dva1 project gary hovey and gordon lacy herzberg jamboree 23 october 2014 nrc-herzberg astronomy...
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DVA1 ProjectGary Hovey and Gordon LacyHerzberg Jamboree 23 October 2014NRC-HerzbergAstronomy Technology Program - Penticton
Development of DVA1 for the SKA
Outline
• DVA1 Overview: Challenges, Motivation• Key innovations• Results
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Development of DVA1 for the SKA
SKA Dishes
• over 50 times more sensitive and capable than existing cm wave radio-telescopes
• 2500 15m offset Gregorian dishes• 350 MHz – 24 GHz
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Development of DVA1 for the SKA
Other Designs
Australian SKA Pathfinder
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Allen Telescope Array
South AfricanMeerKat
Development of DVA1 for the SKA
Evolution of Improved Cost/Performance
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Improving Materials, Design, and Manufacturing
Cost/performance
Development of DVA1 for the SKA
DVA-1: Design Approach and Goals
SKA Challenge: A leap in sensitivity and dynamic range requires a corresponding leap in antenna cost/performance.
Lower cost through− Simplicity of design− Minimal part count− Modular design− Low labour content− Minimal use of custom sizes and part− Use of advanced materials− Use of scalable mass fabrication processes− Optimal optics over the prime frequency range 1-10GHz.− Feed-up design
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Development of DVA1 for the SKA
DVA1: Design Approach and Goals (cont.)
Improved optics and stability performance through• Use of advanced materials
• Shaped optics to maximise Aeff / Tsys
• Improved stability over all load conditions− Feed-high design lowering peak cross section to wind− Compact turning-head and mount to minimise moments− Single piece rim supported reflector
• immunity to translational loads• distortions uniform and low order
− High stiffness and low CTE using carbon fibre composites− Composite reflector with embedded metal mesh
• Reflectivity of Aluminium with the stiffness of carbon.• Low moving mass -> superior closed loop response
• Design for low maintenance upkeep and burden, as well as long life and durability
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Development of DVA1 for the SKA
DVA-1: Designed for High Dynamic Range Capability
• High Thermal Performance• Rim supported monocoque design along with very low CTE materials keeps all
thermal movement both small and very uniform to minimize beam pattern distortion
• High Performance in Wind and Gravity• Central compliant connector allows some structural sag without inducing unwanted
distortion at center of dish
• Rim supported design keeps dish deflections to absolute minimum and concentrates any deflections at rim where effect on performance is small.
• Extremely deep truss back structure keeps dish shape as close to rigid as is possible.
• High Overall Optics Stability• Secondary and feed platform support optimized to maximize stiffness using shape
optimization software.
• Secondary and feed support tubes use CTE matched carbon tubes for high thermal stability.
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Development of DVA1 for the SKA
DVA1: Mechanical Design Features
The main design elements are:
15m Gregorian offset feed-high optics
• Unblocked aperture
• Large space for feeds
• Stiffer, lower cost than feed-low
• Molded single piece rim-supported composite reflectors
• Tubular backup structure
• Tubular composite feedlegs
• Pedestal-type mount allows small offset to elevation axis
• Deep truss backup structure with central pocket for pedestal mount
• Central compliant connector allows movement in wind without distortion
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Development of DVA1 for the SKA
Background and Project Status
• Began investigating composites in 2005• Built two 10m prime focus antennas in 2006-2007• Started collaboration with US-TDP in 2009
− Design phase lead by US-TDP− Construction phase lead by NRC
• 15m Gregorian Offset selected after much investigation• DVA1 CoDR in early 2011• DVA1 PDR in late 2011• CDR in mid 2012• Fabrication reflector and pedestal mid-2013• First light expected in late summer.• Testing: Mechanical, Ku band holography and L-band summer
through fall.
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Development of DVA1 for the SKA
DVA1 Predicted Temperature Stability
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Beam Pattern at 10 GHz.25 Celsius Thermal Change (Blue)Undistorted (Red)
Development of DVA1 for the SKA
Beam Pattern at 18GHz 15 Elevation
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Undistorted (Red). 15 degree Elevation (Blue)Effect mainly a pointing correction as 25kph wind has a negligible effect on pattern
DVA1 Primary Reflector Damage and Repairs
Collapsed Surface After being popped out with air bags
DVA1 Repair Activities
DVA-1 Reflector Repairs
DVA-1 Reflector Accuracy After Repairs
• Post repairerror = 0.89 mm rms
• Weighted error = 0.70 mm rms
• Mold error = .48 rms
Improved Results: GDSatcom Secondary Reflector
•We have now built two sub reflectors for GDSatcom (Antenna contractor for MeerKat)
•RMS of reflector 0.1mm
•Mold RMS 0.058mm
DVA1 - Performance and Status
First Light Spectra
Sun @ 11.75 to 13.25 GHz Nimiq 6 Ku band Satellite12.2 to 12.7 GHz
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Measured Surface ErrorLaser Tracker vs Holography
Azimuth and Elevation Beam Cuts at 12.2 GHz
Development of DVA1 for the SKA
Cost
Item Materials Labour Sub-contract Totals
Reflectors, feed platform and support structuresComposite Dish Surface, Secondary, Central
Reinforcement $111,000 $63,400Composite Backing Pieces, fabrication portion, not
including molds $23,250Dish Rim Connector, labour (material in line 3) $14,000Ball studs $6,132PDSS $84,874Feed Platform $6,700Secondary Support Structure $85,000
Sub Totals $111,000 $77,400 $205,956 $394,356Pedestal Components
Tower, contract with Minex Engineering $300,000Tower, misc extra parts, package 1 $19,920Tower, misc extra parts, package 2 $90,600Tower, additional items $14,836Drive system (motors, control system and encoders) $43,000Painting $5,000
Sub Totals $473,356 $473,356
Grand Total $867,712
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DVA1 - Performance and Status
RF Testing
Ku band holography• Aperture/surface errors• Antenna pattern
Pointing behaviour• Stability• Repeatability• Performance over load cases,
gravity, wind and temperature
Sensitivity• Tipping curves• Aperture efficiency
Ku Band Horn
MeerKat L-band receiver
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23 of 28 Development of DVA1 for the SKA23
Gary Hovey, Project Manager
Gordon Lacy, Project Engineer
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