One band or two?• See SKA Memo 140 for starting point in performance – cost analysis (70-450 MHz)

– No a priori advantages for either 1 or 2-band with current SKA goals– Particular specs and site/operations issues influence relative and absolute costings– Tweaks on original analysis: FoV, array configuration etc

• Processed FoV above ~200 MHz is a major relative cost driver, due b/f – With a “relaxed” FoV spec, 1-band array has cost advantage

• Deployment costs are a significant absolute cost driver for SKA-low– Huge number of elemental antennas demands optimized strategy– Worrying global indifference to Memo 140 absolute costs

• Very sparse array at 450 MHz may be a problem for 1-band calibration (sidelobes)– May just be OK at 400 MHz– Need information from pathfinders– Need to be able to pay the calibration power bill !

• Push for 50 MHz is growing but no-one wants to give up on high-freq (and some want >450 MHz)– We may need 2–bands anyway

• Frequency coverage and FoV are primary inputs for our design brief– Urgent need for science convergence– Active role needed for pathfinders to contribute pre-SRR info

SKA-low (LFAA) – Peter J Hall1