Andrew Faulkner 2 nd SKADS Workshop 10-11 October 2007 SKADS Benchmark Scenario Andrew Faulkner.

Andrew Faulkner2nd SKADS Workshop 10-11 October 2007

SKADS Benchmark Scenario SKADS Benchmark Scenario

Andrew Faulkner


Design and Costing ProcessDesign and Costing Process

Submitted to March ISSC

Memo on SKADS website:www.skads-eu.org/PDF/SKADS_Benchmark_Scenario

_D+C_v1.0.pdf

Published as SKA Memo 93:www.skatelescope.org/PDF/memos/Memo_93.pdf

‘Complete SKA concept’

Strong basis for moving

forward


Top Frequency....Top Frequency....

The cost vs frequency of a close packed aperture array varies as:

Cost ≈ freq 2+ε + infrastructure

cost for ftop of 1.0 GHz < 50% cost for 1.4 GHz

Science expt. requirementsdetermines ftop as ~~1GHz1GHz


The SKADS Benchmark Scenario:

An overall SKA ScenarioAn overall SKA Scenario

100 - 300MHz Dipole aperture array

<300 - 1000MHz Close packed aperture array

0.7 - 20+GHz 6-8m, dishes with single wideband feed

AA only realistic collector for

<300MHz

• Low cost m-2 and they exist!• Large natural FoV• Good at high frequencies• Capable of mass production

• WBFs could be >20:1 freq range• Single feeds can be cooled

economically• Not suitable for arrays

• Small dishes lose efficiency at low freq.

• AA gives v. fast survey speeds and can

look for transients


Outline mid-freq AA specOutline mid-freq AA spec

Frequency range 300MHz – 1000MHz

Organisation Close-packed (for now)

Array size ~60m diameter (~300 tiles)

Tsys <50K

Bandwidth 700MHz

Scan angle ±45° (target ±60°)

Signal digitisation 4-bit


Filled FoV specificationFilled FoV specification

0.001

0.01

0.1

1

10

100

1000

0.1 1 10 100Frequency GHz

FO

V (

de

g2)

Reference Design

SKADS Benchmark

Low-AA: 200 deg2

Mid AA: 250 deg2

6m Dish + WBF 3*(1.4/f)2 deg2

At 1.4GHz ...Ref: 5 deg2

B’mark: 3 deg2

An AA can tailor this

profile e.g. flat, λ2 etc.


Conceptual SKA ConfigurationConceptual SKA Configuration

Station

Core (5Km dia), made up of close packed stations

Central Processingin or near Core

Comms links

Not to scale!DesertDesert


Link to

Correlator

High freq. Dishes withanalogue fibre link

EoR AA antennas withanalogue link (may be close packed)

Notes:1. Power dist. not shown2. All analogue links go to ‘station processing’

Station

Processing

StationStation


Station ProcessingStation ProcessingBunker

StationProcessor 1

StationProcessor 2

StationProcessor X

…..

Dish P1

Dish P2

Dish Px

Low P1

Low P2

Low Pz

.Internal

Digital links

n x Optical fibres per 2nd

stage processor

To C

orrelator

Phase Standard &Distribution

.

.

.

.

..

20GHz Analog fibre links

300MHz Analog links.

.

.

High Freq. dishes

Low Freq. AA

... Control processors

To CentralControl system

10Gb Digital fibre links

Phase transferover fibre (where used)

1st Stage Processors

Mid Freq. AA

0.3-1.0GHz Analog links

Mid P1

Mid P2

Mid Py

Digital

Systems

Only

Analogue

RFI Barrier

RFI Barrier


Antenna Array…Antenna Array…

• Contiguous array• Maintain from underneath• Cover with RF transparent sheet• Bunker in centre

~60m

Tile

Support

Bunker


Bunker racking

Rack cabling

Detailed designDetailed design0.2mm pitch Euro connectors7 rows (5 sig + 2 power)

3.5”2U

ARJ45Large PowerConnector

ComponentsNotes:1. Metalwork not shown2. Mount 16 per rack3. Probably PSUs in the middle and the

bottom to keep leads short. 4. PSU probably 4U

Backplane

Rack MountingRack Mounting

Cooling waterport

Note: water cooling

~500mm

Overall Sysytem:Spacing: 2U (3.5in / 88.9mm)No. per rack: 16 (total 32U)No. of racks: 16Connectors (ARJ45) : 4 rows of 32Connector pitch 0.6inTotal connector width: 19.2in / 488mm

2mm pitch connectors7 rows (5 sig + 2 power)

3.5”2U

ARJ45

Large PowerConnector

To Station processors

Components

~550mm

Power

Time Standard

Control network

Beams to Station processors*

Notes:1. Mechanical and rack support not shown2. 4 rows of 32 ARJ45 connectors give 512

differential inputs. Total 1024 connections. 3. Backplane connectors (50mm long) have

125 signal lines per block, plus 50 power and ground pins.

4. Total signal lines through Euro connectors is 1250.

5. Main board plugs into backplane carrier and is individually connected for power and output.

6. Backplane board permamently fixed into rack

7. *16 x digital outputs used in digital system (8 FoVs with 2 polarisations).

Backplane

CoolantFlow

Cooling waterport Design Blocks

Antenna array Analogue signal transport Analogue beamformingDigital Beamforming2nd Stage ProcessingDigital Data transportDishesMechanical Infrastructure


First costing resultFirst costing result

Infrastructure21%

Analogue Data Transport

21%

Antennas25%

Calibration Source0%

Signal Processing

33%

Projected in 2011 €

Total SKA cost breakdown

Mid Freq AA Antennas

11.3%

Mid Freq AA Analogue Data

Transport9.7%

Mid Freq AA Signal Processing

15.0%

Comms.>480 km9.6%

Comms.<480km8.1%

Clock, control, phase standard

1.4%

Correlator7.9%

2nd stage processors

4.4%

Common Station Infrastructure

1.2%

Low-Freq AA2.5%

Mid Freq AA Infrastructure

9.5%

High Freq Dishes19.2%

Mid Freq AA Calibration source

0.1%

Total: €3.1M

AA station

Total: €1.9B


Pros and ConsPros and Cons

PROS

• Design and engineering led

• Involved most engineering

SKADS groups

• Focussed thinking on issues

• A complete SKA

CONS• Hard to vary the design:

– Mix of technologies

– Geometry

– Performance

• Technology based

• Light on ‘non-SKADS’ systems– Central processing

– Dishes

• Connection to science


Draft Specifications for theDraft Specifications for the Square Kilometre ArraySquare Kilometre Array

The output from a ‘Specification Tiger Team’:R. T. Schilizzi, P. Alexander, J. M. Cordes, P. E. Dewdney, R. D. Ekers, A. J. Faulkner, B. M. Gaensler, P. J. Hall, J. L. Jonas, K. I. Kellermann

Covers science requirements and implementation trade-offs at fixed Cost covering three collector technologies.

The principal input into

SKA2007SKA2007Manchester: 27-28 September

The principal input into

SKA2007SKA2007Manchester: 27-28 September

Available at: www.skatelescope.org


100 500 1000 3000

10

1

100

1000

Frequency (MHz)

Sky

Brig

htne

ss T

empe

ratu

re (

K)

Aeff

Aeff/Tsys

10000

Ae

ff / Tsys (m

2 / K)

1000

5000

No new elements – maybe sparse

above fAA

Sparse AA – element type 3

f sky f AA f max

Sparse AA – element type 2

Fully sampled AAElement type 1


SKA Spec: Key pointsSKA Spec: Key points

• Describes options for SKA low and mid up to 10GHz

• Has a Baseline design with Wide FoV technologies ‘expectations’

• All designs use 15m dishes

– for risk mitigation: low frequency performance & computing cost

• Restricted high frequency operation to 2020, high freqs to follow

• Indicated performance for Key Science Projects

AA for ≤500 MHz in AllAll designs


TT proposals after SKA2007:TT proposals after SKA2007:

Baseline

Design

Sparse AA: 70-200 MHzSparse AA: 200-500 MHz3100 x 15m dishes+WBSPF: <500 MHz–10 GHz

Focal Plane

Array WFoV

Sparse AA: 70-200 MHzSparse AA: 200-500 MHz1615 x 15m dishes+PAFs: 500 MHz–1.4 GHz +WBSPF: 1.5 GHz – 10 GHz

Aperture

Array WFoV

Sparse AA: 70 – 200 MHzSparse AA: 200 – 500 MHzDense AA: 500 – 1000 MHz3100 x 15m dishes+WBSPFs: 800 MHz – 10 GHz

There can be many variations!


Evolving the BenchmarkEvolving the Benchmark

Specification D&C-2Specification D&C-2


D & CD & C-2-2: Goals: Goals

• Communicate SKADS D&C work Internationally

• Bring science experiment reqts into the design process

• Include new Design Blocks

• Update existing Design Blocks with new information

• Optimise System Configurations

• Use information from other international groups


Some Challenges:Some Challenges:

ID Challenge Consequences/ Mitigation

1. Developing 4:1 frequency range antenna elements Use 3 different frequency bands

2. Processing capability within power budget

3. Minimum Tinst – specification: AA-lo of 100 K

AA-hi of 30 K

Reduced sensitivity or higher cost if not met. Less critical for AA-lo

4. Mechanical design and on-site construction for sparsed arrays. System design must be completed first.

Increased cost

5. Power requirements and cooling. Increased running costs

6. Self induced RFI within acceptable limits

7. Multiplexing channels for AA-lo to reduce total processing requirements

Increased costs

8. Demonstration of systematics below level required for the experiments

Unable to perform the science

9. Maintainability and reliability within agreed limits Increased costs

From: Draft Specifications for the Square Kilometre Array


New Design BlocksNew Design Blocks

Science drivers

Central processing

Array geometry

Low System Noise



Science drivers

Central processing

Array geometry

Low System Noise

4 hr integration

360 hr integration

10-sigmaAeff/Tsys = 20,000

Abdalla and Rawlings

e.g detect M* galaxy at

z=0.75 in 25 hours

with Aeff/Tsys= 10,000



Science drivers

Central processing

Array geometry

Low System Noise

Potentially a very big issueMay be the highest system cost!

Calculations by Tim Cornwell, see: SKA Memos: 49 and 64

The AAs could:

be good – low N large D

or bad – many beams, wide FoV



Science drivers

Central processing

Array geometry

Low System Noise

0

2,000

4,000

6,000

8,000

10,000

12,000

0 200 400 600 800 1000

Frequency MHz

Aef

f/T

sys

m2/K

1

10

100

1,000

10,000

Sky

no

ise

Ts

ky -

K

Total Sensitivity

AA-lo

AA-hi sparse

AA-hi close packed

Sky Noise

f max

f AAf sky

0

2,000

4,000

6,000

8,000

10,000

12,000

0 200 400 600 800 1000

Frequency MHz

Aef

f/T

sys

m2/K

1

10

100

1,000

10,000

Sky

no

ise

Ts

ky -

K

Total Sensitivity

AA-lo

AA-hi sparse

AA-hi close packed

Sky Noise

f max

f AAf sky

0

5,000

10,000

15,000

20,000

25,000

0 200 400 600 800 1000

Frequency M Hz

Aef

f/T

sys

m2/K

1

10

100

1,000

10,000

Sk

y n

ois

e T

sky K

Total Sensitivity

AA-lo

AA-hi

Sky Noise

Dense?

Sparse?



Science drivers

Central processing

Array geometry

Low System Noise

Key demonstration to the

International community

• Critical cost driver: 1 K worth ~€10M

– or 2% more sensitivity

– or 4% more survey speed

• Sky noise important at these freqs

– Minimise Trec then +Tsky = Tsys( f )

• All contributions must be investigated


Programme TimetableProgramme Timetable

Initial D&C - 2 meeting 13 September

2007

Work on science reqts & system blocks

Review Meeting 31 October 2007

Preparing written work + science & technical

details

Initial Drafts received 9 November

Review Paper draft (telecon) 23 November

Consolidating paper

Final Draft 7 December

Approval of Paper 11 December

Publication of Paper 12 December

SKA Specification Review Committee: Jan 2008

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Andrew Faulkner 2 nd SKADS Workshop 10-11 October 2007 SKADS Benchmark Scenario Andrew Faulkner.

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