Andrew Faulkner 2 nd SKADS Workshop October 2007 SKADS Benchmark Scenario Andrew Faulkner

2 nd SKADS Workshop October 2007 Design and Costing Process Submitted to March ISSC Memo on SKADS website: _D+C_v1.0.pdf Published as SKA Memo 93: ‘Complete SKA concept’ Strong basis for moving forward

Andrew Faulkner 2 nd SKADS Workshop October 2007 Top Frequency.... The cost vs frequency of a close packed aperture array varies as: Cost ≈ freq 2+ ε + infrastructure cost for f top of 1.0 GHz < 50% cost for 1.4 GHz ~ 1GHz Science expt. requirements determines f top as ~ 1GHz

Andrew Faulkner 2 nd SKADS Workshop October 2007 The SKADS Benchmark Scenario: An overall SKA Scenario MHzDipole aperture array < MHzClose packed aperture array GHz6-8m, dishes with single wideband feed AA only realistic collector for <300MHz Low cost m -2 and they exist! Large natural FoV Good at high frequencies Capable of mass production WBFs could be >20:1 freq range Single feeds can be cooled economically Not suitable for arrays Small dishes lose efficiency at low freq. AA gives v. fast survey speeds and can look for transients

Andrew Faulkner 2 nd SKADS Workshop October 2007 Outline mid-freq AA spec Frequency range300MHz – 1000MHz OrganisationClose-packed (for now) Array size~60m diameter (~300 tiles) T sys <50K Bandwidth 700MHz Scan angle±45 ° (target ±60 °) Signal digitisation 4-bit

Andrew Faulkner 2 nd SKADS Workshop October 2007 Filled FoV specification Low-AA: 200 deg 2 Mid AA: 250 deg 2 6m Dish + WBF 3*(1.4/f) 2 deg 2 At 1.4GHz... Ref:5 deg 2 B’mark:3 deg 2 An AA can tailor this profile e.g. flat, λ 2 etc.

Andrew Faulkner 2 nd SKADS Workshop October 2007 Conceptual SKA Configuration

Andrew Faulkner 2 nd SKADS Workshop October 2007 Link to Correlator High freq. Dishes with analogue fibre link EoR AA antennas with analogue link (may be close packed) Notes: 1. Power dist. not shown 2. All analogue links go to ‘station processing’ Station Processing Station

Andrew Faulkner 2 nd SKADS Workshop October 2007 Station Processing Digital Systems Only Analogue RFI Barrier

Andrew Faulkner 2 nd SKADS Workshop October 2007 Antenna Array… Contiguous array Maintain from underneath Cover with RF transparent sheet Bunker in centre ~60m Tile Support Bunker

Andrew Faulkner 2 nd SKADS Workshop October 2007 Digital Processing Communications –128 inputs at 2GS/s –128 outputs at 2GS/s Processing –10TMacs(not flops) Power –40 watts: keep T junction down ASICS Multi-core processors FPGA 2012 on …. Assume 4-bit digisation ADC critical ‘Only’ 4-bit max Cost, power and integration

Andrew Faulkner 2 nd SKADS Workshop October 2007 Detailed design Design Blocks Antenna array Analogue signal transport Analogue beamforming Digital Beamforming 2nd Stage Processing Digital Data transport Dishes Mechanical Infrastructure

Andrew Faulkner 2 nd SKADS Workshop October 2007 First costing result Projected in 2011 € Total: €3.1M AA station Total: €1.9B

Andrew Faulkner 2 nd SKADS Workshop October 2007 Pros and Cons PROS Design and engineering led Involved most engineering SKADS groups Focussed thinking on issues A complete SKA CONS Hard to vary the design: –Mix of technologies –Geometry –Performance Technology based Light on ‘non-SKADS’ systems –Central processing –Dishes Connection to science

Andrew Faulkner 2 nd SKADS Workshop October 2007 Draft Specifications for the Square Kilometre Array The output from a ‘Specification Tiger Team’: R. T. Schilizzi, P. Alexander, J. M. Cordes, P. E. Dewdney, R. D. Ekers, A. J. Faulkner, B. M. Gaensler, P. J. Hall, J. L. Jonas, K. I. Kellermann Covers science requirements and implementation trade-offs at fixed Cost covering three collector technologies. The principal input intoSKA2007 Manchester: September The principal input intoSKA2007 Manchester: September Available at:

Andrew Faulkner 2 nd SKADS Workshop October Frequency (MHz) Sky Brightness Temperature (K) A eff A eff /T sys A eff / T sys (m 2 / K) No new elements – maybe sparse above f AA Sparse AA – element type 3 f sky f AA f max Sparse AA – element type 2 Fully sampled AA Element type 1

Andrew Faulkner 2 nd SKADS Workshop October 2007 SKA Spec: Key points Describes options for SKA low and mid up to 10GHz Has a Baseline design with Wide FoV technologies ‘expectations’ All designs use 15m dishes –for risk mitigation: low frequency performance & computing cost Restricted high frequency operation to 2020, high freqs to follow Indicated performance for Key Science Projects AA for ≤500 MHz in All All designs

Andrew Faulkner 2 nd SKADS Workshop October 2007 TT proposals after SKA2007: Baseline Design Sparse AA: MHz Sparse AA: MHz 3100 x 15m dishes+WBSPF: <500 MHz–10 GHz Focal Plane Array WFoV Sparse AA: MHz Sparse AA: MHz 1615 x 15m dishes+PAFs: 500 MHz–1.4 GHz +WBSPF:1.5 GHz – 10 GHz Aperture Array WFoV Sparse AA: 70 – 200 MHz Sparse AA: 200 – 500 MHz Dense AA:500 – 1000 MHz 3100 x 15m dishes+WBSPFs: 800 MHz – 10 GHz There can be many variations!

Andrew Faulkner 2 nd SKADS Workshop October 2007 Evolving the Benchmark Specification D&C-2

Andrew Faulkner 2 nd SKADS Workshop October 2007 D & C-2: Goals Communicate SKADS D&C work Internationally Bring science experiment reqts into the design process Include new Design Blocks Update existing Design Blocks with new information Optimise System Configurations Use information from other international groups

Andrew Faulkner 2 nd SKADS Workshop October 2007 Some Challenges: IDChallengeConsequences/ Mitigation 1.Developing 4:1 frequency range antenna elementsUse 3 different frequency bands 2.Processing capability within power budget 3.Minimum T inst – specification: AA-lo of 100 K AA-hi of 30 K Reduced sensitivity or higher cost if not met. Less critical for AA-lo 4.Mechanical design and on-site construction for sparsed arrays. System design must be completed first. Increased cost 5.Power requirements and cooling.Increased running costs 6.Self induced RFI within acceptable limits 7.Multiplexing channels for AA-lo to reduce total processing requirements Increased costs 8.Demonstration of systematics below level required for the experiments Unable to perform the science 9.Maintainability and reliability within agreed limitsIncreased costs From: Draft Specifications for the Square Kilometre Array

Andrew Faulkner 2 nd SKADS Workshop October 2007 New Design Blocks Science drivers Central processing Array geometry Low System Noise

Andrew Faulkner 2 nd SKADS Workshop October 2007 New Design Blocks Science drivers Central processing Array geometry Low System Noise

Andrew Faulkner 2 nd SKADS Workshop October 2007 New Design Blocks Science drivers Central processing Array geometry Low System Noise Potentially a very big issue May be the highest system cost! Calculations by Tim Cornwell, see: SKA Memos: 49 and 64 The AAs could: be good – low N large D or bad – many beams, wide FoV

Andrew Faulkner 2 nd SKADS Workshop October 2007 New Design Blocks Science drivers Central processing Array geometry Low System Noise Dense? Sparse?

Andrew Faulkner 2 nd SKADS Workshop October 2007 New Design Blocks Science drivers Central processing Array geometry Low System Noise Key demonstration to the International community Critical cost driver: 1 K worth ~€10M –or 2% more sensitivity –or 4% more survey speed Sky noise important at these freqs –Minimise T rec then + T sky = T sys ( f ) All contributions must be investigated

Andrew Faulkner 2 nd SKADS Workshop October 2007 Programme Timetable Initial D&C - 2 meeting13 September 2007 Work on science reqts & system blocks Review Meeting31 October 2007 Preparing written work + science & technical details Initial Drafts received 9 November Review Paper draft (telecon)23 November Consolidating paper Final Draft 7 December Approval of Paper11 December Publication of Paper12 December SKA Specification Review Committee: Jan 2008