European Extremely Large Telescope given go-ahead

[Alastair Rae]

Report over on the BBC of plans for a 40m optical scope!

[Kbramley]

oooo looks like even ESO get aperture fever too, but I bet the box that comes in has lots of clouds in it

Good news to see Europe taking a lead in ground based optical telescopes though.

[JulianO]

The red dot finder on this has to be seen to be believed

[Treeden]

£800m.... £800,000,000.... £800 milion pounds.

How on earth can a telescope cost £800m pounds? Yes, it will be the biggest, and probably the best. Yes, it'll be the most high tech telescope ever built, but £800m? Where does that kind of money go? Is it really just another case of contractors and sub-contractors having a feeding frenzy on a budget that has already been agreed? Is it like the MOD procurement debacle all over again? Where.... how?

£800 million pounds? Really? That is totally amazing.

[JulianO]

I'm sure it adds up.

Consider, buying a 24" (0.6m) mirror from Orion costs £5000.

The ELT has 798 1.4meter mirrors in the primary, I don't know what a 1.4m custom built optically perfect mirror costs, Says its 20,000 - then we're already up to 15 million, just for the glass!

Then a 4m secondary, a 3.75m third mirror, a 2.6m 4th mirror capable of taking adaptive optics.

798 1.4m mirrors weighs an awful lot, and you want to move it all to point anywhere in the sky, without it distorting due to gravity.

That needs a heck of a chassis to support it - and of course it needs to be rock solid wherever it ends up.

Then multiple lasers to take out the atmospheric distortion, and all the computing equipment to go with it.

All this to be assembled high above sea level in a far away dessert miles from anywhere.

Its also quite a step up - the biggest current telescopes currently are 10m ones, jumping to 40m is a huge jump, so there are going to be new problems to solve on the way.

[nmoushon]

The ELT has 798 1.4meter mirrors in the primary, I don't know what a 1.4m custom built optically perfect mirror costs, Says its 20,000 - then we're already up to 15 million, just for the glass!

That's if it's just a 'normal' mirror and not one of the adjusting mirrors that adjusts for atmospheric conditions. If they got that kind of budget why wouldn't it be. So I'm sure its a lot lot more than just 15million for the primary mirror. Oh don't forget the secondary mirror to. I bet that suckers going to be bigger than most professional telescopes.

[SamAndrew]

£800m.... £800,000,000.... £800 milion pounds.

How on earth can a telescope cost £800m pounds? Yes, it will be the biggest, and probably the best. Yes, it'll be the most high tech telescope ever built, but £800m? Where does that kind of money go? Is it really just another case of contractors and sub-contractors having a feeding frenzy on a budget that has already been agreed? Is it like the MOD procurement debacle all over again? Where.... how?

£800 million pounds? Really? That is totally amazing.

Seems like a Bargain compared to the Hubble, James Webb Space Telescope, or the cost of sending a rover to Mars.

The money all goes into the design, not the cost of materials, eveything will be custom made by top engineers and scientists; they aren't cheap !

[JulianO]

Seems like a Bargain compared to the Hubble, James Webb Space Telescope, or the cost of sending a rover to Mars.

Indeed - James Webb costing $8.7 billion, for a 6.5m mirror that no one can fix if it goes wrong, can't be upgraded and starts life on top of an explosive filled vehicle that will shake it vigorously!

[palebluedot]

That's if it's just a 'normal' mirror and not one of the adjusting mirrors that adjusts for atmospheric conditions. If they got that kind of budget why wouldn't it be. So I'm sure its a lot lot more than just 15million for the primary mirror. Oh don't forget the secondary mirror to. I bet that suckers going to be bigger than most professional telescopes.

It will indeed have adaptive optics, the primary mirror will be comprised of 984 subcells each with their own actuators. Take a look at what I dug out... amazing read.

E-ESO.pdf

[FraserClarke]

Disclaimer -- I work on the E-ELT, so I'm not an unbiased commentator!

If people are interested in more information, have a look here;

http://www.eso.org/p...nstr/e-elt.html

If you really want to know all the gory details of the design, the whole E-ELT construction proposal is available here (but it's about 200 pages long);

http://www.eso.org/p...constrproposal/

On some of the points that have been raised, JulianO has managed to capture most of the expensive bits. The pointing requirement for the E-ELT is about 0.002 arcseconds -- that's about 1000x better than an EQ6 for comparison. That's not easy!

I think the primary mirror cost is more like $200M€ (about 200k€ per segment, as there are spares). The scaling from a commercial 0.5m mirror is interesting Julian. These are substantially more complex mirror shapes though (off axis paraboloids, which is a lot more complex to make), and made of zerodur/ULE -- which is a factor of 10 more expensive than normal borosilicate ("pyrex") glasses. They're also lambda/15 tolerance, which a lot tighter than most commercial mirrors you can buy. And you've got to make one every 3 days... All that for just 10x more than something you could buy off the shelf! pretty impressive... Of interest, there is a company in North Wales who are currently prototyping their approach to this, so if they are successful some/all of the E-ELT mirror segments could be made there.

The secondary mirror is now "only" a 4 meter mirror. That makes it cheaper and less risky than the previous (42m) design which had a 6m secondary mirror. Of course, it has to sit 50m up in the air, and change it's shape/position every few seconds, so it's not that easy!

M3 is trivial, because it's just like building a normal 4 meter telescope mirror...

M4, which is the 2.7m adaptive mirror has no equivalent in the current world. It has >5000 actuators, each of which changes it's position up to 1000x a second. No-one has built an AO mirror on that scale before (I don't even imagine the military have a need for that).

M5 is a flat mirror, but it's 3m across and needs to tip/tilt back and forwards several hundred times a second -- you've got to work out how not to shake it to pieces!

Then, once you've worked out how to do all of that, you need to build a small football stadium in the middle of the atacama desert 3000m up a mountain (after you've blown ~30m off the top of the mountain to make space). Except your "football stadium" needs to have a sliding roof, and be able to spin round, and precisely control the airflow over the telescope. At least you don't have to worry about putting the seats in...

Oh, and all of this has to be able to survive a magnitude 7 earthquake.

Treeden: 90% of the money goes straight back into European industry, but these industries tend not to make a massive profit on astronomy projects. They like doing them because they're interesting, push their technology forward, and allow them to talk about/promote their work -- unlike some of the perhaps more lucrative, but commercially/security sensitive projects they might be involved in. Astronomy/research projects tend to get a pretty good deal from industry actually!

And, we'll get some pretty cool science out of it all in the end!!

[FraserClarke]

It will indeed have adaptive optics, the primary mirror will be comprised of 984 subcells each with their own actuators. Take a look at what I dug out... amazing read.

E-ESO.pdf

That's a pretty old document palebluedot, based on the 42m design (which is now descoped down to a 39m). The new design has 798 subcells, but the principles are still the same as in that document.

[palebluedot]

Thanks Fraser, looks like the document I found is a little out of date. You are working on an awesome project, you must love your job. Will they change the name now that Brasil has come on board?

[Edit] Bit of a crossover there.

[JulianO]

It's a pretty awesome endeavour, and as our head of dept said, "we should build it, just because we can" - although its almost guaranteed to make new breakthroughs.

[FraserClarke]

Will they change the name now that Brasil has come on board?

Dunno! good question -- I've never considered it! E&SA-ELT ??

[Treeden]

Treeden: 90% of the money goes straight back into European industry, but these industries tend not to make a massive profit on astronomy projects. They like doing them because they're interesting, push their technology forward, and allow them to talk about/promote their work -- unlike some of the perhaps more lucrative, but commercially/security sensitive projects they might be involved in. Astronomy/research projects tend to get a pretty good deal from industry actually!

And, we'll get some pretty cool science out of it all in the end!!

Thanks for the info about the telescope Fraser. It must be very exciting to be involved in the project, and I’m sure you’re right about the very cool science. It is certainly a very impressive instrument indeed.

I didn't intend to put a damper on the project or question it's purpose or value. I love the scale and ambition of it all and I look forward to seeing what it's capable of. One thing I do know though, is that whenever you get a large multi-national project that has a very large budget, especially one that is controlled by several committees, then you will also get the 'opportunists', who only want the largest slice of the cake that they can get their hands on. I don't mean the scientists, but those involved in one-off contracts to supply the resources to build it. I've been around long enough to have seen it elsewhere and unfortunately it's just a part of human nature. It just annoys me when I think of the valuable funding that is wasted this way.

That aside, I wish nothing but the best for the telescope and all who are involved in the project. Good luck and clear skies!

Rob