DVA-1 Baseline Optical Design Lynn Baker USSKA Consortia Meeting Washington DC June 3,4, 2010
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June 3,4 2010 Lynn Baker USSKA Consortia Washington, DCLynn Baker USSKA Consortia Washington, DC 1
DVA-1 Baseline Optical Design
Lynn Baker
USSKA Consortia MeetingWashington DCJune 3,4, 2010
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June 3,4 2010 Lynn Baker USSKA Consortia Washington, DCLynn Baker USSKA Consortia Washington, DC 2
DVA-1 Optics Parameters• Feed opening angle of 55 degrees, nominally -16 db. feed taper on secondary
– Compromise value to accommodate some wideband feeds
– Will accommodate a corrugated horn of appropriate design
– Low edge taper reduces spillover and reduces wide angle sidelobes
– Wider opening angles increases the primary size
– Possible to design a different subreflector, different angle, for a given primary
• Shaping controls distribution of power in the aperture– Trades aperture efficiency versus near in sidelobe levels
– Different shaping has different caustic sizes, effects the accommodation of a PAF
– Shaping gives high efficiency, while maintaining very low wide angle sidelobes
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General Optical Configuration
• Subreflector location is a compromise between support frame and primary size– Lower minimizes secondary / feed framing height
– Higher makes the primary smaller
• Larger opening angle shifts the subreflector lower, primary grows– Effectively favors higher gain feeds
• Feed high is tentatively chosen for mechanical advantages– Feed low has advantages for system noise temperature
– Shielding is needed to mitigate ground noise pickup
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Optics Option For DVA-1, #1
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Optics Option For DVA-1, #2
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Optics Option For DVA-1, #3
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Optics Option For DVA-1, #4
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Optics Option For DVA-1, #5
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Physical Optics Analysis, Gaussian FeedPhysical Optics Analysis, Gaussian Feed
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Final Choice Of Optics
• Interaction with CPG is critical– Provide detailed antenna patterns for science performance evaluation
– Include various feeds including corrugated horn for evaluation
– Compare model results for ATA feed with ATA measured results
• Feed limitations should not effect optics design– “Hardware is destiny”
– Multiple feeds can exploit different features of the optics
• Accomodating a PAF at “prime caustic” is under study– Preliminary analysis suggests a modestly larger PAF will work