Sunelle Otto Hartebeesthoek Radio Astronomy Observatory (HartRAO) July 2011
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Transcript of Sunelle Otto Hartebeesthoek Radio Astronomy Observatory (HartRAO) July 2011
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Probing the field of Radio Astronomy with the SKA and the Hartebeesthoek
Radio Observatory:An Engineer’s perspective
Sunelle OttoHartebeesthoek Radio Astronomy
Observatory (HartRAO)
July 2011
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Outline
• Introduction• The Square Kilometre Array - Background, Pathfinders , Key Science Projects, System design
• Hartebeesthoek Radio Astronomy Observatory - Background, Research work
• Conclusion
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Introduction
• MSc (Electronic Engineering) at Stellenbosch University - thesis work on SKA
• Intern at HartRAO (Hartebeesthoek Radio Astronomy Observatory) - research work
Stellenbosch University
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Background• Square Kilometre Array (SKA) • largest, most sensitive radio telescope• thousands of small dishes and aperture arrays• total collecting area of 1 km²• South Africa vs. Australia• International project • smaller projects to assist in research• SKA pathfinders to demonstrate the technologies
The Square Kilometre Array
SKA configuration design
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Pathfinders• MeerKAT (South Africa)• Started with the XDM
(eXperimental Development Model)
• 15m diameter parabolic reflector dish
• 7 horn cluster feed• Located at HartRAO
The Square Kilometre Array
XDM antenna
7 horn feed
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Pathfinders• KAT-7 (Karoo Array Telescope)• Array of 7 parabolic reflector antennas each 12m in diameter• Wide-band single pixel feeds (WBSPFs)• Demonstrates working of an interferometer
The Square Kilometre Array
KAT-7
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Pathfinders• MeerKAT: final phase of KAT• 64 offset Gregorian antennas • 13.5m diameter• unblocked aperture• multiple receiver systems
The Square Kilometre Array
MeerKAT antenna design(credit: SKA fact sheet 1: MeerKAT, June 2011, www.ska.ac.za)
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Pathfinders• ASKAP (Australian Square
Kilometre Array Pathfinder)• Goal: 36 parabolic reflectors• each 12m diameter• Phased array feeds (PAFs)• Multiple beam formation
capability
The Square Kilometre Array
ASKAP
Phased Array Feed
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Pathfinders• EMBRACE (Electronic Multi Beam
Radio Astronomy Concept)• THEA (Thousand Element Array)• Dense Aperture Arrays • Vivaldi antennas
• LOFAR (Low Frequency Array)• Sparse Aperture Arrays• Dipole antennas
The Square Kilometre Array
Dense Aperture Array
Sparse Aperture Array
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Key Science Projects• Science observations requested by the radio astronomers, SKA drivers• The Cradle of Life
- terrestrial planet formation, molecular chemistry and the search for intelligent life
• Strong-Field Tests of Gravity using Pulsars and Black Holes - Pulsar search and timing, test relativistic gravity and detect gravitational waves
• The Origin and Evolution of Cosmic Magnetism - map the origin and evolution of magnetic fields• Galaxy Evolution, Cosmology and Dark Matter - study the cosmic evolution of HI (neutral hydrogen), dark energy and
dark matter• Probing the Dark Ages - study the epoch of reionisation (EoR)
The Square Kilometre Array
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System designThe Square Kilometre Array
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Hartebeesthoek Radio Astronomy Observatory (HartRAO)
Background• HartRAO is the only major radio astronomy observatory in Africa; KAT-7 is still in testing, MeerKAT in design phase• 26m radio telescope• Single dish observations• VLBI (very large baseline interferometry)
26 m Telescope at HartRAO
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Pointing model• Telescope needs to find and track sources accurately• Need good pointing model• Pointing scans for various sources• Data used to improve the pointing model
HartRAO – research work
Hour Angle pointing error vs HA Declination pointing error vs HA
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Rubidium and Hydrogen Maser clocks• Hydrogen Maser - frequency standard, accurate timing
• Rubidium clock, GPS10RB - Less accurate, corrects time by periodically comparing it with GPS (global positioning system) satellites
• Measure difference between : Maser and Rubidium clock times Maser and GPS clock times• performance of Rubidium
HartRAO – research work
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Rubidium and Hydrogen Maser clocks• slope in the graph : frequency drift of the Maser clock• Phase noise: due to GPS signal path variations through the atmosphere
HartRAO – research work
Rubidium vs Hydrogen maser GPS vs Hydrogen maser
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Rubidium and Hydrogen Maser clocks• 5min averages made, see how Rubidium follows the GPS• Look at frequency stability: Rubidium has short term stability, while GPS has long term
stability
HartRAO – research work
5min averages (Rubidium, GPS) Frequency stability (Rubidium, GPS)
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Building a 1.4GHz receiver• Receiver for a satellite TV antenna• 3m diameter• Testbed for demonstrating
practical radio astronomy at school and University level
• Cylindrical waveguide horn feed with choke ring
HartRAO – research work
3 m dish with 1.4 GHz receiver
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H₂0 Maser in Orion KL• Observations of H₂0 Masers in the Orion KL source region• 22GHz• March 2011 to present• Why? Flares occurred in 1984, 1998 • Flux density reached millions of Janskys
HartRAO – research work
Orion KL
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H₂0 Maser in Orion KL• Average spectrum• Flux Density: 80,000 Jy• compare with data from 2007 when maser was not flaring (light blue)
HartRAO – research work
Average spectrum (lcp and rcp added)
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H₂0 Maser in Orion KL• Time series plot at main peak velocities
HartRAO – research work
Time series plots (lcp)
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Conclusion
• The Square Kilometre Array - Pathfinders - Key Science Projects - System design
• Hartebeesthoek Radio Astronomy Observatory - Pointing model - Rubidium and Hydrogen Maser clocks - 1.4GHz receiver - H₂0 Maser in Orion KL
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Thank you!