System Design choices for the SKA: Cost and performance trade-offs.
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Transcript of System Design choices for the SKA: Cost and performance trade-offs.
Rosie Bolton, Cambridge University 1SKA System level trade-offsSKADS Final meeting, November 2009
System Design choices for the SKA: System Design choices for the SKA: Cost and performance trade-offs.Cost and performance trade-offs.
Rosie Bolton, Paul Alexander, Tim Colegate, Andy Faulkner, Dominic Ford, Peter Hall and
the SKADS System Group.
Rosie Bolton, Cambridge University 2SKA System level trade-offsSKADS Final meeting, November 2009
OutlineOutline
• The SKA Cost/Performance tool
• Populating the tool: Hierarchical telescope design
• Example of design block structure
• Examples of some trade-offs
Rosie Bolton, Cambridge University 3SKA System level trade-offsSKADS Final meeting, November 2009
The SKA Costing toolThe SKA Costing tool
• Concept of “Design Blocks” was introduced in SKADS for D&C 1: Hierarchical Telescope designs made up of discrete blocks and components.
• SKACost tool was developed by the ISPO (Peter Hall, Aaron Chippendale and Tim Colegate)
• Initial SKADS costing based on Excel spreadsheet
• The new SKA costing tool combines the best of these approaches– Advanced cost modelling and uncertainty handling (Monte
Carlo)
– Plug-and-play telescope designs
– GUI for easy browsing and editing
Rosie Bolton, Cambridge University 4SKA System level trade-offsSKADS Final meeting, November 2009
Overview of the toolOverview of the tool
Graphical User Interface
Command-line Interface
Python Interface
Socket-based Interface
Costing/Performance Tool Engine
Telescope Design Data
Design blocks are stored in portable XML format.This could be extended into a full database including other information about components
The engine is written in Python
GUI is the easiest way for non-experts to interact with telescope designs and explore cost trade-offs
Rosie Bolton, Cambridge University 5SKA System level trade-offsSKADS Final meeting, November 2009
Hierarchical designs..Hierarchical designs..
Rosie Bolton, Cambridge University 6SKA System level trade-offsSKADS Final meeting, November 2009
Hierarchical designs..Hierarchical designs..
Rosie Bolton, Cambridge University 7SKA System level trade-offsSKADS Final meeting, November 2009
Hierarchical designsHierarchical designs……
Labour: cost per hour
Tarpaulin: cost per unit area
Wooden poles: cost per unit length
Air con unit: cost per item
Rosie Bolton, Cambridge University 8SKA System level trade-offsSKADS Final meeting, November 2009
Example: parameterised Example: parameterised designs.designs.
• Designs are parameterised – many inputs such as collecting area, number of stations, dish diameter etc.
• Tool supports “Parameter surveys” where successive telescopes can be built by varying one input parameter. This allows cost scaling to be investigated.
Rosie Bolton, Cambridge University 9SKA System level trade-offsSKADS Final meeting, November 2009
Processing boxes in AProcessing boxes in AAAlo stationlo station
Rosie Bolton, Cambridge University 10SKA System level trade-offsSKADS Final meeting, November 2009
Processing boxes in Processing boxes in AAloAAlo station station
• AA lo Station: integer number of processing boards per processing box. More boxes mean shorter analogue cables from antennas.
• “Wrong” number of boxes means inefficient use of processors, so more cost.
• Boxes themselves cost money.
• Example is for a 90m radius station with 1.5m spaced antennas.
Rosie Bolton, Cambridge University 11SKA System level trade-offsSKADS Final meeting, November 2009
Data link cost vs link length Data link cost vs link length (16Tbit/s link)(16Tbit/s link)
• Large data rate link costs from tool show the combine effect of distance break points for different technologies.
• These break have strong implications for cost savings if we change the layout of the Aperture Arrays
Change from short range to
mid range lasers
Introduction of first pre-
amplifiers
Change from short range to
mid range lasers
Introduction of first amplifiers
(80km)
Introduction second
amplifiers (160km)
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Impact of changing the distributionImpact of changing the distribution
• Does this matter? Yes. Look at the estimated costs for 250 AA station links, each with 16 Tbit/s. Vary Bmid – distance within which 95% of all stations are placed, cost implications of the order 100 Million EUR.
• 95% within 10km, very few stations out to 180km
• 95% within 100km, remainder out to 180km
Rosie Bolton, Cambridge University 13SKA System level trade-offsSKADS Final meeting, November 2009
Impact of changing the distributionImpact of changing the distribution
• Does this matter? Yes. Look at the estimated costs for 250 AA station links, each with 16 Tbit/s. Vary Bmid – distance within which 95% of all stations are placed, cost implications of the order 100 Million EUR.
• 95% within 10km, very few stations out to 180km: data links total estimate 60M Euros
• 95% within 100km, remainder out to 180km: data links total estimate 140M Euros
Rosie Bolton, Cambridge University 14SKA System level trade-offsSKADS Final meeting, November 2009
SummarySummary• The SKA cost/performance tool developed in SKADS and major
input from an international team – flexible format designs, extensible python code.
• Telescope designs can be investigated by unplugging one design block and replacing it with another.
• Parameterised designs allow the impact of varying any of the inputs to be assessed – with automated output.
• Currently the tool provides a useful starting point for visualising the overall system and making trade-offs.
• Future work must incorporate some more book-keeping e.g. basis of estimates for cost, improved power information.
• The information in the tool will fit naturally into a database, which will be essential as the SKA project moves forward.