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Antennas for MeerKAT 13-14 March 2008. TDP AWG, 13-14/3/08, San Francisco MeerKAT Semantics K.A.T. = Karoo Array Telescope –KAT is Afrikaans for cat –MeerKAT:

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Presentation on theme: "Antennas for MeerKAT 13-14 March 2008. TDP AWG, 13-14/3/08, San Francisco MeerKAT Semantics K.A.T. = Karoo Array Telescope –KAT is Afrikaans for cat –MeerKAT:"— Presentation transcript:

1 Antennas for MeerKAT March 2008

2 TDP AWG, 13-14/3/08, San Francisco MeerKAT Semantics K.A.T. = Karoo Array Telescope –KAT is Afrikaans for cat –MeerKAT: Afrikaans for “more cats”, also a small furry animal (from the mongoose family)

3 TDP AWG, 13-14/3/08, San Francisco MeerKAT Antenna Team Antenna –Pedestal & reflector Subcontracted to industry Managed by Willem Esterhuyse –Feeds Subcontracted to industry (EMSS Antennas) Managed by LJ du Toit Close interaction with RF & Reflector –RF Subcontracted to industry Managed by Venkat Lakshmanan

4 TDP AWG, 13-14/3/08, San Francisco MeerKAT Intention South African funds (~ $100 x 10 6 ) –Funded by Dept. of Science & Technology –Administered by National Research Foundation –To be built irrespective of SKA site allocation –Must be respectable instrument, not just good –Must be of relevance to SKA –N ~ 80 –D ~ 12m –Full instrument first light Q4, 2012

5 TDP AWG, 13-14/3/08, San Francisco MeerKAT & KAT-7 Site Carnavon, Northern Cape, South Africa

6 TDP AWG, 13-14/3/08, San Francisco MeerKAT & KAT-7 Site

7 TDP AWG, 13-14/3/08, San Francisco MeerKAT Phased Implementation XDM: Q4, 2005 to Q4, 2007 –Almost a done deal KAT-7: Q1, 2008 to Q4, 2009 –This year and next MeerKAT: Q1, 2008 to Q4, 2012 –This year, up to 2012

8 TDP AWG, 13-14/3/08, San Francisco XDM: Q4, 2005 to Q4, 2007 Single dish prototype at Hartebeesthoek, outside Pretoria Composite surface, concrete pedestal, metal support structure Antenna structure & surface R&D, manufacturing by IST Dynamics Diameter 15m, F = 7.5m (F/D = 0.5) El over Az, feed rotator (1.5m diameter disk) Prime-focus fed (four large metal struts) Frequency band: 1414 to 1670 MHz Stepped-horn & stepped-ridge OMT (EMSS), un-cooled Feed cluster: Seven non-overlapping beams (two populated) Two linear polarizations, analogue RF over fiber (COTS) Thermally stabilized COTS LNAs Prototyping test-bed, not a science instrument Used to set up synergy amongst engineering team System Engineering busy evaluating performance

9 TDP AWG, 13-14/3/08, San Francisco KAT-7: Q1, 2008 to Q4, 2009 Seven antenna interferometer, on proposed SKA site First-light scheduled to be Q3, 2009 Limited science instrument, and interferometer test-bed Although small, must be respectable instrument, prototyping errors to be avoided first time around Composite surface, concrete pedestal, metal support structure Antenna structure & surface: Tenders to go out within weeks Diameter 12m, F = 4.56m (F/D = 0.38, optimized for horn & WBF at prime focus El over Az, single-pixel feed, no field rotator Frequency band: 1200 to 2000 MHz (dish tolerances allow >2GHz) Wide flare-angle corrugated horn (four metal struts) Cryogenically cooled OMT & Receiver (probably Sterling) Two linear polarizations, analogue RF over fiber (COTS) Will allow evaluation of remote instrument logistics

10 TDP AWG, 13-14/3/08, San Francisco MeerKAT: Q1, 2008 to Q4, 2012 N ~ 80 interferometer on proposed SKA site Probable topology: Similar to KAT-7 –Unless dynamic range requirements dictate otherwise –Unless wide-band feed require different F/D –Unless upper frequency too high Dynamic Range Considerations –N > 80 to be considered –Main beam stability, sidelobe and polarization requirements? Offset? Offset and folded? Feed rotator required? Tightened mechanical tolerances?

11 TDP AWG, 13-14/3/08, San Francisco KAT-7: Surface Tolerance

12 TDP AWG, 13-14/3/08, San Francisco KAT-7: Status F/D Study –Time scales (dish construction ahead) –Accommodate MeerKAT (XDM was for FPAs) –No finished feed available Ying wide flare horn Parallel dipoles (radiating as log-periodic antennas) –Determine range of possible beam widths

13 TDP AWG, 13-14/3/08, San Francisco KAT-7: Status F/D Study –Look at different system temperatures –Optimise A e / T sys –F/D = 0.38

14 TDP AWG, 13-14/3/08, San Francisco KAT-7: Status Horn –Classic corrugated horn –Wide flare (prime focus) –Size → sub-reflector –J(x)/x distribution –Optimised on-dish Gain Spill over Still varying radius

15 TDP AWG, 13-14/3/08, San Francisco KAT-7: Status Horn –Pattern almost 1 to 2 GHz –Match 1.2 to 2 GHz (without OMT)

16 TDP AWG, 13-14/3/08, San Francisco KAT-7: Status

17 TDP AWG, 13-14/3/08, San Francisco KAT-7: Status Other engineering work for 2008… –OMT development –Cryo-cooling He versus LN 2 choice Development –Cryostat development –Cool-box development –Calibration Signal Injection –LNA choice

18 TDP AWG, 13-14/3/08, San Francisco


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