─юъєьхэЄ тч Є шч ъ¤°р яюшёъютющ ьр°шэ√. └фЁхё юЁшушэры№эюую фюъєьхэЄр : http://www.naic.edu/~astro/chicago2/talks/Beasley-Raconteur_SKA_low_freq.pdf
─рЄр шчьхэхэш : Tue Aug 22 00:38:00 2006
─рЄр шэфхъёшЁютрэш : Sun Dec 23 00:46:01 2007
╩юфшЁютър:
╧юшёъют√х ёыютр: dark energy

Science Opportunities <300 MHz
╖ Raconteur: One who tells stories and anecdotes with skill and wit. ? ╖ Raconteur: SKA-style
н Over-opinionated; off topic; too long; highly subjective & distorted view of situation; н Expendable: may be disregarded (or even lynched) with few resulting legal or conscience issues...

Key SKA Science Drivers
╖ ╖ ╖ ╖ ╖

(<300MHz)

First stars н reionization Large scale structure н Dark Energy Cosmic magnetism ? Strong-field gravity ? Cradle of Life ,...

╖ .... Transients

EOR: HI 21cm signal from the IGM
z=10 129 MHz LOFAR

Power spectrum: pathfinders are critical

SKA

z=12

9

7.6

Tomography: only SKA T_B(2') = 10's mK SKA rms (100hr) = 4mK LOFAR (1000hr) = 80mK

The 21 cm Transition
╖ Map emission (or absorption) from IGM gas
н Spectral line: measure entire history н Direct measurement of IGM properties

Z=?
SF, AS, LH (2004)

21 cm Observations
╖ Challenges
н н н н Terrestrial Interference Ionosphere RFI Astronomical Foregrounds
╖ ╖ ╖ ╖ Tb~200-2000 K Galactic synchrotron Extragalactic sources Smooth spectra!

н Dirty result (model-dependant) ? н Matching array design, brightness fluctuations н Redshift????

╖

Experiments
н Global Signal: CoRE-ATNF н Fluctuations: 21CMA, LOFAR, MWA, PAPER, SKA н Imaging: SKA MWA (from C. Lonsdale)

R #1
╖ We should have a roadmap for EOR:
н н н н Status of existing efforts (highlighting US pathfinders). More work on theory, foregrounds, systematics etc. Work to detect integrated signal... Plan for participation/leadership in "EOR Array" within 5-10 years н MWA SKA... н More ownership, outreach in community to show EOR potential? Not controversial result... EOR is transformational May require full effort of our community in future? CMB 90's... EOR 10's...

Meter-wave Science
╖ Cosmic Evolution & The High Redshift Universe н Evolution of Dark Matter & Energy by differentiating relaxed & merging clusters н Study of the 1st black holes & the search for HI during the EOR & beyond ╖ Acceleration of Relativistic Particles in: н Hundreds of SNRs in normal galaxies at energies up to 1015 ev. н In thousands of radio galaxies & clusters at energies up to 1019 ev н In ultra high energy cosmic rays at energies up to 1021 ev and beyond. ╖ Plasma Astrophysics & Space Science н Ionospheric waves & turbulence н Acceleration, Turbulence, & Propagation in the ISM of Milky Way & normal galaxies. н Solar, Planetary, & Space Weather, Science ╖ Other, pulsars, recombination lines, "discovery science"

LOFAR, LWA, MWA science cases... Dynamic range, not sensitivity, limited н techniques, fun

Underway....
$$ 1000

100 SKA 10 LOFARLOFAR LWA MWA 0.01 0.1 1 EVLA ALMA

10

100

GHz

Investment & interest in m-w science apparent..

Summary <300 MHz
╖ EOR !! ROADMAP... community attention, support. ╖ Need (and can defend) good linkage between last decadal review comments, SKA pathfinder approaches underway, and future plans ╖ Needs ~SKA for imaging!! Warning: ownership... ╖ Other good meter-wave science н planned/underway efforts (MWA, LWA, LOFAR) will clean up н may eventually help justify additional large instrument (~SKA?)

ALMA
╖ ALMA: $1B radio telescope being built by an international collaboration in a remote site in the southern hemisphere. ╖ Science case: broad, excellent, produced in same way (international community consultation) that appears to converging very slowly here... ╖ Recently: long series of international reviews scrutinizing science, technical, management status; expected outcome is additional 40% in funding (in tough budgetary times). ╖ Poor management example?
н First large international ground-based collaboration н Partners: two flagship organizations, new to "equal" collaboration н Result: Complex management structure

Goal: Partners retain control, responsibility for input national resources... $$$$$$$ means attention... OECD framework? "SKA Inc." not easy. Problem: Not R&R... cultures, attitudes

ALMA
╖ Cost
н High-frequency н difficult site, high precision equipment high cost/m2... н Difficult to budget.. Design, budget by committee, email... н Radio community н project management, system engineering experience lacking н lessons learned....

Y2002/Y2000$

1 Management / Admin. 2 Site Development 3 Antenna Subsystem NA Antenna Procurement EU Antenna Procurement 4 Front End Subsystem 5 Backend Subsystem 6 Correlator 7 Computing Subsystem 8 System Eng. & Integration 9 Science / EPO Total Rebaseline project: 40% increase

18 71 230

Ratio 4.6 1.9 1.3

112 50 15 36 21 10 562

1.0 1.1 0.7 1.1 2.2 1.0 1.4 avg

ALMA lessons
╖ ╖ NOTE: with aligned science cases, medium-hard technical issues, strong international community support... 10-15 years to GO. Fact. Decisions will be made according to external events... e.g. political/funding agency schedule, agenda.. unavoidable, may cost you money, time, scope, credibility later. International collaboration is hard. SKA international project structure may be ALMA-like, or dangerously unique. Central control of resources is critical, but difficult to obtain. Pay attention to project management, software, system integration issues. This meeting: estimates of $100M's tossed around. ALMA management: tested by evolution, SKA: proposing intelligent design. Compare ALMA, SKA in 2022?

╖

╖ ╖

Timescales
╖ US: Decadal Review approaching н need clear priorities, aligned with US astronomy community interests, international SKA plans. 2008-2010... ╖ Funding agency timescales...

Dickman/NSF
╖ MREFC Time Frame Issues
╖ Competition for MREFC funds is fierce ╖ MREFC pipeline is massively full (~$2.5B); many are non-astronomy projects ╖ There has been relatively little change in the annual level of the MREFC account over the years ╖ Difficult to predict the timing and fate of astronomy projects in the MREFC queue ╖ OIR/radio balance will likely be an issue in helping decide the next few large astronomy projects -Underlying this is issue of the extent and nature of Federal support for OIR astronomy

Timescales
╖ SKA/ISPO: vehicle for retaining international momentum (e.g. Site, Technology decisions), realistic??

US + International crunch time Time is up.

R #2
╖ SET PRIORITIES NOW
н #1 EOR SKA, World н #2 HI synoptic array (+ PTA) SKA, World н #3 The rest.... US-oriented, self interest, TB...

╖ IMPROVE PROCESS:
н Drive ideas, community to convergence efficiently (leadership, management issues; Ekers revival vs. endless democracy). Driving committees... e.g. this meeting...

Goals of the Meeting--Five Desired Results
1. Statement of our vision for the key scientific objectives of US astronomy at m/cm wavelengths in the next decade and beyond. 2. Statement expressing our understanding of the multidisciplinary context in which the key scientific objectives of US astronomy at m/cm wavelengths are established and a statement of the unique insight that observations at m/cm wavelengths bring in that context. 3. Concise assessment of the primary instrument requirements--parameters of the facilities required--that are necessary to address the key scientific objectives of US astronomy at m/cm wavelengths and the primary technological challenges they present.

Goals of the Meeting--Five Desired Results
4. Statement of the parameters for which the widelyrecognized, international, SKA project meets the primary instrument requirements. Assessment of whether alternative approaches to a monolithic SKA exist for meeting the primary instrument requirements and, if so, note the arguments for pursuing them. (That is, discuss--from a US perspective--whether the SKA is better structured as a telescope or as a program of internationally-accessible, next-generation, facilities). In all cases, discuss the technology development to be done in the US and the role of the TDP in organizing the development. Assessment of the efficacy of the partnership between national centers and academic researchers in the future development of US astronomy at m/cm wavelengths.
?????????????? These goals?...

5.

R #2
н Clarify/empower USSKA management team to drive this process. (DONE??) н LISTEN (NSF timescales; EVLA2 vs. high frequency plans vs. ALMA; SKA partners; TDP response) н TALK (community outreach; what is SKA? political interest; etc.)

R #2
╖ RISKS н Failure to converge community, present a strong case to Dec. Rev. н Failure to support existing pathfinders, develop EOR game plan. н Failure to link US planning with SKA, world (low, mid: OK). н Unrealistic international agenda, schedule. ?? н Failure to produce coherent project plans (domestic/international). н Take advice from SKA-style meter-wave raconteur who spends no time thinking about SKA these days...