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Lee Clement PHYS 2070 1 February, 2011. VLA & SKA. The Very Large Array (VLA). VLA – General Information. Radio observatory Located in New Mexico Operated by the National Radio Astronomy Observatory (NRAO) Part of the National Science Foundation (NSF) Construction began in 1973 - PowerPoint PPT Presentation
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Lee Clement
PHYS 2070
1 February, 2011
VLA – General Information Radio observatory Located in New Mexico Operated by the National Radio
Astronomy Observatory (NRAO) Part of the National Science
Foundation (NSF) Construction began in 1973
Completed in 1980 Cost USD $78,578,000
(NRAO, 2008)
Fictionalized version used in 1997 film Contact Also appears in various other films
Contact, 1997(Source: Wikimedia Commons)
VLA – Design Radio interferometer
27 antennae on tracks in a Y-shaped configuration
Each antenna is 25 m in diameter
Data is combined electronically○ Effective resolution of a
single 36 km diameter dish○ Effective sensitivity of a
130 m diameter dish(NRAO, 2008)
Layout of the VLA(Source: NRAO)
VLA Antenna(Source: Wikimedia Commons)
VLA – Design Aperture size
Four array configurations○ Biggest: 36 km across○ Smallest: 1 km across○ Rotates between them every
4 months
Wavelengths400 cm – 7 mm
○ Short wave radio to Microwaves
(NRAO, 2008)
VLA
VLA Observable Wavelengths(Adapted from Wikimedia Commons)
VLA – Design Field of View (Chandler, 2009)
Depends on antenna configuration and wavelength○ 1.3” at tightest configuration
and shortest wavelength○ 5.6° at loosest configuration
and longest wavelength
Resolution (Chandler, 2009)
Also depends on antenna configuration and wavelength○ 0.05” at tightest configuration
and shortest wavelength○ 14.2’ at loosest configuration
and longest wavelength
M1 (VLA)(Source: NRAO)
M1 (GAO)(Source: PHYS 2070
Lecture Slides)
VLAVLA
VLA – Location
Located on the Plains of San Agustin in New Mexico, USAWest of Socorro
Why?Minimal EM interference
○ In the middle of nowhereDry
○ Good seeing Location of the VLA(Source: Google Maps)
VLA – Requesting Time
Available to everyone regardless of nationality or institution
Two options(1) Web-based proposal submission tool(2) Proposing to NASA missions
Proposals refereed by external expertsCompetitive
Scheduled every 4 months(Chandler, 2009)
VLA – Targets
MultipurposeNo specific missionOccasionally used for atmospheric / weather
studies or satellite tracking (NRAO, 2008)
Saturn(Source: NRAO)
Star Forming Regions in the Milky Way(Source: NRAO)
The Milky Way’s Central Black Hole(Source: NRAO)
VLA – Research
Gamma Ray Burst 13 billion l.y. from EarthDetected in 2009 by NASA’s Swift satelliteUniverse was only 630 million years old!Information about the formation of the
(relatively) early Universe and the first starsChandra et al., “Discovery of Radio
Afterglow from the Most Distant Cosmic Explosion”, Oct. 2009
(Finley, 2009)
VLA – Research The HI Nearby Galaxy
Survey (THINGS)(NRAO, 2008)Combines data from
VLA, Spitzer, & GALEXHydrogen-1 emits radio
at a particular frequency○ VLA measured Doppler
shift to measure rotation of nearby galaxiesNever done before in radioProvides information about
dark matter(Finley, 2008)
THINGS: NGC 2403(Source: NRAO)
VLA – Expansion
Upgraded / replaced by the Expanded Very Large Array (EVLA)(NRAO, 2009)
5 - 20x improvement in sensitivity over VLAResolution improved to 0.004 - 0.2”More streamlined scheduling processMain transition period was 2009 - 2010
SKA – General Information Radio observatory Next step in radio astronomy
2 orders of magnitude improvement in sensitivity over existing meter-centimetre facilities (SKA, 2010)
50x more sensitive than VLA (SKA, 2010)
Intended to complement other observatories ALMA, James Webb Space Telescope
Construction to begin in 2016 (SKA, 2010)
Complete by 2024 Concept has been around since 1991!
Estimated cost: €1.5 billion (SKA, 2010)
Funding from various agencies, mostly American and European
SKA Logo(Source: SKA)
SKA – Design Physical Construction
Will have 1 sq. km (1,000,000 sq. m.) of collecting area○ Possible configurations being
considered (SKA, 2010)
50 stations with 90 m antennae 30 stations with 200 m antennae
○ Will be highly concentrated in the centre of the array with remote stations in a pinwheel arrangement (SKA, 2010)
○ Three types of antennae for various wavelengths
Aperture Synthesized aperture diameter of
several 1000 km (SKA, 2010)
SKA Station Arrangement(Source: SKA)
SKA Receivers(Source: SKA)
SKA – Design Wavelengths
3 m to 12 mm (SKA, 2010)
○ Narrower band than VLA
Field of ViewMore than one!
○ Can observe up to 10 objects simultaneously (SKA, 2010)
○ > 200 sq. deg. at wavelengths > 30 cm (SKA, 2010)
1000 full moons○ ~ 1 sq. deg. at shorter
wavelengths (SKA, 2010)
5 full moons
VLA
SKA & VLA Observable Wavelengths(Source: Wikimedia Commons)
SKA
SKA – Design
ResolutionDepends on FOV
○ 0.1” for 1 sq. deg. observing area (SKA, 2010)
VLA gets 0.05” with tightest configuration
○ 0.2” for 200 sq. deg. observing area (SKA, 2010)
VLA gets 14.2’ with loosest configuration
SKA Sensitivity Map(Source: SKA)
SKA – Location Candidates Two location candidates Australia & New Zealand (SKA,
2010)
Low population density areas○ Large areas with minimal EM
interferenceCan develop across two countriesHigh bandwidth fibre-optic
infrastructureView of the southern sky overlaps
that of ALMA and gives a good view of the centre of the galaxy
Potential Station Placement in Australia & New Zealand
(Source: SKA)
SKA – Location Candidates South Africa (SKA, 2010)
Low EM interference and low population density○ Can spread out
Dry climate○ Good seeing
Low land prices and operating costs
Good existing infrastructure
Potential Station Placement in Africa(Source: SKA)
SKA – Research Five main research projects Cradle of Life (SKA, 2010)
Examining how Earth-like planets are formed
Observing accretion discsAlso able to pick up radio
transmissions of the same strength as a TV signal○ Could check for signs of
intelligent life!
Protoplanetary Disc(Source: SKA)
Detecting Organic Molecules(Source: SKA)
SKA – Research Probing the Dark Ages
(SKA, 2010)
Will probe the gaseous component of the early Universe○ Observe some of the
earliest luminous objects
Look at red-shifted radio emissions from Hydrogen-1○ Similar to THINGS
The Epoch of Reionization(Source: SKA)
SKA – Research Strong Field Tests of
Gravity Using Pulsars and Black Holes (SKA, 2010)
Will test general relativity in very strong gravitational fields○ Pulsars orbiting black
holesOnly possible in radio with
the required precisionAlso looking for
gravitational waves○ Different wavelengths than
LIGO and LISA
Pulsar Orbiting a Black Hole(Source: SKA)
SKA – Research Origins and Evolution
of Cosmic Magnetism (SKA, 2010)
Galaxy Evolution, Cosmology, and Dark Energy (SKA, 2010)
Clustering patternsGrowthStructure
Cosmic Magnetism(Source: SKA)
Galaxy Group HCG 87(Source: NASA)
Literature Cited Chandler C. 2009. Obtaining observing time on the VLA.
http://www.vla.nrao.edu/astro/guides/vlas/current/node45.html Chandler C. 2009. Resolution.
http://www.vla.nrao.edu/astro/guides/vlas/current/node10.html
Chandra P, Frail DA, Fox D, Kulkarni S, Berger E, et al. 2010. Discovery of radio afterglow from the most distant cosmic explosion. ApJL. 712 : L31-5
Cole J. 2009. The expanded very large array project:A radio telescope to resolve cosmic evolution.
http://www.aoc.nrao.edu/evla/ Finley D. 2009. Blast from the past gives clues about early
universe. http://www.nrao.edu/pr/2009/grbz8/ Finley D. 2008. New VLA images unlocking galactic mysteries.
http://www.nrao.edu/pr/2008/things/ NRAO. 2008. An overview of the very large array.
http://www.vla.nrao.edu/genpub/overview/ SKA. 2010. Home page.
http://www.skatelescope.org/pages/page_student.htm