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Deployable optics can bring major cost reductions to the field of Earth Observation. One of the key challenges in the development of a deployable optical system, however, is making sure that it can meet its performance targets following its deployment. In this paper, a novel active correction system for a deployable telescope is described. The correction system co-aligns and phases the primary mirror segments and subsequently corrects remaining aberrations using a deformable mirror. A novel phasing sensor called PistonCam can bring telescope segments into phase while the telescope is staring at extended scenes. By only sampling segment boundaries, PistonCam is able to isolate piston and tip/tilt errors which allows the errors to be corrected more effectively. After phasing process has been completed, a moving scene sharpness optimization technique is used to correct the remaining aberrations with a deformable mirror, The technique does not require a constant scene, unlike existing sharpness optimization techniques. As such, the telescope does not need to track a ground scene during the correction process. The technique can also be used for continuous correction of telescope deformations. The active optics system offers robust aberration correction, is computationally inexpensive and requires limited additional optical hardware.
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Deployable optics can bring major cost reductions to the field of Earth Observation. One of the key challenges in the development of a deployable optical system, however, is making sure that it can meet its performance targets following its deployment. In this paper, a novel active correction system for a deployable telescope is described. The correction system co-aligns and phases the primary mirror segments and subsequently corrects remaining aberrations using a deformable mirror. A novel phasing sensor called PistonCam can bring telescope segments into phase while the telescope is staring at extended scenes. By only sampling segment boundaries, PistonCam is able to isolate piston and tip/tilt errors which allows the errors to be corrected more effectively. After phasing process has been completed, a moving scene sharpness optimization technique is used to correct the remaining aberrations with a deformable mirror, The technique does not require a constant scene, unlike existing sharpness optimization techniques. As such, the telescope does not need to track a ground scene during the correction process. The technique can also be used for continuous correction of telescope deformations. The active optics system offers robust aberration correction, is computationally inexpensive and requires limited additional optical hardware.
A single-track hydrofoil boat has two upside-down T-shaped hydrofoils that are placed behind each other on the centerline of the hull. To keep a single track hydrofoil boat upright during flight, the vertical front support strut is used as a rudder which the pilot steers into the direction of the fall. This is comparable to how a bicycle maintains lateral stability. A generalized dynamical model for single-track hydrofoil boats was developed to predict the roll and yaw motions under a steer input of the front strut. These motions were approximated analytically with conventional aircraft flight dynamics theory. The derivative coefficients that determine the coupling between state variables were derived from basic design parameters of the single-track hydrofoil boat. Validation of the model was done by experiments with the TU Delft Solar Boat 2016. The steer input, roll rate, yaw rate, roll angle, boat velocity and flight height were measured while the pilot generated a sinusoidal steer input at different frequencies and flight velocities. This data was compared with model predictions in the time and frequency domain. It was found that the model predictions are sufficiently accurate for model validation at steer input frequencies of 1 Hz and less. Therefore, the model can be used to design single-track hydrofoil boats and to simulate the dynamics in nominal flight conditions.
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A single-track hydrofoil boat has two upside-down T-shaped hydrofoils that are placed behind each other on the centerline of the hull. To keep a single track hydrofoil boat upright during flight, the vertical front support strut is used as a rudder which the pilot steers into the direction of the fall. This is comparable to how a bicycle maintains lateral stability. A generalized dynamical model for single-track hydrofoil boats was developed to predict the roll and yaw motions under a steer input of the front strut. These motions were approximated analytically with conventional aircraft flight dynamics theory. The derivative coefficients that determine the coupling between state variables were derived from basic design parameters of the single-track hydrofoil boat. Validation of the model was done by experiments with the TU Delft Solar Boat 2016. The steer input, roll rate, yaw rate, roll angle, boat velocity and flight height were measured while the pilot generated a sinusoidal steer input at different frequencies and flight velocities. This data was compared with model predictions in the time and frequency domain. It was found that the model predictions are sufficiently accurate for model validation at steer input frequencies of 1 Hz and less. Therefore, the model can be used to design single-track hydrofoil boats and to simulate the dynamics in nominal flight conditions.
