Sunelle Otto Hartebeesthoek Radio Astronomy Observatory (HartRAO) July 2011
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Transcript of Sunelle Otto Hartebeesthoek Radio Astronomy Observatory (HartRAO) July 2011
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
Outline
• Introduction• The Square Kilometre Array - Background, Pathfinders , Key Science Projects, System design
• Hartebeesthoek Radio Astronomy Observatory - Background, Research work
• Conclusion
Introduction
• MSc (Electronic Engineering) at Stellenbosch University - thesis work on SKA
• Intern at HartRAO (Hartebeesthoek Radio Astronomy Observatory) - research work
Stellenbosch University
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
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
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
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)
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
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
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
System designThe Square Kilometre Array
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
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
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
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
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)
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
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
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)
H₂0 Maser in Orion KL• Time series plot at main peak velocities
HartRAO – research work
Time series plots (lcp)
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
Thank you!