1 / 18

Antennas for MeerKAT

Antennas for MeerKAT. 13-14 March 2008. 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). MeerKAT Antenna Team. Antenna Pedestal & reflector Subcontracted to industry

marinel
Télécharger la présentation

Antennas for MeerKAT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Antennas for MeerKAT 13-14 March 2008

  2. 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. 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. MeerKAT Intention • South African funds (~ $100 x 106) • 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. MeerKAT & KAT-7 Site • Carnavon, Northern Cape, South Africa

  6. MeerKAT & KAT-7 Site

  7. 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. 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. 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. 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. KAT-7: Surface Tolerance

  12. 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 possiblebeam widths

  13. KAT-7: Status • F/D Study • Look at different system temperatures • Optimise Ae / Tsys • F/D = 0.38

  14. 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. KAT-7: Status • Horn • Pattern almost 1 to 2 GHz • Match 1.2 to 2 GHz (without OMT)

  16. KAT-7: Status

  17. KAT-7: Status • Other engineering work for 2008… • OMT development • Cryo-cooling • He versus LN2 choice • Development • Cryostat development • Cool-box development • Calibration Signal Injection • LNA choice

More Related