dva1 project gary hovey and gordon lacy herzberg jamboree 23 october 2014 nrc-herzberg astronomy...

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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Gary Hovey, Project Manager

Gary.Hovey@nrc-cnrc.gc.ca250.497.2363

Gordon Lacy, Project Engineer

Gordon.Lacy@nrc-cnrc.gc.ca250.497.2340

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