An amazing accuracy level of 2 picometres!

[neufer]

LISA Pathfinder – Surfing Gravity Waves
by Tammy Plotner on November 14, 2011

Laser Interferometry Space Antenna (LISA)
Artist's impression - Courtesy: NASA

<<Do you remember the LISA mission? I do! The proposed launch for this unique vision is slated for 2014 and the latest sensor technology is making its own waves… by being far more accurate than expected. Now ESA’s LISA Pathfinder mission is better than ever, and ready to tackle the vast ocean of space in search of elusive gravitational waves…

So what’s new? By employing a near complete version of LISA, the Optical Meteorology Subsystem passed its first test under space-like temperature and vacuum conditions. Not only did it make the grade, but it went far beyond. It surpassed the precision requirement needed to detect gravitational waves by 300%!

Einstein predicted them, but to physically record this phenomenon in space, the LISA Pathfinder will utilize a laser to measure the distance between two free-floating gold–platinum cubes. Here on the ground, the team in Ottobrunn, Germany, are performing the tests are done using mirrors instead of cubes. Not only will the distance between them be cataloged, but their angles with respect to the laser beams. Is LISA good? Darn right. She had an accuracy rating of 10 billionths of a degree! “This is equivalent to the angle subtended by an astronaut’s footprint on the Moon!” notes Paul McNamara, Project Scientist for the LISA Pathfinder mission.

So how are gravitational waves detected? If perfect conditions do exist in space, then the free-floating cubes should mirror each other’s motions. Now, enter Einstein’s general theory of relativity. If some gravitational event should occur – such as the collision of two black holes – this should cause a minute distortion in the fabric of space. These tiny changes should be detectable. However, the accuracy needed to record such an event would need to be about one hundredth the size of an atom… a size called a “picometre”. Originally, LISA was optimized at 6 picometres measured over a timeline of 1000 seconds. But she bettered her record in 2010 and has now reached an amazing accuracy level of 2 picometres.

“The whole team has worked extremely hard to make this measurement possible,” said Dr McNamara. “When LISA Pathfinder is launched and we’re in the quiet environment of space some 1.5 million km from Earth, we expect that performance will be even better.”

The instrument team from Astrium GmbH, the Albert Einstein Institute and ESA are testing the Optical Metrology Subsystem during LISA Pathfinder thermal vacuum tests in Ottobrunn by spacecraft prime contractor Astrium (UK) Ltd. Tentatively set to launch in mid-2014, the LISA Pathfinder is well on its way to ride the gravitational waves and set the pace for ESA’s New Gravitational Wave Observatory. Perhaps within the next 10 years we’ll see even more advancements in finding the “final piece in Einstein’s cosmic puzzle.”>>

[alter-ego]

LISA is a phenomonal challenge. I know this measurement capability will be achieved, but picometer measurment precision over 35cm is one thing, and a very important step to achieve. Maintaining a distance measurement accuracy of 5 million km is quite another. The pather finder is a very important "breadboard" accomplishment to show that free falling bodies follow geodesics in space-time by by more than 2 orders of magnitude better than measured so far. LISA's long baseline will push the drag-free control tecnology to the limit to benefit from this precision, and things are looking up. We do like challenges don't we? It is interesting how we spend a lot of time and money for tecnology development in different arenas. In one case we build earth-bound equipment to look at new phenomena thousands of lyr away, letting nature provide us the experiment, i.e. binary orbital decay revealing gravity waves. While in another case, we spend time and money for technology to look at the same phenomal local to earth, i.e. LISA.
I personally like this approach for confirmation, but the balance between experiments requiring lower accuracy and longer times compared to shorter-term, higher accuracy work seems like a wash to me. Believe me, I am very excited to hopefully see long basline ring laser interferometers reveal space-time fluctuations that are gravity waves in our earth's neighborhood.