MUSTANG (Multiplex SQUID TES Array at Ninety GHz) is a bolometer camera for the Green Bank Telescope (GBT) working at a frequency of 90 GHz.The detector has a field of view of 40 arcsec.To cancel out random emission c...MUSTANG (Multiplex SQUID TES Array at Ninety GHz) is a bolometer camera for the Green Bank Telescope (GBT) working at a frequency of 90 GHz.The detector has a field of view of 40 arcsec.To cancel out random emission change from atmosphere and other sources,requires a fast scanning reflecting system with a few arcminute ranges.In this paper,the aberrations of an off-axis system are reviewed.The condition for an optimized system is provided.In an optimized system,as additional image transfer mirrors are introduced,new aberrations of the off-axis system may be reintroduced,resulting in a limited field of view.In this paper,different scanning mirror arrangements for the GBT system are analyzed through the ray tracing analysis.These include using the subreflector as the scanning mirror,chopping a flat mirror and transferring image with an ellipse mirror,and chopping a flat mirror and transferring image with a pair of face-to-face paraboloid mirrors.The system analysis shows that chopping a flat mirror and using a well aligned pair of paraboloids can generate the required field of view for the MUSTANG detector system,while other systems all suffer from larger off-axis aberrations added by the system modification.The spot diagrams of the well aligned pair of paraboloids produced are only about one Airy disk size within a scanning angle of about 3 arcmin.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 10978021)
文摘MUSTANG (Multiplex SQUID TES Array at Ninety GHz) is a bolometer camera for the Green Bank Telescope (GBT) working at a frequency of 90 GHz.The detector has a field of view of 40 arcsec.To cancel out random emission change from atmosphere and other sources,requires a fast scanning reflecting system with a few arcminute ranges.In this paper,the aberrations of an off-axis system are reviewed.The condition for an optimized system is provided.In an optimized system,as additional image transfer mirrors are introduced,new aberrations of the off-axis system may be reintroduced,resulting in a limited field of view.In this paper,different scanning mirror arrangements for the GBT system are analyzed through the ray tracing analysis.These include using the subreflector as the scanning mirror,chopping a flat mirror and transferring image with an ellipse mirror,and chopping a flat mirror and transferring image with a pair of face-to-face paraboloid mirrors.The system analysis shows that chopping a flat mirror and using a well aligned pair of paraboloids can generate the required field of view for the MUSTANG detector system,while other systems all suffer from larger off-axis aberrations added by the system modification.The spot diagrams of the well aligned pair of paraboloids produced are only about one Airy disk size within a scanning angle of about 3 arcmin.
