CURRENT SKA TDP ANTENNA DESIGN 10 DVA1 Meeting at NSF Arlington VA April 15-16, 2010 Matt Fleming Contributions from Jack Welch Roger Schultz Gordon Lacy

Antenna Design Drivers 1Must achieve survival. ( 100 mph wind ) 2 Low cost per unit area of aperture. ( good sky coverage ) ( installed ) ( low cost materials, low mass design, low fabrication labor ) ( favors symmetric ) 3Very low operational cost for a 30 year life ( very few maintenance visits required ) 4Frequency range of 0.3 to 10 GHz with WBSPF ( 3.5m Gregorian secondary ) ( favors offset ) 5Excellent A e / T sys. ( accurate surfaces, controlled spillover, low diffraction ) ( favors offset ) 6Exceptional dynamic range. ( very rigid surfaces, very good pointing, ) pt source sensitivity survey survey speed Performance vs Cost Tradeoffs These will lead to specifications: ??? DVA1, NSF, Arlington, Matt Fleming slide 2 of 43

Basic fabrication cost drivers Raw material costs. ( fairly constant world wide )( a good design is light weight ) Labor cost. ( varies by type and location based on economic and social conditions ) Understanding these items for every design allows engineering shortcuts We cannot do detailed design on every possible design approach For some designs material is often traded for labor Technology. ( application of intellect to use of material, labor & energy ) Number of units needed. ( investment in tooling ) Transportation. ( where made, where assembled, where installed ) DVA1, NSF, Arlington, Matt Fleming slide 3 of 43

Note on Transportation DVA1, NSF, Arlington, Matt Fleming slide 4 of 43 Physical size of antenna elements will influence transport cost. Remote fabrication of smaller elements allows use of global labor competition. Remote fabrication usually means greater on site assembly labor. Onsite fabrication of large elements can allow lower on site assembly labor. Non modal transport is also possible, but likely more expensive.

Types of Reflectors & Support This is an arbitrary identification system just for discussion This slide just a reminder about initial choices DVA1, NSF, Arlington, Matt Fleming slide 5 of 43

Single piece reflectors often have low labor cost relative to alternate designs. Reflector edge support by itself preserves accuracy extremely well. The reflector surface can act as the structural front side of a deeper system. Rim edge and center support works better if the center has axial flexibility. The concept can work for symmetric or offset designs. Primary as a monocoque element Single shell or stressed skin Jump to single shell On Az-El mount DVA1, NSF, Arlington, Matt Fleming slide 6 of 43

A frame & spar system gives good edge & center support with an open center. Wind & gravity moment loads are reduce with Az & El near the shell center. The support system allows a compact turret head to be nested close to shell. A compact turret head can contain almost all the precision machining needs. A relatively simple pipe pedestal can support the turret head. ( wind & thermal ) ATA Implementation DVA1, NSF, Arlington, Matt Fleming slide 7 of 43

A 6.1m diameter symmetric shell can be made with only a 3mm thickness. The surface accuracy can be quite high. A study showed 3mm alum 3003 will have good repeatability in production. Another study showed 3mm alum 3003 can be extended to a 12m symmetric. JPL, DSN, Prototype DVA1, NSF, Arlington, Matt Fleming slide 8 of 43

Identify 3 Optical Designs of Interest B1 E2 D1 E1 Data points for SKA cost model Inform Tradeoff symmetric vs offset DVA1, NSF, Arlington, Matt Fleming slide 9 of 43

Select 3 Designs for Costing FEA Design & Costing for HMR to meet survival requirements HMR = Hydroformed Metal Reflector DVA1, NSF, Arlington, Matt Fleming slide 10 of 43

Information from Composite Investigations DRAO = Dominion Radio Observatory CART = Composite Application Radio Telescope Prototype 10m complete. Symmetric with Core, Beams & Hub. SKA Memo 116 costing information Starting to investigate Offset monocoque V3 Canada DRAO CART Project and South Africa MeerKAT Project have generated cost and performance information for composite on site reflector fabrication. DVA1, NSF, Arlington, Matt Fleming slide 11 of 43

TDP Antenna Cost ( summary estimates ) 8%15%0% 11% Adding 15% 113, , , , ,000 25% ( survival design shown )( add 15% for performance design ) DVA1, NSF, Arlington, Matt Fleming slide 12 of 43

TDP Antenna Cost (summary estimate ) a little more detail Masses are low DVA1, NSF, Arlington, Matt Fleming slide 13 of 43

Optics 42 used for costing 2 Gregorian feeds with rotary indexer & possibly a PAF Shown with Feed Up but optics can be the same with Feed Down Costing Allows Selection PAF = Phased Array Feed Preffered mechanical configuration Acceptable optical configuration Note feed support locations DVA1, NSF, Arlington, Matt Fleming slide 14 of 43

Computed RMS inches 0.20 mm DVA1, NSF, Arlington, Matt Fleming slide 15 of 43

Computed RMS inches 0.33 mm DVA1, NSF, Arlington, Matt Fleming slide 16 of 43

Computed RMS inches 0.03 mm DVA1, NSF, Arlington, Matt Fleming slide 17 of 43

HM & FRP shells are similar Both hydroformed metal and fiber reinforced plastic create good monocoque structures FRP can replace HM reflectors and can provide edge support DVA1, NSF, Arlington, Matt Fleming slide 18 of 43

Specifications 1 of 2 DVA1, NSF, Arlington, Matt Fleming slide 19 of 43

Specifications 2 of 2 DVA1, NSF, Arlington, Matt Fleming slide 20 of 43

Beginning to work on details Rain snow ice Survival wind Security and vandalism Ease of maintenance DVA1, NSF, Arlington, Matt Fleming slide 21 of 43

Additional Views DVA1, NSF, Arlington, Matt Fleming slide 22 of 43

Structural Simplicity Triangular deep trusses good Cured beams and curved shells bad Tubular structures are very efficient at handling bending and torsion More about PAF position later DVA1, NSF, Arlington, Matt Fleming slide 23 of 43

Pedestal Mount & Frame DVA1, NSF, Arlington, Matt Fleming slide 24 of 43

Deliverable Antenna Elements Primary not shown It is an on site fabrication Pedestal Turret head Secondary Primary center frame Electronics enclosures Secondary and feed support Feed and indexer DVA1, NSF, Arlington, Matt Fleming slide 25 of 43

Pedestal Fabrication Consider use of ring forgings Machined Flange Alternate foundation concepts are still under consideration DVA1, NSF, Arlington, Matt Fleming slide 26 of 43

Transport Check Looks good for global sourcing DVA1, NSF, Arlington, Matt Fleming slide 27 of 43

Turret Head Assembly Deliverable Assembly Includes az drives, bearings, encoders, electronics DVA1, NSF, Arlington, Matt Fleming slide 28 of 43

Transport Check Note 3.1 m secondary shown Looks like a little larger is possible. DVA1, NSF, Arlington, Matt Fleming slide 29 of 43

Primary Center Frame Pentagonal frame shown Machining of this portion may be necessary and a little expensive Tubes all have parallel end cuts DVA1, NSF, Arlington, Matt Fleming slide 30 of 43

Transport Check Not so good Design for assembly or ship prepared kit to near site fabricator for final weld and paint then transport to site. DVA1, NSF, Arlington, Matt Fleming slide 31 of 43

Secondary Support Frame FRP fabrication may be ideal for rear section from the primary lower rim to the feed support plane. If made from metal, we will consider some on site assembly. More information is needed about feed support requirements. DVA1, NSF, Arlington, Matt Fleming slide 32 of 43

Transport Check Not good Density very poor Reconsider this Design for assembly or ship prepared kit to near site fabricator for final weld and paint then transport to site. Electronics enclosure shown DVA1, NSF, Arlington, Matt Fleming slide 33 of 43

Turret Head & Az drives Deliverable Assy Double row ang contact Or crossed roller With oil bath Lubrication 60 months Machined fabrication Az drive modules DVA1, NSF, Arlington, Matt Fleming slide 34 of 43

Azimuth Drives Dual idler supported pinion Multiple modular drives Access to drives Full oil bath lubrication for 60 month period RFI control DVA1, NSF, Arlington, Matt Fleming slide 35 of 43

El Bearings & El drive Gravity loading helpful. Low clearance important Bearing choices tuff. Currently envision a custom actuator DVA1, NSF, Arlington, Matt Fleming slide 36 of 43

Encoders & Pointing Attachment to reflector surface away from loaded areas Long light weight tube might be problematic Both encoders can be interior to the turret head allowing environmental protection and easy cabling. Limit switch gearing Az tube could extend to ground for higher accuracy, but ……. Addition of tilt meter and accelerometer devices may enhance performance Unatainium box on back of dish is the best option DVA1, NSF, Arlington, Matt Fleming slide 37 of 43

Cable Wraps & Enclosures Cooling is important to consider early in the design Current Az wrap 540° and envisioned with only 5 elements Power 1, Power 2, Ground, Control fibers, Signal fibers Security, access, swapping Current El wrap 75° envisioned with many elements Power 1, Power 2, Ground, Control fibers, Signal fibers DVA1, NSF, Arlington, Matt Fleming slide 38 of 43

Feeds and Indexer 1 Space for PAF implies two leg support frame Pivot & structural support Lindgren in can ATA in glass Track ? PAF shown 1m x 1m x 1m Maybe sector not turntable PAF at secondary focus still under consideration Min angle on wraps DVA1, NSF, Arlington, Matt Fleming slide 39 of 43

Feeds and Indexer 2 Some comments: It will be expensive. It will introduce additional deflection. It will introduce additional pointing considerations. It will require more cables and cable wrap loading. Is it really possible to imagine future feed upgrades? I look at the ATA WBSPF with 1.0 to 10.0 GHz, weighing 40 Kg and wonder If we gave 0.3 to 1.0 GHz to another solution then the dish is much simpler. DVA1, NSF, Arlington, Matt Fleming slide 40 of 43

Mount Discussions DVA1, NSF, Arlington, Matt Fleming slide 41 of 43

Issues to remember and questions remaining For the DVA-1 Diameter Primary ( 12 15m )( done ) Diameter Secondary ? ( 4m ) go to ( 3.5 ) Optics design – shaping – illumination angle ? High shrouding concept. Analysis high shroud ? High Low decision ? Diffraction from secondary support braces and other items ? Tolerances on component positions ? Determine spec for high performance US SKA Consortium, Madison, Matt Fleming slide 42 of 35

Questions DVA1, NSF, Arlington, Matt Fleming slide 43 of 43