A nine-aperture, wide-field Fizeau imaging telescope has been built at the Lockheed-Martin Advanced Technology Center. The telescope consists of nine, 125 mm diameter collector telescopes coherently phased and combined to form a diffraction-limited image with a resolution that is consistent with the 610 mm diameter of the telescope. The phased field of view of the array is 1 murad. The measured rms wavefront error is 0.08 waves rms at 635 nm. The telescope is actively controlled to correct for tilt and phasing errors. The control sensing technique is the method known as phase diversity, which extracts wavefront information from a pair of focused and defocused images. The optical design of the telescope and typical performance results are described.

Star-9 is an experimental demonstration of distributed aperture imaging built at the Lockheed Martin Advanced Technology Center. White light from a scene generator enters an array of nine actively controlled telescopes, and is combined at a focused image plane. This paper describes the algorithms used to automatically bring each telescope's relative tip/tilt and phasing errors to within the operational range of the control system. The algorithms work with point-sources as well as with extended scenes. Experimental results and software algorithms are presented.

Star-9 is an experimental demonstration of distributed-aperture imaging built at the Lockheed Martin Advanced Technology Center. White light from a scene generator enters an array of nine telescopes and is combined at a focused image plane. Relative aberrations from each telescope are regulated by a control system using phase diversity and active relay mirrors. A Weiner filter is applied to the image, and the resulting angular resolution and image quality are nearly diffraction-limited with the diameter of the array. The control system takes estimates from the phase diversity algorithm and uses them to command mirrors to adjust tip, tilt, and piston in each telescope. Each active mirror has inductive position sensors for local position control. The mirrors are actuated by picomotors and inchworm motors. In addition to tip/tilt/piston errors, the control system is equipped to correct for pupil geometry and rotation errors, and to perform field of regard steering. In this paper, we present details on the control system's local sensing, control law synthesis, and precision actuation methodology. We also describe the incorporation of phase diversity and automated phasing algorithms with the control system and give performance results.Index Terms-Active optics control system, distributed aperture, Fizeau imaging system, multiple telescope array, phased array telescope.

High spectral resolution Fourier transform imaging spectroscopy has been demonstrated at the Lockheed Martin Advanced Technology Center. A testbed was built using a Michelson interferometer with a two-stage end-mirror control system. Homodyne laser metrology was used to sense relative tip, tilt and piston in the interferometer, and a 3-degree of freedom fast steering mirror in conjunction with a linear actuator stage provided sub-nanometer actuation control over 20 millimeters of piston range. The range of piston over which signal was present allowed for spectral resolution at the nanometer level in the visible / near infrared (VNIR) band for every pixel in the reconstructed image.

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