Space - LARES 'mirror ball' sat will test Einstein's theory

The LARES satellite is just 36 centimetres across(Image: ESA/S. Corvaja)

You don't have to be big to challenge Einstein. A pocked ball just 36 centimetres wide is the latest space probe tasked with measuring general relativity, one of the cornerstones of modern physics.

The Laser Relativity Satellite, or LARES, is a tungsten sphere with reflectors mounted in 92 holes punched into its surface. It is due to launch from Kourou, French Guiana, on a new European Space Agency rocket called Vega, designed to cheaply launch payloads of less than 2500 kilograms. The launch window opens on 13 February.

LARES's orbit will be tracked by bouncing ground-based lasers off the reflectors. General relativity states that gravity arises from the curvature of space and time. If this is true, Earth should drag space-time around with it as it spins, slightly perturbing the orbits of satellites.

Though general relativity is the accepted theory of gravity, it might break down if measured with greater accuracy. The beleaguered Gravity Probe B satellite achieved an accuracy within 19 per cent of the expected orbit change; earlier satellites got within 10 per cent. Researchers hope to achieve 1 per cent with LARES, built by the Italian Space Agency.

Hot spaceport

Expect to see more launches from the Kourou spaceport, which is ESA-owned, in future. Vega is due to launch an experimental ESA craft in 2014 to test technologies – such as a heat shield – for a possible crewed mission.

Vega could also launch small astronomy and climate satellites, says Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

One of the few other small launchers, McDowell says, is the troubled Taurus rocket, built by US-based Orbital Sciences Corporation. It has had two failed launches of climate satellites in recent years – NASA's Orbiting Carbon Observatory and Glory spacecraft.

Vega will help make the European spaceport in Kourou a destination for all kinds of launches, since the powerful Ariane 5 and medium-class Soyuz also launch from there. "It's rounding out European space technology," McDowell says. "They can compete across the board."

Update (8 February 2012): A previous version of this story listed the LARES launch date as 9 February - ESA has revised the date to 13 February.

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