LISA is On! Gravitational Wave Detection is Going to Space

Article written: 21 Jun , 2017

The discovery of gravitational waves by the LIGO experiment in 2015 sent ripples through the scientific community. Originally predicted by Einstein’s Theory of General Relativity, the confirmation of these waves (and two subsequent detections) solved a long-standing cosmological mystery. In addition to bending the fabric of space-time, it is now known that gravity can also create perturbations that can be detected billions of light-years away.

Seeking to capitalize on these discoveries and conduct new and exciting research into gravitational waves, the European Space Agency (ESA) recently green-lighted the Laser Interferometer Space Antenna (LISA) mission. Consisting of three satellites that will measure gravitational waves directly through laser interferometry, this mission will be the first space-based gravitational wave detector.

This decision was announced yesterday (Tuesday, June 20th) during a meeting of ESA’s Science Program Committee (SPC). It’s implementation is part of the ESA’s Cosmic Vision plan – the current cycle of the agency’s long-term planning for space science missions – which began in 2015 and will be running until 2025. It is also in keeping with the ESA’s desire to study the “invisible universe“, a policy that was adopted in 2013. 

To accomplish this, the three satellites that make up the LISA constellation will be deployed into orbit around Earth. Once there, they will assume a triangular formation – spaced 2.5 million km (1.55 million mi) apart – and follow Earth’s orbit around the Sun. Here, isolated from all external influences but Earth’s gravity, they will then connect to each other by laser and begin looking for minute perturbations in the fabric of space-time.

Much like how the LIGO experiment and other gravitational wave detectors work, the LISA mission will rely on laser interferometry. This process consists of a beam of electromagnetic energy (in this case, a laser) being split in two and then recombined to look for patterns of interference. In LISA’s case, two satellites play the role of reflectors while the remaining one is the both source of the lasers and the observer of the laser beam.

When a gravitational wave passes through the triangle established by the three satellites, the lengths of the two laser beams will vary due to the space-time distortions caused by the wave. By comparing the laser beam frequency in the return beam to the frequency of the sent beam, LISA will be able to measure the level of distortion.

These measurements will have to be extremely precise, since the distortions they are looking for affect the fabric of space-time on the most minuscule of levels – a few millionths of a millionth of a meter over a distance of a million kilometers. Luckily, the technology to detect these waves has already been tested by the LISA Pathfinder mission, which deployed in 2015 and will conclude its mission at the end of the month.

Artist’s concept of the LISA mission. Credit: AEI/Milde Marketing/Exozet

In the coming weeks and months, the ESA will be looking over the design of the LISA mission and completing a cost assessment. If all goes as planned, the mission will be proposed for “adoption” before construction begins and it is expected to be launched by 2034. In the same meeting, the ESA also adopted another important mission that will be searching for exoplanets in the coming years.

This mission is known as the PLAnetary Transits and Oscillations of stars, or PLATO, mission. Like Kepler, this mission will monitor stars within a large sections of the sky to look for small dips in their brightness, which are caused by planets passing between the star and the observer (i.e. the transit method). Originally selected in February of 2014, this mission is now moving from the blueprint phase into construction and will launch in 2026.

It’s an exciting time for the European Space Agency. In recent years, it has committed itself to multiple endeavors in the hope of maintaining Europe’s commitment to and continued presence in space. These include studying the “invisible universe”, mounting missions to the Moon and Mars, maintaining a commitment to the International Space Station, and even building a successor to the ISS on the Moon!

Further Reading: ESA

Matt Williams is the Curator of Universe Today’s Guide to Space. He is also a freelance writer, a science fiction author and a Taekwon-Do instructor. He lives with his family on Vancouver Island in beautiful British Columbia.

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8 Responses

  1. xinhangshen says

    Matt Williams, we still don’t know what gravitational waves are because the concept of ripples of spacetime is wrong. Everybody knows that the clocks on the GPS satellites are universally synchronized i.e. they are showing the same absolute time rather than relative time which is claimed by special relativity. Once we know time is absolute, then there is nothing called spacetime continuum in nature and thus there are no ripples of spacetime at all. Please first abandon the concepts derived from Einstein’s wrong relativity theory and develop new theory before making such expensive experiments. What do you think, Matt? I welcome your reply and hope to debate with you if you don’t agree with me.

    • Member

      “Everybody knows”? No they don’t, sir. And stating claims as if they are common knowledge doesn’t make them true. For 20 years, comparisons between atomic clocks aboard GPS satellites to those on Earth have proven time and again that special relativity and general relativity are in fact correct. Comparisons of GPS clocks to each other did not yield perfect synchronization, but variance. The claim they disproved GR is a fringe theory argued by pseudoscience enthusiasts. What’s more, gravitational waves have been detected three times now. I’m afraid you’re claims are without merit here.

    • Nexus says

      “Everybody knows that the clocks on the GPS satellites are universally synchronized”

      That isn’t true, so no, not everybody knows that.

  2. Starreeyed says

    Hey Matt, you must be a neighbor to Fraser.
    Now then, this LISA mission….the two mirror satellites have to maintain to an insanely high degree of precision their distance from the laser satellite. I cannot imagine how that is even possible. Thinking about it, I suppose that they might use x-ray lasers to calibrate the distances…x-rays because the wavelength is much shorter than (say) the IR lasers used to detect gravitational waves. But even so, the technical challenge is mind boggling. All three satellites must use thrusters of some sort for station-keeping…that has me really scratching my head!

    • SteveZodiac says

      Have a look at the ESA report of the pathfinder mission where the masses were stabilised above their target accuracy ahead of the target time frame, the accuracy is indeed mind boggling.

  3. SteveZodiac says

    This is great news opening up a whole new field of Astronomy that does not rely on the EM spectrum so may eventually be able to shed light (no pun intended) on dark matter. It will be interesting to see what level of gravitic disturbance LISA will be able to detect, the collapse of a supernova into a black hole or neutron star? Galaxy crashes? Orbiting binaries?

  4. For the investigation of gravitational waves, as seen from the experiments, laser beams are used. It is claimed that the accuracy of the difference in the time of arrival of the disorder (the space time curvature , or the shrinkage of the space) indicate that it amounts to one millionth of a millionth of a millimeter.
     Now the following questions are raised:
     1. If the device is on Earth, whether there is anywhere on the surface of the Earth, any non-moving fluid, either earth or any vibration outside, without talking about the position of these points in the space (all types of motion of the Earth).
     2. Are lasers something more subtle than any kind of radiation from the universe?
     3. How much will these two satellites move, until the disorder gets to them. ?
    And what about the third satellite?
     4. Does science at all know what black holes are and can they crash and how?
     5. No one has confirmed the Einstein theory of relativity and Lorenz’s transformation with the true cause of the phenomenon. They are all fatamorganes . It all corresponds to scientists, because from fabrication they get big money from states and institutions that want to mend and contaminate the consciousness of human beings. It is one of the means of governing the masses of the people.
     5. I offer one question, if science does not know how to answer it and give true and unmistakable proof, then it is clear that all those who deal with it, do not know the structure of the universe or the causes of the movement of heavenly bodies. QUESTION :
     Einstein and Lorenz, as well as everything related to the collision of black holes, will prove this evidence and show that the universe was formed.

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