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The Matera laser station sees LARES

First measurements have been made by the ASI Centre in Matera. The Italian satellite to study General Relativity was launched on 13 February 2012 from the ESA Spaceport in Kourou by the new European launcher VEGA

LARES has entered its operational phase. The Italian satellite for studying General Relativity was launched on 13 February 2012 by the inaugural flight of the VEGA launcher.

LARES is a passive satellite, it does not transmit its own signal but reflects signals that powerful lasers from a global network of ground stations send towards it. There are other similar satellites, for instance two Italian/US LAGEOS satellites conceived to study space geodesy, but LARES was designed and carried out purposely to study the subtle influence that the mass of our planet, while rotating, induces in the gravitational field and in the space-time tissue around it.

“The LARES satellite, conceived and designed by the University of Salento and the Sapienza University of Rome,” said Ignazio Ciufolini, the project’s PI, “works perfectly after being placed with great precision into the prearranged orbit, thanks to the superb qualification flight of the new launcher VEGA. LARES has already been observed by ILRS (International Laser Ranging Service) numerous stations distributed around the world.”

“Furthermore,” continued Ciufolini, “beyond any of the most optimistic expectations, LARES follows an almost exclusively gravitational orbit, or in the General Relativity jargon follows a space-time geodesic. Its non-gravitational perturbations are really extremely small thanks to its tiny area/mass ratio. The LARES satellite, with a mass of 387 kg and a radius of 182 mm is the densest known object in orbit in the Solar System. LARES will test Einstein’s theory of General Relativity by very accurately measuring the phenomenon of frame-dragging or gravitomagnetism. Finally,” ends Ciufolini, “it will enable various geodynamics and space-geodesy measurements that are indirectly useful in the study of earthquakes."

Immediately after the launch, the scientific team got down to work and started running the computer programmes that predict orbits, sending results to ILRS ground stations that in turn pointed their lasers where the satellite passage was expected. It may seem easy, but LARES is a 36 cm diameter sphere and is situated at an altitude of 1450 km, so a good aim is required.

Ground stations include the ASI Centre in Matera. “As soon as a reliable set of LARES orbital elements was published on the ILRS site and several global network stations linked up with the satellite,” said Giuseppe Bianco, the centre’s manager, “the first was the Moblas 5 site at Yarragadee in Australia, followed by others including the ASI MLRO (Matera Laser Ranging Observatory), which has observed over 20 passages with a ‘single shot’ RMS precision of about 3 mm. LARES is a very efficient reflector and this makes it an easy target for all global network stations.” The ASI station in Matera has made some of the best LARES measurements.

 

However, the scientists’ work will be very long. “Several years of observations will be needed,” maintained Enrico Flamini, programme manager for ASI, “and a great quantity of data will need to be analysed in order to reach the objective of measuring the Lense-Thiring effect, or rather the frame-dragging around the Earth, with the desired precision of 1%, but the first step has been made in a proper way. LARES is in orbit and it reflects a very good signal.”