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The Growth of Radio Astronomy with emphasis on the role of aperture synthesis

The Growth of Radio Astronomy with emphasis on the role of aperture synthesis. The Metre Wavelength Sky Celebrating 50 years of Radio Astronomy at TIFR & 10 years of GMRT at NCRA/GMRT Ron Ekers Pune , India 9 Dec 2013. Path. The beginning of radio astronomy Karl Jansky

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The Growth of Radio Astronomy with emphasis on the role of aperture synthesis

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  1. The Growth of Radio Astronomywith emphasis on the role of aperture synthesis The Metre Wavelength Sky Celebrating 50 years of Radio Astronomy at TIFR & 10 years of GMRT at NCRA/GMRT Ron Ekers Pune, India 9 Dec 2013

  2. Path • The beginning of radio astronomy • Karl Jansky • Grote Reber – non thermal (low frequency) emission • Evolution of Aperture synthesis • Radio Astronomy in India • Discovery of Quasars • Formation of the TIFR radio astronomy group • SKA The m-wavelength sky: R D Ekers

  3. A new kind of telescope opens a new window on the Universe using radio waves Bell Labsshowed little interest and Grote Reber said: “so faint not even interesting as a source of radio interference!” Not accepted by the astronomical community Jansky died in 1950 before the importance of his discovery was appreciated Karl JanskyBell Telephone Laboratory 1932 The m-wavelength sky: R D Ekers

  4. The Discovery of the Non-Thermal Universe • 1939: Grote Reber detected cosmic static by going to longerwavelengths • 3300 MHz • 900 MHz • 160 MHz • Radiation had to be non-thermal • No theoretical basis at the time • 1949 Anomalous solar emission • 1950 Synchrotron radiation theory • 10 years after Reber The m-wavelength sky: R D Ekers

  5. Strongest Radio Sources in Sky:Sun and Cygnus A • Solar emission 1940 • Multiple independent detections • Hey 1946 detects Cygnus A • source with variable intensity • time scale of seconds to minutes • must be small diameter • the first “radio star” • What was it? • no optical counterpart • was the whole galactic plane was made of such stars? • no theory linking diffuse galactic emission to cosmic rays The m-wavelength sky: R D Ekers

  6. Indirect imaging 1891: Michelson defines fringe visibility Gives the Fourier equations but doesn't call it a Fourier transform 1896: Stereo X-ray imaging 1912: X-ray diffraction in crystals 1930: van Cittert-Zernike theorem Now considered the basis of Fourier synthesis imaging Played no role in the early radio astronomy developments but appears in the literature after Born & Wolf Principles of Optics (1960) 1930-38: 3D X-ray tomography Analogue devices to do back projection summation The m-wavelength sky: R D Ekers

  7. X-ray Crystallography 1912 X-ray diffraction in crystals 1936 Lipson & Beeversstrips Fourier synthesis calculations routine in X-ray crystallography 1939 Bragg's X-ray crystallography group flourishing at the Cavendish Laboratory 2D Fourier analysis phase problem, The m-wavelength sky: R D Ekers 7

  8. Ratcliffe and PawseyCambridge and Sydney 1935 Pawsey PhD with Ratcliffe at Cambridge (ionosphere) Pawsey meets Bhabha at Cambridge. 1940 Pawsey joins CSIRO Radiophysics Laboratory in Sydney but maintains strong links with Ratcliffe in Cambridge 1945 Pawsey investigates radio emission from the sun 1946-1949 Pawsey introduces Bracewell to duality of physical and mathematical descriptions following Ratcliffe's style Bracewell sent from Sydney to work with Ratcliffe The m-wavelength sky: R D Ekers 8

  9. Ryle and the Cavendish 1945 Ryle joins Cavendish laboratory uses WWII radar technology for radio astronomy 1946 Ryle and Vonberg interferometric measurement of sunspots Nature 158, 339-340 (Aug 1946) introduces the use of a Michelson interferometer to measure the angular diameter of the source of the radiation and references Michelson The m-wavelength sky: R D Ekers 9

  10. Joe Pawsey and the Cliff interferometers Dover Heights, Australia 1952 The m-wavelength sky: R D Ekers 10

  11. McCready, Pawsey & Payne-Scott 1947 Proc Roy Soc, Aug 1947 - received July 1946! Used the phase of the sea interferometer fringes (lobes) to co-locate solar emission with sunspots They note that its possible in principal to determine the actual distribution by Fourier synthesis using the phase and amplitude at a range of height or wavelength. They consider using wavelength as a suitable variable as unwise since the solar bursts are likely to have frequency dependent structure. They note that getting a range of cliff height is clumsy and suggest a different interference method would be more practical. Ruby Payne-Scott Joe Pawsey 11

  12. Radio astronomers need more resolution • The Australian arrays • 1951 • Christiansen build the Potts Hill grating array • Near Sydney, Australia • 32 steerable paraboloids • 1953 • Chris Cross (Fleurs) • 1955 • First earth rotation synthesis • Christiansen and Warburton The m-wavelength sky: R D Ekers

  13. Fourier Transforms - 1953 Lipson-Beeversstrips 25x25 array to 2 digits 1 person in 24 hours Punched card tabulator 25x25 array to 3 digits in 8 hours (4 operators!) Peter Scheuer with Lipson Beaver strips The m-wavelength sky: R D Ekers 13

  14. Fourier synthesis imaging - 1954 Bracewell and Roberts: Arial smoothing introduces invisible distributions and the principal solution Scheuer: Theory of interferometer methods PhD chapter 5 (unpublished) Full analysis of Fourier synthesis including indeterminate structure Independent developments, but all acknowledge Ratcliffe’s lectures The m-wavelength sky: R D Ekers 14

  15. Christiansen and Warburtonfirst earth rotation synthesis (1955) Chris takes the 1D FT of each strip distribution & does a 2D Fourier synthesis using all strips The way in which a 2D radio brightness distribution may be derived from a number of 1D scans is not obvious. However rather similar 2D problems have arisen in crystallography and solutions for these problems, using methods of Fourier synthesis have been found. Reference to O'Brian (Cambridge) Swarup calculates the Fourier Transforms More than 1 month with electronic calculator The m-wavelength sky: R D Ekers 15

  16. Limb brightening observed Problem of correcting weights in back projections Christiansen and Warburton, Aust J Phys 8, 474 (1955) First earth rotation aperture synthesis imageThe Sun at 21cm1955 The m-wavelength sky: R D Ekers

  17. Australia – India links • 1952 URSI Sydney, Australia • K.S. Krishnan (NPL) notes radio astronomy developments • 1953-1955 Swarup at CSIRO • Meets Bhabha who visits Pawsey • Calculations for the first earth rotation synthesis image • 1955 Potts Hill array of dishes sent to India • Not used for 10 years • 1956 Swarup joins Bracewell at Stanford • Invents the back projection correction • Published by Bracewell in 1967! • Major impact on medical imaging Potts Hill Australia Kalyan India The m-wavelength sky: R D Ekers

  18. First Cambridge Earth Rotation Synthesis Image June 1961 North pole survey 4C aerials 178 MHz 7 years after Christiansen Ryle & Neville, MNRAS 1962 The m-wavelength sky: R D Ekers 18

  19. Cambridge One-Mile Telescope: 1962 The m-wavelength sky: R D Ekers

  20. Nobel Prize 1974 Sir Martin Ryle from the presentation “The radio-astronomical instruments invented and developed by Martin Ryle, and utilized so successfully by him and his collaborators in their observations, have been one of the most important elements of the latest discoveries in Astrophysics.” The m-wavelength sky: R D Ekers

  21. Sydney, Australia 1948 Cliff Interferometer • Cliff interferometer CSIRO, Australia (1948) • Built to identify the radio stars (John Bolton) • Idea from multiple path interference in ship borne radar • Identified the Crab Nebula – key to understanding radio emission • Discovery of extragalactic radio sources at great distances • Centaurus A , Virgo A, Cygnus A, FornaxA The m-wavelength sky: R D Ekers

  22. Centaurus A The m-wavelength sky: R D Ekers

  23. Radio Galaxies • All |b| > 10o radio sources are galaxies (radio galaxies) • 1954: Cygnus A z=0.06 (Baade and Minkowski, ApJ119, 206) • 1955 to 1960: Many new radio galaxies identified • All with very bright elliptical galaxies (often peculiar) • Colliding galaxy theory • Try for smaller radio sources – they will be further away AAS Long Beach

  24. 50th Anniversary of the Discovery of Quasars Mt Palomar 200” The m-wavelength sky: R D Ekers

  25. ParkesRadio Telescope Lunar occultation of a radio source time disappearance and reappearance Credit: Seth Shostack The m-wavelength sky: R D Ekers

  26. 3C 273 identification Cyril Hazard Parkes lunar occultation The m-wavelength sky: R D Ekers

  27. Striking difference in radio spectra Component A S = -0.9 Component B S = 0.0 3C273 Parkes Occultation 1962

  28. 3C273VLA 5GHz 1998

  29. 3C273Optical HST

  30. Dec 1963 - First Texas Symposium on Relativistic Astrophysics • Only gravity of a massive object in the nucleus of a galaxy could provide the energy • Fred Hoyle • relativists with their sophisticated work were not only magnificent cultural ornaments but might actually be useful to science! • The University of Chicago Press, 1965 The m-wavelength sky: R D Ekers

  31. The Nuclei of Galaxies • 1943: Carl Seyfert (Clevland, Ohio) • Enhanced activity in the nuclei of 6 extragalactic nebulae • 3 citations in first 16 years! • 1958: Viktor Ambartsumian (Armenia) • Championed the role of the galaxy nuclei • 1961: Vitaly Ginzburg (Russia) • Showed that gravitational energy could power a radio galaxy The m-wavelength sky: R D Ekers

  32. Nobel Prize 1983 Subrahmanyan Chandrasekhar • for his theoretical studies of the physical processes of importance to the structure and evolution of the stars • White dwarfs, neutron stars, relativistic effects… • For the heaviest stars having a mass in excess of 2-3 Solar masses, the force of gravity becomes so strong that the matter simply disappears in the form of a so-called black hole. The m-wavelength sky: R D Ekers

  33. Radio Astronomy at TIFR • 1963 HomiBhabha (TIFR) forms a radio astronomy group in India • Expats return: Swarup, Menon, Kundu, T.Krishnan • Swarup proposes an equatorially mounted cylinder to do fainter occultations 3C273 impact • Ooty operational 1970 • Ooty synthesis telescope 1984 The m-wavelength sky: R D Ekers

  34. Even bigger visions • 1971 Radhakrishnan starts a new radio group at RRI • Big ideas rather than big facilities • 1976 GovindSwarup’s Giant Equatorial Radio Telescope (GERT) • India, Kenya, Nigeria, Indonesia • Too hard but laying foundations for SKA • 1982 GMRT concept The m-wavelength sky: R D Ekers

  35. VLA New Mexico 1980 The m-wavelength sky: R D Ekers

  36. Giant Metre-wave Radio TelescopeGMRT completed 2000 The m-wavelength sky: R D Ekers

  37. Giant Metre-wave Radio TelescopeGMRT logo Vijay Kapahi The m-wavelength sky: R D Ekers

  38. Giant Metre-wave Radio TelescopeGMRT logo Vijay Kapahi The m-wavelength sky: R D Ekers

  39. Giant Metre-wave Radio TelescopeGMRT logo Vijay Kapahi The m-wavelength sky: R D Ekers

  40. Giant Metre-wave Radio TelescopeGMRT logo Vijay Kapahi The m-wavelength sky: R D Ekers

  41. Giant Metre-wave Radio TelescopeGMRT logo Vijay Kapahi The m-wavelength sky: R D Ekers

  42. 1971 Cyclops 1986-9 Canadian proposal for Radio Schmidt Peter Dewdney 100x12m antennas 1988-1990 Dutch extragalactic HI telescope Robert Braun, Ger DeBrujn and Jan Noordam 1988-1991 Swarup proposals International Radio Astronomy telescope (ITRA) 160 75m dishes, centrally concentrated and baselines to 200km 1990 URSI General Lecture Prague exponential growth and discovery arguments SKA beginnings

  43. Radio Telescope Sensitivity

  44. Exponential Growth • Livingstone Curve • Blewett, Brookhaven 1950 • Fermi 1954 • Livingstone 1962 • Envelope is exponential • Each technology saturates The m-wavelength sky: R D Ekers

  45. The Original Moore’s Law Plot • In 1965 Gordon Moore (co-founder of Intel) noted that the transistor density of semiconductor chips doubled roughly every 18 months. Extrapolation accurate for another 35 years! The m-wavelength sky: R D Ekers

  46. Moore’s Law Intel 2000 Microprocessor performance The m-wavelength sky: R D Ekers

  47. Self Calibration • 1958: Phase and amplitude closure • Jennison (Jodrell Bank) • 1977: Redundant spacing interferometry • Hamaker , O’Sullivan, Noordam (Westerbork) • 1974-79: Phase closure in VLBI imaging • Rogers, Yee, Readhead, Cotton…. • 1980: Antenna based calibration • Clark, Schwab (VLA) • 1983: Self cal ≡ phase closure ≡ adaptive optics • Cornwell The m-wavelength sky: R D Ekers

  48. SKA 2020? The m-wavelength sky: R D Ekers 48

  49. SKA Science The First Stars Cosmic Evolution Cosmic Magnetism Gravitational Physics Origins of Life The m-wavelength sky: R D Ekers

  50. Conclusion The excitement of these powerful new instruments is not in the old questions they will answer but in the new questions they will raise. The m-wavelength sky: R D Ekers

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