DVA1 Project Overview and Status Gary Hovey and Gordon Lacy SKA Project Office Visit DRAO 29 March...

DVA1Project Overview and Status

Gary Hovey and Gordon Lacy

SKA Project Office VisitDRAO 29 March 2014

NRC-HerzbergAstronomy Technology Program - Penticton

DVA1 - Performance and Status

Rough Agenda

• 10:45 DVA1 technical discussions• 11:45 Tour of DRAO labs AFAD, DVA1• 12:15 Lunch here or OK Falls?• 13:30 Tour of OK Falls• 15:30 Tour of DVA1 site• 16:30 Wrap up discussion in meeting room

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Introduction

Asked to address:• Status and Performance• Contribution of DVA-1 for SKA

− Risk retirement tool and plans

Presentation • Motivation and Goals• Key innovations and contributions to SKA• Current Status• Plans

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Background

• Began investigating composites in 2005• Built two reflectors in 2007• Started collaboration with US-TDP in 2009

− Design phase lead by US-TDP− Construction phase lead by NRC

• CoDR in early 2011• PDR in late 2011• CDR in mid 2012• Fabrication reflector and pedestal mid-2013• Integration underway

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DVA-1: Motivation and Goals

Challenge: A leap in telescope sensitivity and dynamic range requires a corresponding leap in antenna technology.

Goal: Investigate, develop and demonstrate innovations that improve antenna cost/performance.Lower cost through

− Simplicity of design− Minimal part count− Modular design− Low labour content− Scalable to mass production− Minimal use of custom sizes and part

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Motivation and Goals (cont.)

Improved performance through• Shaped optics to maximise Aeff

• 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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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 effect on beam pattern

• 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 zero and matched CTE carbon tubes for extremely high thermal stability.


Contribution to SKA

• Overall: Innovative design that has been optimised for low cost, long life and high performance.

• Specifically:− Modular and compact turn head and pedestal design− Low maintenance mechanical drive− Low cost foundation design− Innovative elevation jack-screw− Rotating electronics in pendent enclosure− Rim supported reflector concept− Optimised reflector and feed platform support− Optimised shaped optics− Composite reflector surfaces optimised for SKA− Verification of key estimated vs measured cost-performance

metrics

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DVA1: 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


DVA1: Estimated Sensitivity

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DVA-1 Aeff/Tsys using Corrugated HornsAssumes 15K Receiver


DVA1: Estimated Performance in Wind

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Beam Pattern at 10 GHz.25 kph Wind at 15 degree Elevation (Blue)Undistorted (Red)


DVA1 Predicted Temperature Stability

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Beam Pattern at 10 GHz.25 Celsius Thermal Change (Blue)Undistorted (Red)


DVA1: Estimated Performance over Load Cases

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Freq Peak Scan Scan On-axis Peak Peak Beam Width Case Gain Offset Orthogonal Gain Sidelobe X-pol X Y

(GHz) (dB) mdeg mdeg (dB) (dB) (dB) (deg) (deg)

10.000 63.270 0.51 0.00 63.270 20.857 41.954 0.133 0.133 Undistorted

10.000 63.253 -2.97 -0.18 63.247 20.317 42.196 0.133 0.133 Thermal

10.000 63.162 32.49 0.17 62.482 19.076 43.200 0.134 0.132 Gravity 15 degrees

10.000 63.250 12.82 0.12 63.145 20.674 42.092 0.134 0.133 Gravity 55 degrees

10.000 63.107 -9.29 0.03 63.052 19.501 41.046 0.134 0.134 Gravity 90 degrees

10.000 63.268 5.09 0.15 63.251 20.689 42.014 0.134 0.133 Wind 15 degrees

10.000 63.270 0.23 0.03 63.270 20.834 41.951 0.133 0.133 Wind 55 degrees

10.000 63.270 1.30 -0.11 63.269 20.804 41.954 0.133 0.133 Wind 90 degrees

DVA1 Primary Reflector Damage and Repairs

Collapsed Surface After being popped out with air bags

DVA1 Repair Activites

DVA-1 Reflector Repairs

DVA-1 Reflector Accuracy After Repairs

• Post repairerror = 1.0mm rms

• Excluding repaired areas error = 0.7mm rms

Notes:1. Errors are from ideal and

include mold errors.

2. No aperture weighting used, otherwise rms error would be less.

DVA-1 Secondary Reflector Accuracy

•Un-weighted by illumination: Surface error = 0.2mm rms

•Weighted by illumination Surface error = 0.11mm rms

Improved Results: GDSatcom Secondary Reflector

•We have now built two sub reflectors for the GDSatcom Meerkat project

•RMS of reflector 0.090mm

•Mold RMS 0.058mm

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DVA-1: Composite Performance

Structural Test Composite Design Consideration

Metallic Design Consideration

Creep high static load high static load

Static Strength Material properties Material properties

Fatigue Life High cyclic load High cyclic load

Glass Transition Temp. Choose resin with sufficiently high value.

NA

Impact Resistance Engineering requirement Engineering requirement

Galvanic Corrosion Encapsulate reflective layer Paint and primer

UV, Moisture, Humidity Paint (no primer required) and resin properties

Paint and Primer

Reflectivity Degradation Paint (no primer required) Paint and Primer

Fungus growth Paint Paint


Contributions DVA1 Isn’t Making

• The main goal of DVA1 was to demonstrate several novel design concepts.

• Elements not impacting key design conceptsnor not unique to DVA1 not addressed.− RFI, lightning protection, − ZA and AU safety and electrical code standards, − Optimal and adaptive drive control, − Testing with a full suite of receivers− Automated indexer

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Issues and Technical Risks

• Key retired technical (technology) risksComposite reflectors meet requirements for

− Reflectivity− Mechanical and thermal properties− Surface accuracy

• Outstanding risks low. • Mitigated by simulation/measurement and await system

testing, such as− Optics design errors− Mechanical design errors− Major fabrication errors

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Elements Deferred/Tabled

• Testing with feeds <1GHz• Optimised manufacturing methods, logistics and costing.• Further proof related to QA, life cycle costs, reliability, durability,

manufacturability.

• Concern: In some cases level of evidence/proof required is:− unclear, − somewhat arbitrary and − disproportionate.

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Project Schedule: Construction and Mechanical Test

April• Assemble feed and secondary support• Complete drive and back-end software and test• Install RFoF equipment and Ku receiver.• Lift primary on tower• Measure primary and tower over load cases using laser tracker,

photogrammetry, and tilt meters.

May• Lift feed and secondary support on primary• Initial measurements of DVA1 over load cases using laser tracker,

photogrammetry, and tilt meters.

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Project Schedule: RF Testing

May-June• Basic motion tests• Ku band establishment of initial pointing and focus and holography

July-August• L-band tests with MeerKat/NRC receiver• Pointing tests, offset pointing performance, short term pointing jitter• Calibration observations to estimate antenna parameters such as

aperture and beam efficiencies, sensitivity, spillover contributions to system temperature

August-October• Final testing, analysis and reports

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Questions?

Gary Hovey, Project Manager

[email protected]

Gordon Lacy, Project Engineer

[email protected]

DVA1 Project Overview and Status Gary Hovey and Gordon Lacy SKA Project Office Visit DRAO 29 March...

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