1. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 DS3 The Network and its Output Data Paul Alexander

2. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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”

3. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 processor The physical network:Data flow, processing and analysis & power Telescope response User network signal and data transport

4. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 The Structure of DS3 Six tasks T1 – Network infrastructure and data transmission Manchester T2 – Data handling; control and distributed computing ASTRON T3 – Architecture and the functional simulator Cambridge T4 – Siting and related issues OPAR T5 – SKA for the user Cambridge T6 – Scaleable design and implementation ASTRON

5. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

6. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

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

8. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

9. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

10. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

11. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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.”

12. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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 )

13. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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” Highlights – DS3-T4

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

15. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 DS3-T3: Refining the Benchmark Specification Aperture Array stations on long baselines Benchmark specification has AA providing < 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

16. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 DS3-T3: Refining the Benchmark Specification Consider the ionosphere: typical size of isoplanatic patch at 300MHz is ~ 2 degrees Calibration is relatively straightforward if each station beam subtends an angle smaller than the isoplanatic patch

17. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

18. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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  At 1.4GHz, use FIRST counts (unresolved or model) Require  S ~ 15 mJy; for 70m AA, 70% efficiency f > 20% log(S / Jy) log(N or dN/dS / sq degree) Integrated FIRST source count

19. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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  250 beams (  250 sq degrees or ~ 60 uniform sensitivity) gives 6 10 12 bs  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 10 12 bs  DS3-T3: Refining the Benchmark Specification

20. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

21. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 DS3: The Next 18 Months

22. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

23. Paul Alexander DS3 & DS3-T3 SKADS Review 2006

24. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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

25. Paul Alexander DS3 & DS3-T3 SKADS Review 2006 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)