SKA awarded to Africa

Square Kilometre Array Bid Announcement

At a meeting in Amsterdam, on the 25th May 2012, the independent Square Kilometre Array (SKA) Site Advisory Committee (SSAC), composed of world class astronomers and engineers, has decided that Africa will be hosting the SKA.

The African bid consortium consists of Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia, South Africa and Zambia. Mauritius’s involvement has contributed to this success.

The UoM has taken part in this bid for the SKA since 2004. It has also contributed to this by maintaining an active radio astronomy programme: MRT helical array, CALLISTO and MITRA. Two UoM academics, R. Somanah and G.K. Beeharry, have maintained an active presence in the International SKA Working Group committee. This situation gives Mauritius a unique opportunity to participate in an international cutting edge endeavour.

Square Kilometre Array

The SKA will be about 100 times more sensitive than the largest existing radio telescope on Earth. Five key science projects have been selected:

• The study of Galaxy evolution, cosmology and dark energy.

This project will look at the building of galaxies and subsequent star formation. Observationally about 1 billion galaxies are to be observed at high redshifts (distances). The pervasive question of dark matter and dark energy still eludes us. The nature of dark energy will be probed.

• Strong-field tests of gravity using pulsars and black holes

Up to now Einstein’s Theory of General Relativity (GR) has been successfully tested in the weak limit. For example, the gravitational lensing caused by the Sun on star light has been observed as early as 1919. The gravitational time delay (or Shapiro delay) in which light signals take more time through a gravitational field than they would in empty space, the absence of any field has also been observed.

However, GR has not been tested in the extreme regime, like near pulsars and black holes. The periods of rotation of pulsars are very precise. The timing of the minute variations of this period is invaluable in testing any deviation from GR.

• Investigating the origin and evolution of cosmic magnetism

There are many problems to be solved in magnetism.

1) The origin of cosmic magnetism.

2) Is the whole universe magnetic?

3) How has cosmic magnetism affected stellar and galactic formation?

4) How is magnetism distributed in our galaxy, the Milky Way?

5) How does it compare to other galaxies?

The technique used will be that of Faraday rotation. Polarized light from a source is changed when it passes through an object with significant magnetism.

• The cradle of life searching for life and planets

The origin of life is an important key science project. The planet formation will be studied. The presence of life in other solar systems will be investigated by monitoring the radio emission from systems with habitable planets.

• Probing the dark ages – the first black holes and stars

The Cosmic Background Radiation (CBR) gives us a picture of the universe when it was 300,000 years old. The universe was remarkably smooth at that time. Fluctuations were of the order of 1/100,000.

The optical telescopes can reach up to relatively recent times where structure, like galaxies and clusters of galaxies is present. The SKA will be able to probe the dark ages, which lie between the CBR and the recent structure.

The construction of the SKA is expected to cost about 1.5 billion Euros. The yearly cost of operating and maintaining a large telescope array is typically about 10% of the capital investment.

Yearly about 150 million Euros will be spent on the telescope. A fraction of this money will be spent by the SKA consortium in Mauritius.

CALLISTO and Solar Flares

Solar flares are observed from decameter radio waves to 10 fm gamma-rays. The observations are both ground (e.g. CALLISTO) and space based (e.g. SOHO). These have shown a number of important facts about the corona, coronal mass ejections (CMEs), electron and ion acceleration. In addition, there seem to be a number of magnetic topologies. Flare structure may be linked to power. The energy distribution of flares and their localisation has also been studied. It seems that flares are triggered by the reconnection of magnetic field lines.

Figure 1: World distribution of CALLISTO sites (Courtesy Christian Monstein)

However, the energy transfer for the generation of non-thermal particles is still unclear. It has been suggested that flare-like processes may be the cause of large-scale coronal magnetic field restructuring and heating. CMEs and large flares influence space weather and hence the Earth’s lower ionosphere.

Even after 150 years since their discovery, the field is still observationally driven. We are here dealing with intricate magnetohydrodynamics (MHD) processes in which the interaction between observations and theory is important. It is therefore vital to observe the Sun, on a 24 hour basis, in a wide range of wavelengths. Low frequency radio observations explore the non-thermal to thermal solar emission. It is thus invaluable in several key problems.

The CALLISTO is a helio spectrograph. The CALLISTO network is shown in Figure. Since the Australian sites are not being operated, only the Mauritian and Brazilian nodes are in the southern hemisphere. Since there is a time zone difference, these two modes also provide a near 24 hour coverage.

The time difference is also used for timing flares.

Observation of the 09.08.2011 8:00 UT solar flare, from Mauritius is seen below. The lower frequencies are seen covered by the log-periodic antennas at MRT, as shown in Figure.

MITRA

Figure 2:
Mauritius CALLISTO observation of the 09.08.2011 8:00 UT solar flare

Mauritius and South Africa have jointly embarked in the building of a low frequency array telescope, called Multifrequency Interferometry Telescope for Radio Astronomy (MITRA) with stations in both countries. In Sanskrit mitra means friend. The planning started a few years ago in a collaboration led by Dr Girish Kumar Beeharry, from the University of Mauritius (UOM), and Stuart David MacPherson and Gary Peter Janse Van Vuuren, from the Durban University of Technology (DUT).

The MITRA is a radio astronomy project which aims to do extremely wide field imaging with heterogeneous non coplanar arrays. The first two MITRA nodes are being developed collaboratively at the MRT site and at the DUT campus site, Durban, South Africa. The DUT has received funding to this effect from the Department of Science and Technology, South Africa (DST SA). The design of these nodes is such that each can be expanded in intra-nodal groups of antennas to form a nodal array of antennas. Radio astronomy observations will be done at each node. The radio data from a number of nodes will be combined to form an international aperture synthesis telescope using techniques of Very Large Baseline Interferometry (VLBI).

On 19th September 2011, H.E. Mrs Naledi Pandor, the Minister of Science and Technology of the Republic of South Africa, visited the MITRA at the Mauritius Radio Telescope (MRT) site at Bras d’Eau, Poste de Flacq.

Dr Girish Kumar Beeharry

Head MRT

Figure 3: Prototype MITRA antennas

 

Figure 4: Prototype MITRA antennas FFT response

Figure 5: Prototype MITRA antennas waterfall diagram

Figure 6: HE Mrs N. Pandor visiting the MITRA in Mauritius




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