ESA Approves Gravitational-Wave Hunting Spacecraft For 2034 (newscientist.com)

The European Space Agency has approved the Laser Interferometer Space Antenna mission designed to study gravitational waves in space. The spacecraft is slated for launch in in 2034. New Scientist reports: LISA will be made up of three identical satellites orbiting the sun in a triangle formation, each 2.5 million kilometers from the next. The sides of the triangle will be powerful lasers bounced to and fro between the spacecraft. As large objects like black holes move through space they cause gravitational waves, ripples which stretch and squeeze space-time. The LISA satellites will detect how these waves warp space via tiny changes in the distance the laser beams travel. In order to detect these minuscule changes, on scales less than a trillionth of a meter, LISA will have to shrug off cosmic rays and the particles and light from the sun. The LISA Pathfinder mission, a solo probe launched in December 2015, proved that this sensitivity was possible and galvanized researchers working to realize the full LISA mission.

Comments

Re:Declining intelligence of Slashdot users

[behrooz0az]

I don't beleive the users have become retarded as much as you think they have. It's just that the scientific articles, at least the real ones are becoming extremely specific and focused and small topics that not many people, even smart ones are quallified to actually comment on how right or wrong they are.
We just read and enjoy the cool acronyms and TFA pictures.
oh, and fuck trump while we're at it.

Need this kind of thing to see pre-CMB

[Maritz]

First 300k or so years of this universe was opaque to light, but not to gravitational waves (obviously). So we need these kinds of 'telescope' to see earlier than 300k years or so. Cool mission. Will be interested to see if the Brits are involved or if they're still too busy disappearing up their own arses. Time will tell.

Re:Need this kind of thing to see pre-CMB

[locater16]

I was wondering why it had been approved. So far as I know the first detector was built just to prove the theory. It's such a miniscule effect though that I wonder how effective it'll be.

Re:Need this kind of thing to see pre-CMB

[ivano]

Luckily (or unluckily) the UK's involvement with the ESA is independent from the EU discussions, AFAIK

Re:Declining intelligence of Slashdot users

[Anonymous Coward]

So a comment about wibbly wobbly timey wimey laser beams would go down well..?

Why are they waiting 17 years?

[He Who Has No Name]

The changes in cost to orbit per pound just in the last two years have been game-changing. For all we know in 17 years Elon is going to be negotiating their payload fees from his HQ compound built into the side of the Mariner Valley.

Get the lead out a little, ESA.

Re:Why are they waiting 17 years?

[j-b0y]

Because the technology involved will take some time to develop. You have to have 2 spacecraft pointing a laser at another spacecraft 2,500,000 kilometers away, and measure the change in distance between the two arms to an incredible precision. That's... not easy.

Re:Why are they waiting 17 years?

[techno-vampire]

If I read TFS correctly, they're planning on having three spacecraft with each pointing lasers at the other two. If I'm right, that gives you six sets of data to work with instead of the two that your way does, making it easier to correct for the inevitable station-keeping issues. Alas, even if this goes off on schedule, I'll be in my mid-80s when it launches and I'll be very lucky if I survive long enough to see any results. Still, it sounds like a great idea and I hope they pull it off.

Re:Why are they waiting 17 years?

[avandesande]

In the 80s I used to walk by one of the LIGO prototypes at Caltech. Gravity waves take a long time to transverse the universe, and it takes a long time for us to detect them!

Re:Why are they waiting 17 years?

[Immerman]

Depending on how you count it, it's actually 6 spacecraft, specifically to eliminate the vast bulk of station-keeping issues. Each of the three nodes is actually two separate craft, one nested inside the other, without making any contact, in a "zero-drag satellite" configuration.

The inner craft contains all the measuring equipment, laser emitters, etc, and is only influenced by gravity. The outer "shell" is there specifically to enable the "only influenced by gravity" orbital path - it intercepts the solar wind, photon pressure, etc. before they can reach the inner craft, and then continuously makes tiny corrections to its orbit in order to remain centered on the inner craft.

Re: Why are they waiting 17 years?

[Immerman]

Are you sure? I could swear I read the opposite.

Such an approach would certainly make sense for the solitary proof-of-concept Pathfinder, but I would think that it would introduce an unacceptable amount of noise to the laser interferometers planned for LISA itself.

They cancelled it back in 2012

[Laxator2]

LISA was in development for quite a few years (10 maybe ?) when it was cancelled.
Now that LIGO did find evidence for gravitational waves ESA wants to be at the winner's table, so the bad project is good again.

I think we should call that "having a vision".

Re:They cancelled it back in 2012

[Anonymous Coward]

LISA was started as a joint ESA-NASA mission.
Only NASA cancelled their participation in 2011 because of budget
Since then it has been an ESA mission - and it had the support of the agency (reaffirmed in 2013 in the "cosmic vision" mission selection).

So it was never a "bad project" for ESA - you could say the US congress is lacking vision if they reduce NASA's budget so they can't afford missions like that anymore....

Re:They cancelled it back in 2012

[j-b0y]

LISA was cancelled because JWST was eating the NASA astrophysics budget; ditto IXO cancellation. LISA survived in a much reduced form as NGO, and IXO as ATHENA.

There wasn't any real chance of LISA scooping LIGO/E-LIGO if gravitational waves were really detectable, but the sensitivity of LISA will open up detection of many more classes of GW emitters.

Re:They cancelled it back in 2012

[Anonymous Coward]

Actually it is the very long distance between the satellites that will open up detection of many more classes of GW events, not so much the sensitivity. GW detectors are essentially antenna and the longer distances tune it for much lower frequencies, and thus a different class of events.
For high frequencies events, like the colliding black holes LIGO detected, the Crests and Troughs of the gravity wave will mostly cancel each other out over the length of the detection path making detection actually harder.

Re:They cancelled it back in 2012

[kiminator]

The reduced noise from not being near the ground is also a big bonus. But yes, the difference in detection frequencies is the most significant difference.

Re:Declining intelligence of Slashdot users

[j-b0y]

Slashdot has become a desolate wasteland, just like much of the general interest part of the internet. Specialist forums are still fine.

Wait. Slashdot has always been a desolate wasteland, it was just a much more enjoyable wasteland.

"Reasonable arguments beget angry screeching" - Plague of Gripes

This is a fatally flawed experiment

[Anonymous Coward]

A triangular formation of 3 probes? Seriously? What's needed, bare minimum, is a suite of 4 probes in a tetrahedonal configuration. That way, we get a much more accurate vector reading for the event. They cannot be defeated, we need to know what direction to run!

Re: This is a fatally flawed experiment

[Immerman]

No good - every time you fire your thrusters, even miniscule-thrust ion drives, you're introducing chaotic noise many orders of magnitude larger than the signal you're trying to detect. And any time you're *not* firing your thrusters, the satellites are immediately drifting out of alignment. To get the needed precision they're actually using a "zero drag" satellite-within-a-satellite design so that the free-floating inner satellite is only influenced by gravity, while the outer one is a shell designed to take the signal destroying "hits" from the solar wind, photon pressure, etc. and then correct it's orbit to remain centered around the free-falling inner one.

Just getting three satellites into a stable equilateral arrangement is a fine trick of celestial mechanics - each satellite orbits the sun in a different plane, resulting in an stable equilateral "tumbling triangle" of orbits. https://en.wikipedia.org/wiki/...

And incidentally, while the current gravity-wave detectors are only large enough to detect the high-frequency signals of merging black holes, the LISA is designed specifically to detect lower-frequency signals such as extremely large binaries and other such phenomena, which should be giving off a fairly stable signal. And a stable signal, combined with the tumbling of the array, should allow for fairly accurate 3D directional resolution as the signal fades in and out based on alignment.

Re:This is a fatally flawed experiment

[Immerman]

Not quite - their combined center of mass will follow Earth in its orbit, but each satellite orbits in a different plane so that they form a tumbling triangle.(animation: https://en.wikipedia.org/wiki/... )

I think if you tried to get them into the same plane you would need to have far more eccentric out-of-phase orbits, meaning far larger built-in "noise" (and thus less sensitivity) as their relative distances and speeds continuously varied.

Alternately you could place them all equidistantly around the sun in the same circular orbit - but then the triangle would be too large to detect the signals we're interested in - such as galactic and 10^6 solar-mass binaries (the bigger the detector, the lower the frequency of the signals it can detect) Similarly, the largest stable orbit achievable around Earth is too small and can only detect higher-frequency signals (plus, we've got the Moon to deal with, which destabilizes the entire orbital neighborhood)

Re:This is a fatally flawed experiment

[avandesande]

This doubles the number of optical components and likely the cost.

Re:This is a fatally flawed experiment

[kiminator]

Nah, the construction cost of the satellite itself isn't all that important, not compared to the launch cost. The other commenters have it right: it's about orbital mechanics. You can organize the satellites in a triangle so that they maintain the same shape. I don't think it's possible to add a fourth satellite and keep it in an orbit that's actually stable.

I don't think that a fourth satellite would improve the science all that much anyway.

Re:This is a fatally flawed experiment

[avandesande]

While I agree that the orbital considerations are most important, I think you are way off on cost. Are you even aware of the components that go into these lasers? This system is amazingly complex. The budget right now is 2.4 billion dollars, surely that isn't mostly launch costs.

Re:Declining intelligence of Slashdot users

[Bender Unit 22]

OMG, you're right. I'll start.

There's something wrong about this article, How are they going to orbit the sun, isn't it flat like earth?
We have already established that the moon are a hologram, so naturally they can't orbit that.

Re:Declining intelligence of Slashdot users

[ceoyoyo]

The working scientists and seriously knowledgeable amateurs who hung out here in the late 90s have mostly moved on. Slashdot was invaded by the masses just like everything else on the web.

metric system

[iridium_ionizer]

From summary:

In order to detect these minuscule changes, on scales less than a trillionth of a meter

I think these are called picometers (10^-12 m)

Re: Declining intelligence of Slashdot users

[KGIII]

/. was never good.

Re: Useful

[tigersha]

Like they say in Game of Thrones: I swear by the old Gods and the new that won't happen