Radio Astronomy Module

Home , Bernard Lovell, Grote Reber, Jansky, Very Large Array, Very Long Baseline Array

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 Station First 10% (phase 1) will have max baselines ~50 km

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: Photographs by: Robert Slinsby Robert Slinsby