The Rapid ASKAP Continuum Survey as a virtual map

ASKAP Science

ASKAP is an SKA-precursor telescope that observes radio waves of a mid-band frequency. Other radio telescopes at Inyarrimanha Ilgari Bundara, CSIRO's Murchison Radio-astronomy Observatory, are low-band frequency telescopes.

While the SKA mid-band projects are now based in South Africa, ASKAP showed just how valuable mid-band studies are, how much data can be acquired, and helped engineers and astronomers refine the technologies for SKA. Now that ASKAP is part of the Australia Telescope National Facility, it has a lot to offer researchers from all around the world. 

ASKAP is designed to peer deep into our Universe in record time. This speed, which allows it to survey large parts of the sky quicker than any before, is due to its wide field of view. The telescope uses new technology developed by CSIRO - phased array feeds (PAFs) that sit at the focus of each of its antennas to generate this unique widefield view. 

Because of this, we regularly see many new cosmic objects being discovered by the researchers using ASKAP.

More information can be found on CSIRO’s ASKAP page

What is ASKAP looking for?

Researchers have designed surveys that use ASKAP’s unique capabilities to map the structure and evolution of the Universe by observing galaxies and the gas that they contain. Additionally, the ASKAP observatory team has undertaken the RACS project, which is shown in the image above and has already found 1 million new galaxies.


Survey Science Projects

During ASKAP’s first five years of operation at least 75% of its time is being used for large survey science projects, each needing more than 1,500 hours to complete and all designed to test the telescope’s unique capabilities. The projects were selected in 2009 by an international panel, with the decision based on scientific merit and operational feasibility. 

In August 2021, these projects started their second pilot surveys with all 36 ASKAP dishes and now involved 739 astronomers from 208 institutions around the world. Many papers resulting from the work can be found on the Publications page. Data from their projects is accessible via the CSIRO ASKAP Science Data Archive (CASDA).

Each survey science project has a different research objective that is summarised below in alphabetical order by team name. You can also visit the ASKAP Survey Science Confluence page.


CRAFT (The Commensal Real-time ASKAP Fast Transients survey)
Principal Investigators: Keith Bannister (CSIRO), Ryan Shannon (Swinburne University), Clancy James (ICRAR/Curtin University)
CRAFT is a purely commensal survey for transient sources with timescales shorter than 5 seconds. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. They provide Nature’s ultimate laboratory; their emission is generated by matter under extreme conditions whose properties probe physical regimes far transcending the range achievable in terrestrial experiments. Fast timescale transients open new vistas on the physics of high brightness temperature objects, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic transients affords us an entirely new and sensitive probe on the huge reservoir of baryons in the intergalactic medium. More information: CRAFT webpage

DINGO (Deep Investigations of Neutral Gas Origins)
Principal Investigator: Martin Meyer (ICRAR/University of Western Australia)
DINGO will study the evolution of neutral hydrogen (HI) from the current epoch to redshift about 0.5, providing a legacy dataset spanning cosmologically representative volumes. Measurements will be made of key cosmological distributions, including ?HI, the HI mass function and the halo occupation distribution function. ASKAP data will be combined with optical data to enable a thorough study of the co-evolution of the stellar, baryonic and dark matter content of galaxies. More information: DINGO webpage

EMU (Evolutionary Map of the Universe)
Principal Investigator: Andrew Hopkins (Macquarie University)
EMU is the touchstone radio continuum survey of the southern hemisphere. EMU will image the southern sky to a sensitivity of 20 μJy/beam rms with a resolution of 15 arcsec. Over the initial five years of full ASKAP operations EMU is expected to detect and catalogue about 40 million galaxies, including typical star-forming galaxies over the latter half of the history of the Universe, powerful starbursts to even greater distances, and supermassive black holes in galaxies to the edge of the visible Universe. It will continue to discover new classes of object, and enable research covering the linked evolution of galaxies and their supermassive black holes, the large scale structure and cosmology of our Universe, the astrophysics of galaxy clusters and halos, and the formation of stars and the stellar lifecycle within our Milky Way and nearby galaxies. EMU will provide a lasting legacy as the most sensitive wide area atlas of the southern radio sky for decades to come. More information: EMU webpage

FLASH (The First Large Absorption Survey in HI)
Principal Investigators: Elaine Sadler (University of Sydney) and Elizabeth Mahony (CSIRO)
The First Large Absorption line Survey in HI (FLASH) is a wide-area survey using ASKAP to search for the 21cm HI line in absorption against background radio continuum sources. FLASH observations are carried out using the lowest ASKAP frequency band (711.5-999.5 MHz) providing information on the HI content of the Universe between redshifts z=0.42 and z=1.0, an epoch where the neutral gas content of galaxies is poorly constrained. The science goals of the FLASH survey include determining how the cool HI gas in galaxies has evolved since cosmic noon and examining the gas accretion mechanisms that drive the co-evolution of supermassive black holes and their host galaxies over cosmic history. FLASH will also detect OH 18-cm absorbers in diffuse molecular gas, megamaser OH emission, radio recombination lines, and stacked HI emission. A detailed description of the FLASH survey is outlined in the FLASH survey overview paper available here.
An overview of the FLASH observing parameters and sky coverage is given below:

  • Frequency range: 711.5-999.5 MHz
  • Spectral resolution: 18.5kHz
  • Integration time per field: 2 hrs
  • Footprint: Square6x6
  • Sky coverage: All sky with dec <+15 and |b|>8.5 deg. 600 fields in total (matched to RACS-low footprints).
  • Beam-forming frequency intervals: 5 MHz.

More information: FLASH webpage

GASKAP-HI (The Galactic ASKAP Spectral Line Survey - Neutral Hydrogen)
Principal Investigators: Naomi McClure-Griffiths (ANU), Nickolas Pingel (ANU) and John Dickey (University of Tasmania)
GASKAP-HI is a high spectral resolution survey of the neutral hydrogen (HI) line in the Milky Way and Magellanic Systems. Compared with existing data, GASKAP-HI will achieve about an order of magnitude improvement in both brightness sensitivity and in angular resolution. GASKAP-HI will detect and map diffuse emission from atomic clouds, HI absorption toward background continuum sources from the cold neutral atomic gas, and the structures in the gas that trace the effects of stellar winds and supernova explosions. The Magellanic Clouds will show all these processes as they appear in two other, very different environments. GASKAP-HI will provide stunning images of the interstellar medium that will be indispensable for astronomers working at other wavelengths. More information: GASKAP webpage

GASKAP-OH (The Galactic ASKAP Spectral Line Survey - ground-state Hydroxyl)
Principal Investigators: Shari Breen (SKAO) and Joanne Dawson (University of Macquarie/CSIRO)
The flow of matter and energy between stars and the interstellar medium is at the heart of galaxy evolution. GASKAP-OH will help us learn how galaxies process gas into stars and back again, by observing maser and quasi-thermal emission from the four 18-cm transitions of ground-state hydroxyl (OH) in the Milky Way and Large Magellanic Cloud at unprecedented sensitivity and resolution. The survey will reveal the formation and early evolution of molecular clouds and young stars, and the end-of-life activities of old massive stars, and will refine our understanding of the structure of the Milky Way Galaxy, which has long been better determined in the Northern than the Southern sky. More information: GASKAP webpage

POSSUM (Polarization Sky Survey of the Universe's Magnetism)
Principal Investigators: Naomi McClure-Griffiths (ANU), George Heald (CSIRO) and Craig Anderson (ANU)
Understanding the Universe is impossible without understanding magnetic fields. Magnetic fields are key to the non-thermal Universe, yet it is unclear how large-scale magnetic fields are generated and maintained. POSSUM will use radio source polarization, in particular the technique of rotation measure (RM) synthesis, to perform a wide-field survey that will yield a grid of RMs over a substantial fraction of the sky. The science outcomes of POSSUM will revolutionise our understanding of the ordered components of the Milky Way’s magnetic field, test dynamo and other models of magnetic field generation in galaxies and clusters, and carry out a comprehensive census of magnetic fields as a function of redshift in galaxies, active galactic nuclei, galaxy clusters and the intergalactic medium. POSSUM will develop its primary data products through post-processing of continuum data collected commensally with the EMU and WALLABY surveys. In areas of the sky covered by both EMU and WALLABY, POSSUM will be able to develop particularly precise RMs. More information: POSSUM webpage

VAST (An ASKAP Survey for Variables and Slow Transients)
Principal Investigators: Tara Murphy (University of Sydney) and David Kaplan (Wisconsin)
VAST gives unprecedented opportunities to investigate the sky at radio wavelengths for transients with a timescale as short as five seconds. ASKAP’s wide-field survey capabilities will enable the discovery and investigation of variable and transient phenomena from the local to the cosmological including flare stars, intermittent pulsars, X-ray binaries, magnetars, extreme scattering events, intra-day variables, radio supernovae and the orphan afterglows of gamma-ray bursts. VAST will probe unexplored regions of phase space where new classes of transient sources may be detected. More information: VAST webpage

WALLABY (Widefield ASKAP L-Band Legacy All-Sky Blind Survey)
Principal Investigators: Lister Staveley-Smith and Barbara Catinella (ICRAR/University of Western Australia)

WALLABY is the ASKAP all-sky survey of neutral hydrogen (HI) in the Local Universe out to a redshift of z ~ 0.1. The survey will produce HI data cubes of the sky at an angular resolution of 30 arcsec and a spectral resolution of 18.5 kHz (~4 km/s). WALLABY will reach a sensitivity of 1.6 mJy (rms per beam and channel) and be able to detect the 21-cm HI emission of a few hundred thousand galaxies across the sky. In addition, WALLABY will produce high-resolution data cubes of several thousand selected galaxies across the sky at ~10 arcsec angular resolution. WALLABY will cover ~14,000 deg² of sky during the 5 years of ASKAP survey operations. The exact sky footprint is available from the WALLABY website (

The main scientific goals of WALLABY include: (a) measurements of the velocity fields and rotation curves of galaxies to resolve the long-standing cusp-core tension in ΛCDM theory and to allow the baryonic/dark matter mass dissections of unprecedentedly large samples; (b) a study of the individual and statistical properties of galaxies in and around groups and clusters to better understand galaxy evolution, including the relative roles of tidal and hydrodynamic forces; (c) the most accurate measurement of the HI mass and velocity functions and their variation with environment (local density); (d) the refinement of cosmological parameters and tests of GR and ΛCDM using the spatial and redshift distribution of gas-rich galaxies; (e) a study of the dynamics of high-velocity clouds near the Milky Way and their role in tracing accretion and outflows; and (f) a census of gas-rich galaxies in the vicinity of the Local Group in order to quantify the role of the early ionization field on low-mass galaxy
formation. More information: WALLABY webpage


A section of the atomic hydrogen gas in the Small Magellanic Cloud as imaged with ASKAP. Credit: ANU and CSIRO


What has ASKAP and the survey science projects found?

Early science projects, using only 16 of the 36 dishes, produced incredible new imagery of our universe. GASKAP produced an image of the Small Magellanic Cloud in 2017 (a small segment seen above), showing us the tangled web of gas that makes up our neighbouring galaxy. It reveals the galaxy’s vibrant history, including streams of gas reeled in by the gravitational pull of the Milky Way and billowing voids generated by massive stars that exploded millions of years ago. 

What’s amazing about this image is that it was made in one shot with the ‘wide-angle’ camera of ASKAP. To do this with traditional technology you would have had to point the telescope in 1,344 different places across the face of the Galaxy and run five observing sessions over 15 months. By contrast, ASKAP took just three nights. Data from CSIRO’s Parkes radio-telescope was added to pick up the faint diffuse emission which is essential for understanding the Galaxy as a whole.
Since then, and with 20 more antennas in use, ASKAP has recorded many more astounding galaxies and phenomena – many of them a mystery. 

Read more about:

Visit the ASKAP news page, and our Publications page for more up to date discoveries.


Where is ASKAP data kept?

CASDA provides all ASKAP data (image cubes, basic catalogues, and averaged visibilities) to the public free of charge. Archive products are available as soon as they have gone through a quality control process. The project teams will be providing value-added data products (e.g. large-scale catalogues, rotation measure maps) based on the released data products.
•    Visit the CASDA page
•    Search the archive using a web interface
•    Read the user’s guide to the archive 

ASKAP is an SKA-precursor telescope situated at Inyarrimanha Ilgari Bundara, CSIRO's Murchison Radio-astronomy Observatory, in Western Australia.
We acknowledge the Wajarri Yamaji as the Traditional Owners and native title holders of the Observatory site.