Summary of the Paris SKA Meeting 4-8 September 2006 R. T. Schilizzi

science drivers engineering solutions cost (area, frequency range, FoV, baseline length) funding timeline governance operations impact on the community Main issues for the SKA project

science drivers engineering solutions cost (area, frequency range, FoV, baseline length) funding timeline governance operations impact on the community Main issues for the SKA project = discussed in Paris

What did we do? n SKADS day, impressive range of topics n Information exchange and discussion on Pathfinders and SKADS: status, issues, timeline n EWG Task Force meetings n Reference Design revisited n Magnificent Memos and science-engineering trade-offs n Phase 1 science and engineering issues n Discovery Space; uniqueness and complementarity of science case n Operational issues

What have we achieved? n Preliminary system design documents (170 pages) – major achievement n Pathfinder updates and review n Preparation for Concept Design Review in Jan 08 n Magnificent Memos Must have frequency range MHz Must have long baselines at ν < 1 GHz Multiple simultaneous FoV – no strong science driver (yet) Transient buffer – no immediate hurry to implement Revisit question of filling factor of central core at all frequencies Re-examine fraction of total collecting area on long baselines Optimize survey speed as function of frequency instead of separate optimizations for Aeff, Ω, Tsys (new Memo to be written by SWG)

Reference design n Was taken apart and put back together again Present RD: ambitious with fallbacks Alternative RD: low-risk with enhancements (low-risk = “super-LOFAR” + SD with single pixel feeds) n Recognized that AA and SD-PAF are both on the “innovation path” and need rapid demonstration n Engineers feel present RD is OK if roll-out staged Roll-out could be via low-risk path assuming science limitations are acceptable n Dont have to decide now, but need to have a coherent story for Concept Design Review and US decadal review submission n Recognized differences in EU and US approaches to presenting major projects for funding n Innovation is an important motivator for engineers But so are short timelines!

SKA development n SKA can be built up in stages, in terms of numbers of collectors and baselines, but also survey speed and frequency coverage - need science “ killer-apps ” to drive each stage n Each build stage should be forward compatible – with minimum throw-away n We already “ know ” : Dishes will be part of the solution (40 years experience in high DR imaging) At the low frequency end, aperture arrays will be the most cost-effective solution. n Phased array technology is too great a science multiplier to throw away at this stage

Phase 1 One of the hot topics of the meeting! n “Flagship” science from Phase 1 only if it has Aeff/Tsys = 2000 TBD survey speed 70 MHz<v<3(10?) GHz full FoV down to arcsec resolution Further discussion needed. n Phase 1 configuration: central core + 50 km comprising small dishes ( m 2 AA in the core as next step after EMBRACE?) n Quick return science as input for further funding for full array? n SKA-P1 is an important technology innovation platform n Design could change based on the P-1 experience

Beyond Phase 1 n Is science from “low risk” design a sufficient step forward? (SWG to investigate) n “Strawman” science OK (Aeff/Tsys = ) if increase fraction of collecting area in core, but still keep maximum baseline at >= 3000 km Possible stages of development n Stage1 (2014): 10% SKA, core + 50 km baselines, v<10 GHz n Stage 2 (2020): Aeff/Tsys = 10000, v =3000km n Stage 3 (date?): increase collecting area on long baselines, include high frequencies

Reference Design Cost n Current estimate: 2 B€ in component costs n Needs to be reduced to 800 M€ to meet target cost of 1.3 B€ for an operational array n Cost estimation via ISPO, SKADS, KAT, TDP crucial to engineering decisions and top-level science decisions

Hot issues for SKA operations n A year in the life of the SKA n SKA culture – program or user facility n Power consumption (Mr Fusion) a major issue even for 100 km baselines Need to include decisions on operational issues in overall timeline

Going forward n Phase 1 science case ongoing n Science simulations ongoing n SKADS, pathfinders – key results needed by end-07 n Cost estimates crucial n Risk analysis needed n Update timeline diagram n Work breakdown structure for the complete project adopted as a means of increasing internal and external coherence with entries for SKADS, the Pathfinder projects, and the US Technology Development Program n Operational issues now part of SWG and EWG as well n Next SWG-EWG-OWG gathering is planned in October 2007 in Manchester