Rosie Bolton 2 nd SKADS Workshop October 2007 SKADS System Design and Costing: Update and next steps Rosie Bolton University of Cambridge

Rosie Bolton 2 nd SKADS Workshop October 2007 Outline of Talk  Summary of Design and Costing work done so far:  SKADS Benchmark Scenario  Strengths and weaknesses  Next Steps  Summary of Design and Costing work done so far:  SKADS Benchmark Scenario  Strengths and weaknesses  Next Steps

Rosie Bolton 2 nd SKADS Workshop October MHz MHz SKADS D&C work – Memo 93 Comparison of FoV from SKA Memo 69 and SKADS Benchmark Scenario Detailed design and costing of an SKA meeting the full Benchmark Specification GHz

Rosie Bolton 2 nd SKADS Workshop October 2007 D&C Methodology

Rosie Bolton 2 nd SKADS Workshop October 2007 Overall SKA Configuration Station Core (5Km dia), made up of close packed stations Correlator in or near Core Comms links Not to scale! Desert Station Proces -sing Link to Correlator Mid Freq AA High freq. Dishes with analogue fibre link EoR AA antennas with analogue link (may be close packed)

Rosie Bolton 2 nd SKADS Workshop October 2007 We followed the signal path:

Rosie Bolton 2 nd SKADS Workshop October 2007 We followed the signal path:

Rosie Bolton 2 nd SKADS Workshop October 2007 We followed the signal path:

Rosie Bolton 2 nd SKADS Workshop October 2007 We followed the signal path:

Rosie Bolton 2 nd SKADS Workshop October 2007 We followed the signal path:

Rosie Bolton 2 nd SKADS Workshop October 2007 Cost Breakdown for BS Total SKA cost breakdown Mid Freq AA Antennas 11.3% Mid Freq AA Analogue Data Transport 9.7% Mid Freq AA Signal Processing 15.0% Comms.>480 km 9.6% Comms.<480km 8.1% Clock, control, phase standard 1.4% Correlator 7.9% 2nd stage processors 4.4% Common Station Infrastructure 1.2% Low-Freq AA 2.5% Mid Freq AA Infrastructure 9.5% High Freq Dishes 19.2% Mid Freq AA Calibration source 0.1% Total cost: €1.91Bn (2011) AA costs total 45% (€860M) Comms. costs 18% €340M – with 1/9 th data rate on outer stations. Extra €500M for full data rate.

Rosie Bolton 2 nd SKADS Workshop October 2007 Strengths of the Design and Costing work Carefully considered, highly detailed design – for Mid Frequency Aperture Array. Costing input from relevant experts (the engineers in this room): excellent to have got SKADS Engineers talking to each other. Speed: Excel implementation is easy for users to study, and was relatively fast to develop – five months from start of process to final document. A very good starting point for further work … but why do we need to do more work?

Rosie Bolton 2 nd SKADS Workshop October 2007 Weaknesses of the Design and Costing work  Not very flexible – difficult to change parameters: can only be done with thorough understanding of the limitations of the spreadsheet.  Only one SKA design was considered: e.g. single antenna arrangement for aperture array within stations.  The effects of station arrangement of stations over SKA area were not considered: we assumed 5-arm log spiral.  Error analysis simplistic – all uncertainties assumed uncorrelated  Scaling with quantities to study cost / performance trade-offs graphically is not automated  Some areas were not modelled in detail – e.g. the correlator

Rosie Bolton 2 nd SKADS Workshop October 2007 The Importance of the Design and Costing Work € 1.9 Billion is too much! In order to get the SKA built we must find ways of reducing the system cost. Current “acceptable” estimate would be around € 1.5 Billion (NPV): 20% less than our Memo 93 cost.

Rosie Bolton 2 nd SKADS Workshop October 2007 Next Steps for D&C Effort Central Processing to be considered in detail Inclusion of Science requirements as a driver Differing array designs: will mean changes in infrastructure System temperature considerations – cost is strongly dependent on this Cost modelling analysis

Rosie Bolton 2 nd SKADS Workshop October 2007 SKADS D&C in the context of the SKA Next document to be ready early December Updated costs: improved computing, different array layout In time to give input into new SKA design by ISPO, early 2008 Will enable comparison between SKA configurations and ensure that the SKADS Aperture Array work remains at the forefront of SKA design work