Large Field of View Radio Astronomy; relevant for many KSP s

Transcription

1 Large Field of View Radio Astronomy; relevant for many KSP s SKA Key Science Drivers ORIGINS Probing the Dark Ages When & how were the first stars formed? Cosmology and Galaxy Evolution Galaxies, Dark Energy and Dark Matter Cradle of Life What and where are the conditions for life? FUNDAMENTAL FORCES Strong-field tests of General Relativity Was Einstein correct? Origin & Evolution of Cosmic Magnetism Where does magnetism come from? plus The Exploration of the Unknown as an underlying philosophy for design & costing (see also

2 Overview of the SKADS SKADS; The European SKA Design Study towards the Square Kilometre Array The electronic pointing and control concept for the SKA A European project involving 26 partners from Radio Astronomy Institutes, Universities and Industry in 9 EU countries plus Russia, South Africa, Australia & Canada A Cohering Program toward mid Read.dem. Phase 1

3 SKADS Objectives Overall Total value 35M EC funding M Industry involved from the start SKADS aims to Demonstrate SKA Scientific Viability and Readiness Demonstrate cost-effective Engineering Solutions and Technological Readiness Deliver a costed SKA Design All (to be covered) in SKADS White Paper

4 Phased arrays; the key questions Can we afford them within SKA framework As investment As operating instruments (computationally, reliability, upgradability ) Will they perform Scientifically (Widefield scanned deep polarimetric Imaging) Technically (Noise, beamstability, reliability,..) Will they be there in time For SKA Phase1 construction What wil be the optimal frequency range Related to all the above

5 Phased arrays; why? Maximum Potential for Science return Larger/largest Field of view Maximally using metal infrastructure (on dishes) Filed of View limited by element beam and processing cost Maximal flexibility Electronic control with many beams Cost effective /sqm Rx area Processing limited for AA s At station level plus central with limited stations (say, 250) Low lifetime costs Reliance on Electronics No cooling Graceful degradation Upgrade path intrinsically possible At tile level At processing level Appealing concept associated with Industry interest, innovation

6 Phased Arrays and Reflectors WSRT, e-vla, LOFAR, MWA, LWA, Paper WSRT-Apertif, ASKAP GMRT, MeerKAT,ALMA etc. (SKADS, AAVP) (TDP/Canada e.o) Element antenna pattern Multiple FOV Digital beams Single telescope replaced by phased array station Options: Dense vs. Sparse Arrays Key issue: Cost SKADS Reduction Overview to say, <500 /sqm

7 Aperture Arrays in conceptual perspective; Frequency ranges CONCEPTS REFLECTORS Projects/ Types ATA, Meerkat etc. Reflectors/SPF Fields of View Single Mech. Pointing; Single FOV/ Single beam APERTURE ARRAYS Embrace like Sparse/ Sparse/ Dense Dense LOFAR like All Sky FOV Multiple FOV /Multiple beams Ionospheric cut-off Aperture Arrays 10 GHz Reflectors

8 1000 AAVP: Tailoring the AA-dish system Sparse AA-lo Sky Brightness Temperature (K) T sky A eff Fully sampled AA-hi Becoming sparse above f AA Dishes A eff / T sys (m 2 / K) A eff /T sys Frequency (MHz)

9 SKADS Data Simulations Summary Sky simulations Astrodata simulations z = Court.esy D. Obreschkow...attenuated by AA primary beam, as simulated by OSKAR: simulate a dataset using MeqTrees Box size: 500 h -1 Mpc (or ~700 Mpc) of which this is about 5-millionths of the corresponding sky area: Ultimately SKA can generate the billion-galaxy redshift surveys to probe the underlying cosmology (note s 3 :

10 Example: Connectivity Transfer of Local Oscillator Signals Over Fibre Example: E-Merlin Issue: Longest distance Stability proven to < 200km What on longer distances, not owned H-masers, Satellites? Designing the fiber network Example: e-vlbi/express, LOFAR, e-merlin Issue: Cost over distance Signal Ownership (dark fibre/owned-rented vs. rented/managed) Control/Monitoring Over Fibre network Configurations Scientifically initiated Site, country, cost

11 Costing Tool Correlator 4% Trenching: all 6% Fibre: All Dishes 4% Clock, control, phase standard 1% Back end computer 2% AA-lo "arrays" 11% Fibre:AA-lo intra station 1% Fibre: AA outer 3% Fibre: AA-hi core 2% AA-hi "arrays" 25% Fibre:AA-lo core 2% Dishes 35% Station level processors and racks 4%

12 Technology Example: Photonics; Photonic Beamforming: Demonstrator System Approach: use EMBRACE tile as basis Tile with 8 x 8 elements 16 elements building block Laser Laser LNA LNA LNA LNA LNA LNA LNA LNA Filter Filter Filter Filter Mod Mod Mod Mod Mod Mod Mod Mod Receiver system Photonic Beamformer IC Det Amp Courtesy:P. Maat

13 SKADS examples on modelling antennas A multi-scale antenna problem arrays of subarrays Total Solve Time: ~10 min. (Single CPU 1.73 GHz, 2.0 GB RAM) ~35x faster! Combining antenna EM-models with MW-circuit models An antenna system simulator Using BG:

14 Understanding the Noise budget Aperture Array (based on present R&D) Note: depends on scanangle Spill-over Vivaldi feed loss Low Noise Amplifier Noise mismatch / coupling /2 nd stage Sky Total 0 K 9 K ~16 K 7 K 8 K 40 K Measured Active reflection coefficient while scanning: (noise coupling changes as scan angle changes)

15 EMBRACE breaking new ground

16 An inside look

17 2-PAD in the summer; other feeds tested

18 32 Rx 1400 sqm N/S: BEST 2 (408 MHz 16 MHz Bw) E/W: BEST 3lo ( MHz) 16 Rx 800 sqm Some electronic and Cas A fringes (simulatred and observed) Some electronic. The beamformer is under test

19 SKADS Risk analysis; Categories

20 SKADS Risk analysis; Description

21 Arresting key risks in time Risk factor T sys High/Medi um Medium Low Calibration Medium Low Low Imaging, software High Medium Medium Design for industrialization and low cost, TRL Medium Medium Low Antenna modeling techniques Low Very Low Very low Data processing Medium Medium Low Power Medium Medium Medium

22 SKADS will/has Deliver a costing tool and a costed SKA design architecture using AA s and SPF Given a full cycle of simulated science (SKA simulated skies) and astrodata (toward imaging) results using the Meqtrees tool Given a demonstrated technology and engineering status with TRL s on AA s and insights in how to proceed Organized Europe for the SKA and Communicated the results broadly Given input toward Aperture Array Verif. Program as next step for the SKA Beyond SKADS: An astronomical verified capability of dense AA s (calibrated deep polarimetric imaging, DR) SKA ready final requirements on e.g. Tsys, station processing, power, cost