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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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ska molonglo prototype project skamp
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
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.
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

Argus Technologies

current parameters for most
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
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
continuum correlator
Continuum correlator
  • 96 independent stations: 88 telescope bays + 2 reference antennas
  • Signal pathway complete - commissioning at site
  • Drift scan on sun – first light
skamp 2 2005 2006
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
wide band uncooled low noise amplifiers










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


Noise Temperature (K)

Gain (dB)

Noise Temperature



Frequency (MHz)


molonglo segmented parabola design gives good performance to 2 ghz

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
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, ~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).
wideband feed prototype module
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


beam radiation patterns
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

rapid prototype telescope rpt
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
a further extension uv coverage with additional stations on ns baselines
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
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.
molonglo continuum confusion 10 beams source at 60

beam size:

112” x 112” csc|d|

Rengelink et al 1997


beam size:

43” x 43” csc|d|

beam size:

26” x 26” csc|d|

Bock et al 1999


Wall 1994

1420 MHz

Molonglo continuum confusion (10 beams/source) at δ= -60°
high dynamic range continuum imaging
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.

1 blind hi absorption survey
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)

when how is hi assembled into galaxies baugh et al 2004
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)

(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.

3 cosmic magnetism
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 !

rotation measure grid
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 TN0924-2201 at z=5.19(van Breugel et al. 1999)

summary of skamp project status
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
first fringes single baseline interim correlator
First Fringes – single baseline & interim correlator