LISA Pathfinder exceeds all expectations, and begins the era of gravitational astronomy

LISA Pathfinder has exceeded all expectations, and it is with this result that the ESA work, the Italian Space Agency (ASI), the National Institute of Nuclear Physics (INFN) and the University of Trento has been awarded.

The experiment LISA is a new messenger who will bring us important information about the mechanisms that regulate the life of the Universe, as gravitational waves.

Stated about a year ago the president of the ASI, Roberto Battiston. Moreover, the LIGO and VIRGO scientific collaborations have been recently confirmed its existence. Now what remains to be seen is how the dark side of the Universe, composed of around 95% of matter and dark energy, may have some impact on gravitational waves.

It was the night between the 2nd and 3rd December 2015 when the LISA Pathfinder developed by ESA began its journey to its operational orbit at about 1.5 million from the Earth, directed toward the Sun. It has reached its destination about a year later, at the end of January 2016.

LISA made everyone proud of her. Perfect explorer of space; and pioneer of new missions.

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LISA Pathfinder. Developed by ESA, INFN, ASI and Trento UNiversity

LISA’s work is the result of many sacrifices, that the protagonists of this adventure can remember thread and sign. Why that? LISA Pathfinder has gone through a long series of tests, implemented and corrected by the head project scientists: Michael Armano and Paul MacNamara. Two professionals that have taken a great pride in a meticulous search, and a job, that gave the world important confirmations:

The scientific mission LISA Pathfinder started from a demonstration of the potential key technologies and techniques needed to observe gravitational waves. The latter were predicted by Albert Einstein in 1916, as a direct consequence of general relativity, aimed at defining the curvature in the tissue of space-time that propagates as a wave.

But what are the phenomena that cause gravitational waves? possible hypotheses are the explosions of massive bodies like the approach of supernovae (binary stars that wrap spiral over one another) or the merger of two supermassive blacks holes (with masses equal to millions of billions that of the Sun).

For now what we know is that gravitational waves are gravity waves that travel at the speed of light. The point is that, in the words of Stefano Vitale, of the University of Trento and Co-Investigator for the subsystem of the inertial sensor (ISS):

If we could hear the universe, listening to the changes of gravity, maybe we can observe the universe as it really is, namely a huge gravitational system held together by gravity. So this is one astronomical research tool, the very important cosmological exploration that will open a new frontier in astronomy.

The revolutionary element where it is possible draw attention is that the direct detection of these waves has “opened the dance” era of gravitational astronomy. In other words?

To reveal such events, and to fully exploit the field of exploration opened by the recent discovery of gravitational waves, it is also important to record low-frequency waves, from 0.1 MHz to 1 Hz. But to elaborate this task one should record any tiny changes in distance between objects at millions of kilometers apart: a situation possible only in space, where an observatory is not subject to seismic disturbances, heat and gravity, and reasons of force majeure that limit us in research.

This ESA project is important because it has been able to put a solid foundation for the creation of an observatory future in space, able to detect gravitational waves having longer wavelengths than those found on Earth. A futuristic observatory therefore realized as the third large-scale mission (L3) in the Cosmic Vision Program.

LISA Pathfinder is designed to process multiple tests, among which achieve the best effect of freefall, or an extremely demanding condition but necessary to build the observatory in space. LISA Pathfinder has made largely use of the latest technologies to minimize the external forces that could disrupt the two proof masses: the inertial sensors, the laser metrology system, the control system without dragging and the ultra-precise micro-thruster system have made a difference; making it unique in its kind.

 

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The key mechanism for the LISA Pathfinder mission is shown through the two golden cubes, encased in vacuum containers and shown here without the launch of the locking mechanism.Each of these container has hosted test electrodes, composed of a gold-platinum mixture. It has been used a high-precision laser interferometer to monitor the free fall of two cubes. The optical interferometer is visible between the two masses: one cutting edge tool, made with a block of glass and ceramic Zerodur, and provided with 22 mirrors able to direct the laser beams on its surface. That with their light beams allowed to accurately measure the movement, the exact location and orientation of the cubes without touching them. In order to have data, as much as possible objective.

 

But let’s take a step back. To achieve this result, and exceed all expectations, the ESA team has released two test masses – a couple of cubes of 46 mm composed of a mixture of gold-platinum, into the spacecraft that was then actually moved under the effect of gravity. The result was far from trivial, since in space radiation and solar wind are no forces that could have such an effect on these cubes, if it were not for the effect of gravitational waves.

Scientists responsible for LISA Pathfinder have continuously measured the positions of the cube pair through particular microthrusters, able to perform the right and delicate maneuvers avoiding touching them.

We noticed that the way in which it falls freely in space, the cubes couple should have been extraordinarily firm, since no force – if not the gravitational wave we were looking- is capable of disrupt their gravitational motion.

Said Stefano Vitale, pointing out that this result was obtained with an accuracy five times greater than that required in the design phase.

It will be the next satellite of the constellation e-LISA to continue the LISA Pathfinder mission to explore the deep space. Being sure to gain infinite knowledge exploring the beauty of the Universe.

 

LH

 

 

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