Paul Alexander DS3 & DS3-T3 SKADS Review 2006 DS3 The Network and its Output Data Paul Alexander

SKADS Review 2006 Paul AlexanderDS3 & DS3-T3

DS3DS3The Network and its Output DataThe Network and its Output Data

Paul AlexanderPaul Alexander


OverviewOverview

Overall aim of this design study

Examine the System Design issues associated with producing the most cost-effective overall architectural design for the SKA “network”


processor

The physical network: Data flow, processing and analysis

& power

Telescope response

User network

signal and data transport


The Structure of DS3The Structure of DS3Six tasks

• T1 – Network infrastructure and data transmissionManchester

• T2 – Data handling; control and distributed computingASTRON

• T3 – Architecture and the functional simulatorCambridge

• T4 – Siting and related issuesOPAR

• T5 – SKA for the userCambridge

• T6 – Scaleable design and implementationASTRON


DS3 and the SKA DS3 and the SKA system designsystem design

Concerned with the overall SKA architecture not just the Aperture Array

Will consider compare and evolve:

• SKADS Benchmark specification

• ISPO reference design

• Other emerging system designs


Current StatusCurrent Status

• All tasks underway

• No DS deliverables or milestones in the first 12 month period

• Relatively slow start for some tasks:– Planned in the description of work

– Later than anticipated availability of UK funds

• At kickoff meetings identified:– the need for close inter task discussions and also with the need for close inter task discussions and also with

other DSother DS


Some of the interactionsSome of the interactions

DS2-T2Science

DS3-T3Simulator

DS3-T2Processing

DS3-T1Network

DS3-T6Scaleup

DS3-T4Siting

DS4-T2DSP

DS4-T6…2-PadDS5…

Embrace


Current StatusCurrent Status

• All tasks underway

• No DS deliverables or milestones in the first 12 month period

• Relatively slow start for some tasks:– Planned in the description of work

– Later than anticipated availability of UK funds

• At kickoff meetings identified: – the need for close inter task discussions and also with the need for close inter task discussions and also with

other DSother DS

– cost control and cost constraints central to system designcost control and cost constraints central to system design


Cost modelling in DS3Cost modelling in DS3

• In the original description of work there exist many work packages which are required to produce explicit cost models for particular aspects of SKADS technology

• Cost control central to work in DS3, DS4, DS5 and DS6

• Aim to coordinate this work and provide a good link to the wider project

Single identified point of contact to bring together the SKADScosting work

Provide an interface between SKADS costing work and the

ISPO development of a cost model

Communicate emerging cost output from SKADS to ISPO andcommunicate relevant aspects of ISPO cost model to SKADS

team


Highlights so farHighlights so far

DS3-T1 (more in a moment) Network infrastructure and data transmission

– A first good costing model for the physical network

DS3-T2 (more in a moment) Data handling, control and distributed computing

DS3-T3 (more in a moment) Overall architecture and network simulator

DS3-T5 (planned start end 06) SKA for the user

DS3-T6 – Need to adopt good practice for how we model and go about the

design process especially as we move into the Engineering Design phase

– Initial review of available methodologies


Highlights – DS3-T4 Highlights – DS3-T4

DS3-T4 Siting and related issues

Original view of the task

“The production of a full plan for siting and related issues for the SKA, encompassing environmental issues (including signal conditioning, impact and adopting the advanced technology to arid lands), radio

frequency monitoring/protection over a long term and potential maintenance regimes.”




• Significant unforeseeable changes since SKADS planned in particular delay of site selection well beyond late 2006 as originally envisaged

• Some work originally planned in SKADS will now be done by International Project (specifically the Site Evaluation Working Group and its Task Group on Regulatory Issues, and the ISSC )



• SKADS participants played central roles in helping to define regulatory requirements for radio quiet zones at each possible site

• ASTRON engineers have carried out the extensive and homogeneous Radio Frequency Interference (RFI) monitoring campaign of all four proposed SKA sites

• SKADS participants contributed towards ISPO Memo 73 on “Spectrum Protection Criteria for the SKA”



DS3-T3: Overall Architecture and DS3-T3: Overall Architecture and Network simulation Network simulation


DS3-T3: Refining the DS3-T3: Refining the Benchmark Specification Benchmark Specification

Aperture Array stations on long baselinesAperture Array stations on long baselines

• Benchmark specification has AA providing < 1GHz collector throughout. Can we define more precisely the requirements of an AA station?

• Consider basic parameters: station size, filling factor and data rate

• Constraint: ability to calibrate the station



Consider the ionosphere:

• typical size of isoplanatic patch at 300MHz is ~ 2 degrees

• Calibration is relativelystraightforward if each stationbeam subtends an anglesmaller than the isoplanaticpatch



• For a larger beam we need a more complex ionospheric model which can be solved for if reltively short baselines available as in compact core

• On long baselines however, sparse station coverage

• d ~ 70 m

1d



• Need 1 source on average per beam/isoplanatic patch to calibrate; Poisson statistics to give P(1) for 99% of time needs N = 10 sq deg

• At 1.4GHz, use FIRST counts(unresolved or model)

• Require S ~ 15 mJy; for 70m AA,70% efficiency

• f > 20%

mJy1010150

4.32/12/11

MHzs

f

K

TS s

log(S / Jy)

log(

N o

r dN

/dS

/ sq

deg

ree)

Integrated FIRST source count


• Long baseline AA station– Diameter 70 m

– Filling factor > 20%

– Data rate:• assume 8-bit digitisation for 300 – 1000 MHz

• Per square degree full bandwidth 24 Gbs

• 250 beams ( 250 sq degrees or ~ 60 uniform sensitivity) gives 6 1012 bs

• Compare to LNSD station giving 1 sq degree at 1.4 GHz

• f = 10% and 25 13m antennae

• Beam form in central processor

• Data rate 6.4 1012 bs



DS3: Dynamic range DS3: Dynamic range

• Sensitivity from large collecting area is only sensible if the telescope can also achieve the necessary dynamic range given is FOV, beam shape, side lobes etc.

• e.g. Tim Cornwell as investigated in detail the effects of the telescope quadrupod on the producing asymmetries in the beam and hence limiting the dynamic range:

This is a big issue which needs to be carefully This is a big issue which needs to be carefully considered for any antenna used in a given bandconsidered for any antenna used in a given band


DS3: The Next 18 Months DS3: The Next 18 Months


DS3: Next 18 months DS3: Next 18 months

• People now in post for DS3-T1 and T3 in UK and very significant ramp-up of these tasks is underway confidently expect to meet SKADS milestones and deliverables on time

• DS3-T2 is now ramping up as planned

• DS3-T4 effectively complete; report will be written after ISSC complete site selection

• First “SKA for the user” workshop planned in next 4 months (DS3-T5)

• Scaleup and design issues: work on track as planned



OverviewOverview

Overall aim of this design study

Examine the System Design issues associated with producing the most cost-effective overall architectural design for the SKA “network”

By Network we mean

• The physical network: signal and data transport & power

• The data network: data flow, processing and analysis

• The output network: telescope response warts and all

• The user network: how the telescope appears to the end-user astronomer


The next 18 monthsThe next 18 months

On track to meet milestones and deliverablesOn track to meet milestones and deliverables

• Phase transfer links (T1)

• Frame work for the network simulation / analysis (T3)

• Overview report on site selection (T4)

• Report MDA constructs, interfaces and platforms (T6)

Documents

Paul Alexander DS3 & DS3-T3 SKADS Review 2006 DS3 The Network and its Output Data Paul Alexander