A 941 channel, 1500 Hertz frame rate athptive optical (AO) system has been installed and tested in the coudé path of the 3.5m telescope at the USAF Research Laboratoiy Starfire Optical Range. This paper describes the design and measured perfonnance ofthe principal components comprising this system and presents sample results from the first closed-loop tests ofthe system on stars and an artificial source simulator.
Three advanced Deformable Mirrors were tested as part of the Air Force Research Laboratory's athptive optics program. Two of these mirrors were purchased by the Air Force Research Laboratory for use at the Starfire Optical Range (SOR). One of these, a 941-channel mirror, made by Xinetics under subcontract to Hughes Danbury Optical Systems, is currently in use in the adaptive optics system of the SOR 3.5 m telescope. The other, a 577-channel mirror, was refurbished by ITEK from the Mid-Scale Deformable Mirror. The third mirror, with 349 actuators, was made by Xinetics as a demonsiration of a new actuator bonding technology. For each mirror, the uniformity of the actuator gain was measured using phase-modulating interferometry. These measurements were used to flatten the mirrors and to apply known Zernike modes. Results presented will include actuator performance statistics and mirror figure accuracy for various commanded figures.
The Starfire Optical Range (SOR) has measured stellar scintillation at 0.9 to I .7 microns over a wide range of elevation angles. The telescope pupil was imaged onto a mask with four circular apertures of scaled diameters 0. 1 , 0.2, 0.75 and 1 .5 m. These smaller pupils were then re-imaged onto InGaAs photodiodes operating at 10 kHz. The entire 3.5 m pupil was also imaged onto a fifth photodiode. Since all five signals were recorded simultaneously, the influence of aperture diameter on scintillation statistics can be readily seen. The detectors were located at pupil planes; no fluctuations due to atmospheric tilt were measured. Comparisons of power spectral densities, signal variances and other fluctuation statistics have been made as functions of the aperture diameter and elevation angle. Experimental results and theoretical expectations reveal widespread agreement. Within experimental error, log-normal statistics are followed. High spatial frequency content increased with elevation angle. Aperture averaging of scintillation variance followed a 716th dependence. Increasing the aperture dimensions had an even larger effect on the number of fluctuations below a given threshold. Scintillation in the near-JR has been shown to produce consistent results with previous studies performed at visible wavelengths.
Traditional methods of data collection typically rely on each instrument storing data locally during each data collect run with the files relayed to a central storage location at a later time. For moderate rate systems this is an acceptable paradigm. However, as ultra-high bandwidth instruments become available, this approach presents two significant limitations. First, the bandwidth required for the transfers can become unrealistic, and the transfer times are prohibitive. Second, the increasing complexity, speed, and breadth of instruments presents significant challenges in combining the data into a coherent data set for analysis. The Starfire Optical Range is in the process of implementing a centralized data storage system that provides multi-gigabyte per second transfer rates and allows each instrument to store directly to the primary data store. Additionally, the architecture provides for absolute synchronization of every data sample throughout all sensors. The result is a single data set with data from all instruments frame by frame synchronized.
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