Radio Astronomy module Contact tony@ska.ac.za Notes: NRAO Essential radio astronomy course: http://www.cv.nrao.edu/course/astr534/era.shtml See also http://www.haystack.mit.edu/ edu/undergrad/materials/ra_tutorial.html
Radio Astronomy: Past and Future
Outline The discovery of radio emission from the sky Early instruments SKA South Africa's role in the SKA meerkat XDM KAT-7
Prehistory of RA Oliver Lodge and Nikolai Tesla atttempted to detect signals from the Sun Too much interference Too little sensitivity
The 1920's -1930's Bell Telephone initiates a shortwave transatlantic service Communications are disrupted by static Karl Jansky tasked to determine its orgin: Mostly tropical thunderstorms Steady hiss that rose and fell daily with a period of 23:56 Direction of Galactic centre strongest source Proposal for another antenna and further study rejected and he was reassigned
Karl Jansky
Jansky's 'merry-go-round' 20.5 MHz 100 ft diameter Rotated manually on a set of 4 Ford Model-T tires
Grote Reber (1930's) Learned about Jansky's discovery and wanted to follow up Couldn't get a job at Bell labs or observatories because of the Great Depression So he decided to study on his own
Grote Reber Built telescope at his own expense in his backyard 31.4 ft diameter (~9m)
Grote Reber Worked at night because of interference from car engines 3300 MHz, failed to detect anything 900 MHz, failed 160 MHz, successful in 1938
Grote Reber's recordings 1943
First radio map of the galaxy
Grote Reber (9m)
WWII Radar Delevopment James Hey, Bernard Lovell, Tony Hewish, Martin Ryle, More sensitivity Bigger dishes, some left over
Post-war boom Australia: John Bolton early interferometry using signals bounced off the ocean England: 1940s Jodrell Bank Holland: 1940s - Dwingeloo telescope USA: 1950s John Kraus develops microwave telescopes
Dover Heights, Sydney 1946-'54
Sea interferometry
Cygnus A with sea interferometer Interference fringes enabled calculation that angular size < 8 arcmin
Hole in the ground antenna
Sag A mapped by HITG
Jodrell Bank Lovell Mk1 1957
Parkes (64 m)
Effelsberg (100m)
Aricebo (300m)
GBT (110m)
Westerbork
The Very Large Array compact configuration
The Very Long Baseline Array
How does VLBI work?
ALMA
The Square Kilometre Array Collecting area 1km2 Use innovative technologies to keep cost down Site bid SA ( mid and higher frequency) and Australia (low frequency) Pathfinders meerkat, ASKAP, LOFAR, ATA
SKA key science Tests of general relativity using pulsars & black holes Evolution of galaxies, cosmology, dark matter and dark energy Probing the dark ages the first stars Cradle of life searching for life and planets The origin and evolution of cosmic magnetism Unknown serendipitous discoveries
History of the universe
SKA Reference Design >3000 km Central 5 km All-sky monitor Not to scale digital radio camera Radio camera SKA will be built out from the centre First 10% (phase 1) will have max baselines ~50 km Station
LOFAR < 250 MHz IT telescope Simple antennas but 25000 in full design Clusters over an area of 350 km diameter 15000 funded out to 100 km spread Correlated on BlueGene computer in Groningen
LOFAR science Epoch of reionisation Deep extragalactic surveys Transient sources Ultra-high energy cosmic rays Pulsars
LOFAR
Allen Telescope Array
Radio Astronomy in South Africa
www.ska.ac.za www.kat.ac.za www.hartrao.ac.za
MeerKAT Technology Low-cost dishes Wide-band feeds and receivers Digital signal processing Calibration and imaging High-performance computing Operations and logistics
meerkat development stages Experimental Design model (XDM) KAT-7 MeerKAT Precursor Array meerkat
The experimental Design Model (XDM) Primarily test of construction method 15 m az-el Fibre-glass/resin composite with flame-sprayed aluminium surface http://www.hartrao.ac.za/xdm/
The Karoo Array Telescope aka KAT-7 meerkat
KAT-7 12 m dishes L band 256 MHz bw
KAT-7 layout
KAT-7 as part of meerkat?
meerkat ~ 64 dishes Lowest frequency ~ 700 MHz Upper frequency? 15 Ghz in later stage? Dish size? Dish design? Base of operations (somewhere in Cape Town)
Photographs by: Robert Slinsby Photographs by: Robert Slinsby