1 / 36

RadioTelescopes – a field guide

Explore the fascinating world of radio telescopes with this detailed guide by M. Kesteven. Learn about conventional telescopes, imaging arrays, unconventional arrays, and the evolution of radio telescope technology. Discover how synthesis arrays work and the procedure behind correlating orthogonal fan beams for high-resolution imaging.

territhomas
Download Presentation

RadioTelescopes – a field guide

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. RadioTelescopes – a field guide M. Kesteven 24/September/2001

  2. Conventional telescopes • Main reflector; possibly a secondary • Focal plane • single-pixel camera • Fully-steerable

  3. Parkes 64m

  4. Effelsberg 100m

  5. Green Bank 100m

  6. Fixed Spherical Reflector • Large focal plane • “Steering” : probe the focal plane • Simplified mechanical structure

  7. Arecibo – 300m

  8. Nancay 200m x 40m

  9. Conventional Imaging Arrays • Multiplicity of antennas – multiplicity of baselines

  10. ATCA 6 x 22m 6 km baseline

  11. VLA (NRAO) 27 x 25m antennas Up to 36 km baseline

  12. VLBA (NRAO) 10 x 25m antennas

  13. 64 x 12m high precision antennas

  14. (one possible) SKA – N antennas; up to 3000 km baselines

  15. Unconventional arrays

  16. Molonglo (U. Syd) 1 mile x 40 ft. (843 MHz)

  17. Mauritius 2km and 1km arms (151 MHz)

  18. Evolution : Mills Cross -> VLA Linear array -> fan beam Correlation between orthogonal fan beams -> high resolution pencil beam = central pixel of the array’s synthesised image.

  19. Procedure: • Correlate the EW arm against the NS (multiply and average) • Since each source on the sky has its own noise signal, only • sources common to the two beams give a non-zero signal

  20. Relate to Synthesis Array : Mills Cross : The (u,v) plane :

  21. Mills Cross with multiple E-W beams

  22. Fully implemented Mills Cross : Given enough hardware, we could map a square patch of sky, each pointing defined by txEW andtyNS – we are doing the FT in hardware.

  23. Single Dish – equivalent to superimposed arrays. An incoming wavefront excites currents on the surface – these re-radiate, and combine in a phased way at the receiver.

  24. A correctly focussed antenna has constant path length for all rays from wavefront to the focus -

  25. Westerbork 14 x 25m antennas 2.7 km E-W baseline

  26. Parkes, 64m Effelsberg, 100m Green Bank, 100m

  27. Arecibo, 300m Nancay, 200x40m

  28. Parkes 64m

  29. Green Bank 100m

  30. Molonglo Synthesis Telescope : 2 East-West arms, each ½ mile long. Continuous tracking (part mechanical, part electrical, adjusting the delays). Equivalent to an East-West array (eg, ATCA).

More Related