Sunelle Otto Hartebeesthoek Radio Astronomy Observatory (HartRAO) July 2011

1. Probing the field of Radio Astronomy with the SKA and the Hartebeesthoek Radio Observatory:An Engineer’s perspective Sunelle Otto Hartebeesthoek Radio Astronomy Observatory (HartRAO) July 2011

2. Outline • Introduction • The Square Kilometre Array - Background, Pathfinders , Key Science Projects, System design • Hartebeesthoek Radio Astronomy Observatory - Background, Research work • Conclusion

3. Introduction • MSc (Electronic Engineering) at Stellenbosch University - thesis work on SKA • Intern at HartRAO (Hartebeesthoek Radio Astronomy Observatory) - research work Stellenbosch University

4. The Square Kilometre Array 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 SKA configuration design

5. The Square Kilometre Array Pathfinders • MeerKAT (South Africa) • Started with the XDM (eXperimental Development Model) • 15m diameter parabolic reflector dish • 7 horn cluster feed • Located at HartRAO XDM antenna 7 horn feed

6. The Square Kilometre Array 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 KAT-7

7. The Square Kilometre Array Pathfinders • MeerKAT: final phase of KAT • 64 offset Gregorian antennas • 13.5m diameter • unblocked aperture • multiple receiver systems MeerKAT antenna design (credit: SKA fact sheet 1: MeerKAT, June 2011, www.ska.ac.za)

8. The Square Kilometre Array Pathfinders • ASKAP (Australian Square Kilometre Array Pathfinder) • Goal: 36 parabolic reflectors • each 12m diameter • Phased array feeds (PAFs) • Multiple beam formation capability ASKAP Phased Array Feed

9. The Square Kilometre Array 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 Dense Aperture Array Sparse Aperture Array

10. The Square Kilometre 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)

11. The Square Kilometre Array System design

12. 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

13. HartRAO – research work 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 Hour Angle pointing error vs HA Declination pointing error vs HA

14. HartRAO – research work 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

15. 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 Rubidium vs Hydrogen maser GPS vs Hydrogen maser

16. HartRAO – research work 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 5min averages (Rubidium, GPS) Frequency stability (Rubidium, GPS)

17. HartRAO – research work 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 3 m dish with 1.4 GHz receiver

18. HartRAO – research work 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 Orion KL

19. HartRAO – research work H₂0 Maser in Orion KL • Average spectrum • Flux Density: 80,000 Jy • compare with data from 2007 when maser was not flaring (light blue) Average spectrum (lcp and rcp added)

20. HartRAO – research work H₂0 Maser in Orion KL • Time series plot at main peak velocities Time series plots (lcp)

21. 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

22. Thank you!