SKA newsletter Volume 21 - April 2011 The Square Kilometre Array Exploring the Universe with the world’s largest radio telescope www.skatelescope.org Please click the relevant section title to skip to that section 03 Project news 04 From the SPDO 05 SKA science 08 Engineering update 10 Site characterisation 12 Outreach update 14 Industry participation 17 News from around the world 18 Africa 20 Australia and New Zealand 23 Canada 25 China 28 Europe 31 India 33 US 35 Future meetings and events Project news Project news 04 From the SPDO Crucial steps for the SKA project were At its first meeting on 2 April, the Founding taken in the last week of March 2011. A Board decided that the location of the SKA Founding Board was created with the Project Office (SPO) will be at the Jodrell aim of establishing a legal entity for the Bank Observatory near Manchester in the project by the time of the SKA Forum in UK. This decision followed a competitive Canada in early July, as well as agreeing bidding process in which a number of the resourcing of the Project Execution excellent proposals were evaluated in an Plan for the Pre-construction Phase international review process. The SPO, which from 2012 to 2015. The Founding Board is hoped to grow to 60 people over the next replaces the Agencies SKA Group with four years, will supersede the SPDO currently immediate effect. Prof John Womersley based at the University of Manchester. The from the UK’s Science and Technology physical move to a new building at Jodrell Facilities Council (STFC) was elected Bank Observatory is scheduled for mid-2012. Chair, and Dr Patricia Vogel from the Netherlands Organisation for Scientific The Board also agreed to start the Research (NWO) was elected vice-Chair. recruitment of the SPO director. I have decided to step down in December as Nine countries signed the Letter of Intent international project director after nine years for the Founding Board – Australia, China, in the job. France, Germany, Italy, New Zealand, South Africa, The Netherlands, and the UK. A Richard Schilizzi number of additional countries are expected Director to join the Board in the next month or so. Each country is represented by an agency or government official and a scientist. The SKA Science and Engineering Committee (SSEC) will continue to oversee the activities of the SKA Program Development Office (SPDO) until the end of 2011 when the agreements governing these two organisations expire. The SSEC will also advise the Founding Board on the science and engineering directions to be taken in the international project. Project news 05 SKA science An artist’s impression of the sea of gravitational waves washing over the Earth. The orange bands represent crests of a gravitational wave. The white dots indicate the pulsars being observed as part of the pulsar timing array, while the white beams indicate their lighthouse-like radio beams from which the timing measurements are made. Testing fundamental laws of and magnetic field combines to generate physics with radio pulsars a highly beamed radio signal, much like a lighthouse beam. If the radio beam sweeps Andrea Lommen, Ben Stappers, across Earth, astronomers can detect regular Richard Manchester radio pulses, which is why these neutron stars are known as pulsars. Millisecond When a star more than about ten times pulsars, so called because their pulses the mass of the Sun dies, it does so are separated by only about 1 millisecond spectacularly. It blows off its outer layers (0.001 seconds), are marvellous clocks. in an explosion known as a supernova, Indeed, on long timescales, they rival even which for a brief time can outshine an atomic clocks and so can be used for a entire galaxy of stars. Left behind is a variety of physics experiments in space. neutron star, a dense stellar remnant Most famously, they have been used to test composed largely of neutrons in which our best current understanding of gravity, about 1.5 times the mass of the Sun is Einstein’s general theory of relativity (GR). packed into a region about 10 km across One notable prediction of GR is that two (equivalent to packing 1.5 times the mass closely orbiting objects—such as two neutron of the Sun into a region about the size of stars or two black holes—should produce Washington, D.C.). gravitational radiation, the gravitational equivalent of electromagnetic radiation (i.e. Often a neutron star ends up rotating rapidly, light). Gravitational radiation has now been many times a second, with a strong magnetic detected indirectly by pulsar measurements field. The combination of rapid rotation of several pulsar binary systems, notably Project news 06 PSR B1913+16 (Taylor & Weisberg 2010) in response to gravitational radiation is quite and the double pulsar J0737−3039A/B small. Current estimates are that pulsar pulse (Kramer et al. 2006). arrival times from many pulsars need to be measured to less than 100 nanoseconds In 1982, Don Backer put forth the idea of a (100 billionths of a second) in order to study pulsar timing array, an array of millisecond gravitational radiation. pulsars that could be used to measure gravitational radiation from binary black hole The PPTA is currently timing 20 pulsars, systems; even more exotic, gravitational in some cases with data spans exceeding radiation might also be produced by cosmic 20 years, and achieving precisions on the strings, essentially defects in the structure various pulsars ranging between 45 and 2500 of the Universe. His idea has now been nanoseconds. The PPTA makes heavy use of implemented by three collaborations, the the Parkes telescope, obtaining pulse time of European Pulsar Timing Array (EPTA) the arrival measurements on typical time scales North American Nanohertz Observatory of one every few weeks at each of three of Gravitational Waves (NANOGrav) and frequencies. Bandwidths of up to 1024 MHz the Parkes Pulsar Timing Array (PPTA) - are used with both coherent and incoherent together the three collaborations make up the dedispersion systems. Recent analyses of International Pulsar Timing Array (IPTA). the PPTA measurements have focused on its sensitivity to both a stochastic background By current timing standards (described (or the sea of gravitational waves) and to below) and with estimates of the strength individual sources of gravitational waves of gravitational radiation, the three PTAs (Yardley et al. 2011a, b). The PPTA expect to reach the necessary sensitivity to measurements are important in the IPTA detect gravitational radiation within 5 - 10 context, especially because of the southern years. In the SKA-era, however, gravitational hemisphere location of Parkes allowing it to astronomy will have matured – and the observe pulsars in the southern sky, thereby focus will change towards characterisation ensuring coverage over the entire sky. of sources. Using the SKA, for example, we expect to recover waveforms for individual NANOGrav is currently timing 17 pulsars, black hole binaries, and thereby recover the with precisions on the various pulsars mass, spin, and distance of each of the black between 40 and 1900 nanoseconds holes. by using the Green Bank and Arecibo telescopes roughly once per month. Recent A pulsar timing array detects gravitational accomplishments include an impressive radiation by measuring differences between leap in observing bandwidth at Green Bank the time that radio pulses are predicted to from 64 MHz to 800 MHz; a similar upgrade arrive and the time they do arrive. Those under construction at Arecibo increases differences may be caused by gravitational their sensitivity to weak pulsars by a factor radiation sweeping over the Earth, much of 12.5, which implies an increase in pulsar like a ball floating on the water bobs around timing precision. NANOGrav has also just as water waves roll under it. Gravitational demonstrated that it is possible to extend radiation is quite weak, however, so that the the gravitational frequency range of a pulsar amount by which the pulsar periods change timing array by observing daily. In this case, Project news 07 it would be possible to characterise bursts EPTA published the best current limit on the of gravitational radiation - events of order a cosmological gravitational wave background month or shorter, such as highly eccentric (a sea of gravitational waves). The method is black hole binaries or, more esoterically, the based on a Bayesian approach, considering cusp-like decay of cosmic strings (Finn & the pulse time of arrivals as the superposition Lommen 2010). of the various sources of noise, either deterministic or stochastic, and marginalising The EPTA is a multi-national and multi- over everything but the gravitational wave telescope European collaboration. It employs signal. Further, recent hardware upgrades the data from five large diameter radio at Nançay, Jodrell, and Effelsberg have telescopes, four of which have ongoing pulsar enabled coherent dedispersion across 512 observing programs: the Effelsberg radio MHz bandwidths at all telescopes for the first telescope, the Nançay radio telescope, the time. This project is complimented with the Westerbork telescope array, the Lovell radio Large European Array for Pulsars (LEAP) telescope and the Sardinia radio telescope project in which the aim is to add coherently (first light mid-2011). Each telescope the five telescopes in a phased array, with is equipped with state of the art pulsar an effective area equivalent to Arecibo; instrumentation for high precision timing; tests using data from the WSRT synthesis observations are obtained at least once telescope have been successful. The per month and timing precisions obtained completion of baseband recording systems at on the various pulsars range from 134 to all stations will enable coherent summing of 910 nanoseconds. In a recent paper (van all dishes in the near future.