Massive Construction Effort Begins For World's Largest Telescope

An anonymous reader writes with this selection from a press release issued by the Harvard-Smithsonian Center for Astrophysics: "Astronomers have begun to blast 3 million cubic feet of rock from a mountaintop in the Chilean Andes to make room for what will be the world's largest telescope when completed near the end of the decade. The telescope will be located at the Carnegie Institution's Las Campanas Observatory-one of the world's premier astronomical sites, known for its pristine conditions and clear, dark skies. Over the next few months, more than 70 controlled blasts will break up the rock while leaving a solid bedrock foundation for the telescope and its precision scientific instruments."

Comments

Ground vs Space

[zAPPzAPP]

It seems whenever I read an article about something new and great discovered by a telescope, it mentions one of the orbiting sattelite type telescopes.

I can't remember when I last heard from a ground based one, except for routine things as continuously sweeping certain areas of the sky for anomalies, like a space surveillance camera.

Now I don't follow astronomy closely, so my viewpoint is based on what of it gets through to general science news sites.
But are huge investments in ground based telescopes like this still worth it compared to the alternative?

Re:Ground vs Space

[Anonymous Coward]

Most optical observations are done by the ground-based ones. They're more available (there's more of them than there are of the Hubble), flexible, and they're enormous.

What recent stories are you talking about? Among big media ones, I recall some supernova stuff (ground-based telescopes), dark matter stuff in Abell 520 (ground-based Canada France Hawaii telescope and Hubble), and of course planet stuff (ground-based telescopes). Of stuff that doesn't make it to the media, the bulk of optical observing comes from the ground-based ones.

For the same price as a large space-based telescope, you can build a much larger ground-based one. You have to contend with atmosphere (which is why they're always on mountains), but we're getting better at dealing with that. Space-based telescopes make a trade-off: less light gathering as they're smaller, but potentially higher resolution/clarity as you don't have to deal with the atmosphere.

Non-optical telescopes are different though. The atmosphere is quite opaque to much of the non-optical spectrum; far-infrared, X-Ray, and Gamma Ray instruments do best outside the atmosphere. The microwave observatories are out there as well, though I think that's more to avoid noise than atmospheric opacity, as the CMB is very weak.

Re:Ground vs Space

[rimcrazy]

With the advances in both active (compensation for deformation of the mirror due to gravity and it's position) and adaptive (compensation of the mirror to negate the effects of atmospheric distortion) optics ground based telescopes can come close to if not equal what can be done in space. When you couple the fact that you can build much larger apertures on the ground for significant less money than what is launched into space I wonder why they are still fooling around with space based telescopes.

Hubble has a 2.4M mirror and cost about 1.5B at launch and over it's lifetime a total of about 6B when you figure in all of the shuttle trips for maintenance and the ground support costs. The 10M Keck telescopes cost 94M each when they were built. The James Webb telescope has become a CF of huge proportions with an estimated cost of close to 8.8B through 2018.

Don't get me totally wrong here. Some magnificent discoveries were made with Hubble along with Swift and Chandra. We do need some space based telescopes but the cost of space base instruments is enormous compared to ground based and there are significant advancements that are being made with sensors and other ground base instruments that are pushing the need for space base instruments further out of the picture.

Re:Ground vs Space

[mrsquid0]

This is largely an illusion. Most space-based telescopes are run either by NASA or ESA, and both of those organizations have very large public relations offices. These offices issue a lot of press releases and put a lot of effort into getting results from their satellites into the media. The Space Telescope Science Institute was one of the pioneers of this approach to popularizing astronomy, and they were very successful at it. Ground-based observatories tend not to have big public outreach budgets, and usually do not have large numbers of people dedicated to getting their results into the media, so we do not see their results on the front pages of the New York Times or the Economist as often.

Space- and ground-based observatories generally do very different things and complement each other instead of compete with each other. For example, I have used ground-based observatories to take spectra of very faint sources and combined them with X-ray, ultraviolet, and optical observations from Swift and Hubble. The science that comes out of these observations would be impossible without observatories both on the ground and in orbit.

It'll be the largest optical telescope, IF...

[Shag]

and only if, it's completed before the (larger) Thirty Meter Telescope in Hawaii, and the (larger still) European Extremely Large Telescope in Chile.

And even if it is completed before TMT and E-ELT, as soon as either of them is completed, it'll lose the title.

Did I mention both TMT and E-ELT are also targeting completion by the end of the decade? Yup.

So, good luck, GMT!

(And it goes without saying that non-optical radio telescopes, which use dishes instead of mirrors, have long been much larger. And that even submillimeter telescopes, which also use dishes, are working on staying larger, with the 25-meter CCAT planned for Chile later this decade.)

Re:It'll be the largest optical telescope, IF...

[WrongSizeGlass]

Even if it never holds the title for the "World's Largest Telescope", a 28-foot diameter primary mirror is a very big telescope ... and it will continue to work after even larger telescopes are built.

Re:It'll be the largest optical telescope, IF...

[Shag]

Yep, of course. In fact, the telescope I run at my job had "the largest monolithic mirror ever made" from 1999 until 2004 (when Roger Angel started cranking out 8.4-meter ones). Wasn't considered the largest telescope, of course, because segmented 10-meter mirrors of the Keck twins (1992 and 1996) next door to it were larger overall, just segmented.

That said, using the phrase "world's largest" in the headline before the first concrete pour invites comments like mine. ;)

uhm

[Real_Reddox]

Astronomers have begun to blast 3 million cubic feet of rock

I think you'll find that the people blasting rock aren't astronomers...

Job safety

[gtirloni]

Besides knowing the depths of the space, they are also construction workers.

more than 70 controlled blasts

[MichaelSmith]

And here's me thinking they were going to blow stuff up at random in the hope a telescope would come out of it.

"Ludicrous Speed"

[zrbyte]

I just love the naming convention of these telescopes. The guys in the organizational committee must have been watching too much Spaceballs

There's the Very Large Optical Telescope, then there's the Overwhelmingly Large Telescope and the European Extremely Large Telescope. What's next? Ridiculously Large Telescope?

Re:"Ludicrous Speed"

[Anonymous Coward]

They've gone to PLAID! (Particularly Large Array of Independent Dishes)

Re:Why not on Nullarbor Plain?

[TapeCutter]

It's only marginally above sea level, so the atmosphere is too thick for proffesionals. It is however a wonderful sight for the unaided eye.

Re:Where is Greenpeace?

[Dusty101]

Extended and ongoing environmental impact studies are part and parcel of the final process of choosing a telescope site these days. We do try to be very careful to be considerate when building these facilities & work with teams of local environmental biologists. Also, in most cases nowadays, one of the preconditions for site use is that the site is returned to its original pristine state once the telescope in finally removed again.

There is, however, sometimes still local opposition. E.g. in Hawaii, this is usually on native cultural grounds, & nowadays, an effort is made to involve local native cultural leaders (in the early days, some culturally insensitive decisions were made, and both sides of the debate are aware of this).

In the case of Chile, such facilities are often welcomed, as they're much less damaging than the extensive mining operations already in existence there, but still provide good engineering and other technical jobs for Chileans. Plus, many Chileans are proud that their country can boast some of the finest such research facilities in the world.

(Full disclosure: I am both a professional observatory staff astronomer and a longtime member of Greenpeace).