The launch of a prototype satellite to look for ripples in space and across time is back on track following a potential technical concern with Europe's Vega rocket.
The spacecraft, known as LISA Pathfinder, is scheduled for lift-off on Thursday from the European Space Agency's launch site at Kourou, French Guiana.
Managers had delayed the launch for a day to review engineering data about how much heating the rocket's liquid-fuelled fourth-stage would be subjected to during its flight.
The rocket is designed to deliver the 1900kg satellite into an orbit 1.5 million km from Earth.
From that vantage point, the prototype Laser Interferometer Space Antenna, or LISA, spacecraft will spend about six months testing a technique to detect ripples in space and across time, a phenomenon predicted but never proven by physicist Albert Einstein 100 years ago.
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The ripples, known as gravitational waves, are caused by massive celestial bodies warping space, similar to a bowling ball rolling across a trampoline.
Like light, gravity travels in waves, though so far attempts to detect them with ground-based observatories have been unsuccessful.
LISA Pathfinder is intended to pave the way for an operational gravity wave detector that would use three satellites, formation-flying in a triangle one million km apart.
The satellites would contain small metal cubes that would oscillate as a gravitational wave passes through, similar to a buoy rising and falling on the ocean.
Using a laser to measure tiny changes in the distances between the cubes, scientists hope to track the subtle flexing of space and time.
LISA Pathfinder will demonstrate the concept with the two metal cubes, positioned 38cm apart inside a single spacecraft.
The LISA Pathfinder mission costs about 400 million euros ($A581.10 million).
