Australian Square Kilometre Array Pathfinder (ASKAP) Telescope 

The Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located in the Murchison region of Western Australia. It consists of 36 dish antennas working together and was designed to image large areas of the sky using advanced receivers known as Phased Array Feeds (PAFs).

Radio telescopes make images of the sky at radio wavelengths, revealing information that our eyes cannot see.

They can detect many interesting objects in our Universe, from clouds of cold gas that may eventually collapse to form new stars, to the high-energy jets emerging from super-massive black holes at the centres of other galaxies far from the Milky Way.

Most radio telescope antennas can only look in one direction, but ASKAP's phased array feed receivers allow this telescope to look in several directions at the same time, like an insect's compound eye. This means we can image very large areas, making ASKAP an excellent instrument for large-scale surveys and detecting when things change.

Phased array feeds (PAFs) generate much more data than traditional receivers, meaning that ASKAP needs a lot of computing power. Some of this computing power is located alongside the telescope at the observatory, but we also need a high-speed data link back to the Pawsey Supercomputing Centre in Perth. This is where astronomers turn the raw data from the telescope into images of the sky.

Watch ASKAP Live

This live display shows what the telescope is doing right now: https://apps.atnf.csiro.au/ASKAPLive/

  • The Left-most circle shows progress through the current observation.
  • The sky map in the centre shows where the telescopes are pointing (each antenna is represented as a + symbol, and the filled blue circles show the location of several radio galaxies outside the Milky Way.
  • If you watch for some time you can see how these sources appear to move across the sky due to the rotation of the Earth.
  • The Sun and Moon are shown as larger orange and grey circles.
  • The blue line represents the plane of the Milky Way, our own galaxy.
  • The right-hand display shows the status of the antennas themselves, each of which has thousands of individual components that are constantly monitored.
  • The whole telescope can be controlled remotely via the internet.

Wide Field of View - giant radio eyes on the sky

The key feature of ASKAP is its wide field of view, generated by its unique phased array feed (PAF) receivers. Together with specialised digital systems, the PAFs create 36 separate (simultaneous) beams on the sky which are mosaicked together into a large single image.

ASKAP’s ‘field of view’ is depicted showing the 36 beams as individual circles. We get all of this in one go. By comparison, the field of view of a traditional telescope would be a single slightly smaller circle. The moon diameter is half the diameter of one of these circles.

 

ASKAP's rapid survey capability makes it the world’s fastest survey radio telescope. The PAF receivers have been specifically developed for ASKAP by CSIRO and this is the first time this type of technology has been used in radio astronomy.

Traditional radio telescopes are good at providing a detailed view of a distant object. ASKAP can image (in 3D) large areas all at once, with much greater sensitivity than previous all-sky surveys. ASKAP has also been designed to be extremely fast - it will be able to detect millions of radio sources in a matter of days, opening new fields of research.

Phased Array Feed Receiver 

A phased array feed is an advanced electronic device which converts radio waves into electrical signals that astronomers use to create images. Each PAF is made up of 188 individual receivers, positioned in a chequerboard-like arrangement.

Most radio astronomy receivers can only pick up signals coming from the direction the dish antenna is pointing. In contrast, our PAFs are designed to detect signals coming from many directions simultaneously. This has a similar effect to a wide-angle lens, allowing each antenna to see 36 times more than a traditional radio telescope receiver.

Because the signals we study come from very distant objects, they are extremely weak by the time they reach Earth. Our dish-shaped antennas help to boost the signal strength of these weak, natural radio waves but the receiver must do the rest of the work with its sensitive amplifiers.

The PAFs were assembled in our CSIRO workshops in Sydney – for 36 PAFs, there are some 6 million parts, including 20,000 printed circuit boards. Each antenna has 216 optical fibres that transport data to the MRO Control Building – that’s a total of 7776 fibres. The total length of this fibre is approx. 15,500km – enough to wrap around the Moon 1.5 times! These fibres transport data at a rate of 1.9 Tb/s from the antennas to the correlator for on-site processing. After this processing takes place, the data is sent along high-speed optical fibres (40 Gbit/s) down to the Pawsey Supercomputing Centre in Perth.

ASKAP Specifications

  • Total collecting area of 4,000 square metres, from 36 antennas, each 12 m in diameter

  • System temperature less than 50 K

  • Frequency range from 700 MHz to 1.8 GHz

  • 300 MHz instantaneous bandwidth

  • 36 independent beams, each of about 1 square degree, yield overlapping to a 30 square degree field-of-view at 1.4 GHz

  • 6 km Maximum baseline

  • Full cross-correlation of all antennas

  • Remote array station capability located in NSW, approximately 3,000 km from the core site.

With the 12-antenna sub-array that has been operating since October 2016, we have collected and archived nearly 2 PB of early science data, which is being processed and imaged by our global science team members. The results will be made available to the world on the CSIRO ASKAP Science Data Archive when it has been shown to pass quality control standards.

What are some of the early science results from ASKAP?

ASKAP’s extremely wide field of view makes it very good at detecting transient events and variable sources. Astronomers have already recorded an explosive event known as a fast radio burst (FRB) in the distant Universe. Scientists haven’t worked out what causes these sudden bursts of radio emission yet but ASKAP is set to become the fastest FRB finding instrument in the world.

ASKAP has also been used to detect extremely distant objects, including a recently-discovered galaxy 5 billion light years away. The discovery was made via spectral line absorption - using radio frequencies that are only free of human interference at an extremely remote site like the MRO. Studying objects at this distance provides a window into the past and gives us new insight into the history and evolution of the Universe.

One of the key science goals of ASKAP is the study of neutral hydrogen emission from galaxies. The GASKAP science team recently used ASKAP early science data to make the best image of hydrogen gas structures in the Small Magellanic Cloud, a dwarf galaxy that is slowly merging with the Milky Way. This image reveals the inner workings of the galaxy in intricate detail and was made in a small fraction of the time required to observe the previous record-holder.

The WALLABY survey science team has collected just over 700 hrs of commissioning and Early Science observations on four different science fields: the NGC 7232 and Dorado groups, Fornax cluster, and field around the M83 spiral galaxy.

 

The 220 TB of raw data will produce high resolution neutral hydrogen image cubes with full WALLABY sensitivity (i.e. have an RMS noise of 1.6 mJy/beam per 4 km/s channel) of the four fields. These cubes will provide detailed maps of the hydrogen gas content of the nearby systems and enable the discovery of new galaxies. 

The next step for us will be verifying the ASKAP data products and analysing them for scientific purposes. The next step for ASKAP will be incorporating all 36 PAFs (the last one was installed on 17 November 2017) and other newly implemented features to transform itself into a high-speed, high resolution survey instrument that will truly help us discover and understand the Universe.

ASKAP Image Gallery

A full gallery of ASKAP images is available here

CSIRO's new ASKAP antennas at the Murchison Radio-astronomy Observatory. Credit: CSIRO

ASKAP Location

ASKAP is located at CSIRO's Murchison Radio astronomy Observatory (MRO) in Mid West Western Australia (800 km NE of Perth). The MRO has been purpose-built for ASKAP and for hosting international radio astronomy projects including EDGES, the Murchison Widefield Array and the future Square Kilometre Array.

CSIRO acknowledges the Wajarri Yamaji as the traditional owners of the land on which the MRO is situated and we participated in negotiating an Indigenous Land Use Agreement (ILUA) for the MRO to operate. The ILUA provides for educational, social and economic benefits flow to the traditional owners of the site. It includes a cadetship program that runs for the life of the telescopes, our staff also visit the remote Pia Community School as part of a student mentoring program and we’ve co-created resources on Wajarri culture and astronomy. A new ILUA for the future Square Kilometre Array telescope will expand on these benefits.

The Australian and Western Australian Governments have established a ‘radio quiet’ zone to protect the MRO site from noise created by modern life. The zone is an area 520km in diameter, centred on the MRO, in which licenced communications and electronic devices such as television transmitters, mobile telephones base stations and CB radios are controlled to limit electromagnetic interference to the radio telescopes on site.

The MRO is closed to the public but you can take in all the awesome infrastructure with this fly over the site.

News from ASKAP's Project Scientist

For all the latest news on ASKAP commissioning check out the monthly ASKAP Commissioning Update from our ASKAP Project Scientist, Dr Aidan Hotan

ASKAP
Access: 
Public