Transcript SKADS-LOGO

Engineering Overview
Andrew Faulkner
Engineering Aims
From Science simulation specifications (DS2 T1):
• Simulate the performance for the overall SKA, (DS2 T2)
• Optimise SKA architecture through simulation (DS3 T3)
• Prove a mid-frequency, 0.3-1.0 GHz, Aperture Array:
– Operation, collector cost and radio-astronomy demonstrator (DS5)
– Develop components & sub-systems (DS3 T1, 2; DS4 T1-5, DS6)
– Build small, high-performance demonstrator (DS4 T6)
• Produce costed design for SKA (DS8) with ISPO
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A start-up year.....
• Patchy progress by country, primarily due to funding
• Teams being built up or in place
• Considerable thought on system issues
• Relationship with Reference Design (memo 69)
• Some evolution of system ideas
Details by DS Later
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Communications
• Significant meetings:
– EMBRACE & BEST ongoing project meetings
– ‘Technical’ Meeting: Scientists + Engineers
– Simulation Meeting: DS2-T2 + DS3-T3
– Kick-offs:
• DS2-T1
Science Simulation
• DS3-T1
Data Transport + Phase Transfer
• DS4-T1, T2+T3, T4
Front-end; RFI+Digitisation; Antenna
• Wiki Site for Project communications and interaction
– www.skads-eu.org  wikis
• Email Exploder + Archiving (see wiki)
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Country Progress
• The Netherlands
• Italy
– Early start,
– EMBRACE ~on schedule
– Excellent participation
– BEST1 going well
– BEST2 projected 2Q2007
– Rx for EMBRACE underway
• UK
• Spain
– Slow start, due to Finance
delay
– Major recruitment programmes
– System config. by academics
• France
– Engineers in place, working on
EMBRACE
– Kick-off DS4-T3
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– Engineers in place
– Participating DS4-T4
– Initial work completed & reported
• Other Participants
– SA: KAT
– Australia: xNTD
– Canada: PHAD
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Underway
and active
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Despite slow start-up:
SKADS is
Targeted to
Finish on time
Crucial for International SKA timeline....
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SKADS‘Benchmark’ design
Kickoffs and System discussions
Show the need for a
Starting Specification...
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‘Benchmark’ Specification
We need a target specification now to ‘aim’ at, for:
•
Scientists in DS2-T1 to simulate their observations
•
Technical and network simulations in DS2-T2 and DS3-T3
•
Engineers to realistically design to and evaluate
•
Early costing.....
This will be the basis to evolve the final spec.
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Firstly, two questions....
1. What is the TOP frequency we are planning for
an Aperture Array?
2. Do we believe that Aperture Arrays will be the
ONLY collecting area over a frequency band?
• Ability to image
• Dynamic range etc
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Top Frequency....
The cost of a close packed aperture array varies as:
Cost ≈ freq 2+ε + infrastructure
•
Top freq2 due to linear pitch is ~λ/2
•
BUT:
ε due to additional bandwidth and higher
MUST support the science!
cost ADC and analogue parts etc. (0→1)
•
Infrastructure is relatively low cost
Cost viability of AA critically dependent on top freq.
e.g. cost for Nyquist sampled 1.0 GHz < 50% cost for 1.4 GHz!!
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SKA Reference Design
LOFAR, MWA etc.
AA duplicates freq.
EOR AA
All Sky AA
~10m Dishes FPA
~10m Dishes WBF
0.1
≥ 10m for 300 MHz
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0.3
1.0
FPA for FOV
Assuming we
3.0
10.0
30.0
GHz
How to switch w/very
large FPA? in AA....
have confidence
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AA fully used
AA a critical part of SKA:
Large FOV, excellent at low freq
EOR AA
Mid-Freq AA
~10m Dishes FPA
Not required?!
~6m Dishes WBF
0.1
0.3
1.0
3.0
10.0
30.0
GHz
6m dish: larger natural FOV
easier hi-freq, ‘cheap’
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FOV specification
EOR AA: 200 deg2
1000
Reference Design
10m Dish +
FPA-2: 5 deg2
100
FOV (deg2)
10
1
10m Dish + WBF
(1.4/f)2 deg2
10m Dish +
FPA-1: 50 deg2
0.1
0.01
0.001
0.1
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Frequency GHz 10
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FOV specification
EOR AA: 200 deg2
1000
Reference Design
SKADS Benchmark
100
Mid AA: 250 deg2
FOV (deg2)
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6m Dish + WBF
3*(1.4/f)2 deg2
1
0.1
0.01
0.001
0.1
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At 1.4GHz ...
Ref:
5 deg2
B’mark: ~4 deg2
1
Frequency GHz 10
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Further Notes
• 300-500 MHz is a problem:
– Dishes perform less well at low frequencies
– Sky noise is increasing, which needs bigger collecting area
• Consider frequency dependant AA: more collecting area at lower
frequencies <500MHz.
• Consider allowing >1.0 GHz (1.2 GHz?) with grating lobes on AA.
• Are there any ‘low cost’ 10+m dishes?
• 6m dish design will be proven by ATA
• No consideration has yet given to multiple beams or very large
(>500 deg2) FOVs to trade with sensitivity
• WBFs will be proven (0.5-11 GHz): modify for 0.9-25 GHz?
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Some perceived issues with AA
• Community skepticism on cost and performance
• Limited scan angle range: ±45° to ±60°
(dishes may be < ±90°)
• Geometrically reducing aperture with scan angle
• Quality of beam formation
– Effects of strong sources anywhere in the sky
– Sources in the sidelobes
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SKADS will ....
Use two SKA Specifications for Simulations and Costing
(Engineering will only R & D the Benchmark Design):
Reference Design
SKADS Benchmark
• EOR Aperture Array
• Fish-eye lens AA
0.3 – 1.0 GHz
• 10m dish +
• FPA1 0.3 – 1.0 GHz
• FPA2 1.0 -3.0 GHz
• WBF 3.0 – 25 GHz
• EOR Aperture Array
• Mid-freq AA
0.3 – 1.0 GHz
• 6m dish +
• WBF 0.9 – 25 GHz
Compare: Science capability + Cost information
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‘Fleshed out’ Specifications
based on SKA memos are on the WIKI
Please put up comments on-line!
Over to the Science......
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