The Square Kilometer Array: Introduction and Current Developments Jim Cordes, Cornell University

1. 20 50 The Square Kilometer Array: Introduction and Current DevelopmentsJim Cordes, Cornell University • The SKA Project • SKA science case • Fundamental questions in physics, astrophysics and astrobiology • Unprecedented capacity for discovery • International and US activity • Issues • Siting • Finance • Phased deployment • Rescoping Jim Cordes: SKA: Introduction and Current Developments

2. 20 50 SKA: What is It? • An array telescope that combines complete sampling of the time, frequency and spatial domains with a 20 to 50 increase in collecting area (~ 1 km2) over existing telescopes. • Frequency range 0.1 – 25 GHz (nominal) • Limited gains from reducing receiver noise or increasing bandwidth on current arrays • Innovative design needed to reduce cost • 106 meter2 ~ €1,000 per meter2 • c.f. existing arrays ~ €10,000 per meter2 • An international project from the start • International funding • Cost goal ~ € 1 billion • 17-country international consortium • Executive, engineering, science, siting, simulation groups • Timeline for construction extends to 2020 • Can be phased for different frequency ranges • Can do science as you build (“go as you grow”) Jim Cordes: SKA: Introduction and Current Developments

3. Science with the Square Kilometer Arrayedited by Chris CarilliSteve RawlingsSpecial issue of New Astronomy ReviewsVolume 48, December 2004, 979-1605(48 chapters) • Five key science projects • Discovery science • Enabling understanding in fundamental physics and origins Jim Cordes: SKA: Introduction and Current Developments

4. Five Key Science Areas for the SKA Jim Cordes: SKA: Introduction and Current Developments

5. Was Einstein Right About Gravity?The SKA as a Pulsar/Gravity Machine • Relativistic binaries (NS-NS, NS-BH) for probing strong-field gravity • Orbit evolution + propagation effects of pulsars near Sgr A* • Millisecond pulsars < 1.5 ms (EOS) • MSPs suitable for gravitational wave detection • 100s of NS masses (vs. evolutionary path, EOS, etc) • Galactic tomography of electron density and magnetic field; definition of Milky Way’s spiral structure • Target classes for multiwavelength and non-EM studies (future gamma-ray missions, gravitational wave detectors) Millisecond Pulsars Relativistic Binaries Today Future Today Future SKA SKA Blue points: SKA simulation Black points: known pulsars only 6! ~104 pulsar detections Jim Cordes: SKA: Introduction and Current Developments

6. Flowdown from SKA Science to Technical Requirements Jim Cordes: SKA: Introduction and Current Developments

7. SKA Frequencies and Technologies Jim Cordes: SKA: Introduction and Current Developments

8. The Collecting Area Plateau in Radio Astronomy • Increased collecting area enables: • Detection of L* galaxies in HI at z ~2 • Epoch of Reionization analysis • GRB afterglows 100 fainter than currently • Detection/timing of pulsars near Sgr A* • Gap structure in young, protoplanetary disks Recent growth in sensitivity has exploited low-noise devices, developments in digital signal processing bandwidth, and calibration and imaging techniques. Jim Cordes: SKA: Introduction and Current Developments

9. The 6th Key Science Area:Exploration of the Unknown • Today’s hot new issues are tomorrow’s old issues. • The excitement of the SKA will not be just the old questions it will answer but in the new questions it will raise. • We build telescopes for … discovery and understanding. What is the right mix? Entirely new classes of objects and phenomena will be discovered if the SKA has appropriate flexibility in its operations (digital signal processing capabilities, array configuration, field of view, etc.) c.f. Exploration of the Unknown, Wilkinson et al. in SKA science book Jim Cordes: SKA: Introduction and Current Developments

10. Key Discoveries that Illustrate Discovery Space in Radio Astronomy Jim Cordes: SKA: Introduction and Current Developments

11. Nobel Prizes from the Discovery Space in Radio Astronomy Jim Cordes: SKA: Introduction and Current Developments

12. High sensitivity: Large processing FOV , , t, pol , , t Combine Greater Sensitivity with Wide Field of View Processing The SKA combines a > 20 boost in sensitivity with unprecedented utilization of the field of view Jim Cordes: SKA: Introduction and Current Developments

13. The International SKA Project • International SKA Project Office (ISPO) • Richard Schilizzi (Director) • Peter Hall (Project Engineer) • Project Scientist (TBD) • Is conducting site testing in advance of site selection • International SKA Steering Committee (ISSC) • 21 total members (7 Europe, 7 US, & rest of the world) • Working groups: Science, Simulations, Site Evaluation, Engineering, Operations, Outreach • Advisory Committees (Science, Site Selection, …) Jim Cordes: SKA: Introduction and Current Developments

14. Jim Cordes: SKA: Introduction and Current Developments

15. Siting the SKA • Current siting “decision” is late 2006 (ISPO) • Argentina, Australia, China, South Africa: proposals expected by end of 2005 • Working plan: single site for all frequencies, covered with 2 to 3 antenna technologies (subject to optimization vs. cost/performance) • Dipoles  ≤ 0.3 GHz • Aperture array or dishes 0.3 ≤  ≤ 2 GHz • Paraboloids ~ 1 ≤  ≤ 25 GHz • US perspective: good to explore alternatives to a single-site • SKA low-frequency array in southern hemisphere • radio quiet zone •  ≤ 2 GHz • SKA high-frequency array built upon the EVLA+VLBA ?? • Better tropospheric properties than some southern sites, RFI less an issue • leverages existing investments • recognizes international utilization of EVLA, VLBA • Proposed by the US SKA Consortium to the International SKA Steering Committee as a Discussion Document (2005 April) Jim Cordes: SKA: Introduction and Current Developments

16. Discussion Issues • Design and usage issues for the SKA • Phased deployment of the SKA vs. frequency? • Tradeoffs between science goals and cost? • Size of core array usable for searching? • Polarization calibration across wide FOV • How to deal with the huge number of new pulsars: • Time only the best after initial quick assessment? • Require multibeam capability? Jim Cordes: SKA: Introduction and Current Developments

17. Discussion Issues • Astropolitics: • SKA science case needs continual promotion • Need to jointly promote gravity studies: • Laboratory and spacecraft gravitational wave detectors • Pulsars as clocks and gravitational laboratories • Sometimes perceived as having no connection and/or in competition • Joint SKA and LISA meeting? Jim Cordes: SKA: Introduction and Current Developments

18. SKA Development in the US US Concept: Large-N/Small-D (LNSD) • The US SKA Consortium prepares whitepapers on the LNSD concept for consideration by the International SKA Steering Committee and also for a SW US high-frequency SKA site • Allen Telescope Array • Low-frequency arrays (MWA, LWA) = science and technology precursors • Deep Space Network Array: closely related to US SKA concept, strong possibilities for economies of scale • Explicit SKA development: • NSF ATI Grant: ($1.5M) 2002-2005 • Technology Development Project (TDP) • $32M over 5 years (NSF proposal pending) • End to end development, costing, preliminary design • Organized through the US SKA Consortium (17 institutions) • Managed by NAIC/Cornell • Facilitates and unifies SKA development at NRAO, NAIC, and institutions involved with low-frequency array development • The next steps await outcome of the NSF’s “Senior Review” (Spring 2006) Jim Cordes: SKA: Introduction and Current Developments

19. Further • The SKA is still TBD with respect to design, science emphasis, feasibility, funding • The SKA is in fierce competition for funding all around the world • We need to promote the pulsar/gravity KSP as strongly as possible • The KSPs are not frozen categories: creatively enhance or supplant them! Jim Cordes: SKA: Introduction and Current Developments

20. Jim Cordes: SKA: Introduction and Current Developments