Extensive system modeling and analysis clearly shows that system latency is a primary performance driver in closed loop adaptive optical systems. With careful attention to all sensing, processing, and controlling components, system latency can be significantly reduced. Upgrades to the Starfire Optical Range (SOR) 3.5-meter telescope facility adaptive optical system have resulted in a reduction in overall latency from 660 μsec to 297 μsec. Future efforts will reduce the system latency even more to the 170 msec range. The changes improve system bandwidth significantly by reducing the "age" of the correction that is applied to the deformable mirror. Latency reductions have been achieved by increasing the pixel readout pattern and rate on the wavefront sensor, utilizing a new high-speed field programmable gate array (FPGA) based wavefront processor, doubling the processing rate of the real-time reconstructor, and streamlining the operation of the deformable mirror drivers.
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.
A 941 channel, 1500 Hertz frame rate adaptive optical (AO) system has been installed and tested in the coude path of the 3.5m telescope at the USAF Research Laboratory Starfire Optical Range. This paper describes the design and measured performance of the principal components comprising this system and present sample results from the first closed-loop test of the system on stars and an artificial source simulator.
This paper describes installation of a long wavelength infrared (LWIR) acquisition camera on the Starfire Optical Range (SOR) 1.5 meter telescope, and reports initial performance results. This camera was designed for acquisition of satellites night or day, irrespective of target illumination. The camera may also have wide field-of-view astronomy applications. The optical design for this LWIR acquisition camera maps a 128 X 128 pixel Si:As impurity band conduction detector array onto the two milliradian telescope scene. A warm, aspheric germanium lens images the f/217 telescope beam onto a cold field stop, and the telescope pupil onto a cryogenic chopping mirror. The cryogenic chopping mirror has an opaque mask which serves as a radiation stop. A second, cooled, aspheric germanium lens reimages the field stop onto the detector array. Operation of the camera over the 7 - 24 micrometers detection band of the array is possible by replacing the interference filter and zinc selenide vacuum window. Problems and solutions pertaining to integration of the camera and cryocooler system on the telescope are described. Initial performance data reported include: optics/array radiometry, telescope background measurements, cryocooler induced telescope jitter measurements, and cryogenic chopping mirror characteristics.
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