In a June 7 2016 article at the Institute of Electrical & Electronic
Engineers (IEEE) Spectrum magazine web site, Rachel Courtland
reports on LISA Pathfinder, a spacecraft launched late last year, which
has successfully tested technologies for a full-blown Laser Interferometer
Space Antenna (LISA) space-based gravitational wave observatory.
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Originally Posted by Rachel Courtland, IEEE
This basic vision for a space-based gravitational wave observatory, which those planning a European mission generally call the Laser Interferometer Space Antenna (LISA), is about 30 years old. And it could be 20 years more before we see it in action. But results released today by the European Space Agency’s LISA Pathfinder team suggest it’s possible to achieve the sensitivity needed to build it. Such a space-based observatory would use a technique similar to its Earth-bound cousin LIGO—which announced the first direct detection of gravitational waves earlier this year—to detect slight ripples in the fabric of space-time. But the quarry would be gravitational waves in a frequency range that’s inaccessible here on Earth, one that includes sources such as merging supermassive black holes in the heart of colliding galaxies.
LISA Pathfinder, which launched late last year, contains a small pair of gold-platinum “test masses” and a laser interferometer to measure changes in the distance between them. The mission, a shrunken-down version of what in LISA would be an “arm” made by two spacecraft, isn’t designed to detect gravitational waves. Instead, it’s intended to test out some of the basic technologies required to do so and show that a spacecraft can have low enough noise to be sensitive to passing gravitational waves.
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Quote:
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Originally Posted by Rachel Courtland, IEEE
The results, published today in Physical Review Letters, indicate that LISA Pathfinder exceeded its requirements. At the frequencies gravitational wave scientists are interested in, the spacecraft can discern an acceleration between the test masses of less than a femto-g, or one millionth of a billionth of the acceleration due to gravity on the surface of the Earth. Says principal investigator Stefano Vitale: “The closest thing to a force on the test masses corresponding to a femto-g is the weight a bacterium in your hand.”
“This paper is a green light for LISA,” adds Vitale, a professor at the University of Trento in Italy. “For us it’s an enormous sense of achievement."
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Physics Review Letters, "Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results", M. Armano et. al. 7 June 2016 -
http://journals.aps.org/prl/abstract...ett.116.231101
LISA Pathfinder European Space Agency web site -
http://sci.esa.int/lisa-pathfinder/
IEEE article here -
http://spectrum.ieee.org/tech-talk/a.../esa-grav-wave
LISA Pathfinder tests concept of space-based gravitational wave detector - IEEE
