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The SKA Molonglo Prototype (SKAMP) Project Molonglo 40th Anniversary, November 2005

The SKA Molonglo Prototype (SKAMP) Project Molonglo 40th Anniversary, November 2005. SKA Molonglo Prototype Project (SKAMP). A new low-frequency spectral line instrument. Funded by the ARC, the Science Foundation and the Major National Research Facilities Program.

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The SKA Molonglo Prototype (SKAMP) Project Molonglo 40th Anniversary, November 2005

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  1. TheSKAMolongloPrototype(SKAMP)ProjectMolonglo 40th Anniversary,November2005

  2. SKA Molonglo Prototype Project (SKAMP) • A new low-frequency spectral line instrument. • Funded by the ARC, the Science Foundation and the Major National Research Facilities Program. • Project Goal: complete signal pathway – 2:1 dual polarisation line feed; room temperature electronics; wideband digital signal processing; FX correlator. • Features: wide field of view, imaging, polarisation, spectral line capability, RFI mitigation (adaptive noise cancellation). • Strategy: parallel 3-stage re-development of MOST • Science & technology prototyping for the Square Kilometre Array (SKA) – 1% collecting area, wide-field imaging.

  3. What is the SKA? • Next generation radio telescope – 100 times improvement in many parameters. • Global collaboration. • Proposed Australian site in Mileura, WA. • Operational 2020. • 6 Key science projects.

  4. Anne Green Duncan Campbell-Wilson Adrian Blake Ludi de Souza Tim Adams Martin Leung Sergey Vinogradov Daniel Mitchell Elaine Sadler 3 site Technical Officers Michael Kesteven Tony Sweetnam John Bunton Frank Briggs John Kot Bevan Jones Martin Owen Peter Liversidge SKAMP Team CSIRO – ATNF & ICT University of Sydney Argus Technologies

  5. Current Parameters for MOST • Single frequency - 843 MHz continuum • 3 MHz bandwidth, RHC polarisation • 43" spatial resolution • 18,000 sq metres collecting area • Tsys 55K • Field of view: >5 square degrees • Sensitivity (7 position switching): 0.8 mJy • Sensitivity for full 12 hr: 0.3 mJy • Dynamic range: ~200:1

  6. SKAMP 1 (2004 – 2005) • Continuum correlator: 96 station, 4.4 MHz bandwidth, 843 MHz central frequency – > 4000 independent baselines, data rate 1sec • Sensitivity 0.8 mJy (12 hrs for complete synthesis; 7-position switching to gain wide field of view) • Continuous uv-coverage – correlation of inter-arm & between-arm stations to give good image fidelity • Programmable logic chips - FPGAs

  7. Tim Adams & John Bunton

  8. Continuum correlator • 96 independent stations: 88 telescope bays + 2 reference antennas • Signal pathway complete - commissioning at site • Drift scan on sun – first light

  9. SKAMP 2 (2005 – 2006) • Spectral-line capability: 830 - 860 MHz with 2048 channels via FX correlator. • Existing front end retained – 96 stations; full correlation of all stations is highly redundant • Unchanged Tsys and angular resolution • Optic fibre distribution network designed – trenching and conduit completed • Field of view roughly 4 square degrees • Sensitivity for 12 hrs observation: 0.15 mJy • Confusion limit of 0.12 mJy for 43" resolution • Spectral line measurements not confusion limited

  10. 50 30 40 30 15 20 10 0 0 Wide-band uncooled Low Noise Amplifiers Prototype 300-1000 MHz HEMT based LNA (Ralph Davison) • ~20K noise temperature • Ambient temperature operation • Possible extension to operate 300-1400 MHz • Design simplified if higher input impedance tolerated (50Ω input impedance design now) • Mass production (8000 units) requires simple assembly design Gain Noise Temperature (K) Gain (dB) Noise Temperature 300 650 Frequency (MHz) 1000

  11. x focus Molonglo segmented parabola design gives good performance to ~2 GHz Piecewise linear fit to parabola shape Flat mesh tied on supports at points shown • Mesh supported at 0.6 m (2 ft) intervals in x direction. • Each section gives the same error for a linear fit to a parabola. • 0.1 dB loss at 1420 MHz. • f/D = 0.25

  12. Simulations to test surface approximation S. Vinogradov

  13. SKAMP 3 (2006 – 2007) • Dual polarisation feed module – under range test. Next stage to mount on Rapid Prototype Telescope (RPT). Baseline ripples to be measured. • First feed prototype 700 – 1100 MHz. Instantaneous bandwidth 100 MHz. • Once prototype approved, construct feeds for complete RPT. • Stage 1 RF beamformer – switched delay lines, design set by maximum frequency, ~3l length, 100 phase step gives sufficient accuracy. Stage 2 beamforming also in feedline. • New mesh will reduce leakage to give Tsys of 40K. • 12 hr sensitivity at 843 MHz ~0.1 mJy. Confused! • Polarisation not confusion limited (assume 5% mean source value).

  14. Wideband feed prototype module • 8-element module, 1.4 m length • Wide-band dipoles – no moving parts • Polarisation axes oriented along & across axis of feed – better performance than dual-slant feeds • Range tested for 700 -1000 MHz Leung

  15. Beam & radiation patterns • Beam pattern – first sidelobe -12dB; cross polarisation -30dB at meridian, worst at high scan angle, up to -12dB • Scanning gain curve – flat to ±45°; cross polarisation -25dB or better • Transverse illumination pattern – HPBW 80°; cross polarisation worst at high scan angle, about -15dB Figures show beam patterns and scanning gain variation for the two polarisations, transverse and longitudinal

  16. Rapid Prototype Telescope (RPT) Visit by South African team • Double mesh trial – reduce leakage • Predict improve Tsys to 40K • Construction of a 17m bay to test feeds in realistic environment

  17. RFI at Molonglo 200-1500 MHz (Measured 25 June 2001) UHF TV VHF TV GSM

  18. RFI measurements in the fieldat Dept of Defence HQ site Campbell-Wilson, Briggs, Mitchell

  19. Dual feed system for 6-m Reference Antenna for adaptive noise cancellation

  20. A further extension: uv-coverage with additional stations on NS baselines?? • Good image fidelity in 6 hours • Small reduction in sensitivity • Double survey speed • Model for 5 additional stations • (Bunton 2005)

  21. Key science goals • Blind survey of HI absorption in high redshift galaxies – initially z~0.7, extend later. Test of mass-assembly of galaxies predictions from CDM scenario. • HI in emission – measure mass function directly. Redshift range z = 0.17 – 0.3. Challenging. • Cosmic magnetism studies – measure diffuse Galactic polarisation and a RM grid from many extragalactic sightlines. • High redshift galaxies found as USS sources.

  22. beam size: 112” x 112” csc|d| Rengelink et al 1997 WENSS 325 MHz beam size: 43” x 43” csc|d| beam size: 26” x 26” csc|d| Bock et al 1999 SUMSS 843 MHz Wall 1994 1420 MHz Molonglo continuum confusion (10 beams/source) at δ= -60°

  23. High image fidelity results from gooduv-coverage

  24. High-dynamic range continuum imaging StageI correlator will allow self-calibration strategies for MOST Current MOST imaging dynamic range is 100-200:1 (similar to intrinsic dynamic range of VLA) Self-calibration on VLA enables imaging dynamic ranges of more than 105:1 (MGPS Green et. al.) Current dynamic range of MOST limits imaging of faint sources, such as filaments of supernova remnants, near bright sources like the Galactic Centre.

  25. 1. Blind HI-absorption survey • New spectral line capability • Measurements of HI absorption at z ~ 0.75 that capitalise on the large collecting area of MOST • >10,000 sightlines to search for HI absorption – expect to detect ~50 sources in limited • redshift range in 2400 sq deg • Few detections – eg Darling et al. (2004) of galaxy z=0.78 in front of z=1.992 quasar. (Lane 2000) Stage 2: enables ΩHI measurements at z ~ 0.75, where existing results are not well constrained (Lane and Briggs 2001)

  26. When & how is HI assembled into galaxies? (Baugh et al 2004) Data-free zone

  27. 2. High-redshift HI emission in galaxies HIPASS (500s) (12 h) Molonglo (10x12 h) log10 Mlim (HI) (M⊙) Typical bright spiral HI in the nearby Circinus galaxy (Jones et al. 1999) The Molonglo telescope will reach HI mass limits typical of bright spiral galaxies at z=0.2 (lookback time ~3 Gyr), allowing a direct measurement of evolution in the HI mass function. Challenging project.

  28. 3. Cosmic Magnetism Magnetism is crucial for : • cloud collapse / star formation • stellar activity / stellar outflows • ISM turbulence / gas motions • supernova remnants • stability of galactic disks • acceleration / propagation / • confinement of cosmic rays • heating in galaxy clusters • AGNs / Jets MHD turbulence Proplyd in Orion Merger in gal. cluster SN 1006 Magnetism is one of the fundamental forces in Nature, but its role and origin is largely unknown !

  29. Rotation Measure Grid • Probes magnetic fields in galaxies, the Milky Way & clusters • Rotation measure grid of background sources and polarisation of the diffuse Galactic field 300 RMs through the LMC (Gaensler et al 2004)

  30. 4. High-redshift radio galaxies from spectral studies, if lower frequency range implemented Radio spectral index measurements over the range 300 –1400 MHz are an efficient way of selecting high-redshift (z>3) radio galaxies (e.g. de Breuck et al. 2000, 2004). Radio galaxy TN0924-2201 at z=5.19(van Breugel et al. 1999)

  31. Summary of SKAMP Project status • 96-station continuum correlator being commissioned – first light. (SKAMP 1) • Optic fibre network conduit laid, fibre on order; spectral-line correlator designed and being built, calibration & image processing software being planned. (SKAMP 2) • 8-element module of prototype feed under test; RPT nearing mechanical completion; RF beamformers in design. (SKAMP 3) • Simulated performance - sensitivity 0.12 mJy for 12 hour observation – for 43” resolution, data are confusion limited for continuum images but not for spectroscopy or polarimetry

  32. A new lease on life for a mature instrument

  33. First Fringes – single baseline & interim correlator Team: Green Campbell-Wilson Kesteven Bunton Adams *Leung Blake *Chippendale Vinogradov *Mitchell Briggs Sweetnam Sadler

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