Apr 16, 2010
Two space telescope projects of interest to South AfricaBack
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Interferometry involves using two or more radio telescope dishes to look at the same object in the sky. The signals received by each dish are fed into a computer and because the dishes are not in exactly the same place (even if they they are only a few tens of metres apart) the distance travelled by the signals to each is not identical and combining them creates an interference pattern that can be analysed by computer to provide high-resolution images of celestial objects.
In the case of VLBI, however, the dishes are very far apart - often on different continents, because the longer the baseline, the higher the resolution of the images that can be obtained. And space VLBI extends the baseline even further than is possible on Earth by adding a spacecraft.
South Africa would provide part of the terrestrial component of the baseline, helping extend it to the maximum. The South African radio telescope that would be involved would be the 26 m dish at the Hartebeesthoek Radio Astronomy Observatory, west of Pretoria, which has lots of experience in VLBI work. The seven dish MeerKAT Precursor Array telescope in the Karoo is currently still functioning as an engineering test bed and not as an operational radio telescope, but it could get involved in the long term.
Radioastron is a project led by the Russian space agency Roscosmos, while VSOP-2 (which is also called Astro-G) is led by the Japanese Aerospace Exploration Agency.
In the case of Russia, the Radioastron spacecraft will deploy a 10 m diameter radio telescope dish. Radioastron was first announced in 2005 with a target launch date of 2007, but the project has suffered from delays and its is now hoped to launch it in June this year. The spacecraft is reportedly currently undergoing final assembly and tests by its manufacturer, Lavochkin, and is based on this company's Spektr-R satellite design. The intention is to launch it on a Zenit-2 rocket with a Fregat-SB booster from the Baikonur Cosmodrome in Kazakhstan.
VSOP-2 stands for VLBI Space Observatory Programme-2 and the Japanese spacecraft will deploy a 9 m dish. It too, has suffered delays, originally being aimed at a launch this year or early next. However, it is now scheduled for launch in 2013. It is expected to be launched on a Japanese H2A rocket, probably from the country's Tanegashima Space Centre, located on a small island to the south of Kyushu (the southernmost of Japan's four main islands). The H2A is Japan's main large-scale launch vehicle. The VSOP-2 project follows a successful previous Japanese space VLBI mission, VSOP.
Radioastron is aimed at studying active galactic nucleii, the structure of star-mass black holes, neutron and possible quark stars in the Milky Way, the structure and distribution of interplanetary and interstellar matter, the structure and dynamics of star-forming regions (using maser and megamaser spectral line emission), and parameters of the currently-accepted model of the cosmos, including dark energy and dark matter.
Quark stars are currently theoretical concepts. Quarks are elementary particles which make up protons, neutrons and mesons, and quark stars would be composed only of these quarks (which come in six types). Maser is an acronym for microwave amplification by stimulated emission of radiation, and is a high frequency microwave amplifier.
Dark matter is believed to make up most of the matter in our universe and is so named because it neither emits or reflects light, making it invisible, although the influence of gravity from dark matter is detectable. While conventional matter makes up a mere 4,6% of the universe, and dark matter 23%, the even more mysterious dark energy is believed to account for 72% of our universe. Dark energy may be the force driving the observed expansion of the universe.
SA would maximise baseline for two international space telescope projects
Radioastron should be launched this year, VSOP-2 in 2013
Edited by: Martin Zhuwakinyu© Reuse this Comment Guidelines (150 word limit)
Creamer Media Senior Deputy Editor
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