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

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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June 3,4 2010 Lynn Baker USSKA Consortia Washington, DCLynn Baker USSKA Consortia Washington, DC 4

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