DS3 The Network and its Output Data Paul Alexander

1. DS3The Network and its Output DataPaul Alexander SKADS Review 2006

2. Overview • Overall aim of this design study • Examine the System Design issues associated with producing the most cost-effective overall architectural design for the SKA “network” SKADS Review 2006

3. processor User network Telescope response The physical network: Data flow, processing and analysis signal and data transport & power SKADS Review 2006

4. The Structure of DS3 • Six tasks • T1 – Network infrastructure and data transmissionManchester • T2 – Data handling; control and distributed computingASTRON • T3 – Architecture and the functional simulatorCambridge • T4 – Siting and related issuesOPAR • T5 – SKA for the userCambridge • T6 – Scaleable design and implementationASTRON SKADS Review 2006

5. DS3 and the SKA system design • Concerned with the overall SKA architecture not just the Aperture Array • Will consider compare and evolve: • SKADS Benchmark specification • ISPO reference design • Other emerging system designs SKADS Review 2006

6. Current Status • All tasks underway • No DS deliverables or milestones in the first 12 month period • Relatively slow start for some tasks: • Planned in the description of work • Later than anticipated availability of UK funds • At kickoff meetings identified: • the need for close inter task discussions and also with other DS SKADS Review 2006

7. Some of the interactions DS3-T1 Network DS3-T6 Scaleup DS3-T2 Processing DS4-T2 DSP DS2-T2 Science DS3-T3 Simulator DS4-T6… 2-Pad DS5… Embrace DS3-T4 Siting SKADS Review 2006

8. Current Status • All tasks underway • No DS deliverables or milestones in the first 12 month period • Relatively slow start for some tasks: • Planned in the description of work • Later than anticipated availability of UK funds • At kickoff meetings identified: • the need for close inter task discussions and also with other DS • cost control and cost constraints central to system design SKADS Review 2006

9. Cost modelling in DS3 • In the original description of work there exist many work packages which are required to produce explicit cost models for particular aspects of SKADS technology • Cost control central to work in DS3, DS4, DS5 and DS6 • Aim to coordinate this work and provide a good link to the wider project Single identified point of contact to bring together the SKADS costing work Provide an interface between SKADS costing work and the ISPO development of a cost model Communicate emerging cost output from SKADS to ISPO and communicate relevant aspects of ISPO cost model to SKADS team SKADS Review 2006

10. Highlights so far DS3-T1 (more in a moment) Network infrastructure and data transmission • A first good costing model for the physical network DS3-T2 (more in a moment) Data handling, control and distributed computing DS3-T3 (more in a moment) Overall architecture and network simulator DS3-T5 (planned start end 06) SKA for the user DS3-T6 • Need to adopt good practice for how we model and go about the design process especially as we move into the Engineering Design phase • Initial review of available methodologies SKADS Review 2006

11. Highlights – DS3-T4 DS3-T4 Siting and related issues Original view of the task “The production of a full plan for siting and related issues for the SKA, encompassing environmental issues (including signal conditioning, impact and adopting the advanced technology to arid lands), radio frequency monitoring/protection over a long term and potential maintenance regimes.” SKADS Review 2006

12. Highlights – DS3-T4 DS3-T4 Siting and related issues • Significant unforeseeable changes since SKADS planned in particular delay of site selection well beyond late 2006 as originally envisaged • Some work originally planned in SKADS will now be done by International Project (specifically the Site Evaluation Working Group and its Task Group on Regulatory Issues, and the ISSC ) SKADS Review 2006

13. Highlights – DS3-T4 DS3-T4 Siting and related issues • SKADS participants played central roles in helping to define regulatory requirements for radio quiet zones at each possible site • ASTRON engineers have carried out the extensive and homogeneous Radio Frequency Interference (RFI) monitoring campaign of all four proposed SKA sites • SKADS participants contributed towards ISPO Memo 73 on “Spectrum Protection Criteria for the SKA” SKADS Review 2006

14. DS3-T3: Overall Architecture and Network simulation SKADS Review 2006

15. DS3-T3: Refining the Benchmark Specification Aperture Array stations on long baselines • Benchmark specification has AA providing n < 1GHz collector throughout. Can we define more precisely the requirements of an AA station? • Consider basic parameters: station size, filling factor and data rate • Constraint: ability to calibrate the station SKADS Review 2006

16. DS3-T3: Refining the Benchmark Specification Consider the ionosphere: • typical size of isoplanatic patch at 300MHz is ~ 2 degrees • Calibration is relativelystraightforward if each stationbeam subtends an anglesmaller than the isoplanaticpatch SKADS Review 2006

17. DS3-T3: Refining the Benchmark Specification • For a larger beam we need a more complex ionospheric model which can be solved for if reltively short baselines available as in compact core • On long baselines however, sparse station coverage • d ~ 70 m SKADS Review 2006

18. log(N or dN/dS / sq degree) log(S / Jy) DS3-T3: Refining the Benchmark Specification • Need 1 source on average per beam/isoplanatic patch to calibrate; Poisson statistics to give P(1) for 99% of time needs N = 10 sq deg-1 • At 1.4GHz, use FIRST counts(unresolved or model) • Require DS ~ 15 mJy; for 70m AA,70% efficiency • f > 20% Integrated FIRST source count SKADS Review 2006

19. DS3-T3: Refining the Benchmark Specification • Long baseline AA station • Diameter 70 m • Filling factor > 20% • Data rate: • assume 8-bit digitisation for 300 – 1000 MHz • Per square degree full bandwidth 24 Gbs-1 • 250 beams ( 250 sq degrees or ~ 60 uniform sensitivity) gives 6 1012 bs-1 • Compare to LNSD station giving 1 sq degree at 1.4 GHz • f = 10% and 25 13m antennae • Beam form in central processor • Data rate 6.4 1012 bs-1 SKADS Review 2006

20. DS3: Dynamic range • Sensitivity from large collecting area is only sensible if the telescope can also achieve the necessary dynamic range given is FOV, beam shape, side lobes etc. • e.g. Tim Cornwell as investigated in detail the effects of the telescope quadrupod on the producing asymmetries in the beam and hence limiting the dynamic range: This is a big issue which needs to be carefully considered for any antenna used in a given band SKADS Review 2006

21. DS3: The Next 18 Months SKADS Review 2006

22. DS3: Next 18 months • People now in post for DS3-T1 and T3 in UK and very significant ramp-up of these tasks is underway confidently expect to meet SKADS milestones and deliverables on time • DS3-T2 is now ramping up as planned • DS3-T4 effectively complete; report will be written after ISSC complete site selection • First “SKA for the user” workshop planned in next 4 months (DS3-T5) • Scaleup and design issues: work on track as planned SKADS Review 2006

23. SKADS Review 2006

24. Overview • Overall aim of this design study • Examine the System Design issues associated with producing the most cost-effective overall architectural design for the SKA “network” • By Network we mean • The physical network: signal and data transport & power • The data network: data flow, processing and analysis • The output network: telescope response warts and all • The user network: how the telescope appears to the end-user astronomer SKADS Review 2006

25. The next 18 months On track to meet milestones and deliverables • Phase transfer links (T1) • Frame work for the network simulation / analysis (T3) • Overview report on site selection (T4) • Report MDA constructs, interfaces and platforms (T6) SKADS Review 2006