The LISA Pathfinder spacecraft has demonstrated five times better precision than expected

Gravitational-wave sensing spacecraft exceeds expectations

European space probe LISA Pathfinder, designed to measure Einstein-predicted gravitational waves, has demonstrated higher precision than originally required.

The spacecraft, operated by the European Space Agency (ESA), has been running an experiment for the past two months in which two gold-platinum cubes placed in separate compartments 38 cm apart from each other have been falling freely in space affected only by gravitational forces.

The experiment is the first demonstration of technology that will be used in future to build a large space-based observatory, which would measure gravitational waves triggered by massive objects in the Universe.

The experiment, described in the latest issue of the journal Physical Review Letters, demonstrated a level of precision five times than originally required.

“LISA Pathfinder's test masses are now still with respect to each other to an astonishing degree, ” said Alvaro Giménez, ESA’s director of science.

“This is the level of control needed to enable the observation of low-frequency gravitational waves with a future space observatory.”

The experiment observed signals of two black holes, each about 30 times the mass of the Sun, as they spiraled towards each other and eventually merged into a single vast object.

This process of moving and merging of massive objects in space was identified by Albert Einstein more than a hundred years ago as the probable cause of disturbances in space time, or gravitational waves. These disturbances, however, are so small that extremely sophisticated technologies are needed to detect them. Such technologies are only available now. 

These ripples in space time were detected for the first time in September 2015 by the ground-based Laser Interferometer Gravitational-Wave Observatory (LIGO).

Despite its breakthrough measurements, the LIGO observatory has its limitations. With a frequency of about 100 Hz, it cannot detect oscillations caused by supermassive black holes.

The technology used in LISA Pathfinder could be used in future to carry out such a task.

LISA Pathfinder was launched on 3 December 2015 and reached its operational orbit roughly 1.5 million km from Earth towards the Sun in late January 2016.

The mission started operations on 1 March, with scientists performing a series of experiments on the two 2kg test masses, both 46mm in size, to measure and control all of the different aspects at play, and determine how still the masses really are.

The first two months of data show that, in the frequency range between 60 mHz and 1 Hz, LISA Pathfinder's precision is only limited by the sensing noise of the laser measurement system used to monitor the position and orientation of the cubes.

“The performance of the laser instrument has already surpassed the level of precision required by a future gravitational-wave observatory by a factor of more than 100,” said Martin Hewitson, LISA Pathfinder senior scientist from Max Planck Institute for Gravitational Physics and Leibniz Universität Hannover, Germany.

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