29 jan 2003 anita workshop - skamp & vo considerations - g. "Ñima" warr 1 the skamp...

29 Jan 2003 ANITA Workshop - SKAMP & VO Considerations - G. "Ñima" Warr 1

The SKAMP Project & Virtual Observatory Considerations


The SKAMP Project & Virtual Observatory Considerations

Outline:• SKA (Square Kilometre Array) overview• SKAMP (SKA Molonglo Prototype) Project

o Aims & Overviewo Status

• SKAMP VO Considerationso Data & data-pipeline


The SKA will be 100 times more sensitive than present radiotelescopes

VLA and Arecibowere such largeadvances that collecting areaunchanged for decades…

Need technologyshift to progress!


Probing the distant universe

HST VLA SKA

In the past few years, optical telescopes have begun to probe the ‘normal’ galaxy population to z~3


Proposed SKA Specifications (SKA Technical Workshop, 1997)

Frequency range 150 MHz – 20 GHz

I maging field of view 1 degree at 1.4 GHz

I nstantaneous beams 100

Angular resolution 0.1 arcsec at 1.4 GHz

Spectral channels 10,000

I mage dynamic range 106 at 1.4 GHz

Brightness sensitivity 1K at 1.4 GHz


SKA Design Considerations

• Large collecting area for high sensitivity (1 km2), 100x sensitivity of current VLA.

• Array elements (stations) distributed over a wide area for high resolution (needed to avoid confusion at very faint flux levels).

• For good uv plane coverage (especiallyfor HI observations), stations can’t be too sparse.

SKA will be an international US$1 billion project


US ATAUS ATA

Australia Australia Luneburg Luneburg LensesLenses

Dutch Dutch phased phased arrayarray

SKA antenna concepts

China China (Arecibo (Arecibo like)like)

Canada Canada Large Large reflectorreflector

Australia Australia cylindriccylindrical al paraboloparaboloidid


The Square Kilometre Array Molonglo Prototype (SKAMP)

1.6 km

12 m··· 44 antenna segments ··· ··· 44 antenna segments ···

············ ············

1 2 3 ················· 44 45 ························· 88

FX Correlator~90 Inputs

~4000 Baselines~2000 Frequency Channels

··············································

·····

··············································

·····

Interference Mitigation Antennas

89

90

Data Processing, Storage and Serving

Goal: To equip the Molonglo telescope with new feeds, low-noise amplifiers, digital filterbank and FX correlator with the joint aims of:

•developing and testing SKA-relevant technologies and

•providing a new capability for low-frequency radio astronomy in Australia


Team:

Anne Green1, Tim Adams1, John Bunton2, Duncan Campbell-Wilson1, Aaron Chippendale1,3, Bevan Jones4, Michael Kesteven3, Dimiter Nedialkov1, Andrew Parfitt2, Elaine Sadler1, George “Ñima” Warr1,3

[1] School of Physics, University of Sydney[2] Telecommunications and Industrial Physics, CSIRO[3] Australia Telescope National Facility, CSIRO[4] Argus Technologies

The Square Kilometre Array Molonglo Prototype (SKAMP)


SKAMP Funding

• $25,000 USyd Sesqui seed funding for SKAMP Stage I

• $1.7 million MNRF funding for components & technician for SKAMP Stage II & III

• $240,000 ARC Linkage Project for ultra-wideband linefeed for SKAMP Stage III

Awaiting outcome (late March ’03):• $192,000 ARC Linkage (CSIRO) 3-year

Post-Doctoral Fellow for Control & Pipeline system


From MOST to SKA Prototype

Current Survey (1997-2003):The Sydney University Molonglo Sky Survey (SUMSS), imaging the whole southern sky (δ < -30°) at 843 MHz to mJy sensitivity with 45” resolution (i.e. similar to NVSS). [843 MHz, 12hr synthesis, 2.7° diameter field]

Next: Use existing telescope as SKA testbed and science facility:• Frequency agility: 300-1420 MHz (250 MHz BW)• Multi-beaming (3 independent fanbeams)• 2048 Spectral channels, 4000 baselines• Continuous uv coverage• Wide field of view (1.5°-1420 MHz, 8°-300 MHz)

1.6 km

12 m··· 44 antenna segments ··· ··· 44 antenna segments ···

FX Correlator~90 Inputs

~4000 Baselines~2000 Frequency Channels

··················································· ···················································


From MOST to SKA PrototypeA three stage approach…

I. 2003 Narrowband continuum correlator (843 MHz, 4 MHz bandwidth, 88+8 stations = 4,560 baselines) [In parallel with SUMSS]

II. 2004 Increase bandwidth and add spectral capability (800-850 MHz, 4,560 baselines, 2,000 frequency channels) [Use existing linefeed]

III. 2006 New linefeed + enhanced correlator (300-1420 MHz, 250 MHz bandwidth, 4,560 baselines, 2,000 frequency channels)


Continuous uv coverage gives excellent image quality

Continuous uv coverage from 90 m to 1.6 km in 12hr synthesis

SKA will also have fully-sampled uv data

1.6 km

750 m

(Bock et al. 1999)


Stage I correlator will enable high-dynamic range imaging

MOST imaging dynamic range is 100-200:1 (similar to intrinsic dynamic range of VLA)

Use of self-calibration on VLA has enabled imaging dynamic ranges of 105-106:1

A correlator will allow use of self-calibration methods on MOST

Current imaging dynamic range of MOST limits imaging of faint sources (eg young supernova remnants) near bright sources

(eg Galactic Centre)

(MGPS Green et. al.)


Stage II FX correlator enables spectroscopic measurements

800-850 MHz 2,000 spectral channel FX correlator enables, eg:• Measurements of HI absorption at z = 0.7 to 0.8 that capitalise on the large collecting area of MOST• Measurements of the recombination lines of C and H enabling determination of constrains on the physical conditions in the ISM (Anantharamaiah & Kantharia 1999)

Stage II enables ΩHI measurements at z = 0.7 to 0.8,

where other methods are not well constrained

(Lane 2000)

(Lane and Briggs 2001)


Stage III Science Goals: 1. Radio galaxy spectral index

FX correlator: wide-band radio spectrometry

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).

Radio galaxy TN0924-2201 at

z=5.19 (van Breugel et al. 1999)


Stage III Science Goals: 2. High-redshift HI in galaxies

8

9

10

11

0 0.05 0.1 0.15 0.2 0.25 0.3

Redshift z

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.


Stage III Science Goals: 3. Other science projects

FX correlator (2048 channels, each 0.2–25 km/s)

Redshifted HI absorption (z=0 to 3)

OH megamasers

Galactic recombination lines (H,C) Pointing agility

Rapid response to GRBs

Independent fan beams

Monitoring programs (SETI, pulsars etc.)

Optional 64 fanbeams within main beam

Pulsar searches (high sensitivity, wide field of view)


SKA Molonglo Prototype Technologies

Multibeaming

Wide instantaneous field of view

Digital beamforming

Wide-band FX correlator (2,048 channels, 3,828 baselines) “Mega MOST” ~1 million frequency-image points on sky

Remote operationCollecting area 18,000 m2 ~= 1% of SKA (i.e. equivalent to 1 SKA station)

Frequency and pointing agility

Wide-band line feeds and LNAs

Cylindrical antenna prototype

Adaptive null steering and adaptive noise cancellation (RFI)


Status of SKAMP Stage I Continuum Correlator

• Conceptual design complete• Input intermediate-frequency signal tap and

SUMSS isolation circuit complete and in production• Digitiser, delay and fringe-stopping unit:

o Internal FPGA design 60% completeo Circuit board design 20% complete (ADC prototyped)

• Correlator:o Internal FPGA design 80% completeo Circuit board design 50% complete

• Work commenced on control & pipeline system


VO Considerations – SKAMP produces masses of raw data

Cylindrical Parabolic Collectors (Two collinear 778 m x 12 m)

300-1420 MHz Feed and LNA(7,400 feeds, 14,800 LNAs)

Delay line beamforming(Over 9 feeds)

Analog to Digital Converter(1,600 8 bit 250 MHz BW ADCs)

Digital delay beamforming(80 10 m x 10 m patches)

Digital filterbank (160)(Two polarisations @ 250 MHz/patch)

FX Correlator(3,160 baselines, 2,048 channels)

Signal processing & storage(imaging, spectrometer, searching...)

Independent fanbeams(3 within 9 feed field of view)

400 GB/s raw data rate = 17 PB/12 hr obs

52 MB/s for 1s correlator dump period = 2.2 TB/12 hr obs0.8 MB/s for 60s correlator dump period = 37 GB/12 hr obs

Interference mitigation for low-earth-orbit satellites may require 0.1s or faster correlator dumps.

500 MB/s per beam

SKAMP Stage I continuum correlator dumps 4,560 baselines per second for one (4 MHz wide) frequency band. SKAMP I gives 1.6 GB/12 hr observation.

SKAMP III


SKAMP Data Pipeline

• Intention is to create an automated data pipeline.• Stage I data to be stored in RP-FITS format utilising

modified ATNF software routines.• Initially MIRIAD will be used to invert the visibility

data into images for comparison with SUMSS images.

• Aaron Chippendale investigating high dynamic range imaging and use of AIPS++ routines to invert data.

• We will investigate implementing interference mitigation algorithms in the pipeline. Daniel Mitchell has done some preliminary calculations on the correlator dump time required for this.


The End

29 jan 2003 anita workshop - skamp & vo considerations - g. "Ñima" warr 1 the skamp...

Documents

skamp funding

skamp stage

project slide

george ima warr

australia slide

control pipeline system

molonglo telescope

arc linkage project