This paper describes the design and summarizes the performance of the recently completed SOAR telescope Active Optical System (AOS). This system is unique in that it uses a thin, solid 4.3-meter diameter ULE lightweight meniscus primary mirror only 100 mm thick. The figure of the primary mirror surface is controlled with 120 electro-mechanical actuators that are force feedback controlled. The telescope is calibrated against the sky using a calibration wave-front sensor; as this calibration progresses, feedback forces, initially set from finite element analysis predictions, are replaced with sky database look-up tables. The system also includes a 0.6-meter diameter secondary mirror articulated by a hexapod for real-time optical alignment of the telescope, a 0.6-meter class tertiary mirror that also works as a 50 Hz tip tilt corrector to compensate for atmospheric turbulence and a rotary turret mechanism for directing the light to either of two nasmyth or three-bent cassegrain instrument ports. An operation control system interfaces with the telescope control system and each of the hardware assemblies.
The paper provides an overview of the design of each assembly as well as summarizes results of performance testing the system.
The SOAR Telescope project has completed development of the Active Optical System (AOS) software system. This paper describes the two Computer Software Components (CSCs) that are part of the SOAR/AOS software. The first CSC is referred to as the Operations Control (OpCon) Software. The OpCon Software contains all of the software necessary for running and monitoring the Adaptive Optics Control System (AOCS). This includes the software to run the Primary Mirror Assembly (PMA), to command the Secondary Mirror Assembly (SMA) and the Turret Controller, to set the modes of the Tip/Tilt mirror, and to monitor and report status from the status data acquisition board. It includes the command and data interface to the Telescope Control System (TCS). It includes the AOCS state logic and the input routines for reading the database of command vectors. The second CSC is called the Database Generation (DBGen) Software. The DBGen Software contains the software that generates the database of PM force vectors and SM command vectors. This software uses either theoretical data or measured wavefront data to build the databases.
This paper focuses particularly on the PMA actuator control software. We describe the use of Nastran modeling data for initial deployment of the telescope and the concept for using actual measured data for calibration optimization. We also describe the software implementation designed to allow the actuator control system to meet its timing requirements during telescope slew and to meet the primary figure requirements during telescope observations.
The SOAR Telescope project has embarked on the development of a very high quality 4.2-meter diameter optical telescope to be sited on Cerro Pachon in Chile. The telescope will feature an image quality of 0.18 arc seconds, a moderate field of 11 arc minutes, a very large instrument payload capacity for as many as 9 hot instruments, and an Active Optical System optimized for the optical to near IR wavelengths. The active optical system features a 10 cm thick ULETM primary mirror supported by 120 electro- mechanical actuators for a highly correctable surface. the 0.6 meter diameter secondary is articulated by a hexapod for real time optical alignment. The 0.6-meter class tertiary will provide fast beam steering to compensate for atmospheric turbulence at 50 hertz and a turret for directing the light to either of two nasmyth or three-bent cassegrain ports. Both the secondary and tertiary are light- weighted by machining to achieve cost-effective low weight mirrors. This paper discusses the unique features of this development effort including many commercial products and software programs that enable its technical feasibility and high cost efficiency.
The Advanced X-ray Astrophysics Facility (AXAF) consists of a nested set of six Wolter Type 1 x-ray telescopes. Each telescope consists of two mirrors (a parabola and a hyperbola). The high resolution optical performance required by AXAF and the size of the mirrors necessitates enormous quantities of data to characterize the optics. We will describe an end-to-end data system to be used for the metrology and fabrication of these 12 mirrors. The data system must have the capability of collecting optic metrology data from several instruments, processing and analyzing data, and generating machine instructions for the next grinding or polishing cycle. This system consists of personal computers interfaced to metrology instruments for the automatic collection of data, personal computers that control grinder/polishers, a mainframe computer for storing and managing data, and workstations for data processing and analysis. All of these computers are networked together to facilitate data transfer between computers. The system also includes an extensive library of software whose functions include processing mechanical and interferometric measurements, fitting polynomials to the data, performing frequency analysis of the data, and doing performance predictions. This data system has been used in the fabrication of the first two AXAF mirrors, produced by Hughes Danbury under contract to TRW. These mirrors are the first in a telescope that will be well beyond the performance of any existing x-ray telescopes.