This paper describes a set of detailed modes, set up in frequency domain and in time domain, that were used to support the analysis, design, test and performance verification phases of the SAAO Adaptive Optics (AO) System, which is being installed atop the 10000 ft Haleakala on the island of Maui in Hawaii. The AO system consists of a 941 actuator deformable mirror, a state-of-the-art 32 by 32 channel wavefront sensor and high speed reconstructor and control electronics, a high bandwidth fast steering mirror and sensor for tracking and jitter control, and the various other optical elements that are essential to close the AO loops. The high fidelity of the mode, which includes details such as the optical misregistrations, timing latencies, wave optics and atmospherics, allows us to tune it to match test results. Thus anchored, the mode is then sued to make performance predictions. The model provides a valuable tool in understanding and testing such highly complex electro- optic systems.
This paper describes laboratory evaluations of the SAAO Adaptive Optics (AO) System, which is installed at the Air Force AEOS facility at Haleakala on the island of Maui in Hawaii. The AO system includes a 32 by 32 channel wavefront sensor, a high-speed wavefront reconstructor, a 941-actuator deformable mirror, a high-bandwidth steering mirror, and a tracking sensor for tilt control. The performance metrics discussed include track bandwidth, track jitter vs. target brightness, AO system temporal response, and the resulting Strehl ratios and MTF for a range of target brightness. Test methods and results are described.
After successful testing at the Raytheon facility in Danbury, Connecticut, the completed SAAO adaptive optical system has been shipped to the AEOS site on Haleakala, Maui, Hawaii. The system is undergoing final integration with the AEOS observatory. This paper describes the adaptive optics system design, including an overview of al major subsystems, the electronics, and the software. We discuss the design trades and system engineering that led to the final configuration. Also included is a review of opto-mechanical aspects of the system.
We have used the advantages of the photolithographic process to build a Hartmann-Shack type wavefront sensor using a 65 X 50 element binary optic lens array as the wavefront sampling element. The inherent accuracy and versatility of the lithographic process has reduced sampling and calibration errors associated with classic Hartmann sensing by allowing the lens array geometry to be tailored to CCD detector geometry with extreme precision. Combined with a quad-cell centroiding algorithm and wavefront reconstruction routines based on the successive over relaxation (SOR) algorithm, we present a wavefront sensor with submicron spot position accuracy, uniform response curves for all spots in the array, high dynamic range, and relative insensitivity to laboratory environmental vibrations. Experimental results obtained during a comparison of its performance to established wavefront methods are presented.
The enhanced reflectance achieved by recent developments in x-ray multilayer technology has made normal-incidence x-ray/EUV telescopes feasible for many applications of interest. Conventional optical designs with obvious advantages over the somewhat cumbersome grazing incidence designs of Kirkpatrick, Baez, and Wolter can thus be utilized. Preliminary results of actual flight data suggest great promise of scientific achievement from this new technology. It is widely recognized that "supersmooth"
substrates are required since microroughness can decimate the reflectance of the multilayer. However, high x-ray reflectance is a necessary but not sufficient condition for producing high quality images. A second and equally important condition is the ability to concentrate the reflected radiation in a very small region in the focal plane. Optical substrates with satisfactory "figure" and "finish" for x-ray/EUV applications have been successfully demonstrated. However, small angle scatter from
"mid spatial frequency" optical fabrication errors will limit the practical resolution attainable from this promising new technology. The surface
power spectral density function over the entire range of relevant spatial frequencies is thus required to accurately predict image characteristics.
The results of parametric optical performance predictions indicate that subarcsecond resolution is possible provided sufficiently smooth layer
interfaces are maintained. However, optical fabrication tolerances imposed on the substrate may require advances over the current state of the art.