Space

ESA's gravitational wave satellite shut down after 16 months

The now-defunct LISA Pathfinder satellite was just the first step in the LISA mission, which will launch as a trio of satellites in 2034 to detect low-frequency gravitational waves from anywhere in the universe
The now-defunct LISA Pathfinder satellite was just the first step in the LISA mission, which will launch as a trio of satellites in 2034 to detect low-frequency gravitational waves from anywhere in the universe
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The now-defunct LISA Pathfinder satellite was just the first step in the LISA mission, which will launch as a trio of satellites in 2034 to detect low-frequency gravitational waves from anywhere in the universe
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The now-defunct LISA Pathfinder satellite was just the first step in the LISA mission, which will launch as a trio of satellites in 2034 to detect low-frequency gravitational waves from anywhere in the universe
LISA Pathfinder performed better than expected, and its technologies will go on to be used in the main LISA mission in 2034
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LISA Pathfinder performed better than expected, and its technologies will go on to be used in the main LISA mission in 2034

The European Space Agency's LISA Pathfinder satellite was shut down this week, after 16 months of service in the hunt for gravitational waves. But this is only the beginning: the Pathfinder satellite was a testbed for technology that will eventually be used in the main LISA mission, which is set to become the largest gravitational wave observatory ever built.

LISA Pathfinder's on-board systems were powered down on July 18, just after 8pm Central European Time. To keep the now-defunct satellite from crashing back to Earth, it was nudged into a safe parking orbit, which will keep it away from the planet for the next 100 years.

"When we were in contact with LISA Pathfinder yesterday evening for the last time and said goodbye to the satellite, it was a unique and emotional moment," says Karsten Danzmann, co-Principal Investigator of the LISA Pathfinder mission. "After years of planning and the launch of the satellite in December 2015 we have been spending many days and nights since early 2016 paving the way for the future of gravitational-wave astronomy with LISA Pathfinder."

The point of Pathfinder was to test the technology that will eventually make its way into the main LISA mission, scheduled for launch in 2034. The scientists report that the project passed with flying colors, with the systems operating optimally and measurements that surpassed expectations. Over the intervening years, the core concepts will be scaled up so LISA can listen in on low-frequency gravitational waves.

LISA Pathfinder performed better than expected, and its technologies will go on to be used in the main LISA mission in 2034
LISA Pathfinder performed better than expected, and its technologies will go on to be used in the main LISA mission in 2034

These ripples in the fabric of spacetime were first predicted by Einstein over 100 years ago, and were one of the last pieces of the puzzle of general relativity to be directly observed. In 2015, the LIGO facility detected the physical effects of gravitational waves for the first time, before going on to witness them twice more over the years. But in order to better learn about the phenomenon, we need more precise instruments, and by virtue of floating in space, LISA can pick up far smaller distortions than the ground-based LIGO facility.

Although gravitational waves are caused by cataclysmic events like the merging of two black holes, by the time their ripples reach us their effects can only be seen on the subatomic scale. To detect these incredibly tiny wobbles, LIGO and LISA both work off the process of laser interferometry, beaming a laser between two points and watching for any changes in the distance between them.

On LISA Pathfinder, these two points were free-floating cubes made of gold and platinum, spaced 38 cm (15 in) apart. In the LIGO facility, the points were 4 km (2.5 miles) apart, but the future LISA mission blows both of them away. It will be made up of a constellation of three separate satellites beaming lasers to each other in a triangle, where each side is 2.5 million km (1.6 million miles) long. At this scale, the scientists on the project say that LISA would be able to detect gravitational waves coming from virtually anywhere in the universe.

Source: Albert Einstein Institute Hannover

3 comments
Bob
There are so many anomalies in gravity with so many moving masses that the gravitational constant can only be measured to a few decimal places. I'm not sure that gravity waves have truly been discovered. The precision required is just not possible with so many interferences. This sounds more like seeing what you want to.
JimFox
Bob, have you let the ESA scientists know this? [Sarc off]
Bob
Well Jim, I have no doubt that they know it. I also know that after investing so much money, the investors want to see results. If you had ever been involved in gravity measuring experiments, you would realize that the claims made right down to the estimated masses involved were optimistic speculation. Not knowing the distances to the source made this somewhat of a joke. Any time you are taking measurements at the limit of detection, you are dealing with detector noise. For these noise signals to occasionally match up is more likely random chance than anything else. At this level, it takes a lot of measurements to even get a good estimate. Until they start getting more confirming data, I am unconvinced that they actually measured it and are just jumping the gun. You may want to read up on gravity and wave theory(especially the sections on constructive and destructive interference) before hitting the [Sarc] button.