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Newsletter #3

September 2007

edited by Steve Torchinsky

Message from the Coordinator ................................................ 2

Arnold van Ardenne

Message from the Chairman of the SKADS Board ...................... 3

Peter Wilkinson

EMBRACE Beamformer chip at ASTRON ..................................... 3

Klaas Visser, Erik van der Wal, Mark Ruiter, Dion Kant

BEST ......................................................................................... 4

Stelio Montebugnoli

Simulations for the SKA: Pushchino 2007 ................................. 5

Steve Torchinsky

System Design and Costing: Progress Summary ........................ 7

Rosie Bolton

SKADS Recruitment ................................................................... 8

Steve Torchinsky

Square Kilometre Array Design Studies

is partly funded by

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Message from the Coordinator

Arnold van Ardenne, SKADS Coordinator

This third SKADS Newsletter is to some extent

focused on the SKADS achievements leading up

to the Mid Term Review in October and the

second workshop preceding it. In preparation

for these events, a new and updated SKADS

brochure is in the making and will be ready in

September.

Before that however, a lot has happened and has

been summarised in the second Annual Report.

The report illustrates and underpins the

technological progress, the establishment of a

framework of scientific and technical simulations

and the development of a system level costing

tool. While impressive in itself, it is also fair to

say that SKADS has greatly enhanced the

visibility of the SKA in Europe and elsewhere. As

a result, SKADS contributed to the identification

of the SKA on the ESFRI roadmap and provided

input to the next step i.e. the European FP7

programme PrepSKA aiming for the construction

of the SKA. SKADS also firmly established its

key technology area i.e. aperture arrays as a

concept technology for the SKA. This

technological scope is relevant to other

implementations as well, for example, focal

plane arrays.

Thanks to all involved in SKADS, the scientific

and engineering section of the Annual Report

was ready on time and is available on the SKADS

wiki site. The final version will be posted on the

SKADS website.

Proceeding from the last SKADS Newsletter, the

emphasis of SKADS activities supplementing the

work in the DS’s was on (i) defining and

specifying the architectural framework of the

SKA against which the science and astronomical

data simulations and costing, could be

referenced; the “SKADS Benchmark scenario”. In

this SKA scenario, the Aperture Arrays concept is

assumed for frequencies up to about 1 GHz

combined with a different high frequency

concept (i.e. a small dish concept).

(ii) Positioning and shaping SKADS as a coherent

European pathfinder project inside Europe and

elsewhere and to illustrate the technical and

scientific feasibility of the Benchmark scenario

(iii) defining a solid costing approach and

system level costing tool which resulted in a

report that was presented at the SKA ISSC

meeting last March (iv) preparing and

negotiating with IST-CENTRA from Portugal as

new participant and preparing for the leave of

four (University) participants (v) increased

interaction with the International SKA (Project

Office) activities at large (vi) executing of the

FP6 Marie-Curie SKADS program in support of

SKA(DS) science and technology toward

educating younger people.

From 30 July to 1 August, 2007 a successful

inter-SKADS workshop on “Simulations with the

Square Kilometre Array was held at the

Pushchino Radio Astronomy Observatory, Russia

Thanks to this activity, which brought together

most people working in DS2 and other scientist

interested in this topic, the status and the

connection was made clear on science

simulations and astronomical data.

As the nearest upcoming next SKADS event, I am

happy to note that the first Marie Curie MCCT–

SKADS Workshop has been completely booked!

It will be held from 23-29 September in Bologna

and hosted by INAF, Istituto di Radioastronomia

in the lovely Castel San Pietro Terme. This event

is sponsored by the Marie Curie MCCT-SKADS

programme, within the Sixth Framework

Programme of the European Commission. The

programme consists of lectures and scientific

talks in view of SKA and future interferometers

and is spread over a full week, with morning and

afternoon sessions. Details can be found directly

(see www.ira.inaf.it/~school_loc/) or through the

SKADS website.

Details of the next workshop on phased array

technologies for radio astronomy to be held in

November in Dwingeloo, will be posted soon.

See also http://mcct.skads-eu.org/ for the

MCCT-SKADS program at large.

September will be a busy month. The SKA2007

Inter Working Group meeting will be held in

Manchester from the 27th to the 29th, and this

is closely followed by the symposium “From

Planets to Dark energy: the Modern Radio

Universe” which celebrates the 50th anniversary

of the Lovell telescope.

The second SKADS Annual workshop will be held

from 10-12 October just prior to the SKADS Mid

Term Review. This important event will

publicise the huge progress made in SKADS,

especially regarding the feasibility and

exceptional scientific possibilities using the

widefield imaging capabilities of the SKA. A

preliminary program has been posted on the

SKADS website including a registration form.

The workshop will be held at the Observatoire

de Paris and will have a conference dinner on the

Eiffel Tower overlooking Paris at night!

Enjoy reading!

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Message from the SKADS Board

Peter Wilkinson, Chairman, SKADS Board

The major results of the 4th SKADS Board

Meeting held in The Hague on 28/29 June 2007

were as follows:

The Mid-term review and SKADS workshop:

The EC Mid-Term Review meeting will be held in

Paris at the Institute D’Astrophysique on

October 12. SKADS will be represented by the

Management Team and the Board Chair. The

EC’s External reviewer will be Professor John

Seiradakis (U. Thessalonika) and the EC will be

represented by Dr. Elena Righi-Steele. Prior to

this meeting the 2nd SKADS workshop will be

held in the IAP on October 10/11 with the

External and EC reviewers in attendance.

The 2nd Annual Report will be used as the focus

for both meetings. The Board agreed that the

DS2/DS3 deliverables look good for “T0+24”

months. The DS4/5 technical deliverables are

also looking good but are formally a little late

for T0+24, however the rate of progress is good

and the finishing schedule is expected to be

met. The DS6 technical deliverables are on time.

The Board was therefore confident that there are

no “red-flags” and that the workshop and MTR

should go well.

A new SKADS brochure will be produced for the

workshop and MTR and for the international SKA

meetings starting in late September.

SKADS Science

Over and above the simulation work in DS2 the

Board agreed that the “SKADS Virtual Telescope”

exercise led by Oxford was very useful and

should be closely linked in with the international

Science WG programme. The Board strongly

encouraged the production of a “4 years in the

life of” document and a proceedings from the

July Pushchino meeting by the time of the

Autumn meetings

The Board commended the Project Scientist and

the French SKADS team for their efforts in

raising the profile of the SKA in France.

SKADS Costing Exercise

The Board was impressed with the work of the

Design/Costing team, led by Cambridge, and

noted with pleasure that alignment of concepts

with the ISPO-sponsored team has already taken

place. The combined team is now working

towards a single set of flexible software tools as

the next-generation effort. Back-end processing

remains a major strategic issue.

SKADS and the international strategic context

The Board was made aware that the Funding

Agencies have “bought into the project” and that

the UK agency (STFC) is taking a lead role.

SKADS leading players are strongly linked with

international project and SKADS as a whole is

contributing strongly to the global development

effort. The EC is facilitating the next, fully

international, phase via FP7 PrepSKA for which

we in Europe need to seek matching funds to

continue the R&D effort after SKADS comes to an

end in mid-2009.

In this context the ASTRONET questionnaire

reply for SKA is important. The SKA Project

Director agreed to seek advice from European

ISSC representatives before submitting his reply.

We also hope to get an invitation by Michael

Grewing to talk to the ASTRONET ground-based

astronomy working group.

Finally the Board was clear that the SKA project

needs to clarify/specify “the minimum capability

demonstrator” for aperture arrays so that we

know the “height of the fence to be jumped” for

the inclusion of AAs in the first construction

phase to be started in, or around, 2012.

EMBRACE Beamformer Chip

Klaas Visser, Erik van der Wal, Mark Ruiter,

Dion Kant

The EMBRACE design team at ASTRON,

successfully completed the tape-out of the

beam-former chip before the dead-line on July

31. The beam-former chip is an analogue RF

integrated circuit (RFIC), which is an essential

part for aperture array technology.

The main function of the chip is to combine the

four input signals, coming from the antennas,

into two independent beams. The signal chain of

this chip includes a low noise dual feedback

amplifier, poly-phase networks, switching

networks, amplitude correction facility as well as

the output drivers.

This beam-former chip will replace roughly 90

percent of the electronics on the current

EMBRACE prototype boards. Apart from gain

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stages it replaces 8 KDI vector modulators, as

used in the THEA demonstrator. The analogue

processing power of the chip can be expressed

in the equivalent number of Flops, as a digital

solution would need to perform a similar task. A

conservative number leads to 24 GFlops of

processing power.

The chip was designed in the SG25H1 process of

IHP-microelectronics. This process is a 0.25 μm

SiGe:C BiCMOS technology, with npn Hetero- junction bipolar transistors with an fT and fmax

of respectively 180 and 220 GHz.

Some key figures to indicate the complexities of

the design :

● 12480 SiGe Hetero-junction bipolar

transistors

● 17745 CMOS transistors

● 136314 Connections

● 12.6 sq millimetre die size

The design was made using a combination of

Cadence and Agilent ADS software on two dual

Xeon workstations equipped with 8 GByte RAM

each. At the end, the design database consumed

roughly 400 GBytes of disk space and both

systems were fully stretched to their limits.

BEST

Stelio Montebugnoli, DS6 Leader

The BEST-2 test bed is the second level

demonstrator resulting from the

re-instrumentation of part of the Northern Cross

radiotelescope. After a number of important

mechanical modifications to the eight

North-South cylindrical concentrators, the

collecting area of about 1360 m2 has been

upgraded with new, high performance and low

cost receivers.

This demonstrator allows us to optimise

solutions for many of the critical design blocks,

including the low cost front ends, the high

performance analogue optical links, the

wide-band high dynamic range data acquisition

and processing systems, and the software for

adaptive beamforming (i.e. MVDR) as well as for

calibration. The plan is to have the

demonstrator ready to observe the “first

radiosource” (i.e. Cassiopeia) in time for the

SKADS Mid Term Review.

The 8 cylindrical antennas modified to set up the BEST-2

demonstrator

One of the most challenging elements is the FX

correlator. A very fast 32-channel modular

correlator is under development using one

single Bee2, 8 IBOBs and 16 A/Ds boards from

Berkeley University.

A/D and IBOB boards

Bee2 5xFPGAs board

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Simulations for the SKA:

Pushchino 2007

Steve Torchinsky

The historic Pushchino Radio Astronomy

Observatory was the venue for a milestone event

in the SKADS project. The workshop entitled

"Simulations for the SKA" brought together

elements from simulations efforts in pure

science, telescope configurations, network, and

costing.

Pushchino is just over 100km south of Moscow,

and has a history going back to the 1950's

Soviet Union when it was conceived as a Science

Village, home to over 20 000 scientists, mainly

working in biological science, but also the site of

world class radio astronomy facilities.

From July 30th to August 1st, Pushchino

welcomed over 30 participants, 20 from outside

Russia. A major goal of SKADS is the synthesis

of efforts in science and technology, ultimately

leading to the design of a cost effective and high

performance SKA. Within SKADS, this workshop

was a joint effort of Design Studies 2 and 3

(Science and Networking) together with design

and costing work carried out with input from

from DS4 (Enabling Technologies) and Design

Studies 5 and 6 (EMBRACE and BEST).

The first day concentrated on the science

simulations, and there were presentations from

nearly all the SKA Key Science Projects, but first

of all, the tone of the meeting was set with a

brief overview of SKADS by Steve Torchinsky

followed by a summary of the SKADS Design and

Costing effort by Rosie Bolton. Participants were

encouraged to explore new scientific avenues,

but they were reminded that ultimately the

science simulation work should be brought to

Earth with concrete numbers on technical

requirements.

Paola di Matteo presented her results from work

at the Observatoire de Paris in the Epoch of

Reionisation. Danail Obreshkow presented

results in HI and continuum simulations in the

relatively nearby Universe, and this was followed

by Rense Boomsma's talk on high redshift HI

simulations. With the comment "only baselines

out to 100km are interesting," Rense was the

first of several to express a desire for more

collecting area in the core. However, this was

offset by the subsequent presentation on

confusion limits by Yuri Ilyasov.

Filipe Abdalla presented the future promise of

SKA for advancing cosmology, especially our

understanding of Dark Energy, and also the

possibility of constraining the neutrino mass

using multiple large-scale surveys of different

galaxy types.

Returning to the relatively local neighbourhood,

Roy Smits presented the requirements for the

pulsar survey. This turns out to be the most

technologically demanding of the surveys, with

huge requirements for processing. The pulsar

survey requires approximately 50% of SKA

collecting area in the core, and this differs

significantly with the current SKADS Benchmark

Scenario.

Maxim Pshirkov presented a second pulsar talk,

explaining the possibility to probe the galactic

bulge for Dark Matter using pulsar timing

residuals from microlensing. This method

effectively maps compact objects in the galactic

bulge and is insensitive to Dark Energy which is

a distributed phenomena.

The next presentations were related to

observations of magnetic fields, including a

summary of Rotation Measure mapping by

Tigran Arshakian, which was followed by Rosie

Bolton discussing Faraday Rotation in clusters as

a probe of the structure of magnetic fields in

clusters. Vladimir Shishov then concluded the

morning session with a presentation on

interplanetary and interstellar turbulent

plasmas.

The afternoon of the second day was devoted to

telescope simulations beginning with an

overview by Tony Willis of the current state of

software. There was also a poster contribution

from Dharam Vir Lal on array configurations.

The rest of the day was a high-intensity

workshop on the MeqTrees simulation software

led by MeqTrees developer, Oleg Smirnov. Oleg

walked us through a number of telescope

simulations, but one afternoon is not enough to

master the process. Another MeqTrees

workshop, this time over a period of several

days, will be organised in January in Groningen.

After the intense day, it was very welcome to

walk in the warm, sunny weather, and visit the

PRAO instruments, led by our host, Rustam

Dagkesemanskiy. Pushchino has three major

instruments: a 22m reflector used for mm-wave,

an array of 16384 dipoles for use at wavelength

3m, and a cylindrical-cross radio telescope with

two arms, each of 1km length used for

observations in the wavelength range 2.5m to

10m. The hard day of thinking, followed by a

bit of walking, and for some, climbing towers,

was followed by an abundant Russian dinner of

fresh salmon, caviar, and vodka along with the

many traditional Russian toasts.

Despite the vodka, we all managed to restart the

next morning, and Jan Noordam opened the

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final day with a look at calibration for LOFAR.

Yuri Ilyasov was next, presenting the design for

the wideband feed on KAT.

This was followed by some lively discussion

touching on all topics of the workshop. There

were especially some notable exchanges on the

topics of processing power requirements and

the amount of collecting area necessary in the

core.

The final few talks wrapped up the workshop

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These two snapshops of participants at the Pushchino meeting clearly show transient phenomena, and the

importance of a fully- sampled, wide field- of- view together with a short time constant.

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with overviews of the simulation efforts. Steve

Rawlings presented the status of the "4 Years in

the Life of SKA" exercise. The results will be

published in October, and the next stage is "16

Years in the Life of SKA" going from SKA Phase-I

through to the full SKA. Steve Rawlings left us

with the tantalising possibility of directly

measuring the expansion of the Universe by

multiple surveys over a period of ten years.

Rosie Bolton had the difficult task of bringing all

the workshop presentations together and

summarising the technical requirements for the

SKA, and the implications for the overall cost.

The pulsar survey requirements will necessitate

the biggest change to the SKADS Benchmark

Scenario, but data-rate is a constraining factor

for all the Key Science projects. In particular, if

the full data-rate is required from all SKA

stations, even the distant ones, then the cost of

the SKA rises dramatically. Rosie also pointed

out that the time it takes to complete a survey is

a factor. Allowing for more time to complete a

survey can ease some of the technical

requirements in the SKA.

Finally, Hans-Rainer Klöckner and Cormac

Reynolds gave overviews of the science and

telescope simulations carried out within SKADS

Design Study 2 (Tasks 1 and 2). This effectively

summarised the Pushchino Workshop and we

ended with a final talk by Steve Torchinsky

requesting contributions for the proceedings,

reminding everyone to begin publishing their

results, and, of course, thanking all the

participants, and especially our Pushchino hosts,

Rustam Dagkesemanskiy and Vladimir

Shoutenkov, for a very productive and enjoyable

workshop.

All the Pushchino presentations, along with

many photos, are available on the SKADS Wiki at:

http://webmail.jb.man.ac.uk/skadswiki/PushchinoMeeting

System Design and Costing:

Progress Summary

Rosie Bolton

The SKADS Design and Costing work over the

past nine months has been largely focussed on

producing a detailed design and corresponding

cost estimate for an SKA meeting the SKADS

Benchmark Scenario within the Reference

Design. This work has taken input from relevant

experts within SKADS to get the best estimate of

the component costs. The result was a very

detailed snap-shot cost of an SKA design and

was published as SKA Memo 93.

In brief, an SKA system meeting the Benchmark

Scenario comprises a Low-Frequency array,

similar to LOFAR, receiving at 100-300 MHz, a

Mid-Frequency array, similar to Embrace,

working at 300-1000 MHz and ‘Small’ (~6m)

dishes with single pixel feeds operating at

frequencies from 1-25 GHz. (see figure on

page 8)

The estimated cost for such a system is €1.91

Bn, in 2011 money (see piechart on page 8). The

uncertainty on this estimate is around 10%.

Costs specific to the Mid-Frequency AA design

amount to 45% of the total, the dishes

contribute 19%.

Transporting the data from the stations to the

correlator is expensive: the communications

costs amount to €800 Million if the full data rate

is assumed to be used out to the longest

baselines. Reducing the data rate from the

stations that are over 480 km from the core by a

factor of 9 (as is assumed in the €1.91 Bn total),

brings down the communications costs by €500

Million. With this reduction the communications

costs still make up 18% of the total SKA cost.

Full details of the design and associated costs

can be found in Memo 93 - essential reading for

all SKADS members.

The costing process has now completed its first

full cycle and we are in a position to review the

design and make cost/science trade-offs. With

the SKA Specification Tiger Team reviewing the

SKA design, now is a good time to re-think what

the firm requirements of an SKA are for each of

the Key Science Experiments, possibly

developing alternative observing strategies to

enable a lower-cost solution. One draw-back of

the design and costing work presented in Memo

93, is the lack of easy scaling in the model:

whilst the spreadsheet format allows some

values to be altered, not everything scales

automatically with these changes.

It is desirable to improve the flexibility of the

SKADS costing model so that it enables direct

comparisons to be made across a range of

differing SKA designs. The ISPO costing tool

‘SKACost’ (see SKA Memo 92), which has been

developed by Aaron Chippendale and Tim

Colegate (both ATNF/CSIRO), is an SKA costing

code written in Python. This code has some

features that are very good – including Monte

Carlo error analysis, but no easy user interface

allowing manipulation of the telescope design. It

also did not include an Aperture Array.

Tim Colegate, Aaron Chippendale and Adriaan

Peens-Hough (from SA SKA) visited Cambridge

for two weeks in June/July and we agreed on a

way forward. The plan is to improve the usability

of the tool by allowing interaction via a graphical

user interface and to include the AA in the

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model. The code will take on the form of a

flexible framework into which components and

groups of components (the “Design Blocks” in

SKADS parlance) can be placed. Design blocks

(which can be user-defined or taken from a

database) are then pieced together to make up

the full telescope system.

The new SKACost tool will be available over the

coming months, initially via a web interface, with

the full version following in the coming year. It

is vital that Scientists and Engineers understand

how important cost is as a driving force for the

SKA design – the new modelling tool will allow

cheaper alternatives to existing designs to be

considered and compared fairly.

SKADS Recruitment

Steve Torchinsky, Project Scientist

Henrik Olofsson will join the SKADS team at

Observatoire de Paris starting in December

2007. He completed his PhD in 2003 from

Chalmers University of Technology in

Gothenburg, Sweden. His topic was "Satellite

and Ground based observations of Massive Star

Forming Regions." Much of his work to date has

been with the Swedish mm/submm wave

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A schematic view of a station as costed in Memo 93. The Mid frequency aperture array is a fully-filled circular array of square

tiles. Signal processing (to form station beams) is done in a bunker situated underneath the array.There are assumed to be

250 stations to form the SKA each of which transmits signals back to the correlator near the core via optical links.

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