The South African National Space Agency (Sansa) and its Russian counterpart, Roscosmos, will, all being well, sign two agreements this month. One concerns the Radioastron space telescope mission and the other the Glonass navigation satellite constellation – the Russian equivalent to America’s global positioning system.

In addition, and separately, Roscosmos has indicated to South Africa that its is open to carrying out joint Russian-South African scientific experiments on the International Space Station. (These would be executed by Russian crew members on the space station, and would not involve sending South Africans into space.)

The Radioastron agreement will result in South Africa joining this Russian-led inter- national space telescope programme. In terms of the agreement, South Africa will have to cover the costs of its participation in the mission, but Sansa is reportedly optimistic that the necessary funding will be authorised. South Africa will also have full access to all the data collected by the mission.

The Radioastron mission is led by the Astro Space Centre of the Lebedev Physical Institute of the Russian Academy of Sciences. The other participants in the programme are Australia’s Commonwealth Scientific and Industrial Research Organisation, the European Space Agency, Finland’s Helsinki University of Tech- nology, India’s Tata Institute for Fundamental Research and the US National Radio Astron- omy Observatory.

The Radioastron spacecraft is equipped with a 10 m diameter radio telescope dish, which is operated in conjunction with ground-based radio telescopes in a space very long baseline interferometry (VLBI) programme that will focus on the centimetre and decimetre wavelength bands. (It is expected that South Africa will use the Hartebeesthoek Radio Astronomy Observatory’s 15 m dish for the Radioastron mission.)

Interferometry is the use of several radio telescopes in different locations to simultaneously focus on and image 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, 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.

The baseline is the distance on the earth’s surface between the telescopes, and VLBI involves the use of telescopes in different continents and, indeed, in different hemispheres. The more telescopes involved and the longer the baseline, the greater the resolution that can be achieved. With space VLBI, a space telescope is connected with terrestrial instruments to create huge baselines.

With a mass of 3.8 t, Radioastron is the biggest radio telescope in space. It has a highly elliptical orbit, with a perigee (point closest to the earth) of about 10 000 km and an apogee (point furthest from earth) of some 350 000 km, which takes it almost as far as the moon (the moon’s average distance from earth is 384 400 km). Radioastron takes eight days and seven hours to execute one orbit of the earth. It is expected to have an operational life of at least five years and will complement the American Hubble Space Telescope, which is an optical telescope.

Regarding Glonass, the agreement will see South Africa hosting a laser ground station which will support the system. This laser will be used to very accurately measure the altitude of Glonass satellites as they overfly South Africa. The data from these measurements, and from those taken by other laser ground stations around the world, improves the accuracy of the Glonass navi- gation system. Moreover, in terms of the agreement, the laser base station will, for agreed periods, be available to South Africa for its own measurement and research projects.

To subscribe to Engineering News's print magazine email subscriptions@creamermedia.co.za or buy now.