SKA – MID Sensitivity Mike Jones Jamie Leech Angela Taylor University of Oxford with data from Miroslav Pantaleev (Chalmers) Isak Theron (EMSS) Yang Wu (JLRAT)

Sensitivity Calculations Figures of Merit: Sensitivity: (A/T) Single-pointing mapping speed: (A/T)2 Survey mapping speed: (A/T)2W Calculate: Full optics simulation of feed+telescope Forward gain: A Coupling to environment: Tspill Receiver model: Trec A/(Tspill + Trec)

Band 1 and 2 – Trec

Band 1 and 2 – A/T per dish

Band 1 and 2 – A/T per dish Selected design

Band 1 – Cryogenic vs. Warm

Band 1 and 2: mapping speed Using these per dish sensitivities + accounting for differences in dish numbers (133 vs 64) and solid angles, get equivalent mapping speeds, (A/T)2, (A/T)2 W Band 2: SKA1 dishes = 2.9 – 3.2 MeerKATs (+ MeerKAT) = 3.9 – 4.2 MeerKATs total 15 – 17x MeerKAT (single pointing) 12 – 14x MeerKAT (survey) Band 1: SKA1 dishes = 1.5 – 2.3 MeerKATs (+ MeerKAT) = 2.5 – 3.3 MeerKATs total 6.25 – 11x MeerKAT (single pointing) 5 – 9x MeerKAT (survey)

SKA DISH Band 5 After the SKA rebaselining process Band 5 (4.6-13.7 GHz) was re-prioritized to second highest science priority (after Band 2). Key science goals include stellar debris disks, looking for the transition from dust to “rock” sized objects – the so-called “Cradle of Life” Oxford became involved in the first half of 2015, securing STFC funding for prototype band 5 receiver development in Sept 2015. SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

SKA DISH Band 5 frontend Rx SKA DISH is an offset Gregorian design, using shaped optics to improve aperture efficiency. The primary and secondary designs is now finalized, but the feedhorn design is still an open question, particularly at band 5 and band 1 which required a large bandwidth (band 5 is 4.6-13.7 GHz) i.e. 3:1 bandwidth ratio between top and bottom of band. SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

SKA DISH Band 5 Initial work – performance analysis of baseline design. This has led to: A draft SKA Engineering Change Proposal (ECP) to consider the advantages of splitting band 5 into two 1:1.85 bands, and use conventional corrugated feedhorns to improve the optical performance (beam circularity and cross-polarization) and importantly the sensitivity – via reduction in coupling to the ground via spillover and improvements in aperture efficiency. Using TICRA’s GRASP, a full physical optics modelling package. SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

SKA DISH Band 5 frontend Rx Baseline feedhorn design – a 3:1 Quad-ridge Feed Horn (QRFH) Currently in development by JLRAT, China. Also 5:1 feed versions for SKA band B under development by Chalmers. Development of good broadband quadridge feedhorn designs is still a major research area… A JLRAT QRFH prototype

SKA DISH Band 5 frontend Rx Possible alternative: cover the same band using two conventional 1.1.85 bandwidth corrugated feedhorns. Corrugated feedhorns are a widely used, well understood and mature technology in radio astronomy. Perform very well up to ~2:1 bandwidths. Band 5 (4.6 -13 .7 GHz) becomes two bands: 5a (4.6-8.4) 5b (8.4-13.7GHz). SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2 Example corrugated design for SKA band 2 (design courtesy of EMSS, Stellenbosch)

Bare horn pattern comparison JLRAT QRFH Chalmers Band B QRFH SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2 Scaled EMSS corrugated horns: Note: much higher beam circularity Lower sidelobes Much lower Cross-pol

Full optics beam comparison JLRAT QRFH Chalmers Band B QRFH SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2 Scaled EMSS corrugated horns: Note: Much lower Cross-pol

Band 5 – Cross-polarization SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

Aperture efficiency SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

SKA DISH Band 5: Trec SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

Tsys - Zenith SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

A/T - Zenith SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

Mapping Speed - Zenith SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

Mapping Speed – 60 degrees SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

Mapping Speed – JLVA compare Using these per dish sensitivities for the band 5 centre frequency of 9.2 GHz: Compare QRFH and split band corrugated horns for (1) Just SKA1 And (2) SKA1 + MeerKAT dishes equipped with as yet unfunded band 5 (or 5a/5b) receivers. Get equivalent mapping speeds, (A/T)2 in units of the JVLA mapping speed at this frequency: Baseline Single QRFH: SKA1 = 6.25x JLVA (single pointing), 17x JVLA (survey) SKA1 + (unfunded MeerKAT Rx) = 12.3x JVLA (single pointing), 34x JVLA (survey) ECP 2x Corrugated split band: SKA1 = 17.6x JLVA (single pointing), 49x JVLA (survey) SKA1 + (unfunded MeerKAT Rx) = 33.6x JLVA (single pointing), 93x JVLA (survey) SKA is in design phase – completing detailed design by 2017. 4 areas in Oxford: Software; SKA-LOW Digital signal processing and architecture; Dish receivers; Non-imaging processing (pulsars). Software – at OERC. Areas as listed Dishes – picture is a Gifford McMahon cold head! Aim is to reduce power consumption by a factor of a few for SKA1, order of magnitude for SKA2

Band 1 and 2 – A/T