Alexander, and Larry Dewell "Terrestrial Planet Finder Coronagraph pointing control system design and evaluation for flight baseline 1", Proc. SPIE 5867, Optical Modeling and Performance Predictions II, 58670Z (18 August 2005);

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