Europe has launched the Lisa Pathfinder satellite, an exquisite space physics experiment. It will test the technologies needed to detect gravitational waves, the warping of space-time produced by cataclysmic events in the cosmos. Having such a capability would make it possible to detect the merger of monster black holes, a marker for the growth of galaxies through time. Lisa Pathfinder went into orbit on a Vega rocket from French Guiana. The satellite is being sent in the direction of the Sun, to a point some 1.5 million km from Earth. The expectation is that the European Space Agency (Esa) mission will operate for about a year. Pathfinder contains just the single instrument, which is designed to measure and maintain a 38cm separation between two small gold-platinum blocks.
These “proof masses” will be allowed to free-fall inside the spacecraft, and a laser system will then attempt to monitor their behavior, looking for path deviations as small as a few picometres. This is well less than the diameter of an atom. Scaled up, it is like tracking the distance between the tops of London’s Shard skyscraper and New York’s One World Trade Center, and noticing any changes down to just fractions of the width of a human hair. Lisa Pathfinder is particularly noteworthy from a British perspective, being the first Esa mission to be led industrially by the UK since the Giotto probe was sent to Halley’s Comet in the 1980s. Engineers at Airbus Defence and Space in Stevenage assembled Pathfinder and have been at the Kourou spaceport for the past month and a half, getting it ready to ride on the Vega rocket.
Two black holes orbit one another in deep space. As the massive objects circle each other, they get closer and closer until the two black holes merge, creating actual ripples in the fabric of space-time. While these ripples called gravitational waves have never been directly observed before, a new spacecraft could bring humanity one step closer to finding clear evidence of the never-before-seen signatures of some of the most extreme collisions in the universe. Such evidence could help confirm yet another piece of Albert Einstein’s general theory of relativity. Scientists will use the (ESA) LISA Pathfinder, to work out the kinks of the technologies needed to one day detect these cosmic waves sent out from black hole mergers.
Gravitational waves have never been directly measured before, and LISA Pathfinder probably won’t be the spacecraft to do it in earnest, but it could pave the way for such a platform. However, by testing the propulsion system and other engineering components used in this mission, scientists could one day launch a much larger craft that has a better chance of actually parsing out the signal of these waves from the cosmic background noise. “With LISA Pathfinder we will demonstrate crucial technologies for future missions such as eLISA and will be one large step closer to the detection of gravitational waves from space“, Karsten Danzmann, director at the Max Planck Institute for Gravitational Physics in Germany, said in a statement.
LISA Pathfinder which will eventually reach an orbit about 1 million miles from Earth will use technologies never before tested in space, according to ESA. One of the instruments comes complete with a pair of identical gold cubes that will each be “suspended in its own vacuum container,” ESA said. This suspension in weightlessness will create a drag-resistant environment that should allow scientists to learn more about what kind of technical capabilities they need to eventually launch a larger mission with an even better shot of properly detecting these waves. Scientists working with the Pathfinder will be able to measure the distance between the cubes to fractions of a millimeter. In the full scale version of this kind of system, researchers will use these exacting measurements to know when a gravitational wave passes through the craft. If the distance between the cubes changes without other gravitational force, then scientists should be able to detect it and know whether a ripple in space-time changed the distance between the two objects. “LISA Pathfinder is a pioneering mission. Not only are these technologies new, they cannot be properly verified on the ground,” ESA wrote. “This is because Earth’s gravity and environment would overwhelm the test results. Only in space can the subtle effects of the low-frequency gravitational waves be detected with exquisitely precise instruments.”
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