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. 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.

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

SKAMP Team SKAMP Team 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 University of Sydney CSIRO – ATNF & ICT Argus Technologies

Current Parameters for MOST Current Parameters for MOST Single frequency MHz continuum 3 MHz bandwidth, RHC polarisation 43" spatial resolution 18,000 sq metres collecting area T sys 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

SKAMP 1 (2004 – 2005) 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

Tim Adams & John Bunton

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

SKAMP 2 (2005 – 2006) SKAMP 2 (2005 – 2006) Spectral-line capability: 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

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

x focus Molonglo segmented parabola design gives good performance to ~2 GHz 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 Piecewise linear fit to parabola shape

Simulations to test surface approximation S. Vinogradov

SKAMP 3 (2006 – 2007) 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, ~3  length, 10 0 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).

Wideband feed prototype module 1.8-element module, 1.4 m length 2.Wide-band dipoles – no moving parts 3.Polarisation axes oriented along & across axis of feed – better performance than dual-slant feeds 4.Range tested for MHz Leung

Beam & radiation patterns 1.Beam pattern – first sidelobe - 12dB; cross polarisation -30dB at meridian, worst at high scan angle, up to -12dB 2.Scanning gain curve – flat to ±45°; cross polarisation -25dB or better 3.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

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

RFI at Molonglo MHz (Measured 25 June 2001) GSM VHF TV UHF TV

RFI measurements in the field at Dept of Defence HQ site Campbell-Wilson, Briggs, Mitchell

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

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)

Key science goals 1. 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. 2. HI in emission – measure mass function directly. Redshift range z = 0.17 – 0.3. Challenging. 3. Cosmic magnetism studies – measure diffuse Galactic polarisation and a RM grid from many extragalactic sightlines. 4. High redshift galaxies found as USS sources.

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

High image fidelity results from good uv-coverage

High-dynamic range continuum imaging StageI correlator will allow self-calibration strategies for MOST Current MOST imaging dynamic range is :1 (similar to intrinsic dynamic range of VLA) Self-calibration on VLA enables imaging dynamic ranges of more than 10 5 :1 Current dynamic range of MOST limits imaging of faint sources, such as filaments of supernova remnants, near bright sources like the Galactic Centre. (MGPS Green et. al.)

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. Stage 2: enables Ω HI measurements at z ~ 0.75, where existing results are not well constrained (Lane 2000) (Lane and Briggs 2001)

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

2. High-redshift HI emission in galaxies 2. High-redshift HI emission in galaxies HIPASS (500s) Molonglo (10x12 h) (12 h) log 10 M lim (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.

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

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)

4. High-redshift radio galaxies from spectral studies, if lower frequency range implemented 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 TN at z=5.19 (van Breugel et al. 1999)

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

A new lease on life for a mature instrument

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