Your Thoughts on a High Altitude Telescope

[Drakkith]

Hey PFers. I'm just wondering what your thoughts on a High Altitude Telescope are.
What I mean is pretty much a telescope on a platform suspended in air on balloons at 40,000+ feet. The whole thing would be solar powered, with a couple of engines capable of station keeping, with the appropriate support hardware for data transfer, communications, ballast, etc.

My thinking was that something like this would be several orders of magnitude cheaper than space telescopes such as the HST, and much much easier to service, upgrade, etc, while having nearly the same capabilities. At 40k-50k feet your above about 90% of the atmosphere, greatly reducing it's effects.

So, is my thinking somewhat correct?
What are some obvious downsides? Obviously keeping a telescope stationary and on target while on a platform in the air would require a little more work than my own mount and tripod I use with my personal scope, but it doesn't seem unachievable given that we have giant multi-meter telescopes with movable mirrors and such currently.

 

[Ryan_m_b]

Various companies have invested in stratellite technologies in recent years (I was going to link to wiki but it seems some company has claimed the page for their own product), high altitude blimps capable of reaching 20km in height. A lot of different groups are very interested in this technology for telecommunications; cover a stratellite with dishes and it could provide a variety of wireless signals to a huge (European country sized) area. Advantages over satellites would be potential cheaper cost and the ability to simply order the thing to fly itself back to Earth for maintenance, with solar power they would also be very eco-friendly.

Problem is this type of technology is a long way from commercialisation, with regards to using it to put a telescope on I'm not seeing any show stopping problems but the tech has to be there first.

 

[russ_watters]

Would this be sort of like a telescope in an airplane...? http://www.popsci.com/technology/article/2010-01/inside-sofia-nasas-airplane-mounted-telescope

 

[Drakkith]

Hah! Interesting and funny! But yes, something like that. But much better! (Or so I will push!)

 

[Vanadium 50]

I don't think it's cheaper. The HST is in free fall. Atacama is on the ground. You need a very, very, very, very stable platform, which is heavy and expensive. Remember, the whole point of this is to beat atmospheric density fluctuations, and if you can't make the platform even more stable than that, you're wasting your time.

I am always impressed by people who think something they have never done is "just a little more work".

 

[Drakkith]

The whole platform wouldn't need to be 100% stable, just the telescope itself. That would seem to be an easier route than the entire platform, but I don't know for sure. Heck, they were able to keep a telescope stable in a 747 with the door open in Russ's link. A stationary platform seems to be a much more stable route than a moving aircraft to me. Am I incorrect?

 

[Barakn]

The balloons would have to be hydrogen or helium-filled, and both gases are both notorious for being able to escape. Combine that with the extraordinarily thin plastic that is needed to lighten the load, and suddenly you are faced with the task of periodically replacing balloons or gas, not to mention repair or replacement of telescope parts, at an altitude of 40,000 feet, something I doubt will be nearly as easy as you seem to think it is. Also the telescope will have a large area above it obscured by balloon, motors, etc., so it will be forced to look more horizontally, through the upper reaches of the atmosphere you just spent so much trying to get above. Also, the presence of atmosphere will make this telescope unusable during daylight or moonlight, unless it's an x-ray telescope. So for visible light, this setup would combine the worst features of a ground telescope with the worst features of a satellite telescope.

 

[Drakkith]

There is no reason the telescope and platform would need to be directly underneath the balloons that I know of. Put them off to the sides well out of the way. A ballast would enable the whole thing to remain floating as the balloons lose their gas. As the boyouncy falls so does the weight. As for repairs and servicing, just let the whole thing fall slowly down, retrieve it and fix it, then send it back up. I don't see any glaring reason that any of this would be too difficult, other than the fact that it simply hasn't been done before.

 

[Chronos]

The Hubble was a great idea for a high altitude telescope. A wee costly to rocket it up there, but, once there it is pretty stable. The James Webb telescope should be even more spectacular, assuming it does not get cancelled.

 

[Drakkith]

The Hubble was a great idea for a high altitude telescope. A wee costly to rocket it up there, but, once there it is pretty stable. The James Webb telescope should be even more spectacular, assuming it does not get cancelled.

Absolutely. It would be a shame if we did not send up a replacement for it in my opinion.

 

[twofish-quant]

Hey PFers. I'm just wondering what your thoughts on a High Altitude Telescope are. What I mean is pretty much a telescope on a platform suspended in air on balloons at 40,000+ feet.

I think it's a great idea. So too are the groups that have done it :-)

http://en.wikipedia.org/wiki/Balloon-borne_telescope

There are also airborne telescopes

http://en.wikipedia.org/wiki/Kuiper_Airborne_Observatory
http://en.wikipedia.org/wiki/Stratospheric_Observatory_for_Infrared_Astronomy

I knew someone that worked on Kuiper. He said that one of the tricky parts was that when you cut a hole in the back of an airplane that's going to be open in flight, the FAA wants you to recertify that the airplane is still airworthy. Unfortunately, there wasn't a "standard procedure" for doing that with airborne telescopes so they had to work with the FAA to develop them.

 

[Drakkith]

Ahah! It has been done before! Thanks for the links twofish!
On an unrelated note, it looks like I'm about to pass you in post count! I need another hobby I think!

 

[Barakn]

Of course it's been done before. You made it sound like you were trying to make a permanent telescope large enough to replace Hubble. The telescopes flown by balloon are usually small proof-of-concept telescopes flown in the Antarctic polar vortex for weeks, not years.

 

[Drakkith]

Of course it's been done before. You made it sound like you were trying to make a permanent telescope large enough to replace Hubble.

Sure, why not.

The telescopes flown by balloon are usually small proof-of-concept telescopes flown in the Antarctic polar vortex for weeks, not years.

Interesting. Any idea why they were flown there of all places?

 

[Bobbywhy]

High altitude telescopes may have some advantages over ground-based telescopes, especially eliminating much of the atmosphere which blurs the images. But with advances in adaptive optics this advantage is diminished because of the technical successes the AO technology has provided astronomers. Now, if you have around ONE BILLION dollars to invest, which would you choose: land-based or high-altitude? Here's what the latest Thirty Meter Telescope group chose. Atop volcano Mauna Kea in Hawaii.

"Ground-based astronomy has taken a big leap forward today as the Gemini South telescope unveiled the first ultra-sharp image produced using a next-generation adaptive optics system. The Thirty Meter Telescope will use a similar, even more advanced system when it goes into operation later this decade."

http://www.tmt.org/

 

[Barakn]

Sure, why not.



Interesting. Any idea why they were flown there of all places?

With the balloon trapped in the Antarctic polar vortex, it sails around and around the continent of Antarctica and is thus almost always within radio range, and when it lands it doesn't land in the water and let the payload sink out of sight. If let loose from just about anywhere else, the balloon will eventually end up over the Pacific Ocean for long periods of time. Also, the polar vortex air is dry, which helps for those wavelengths (infrared, sub millimeter) where water attenuation of signal is high.

 

[Drakkith]

That makes sense. Also, thanks for the link Bobbywhy, I had no idea we had Adaptive Optics that good!

 

[twofish-quant]

High altitude telescopes may have some advantages over ground-based telescopes, especially eliminating much of the atmosphere which blurs the images. But with advances in adaptive optics this advantage is diminished because of the technical successes the AO technology has provided astronomers.

Removing atmospheric blurring while somewhat useful isn't the main point of high altitude or space telescopes. The main point is to observe frequencies that can't easily be observed from the ground. The main useful part of Hubble isn't that it has clear images, but rather that it can observe in the near UV, which is blocked by the atmosphere, and whose measurements are rather critical for quasars observations.

Now, if you have around ONE BILLION dollars to invest, which would you choose: land-based or high-altitude? Here's what the latest Thirty Meter Telescope group chose. Atop volcano Mauna Kea in Hawaii.

1) you usually don't have one billion to invest

2) if you do, then a lot depends on figuring out what everyone else isn't doing. There isn't a single best type of telescope, rather you try to spread the money so that everything is covered.

 

[Vanadium 50]

Which is why they work. If you are using radio frequencies, typical resolutions for balloon-borne experiments are a few degrees. (To remind people, a square degree is about five times the area of the moon) This is ~4 orders of magnitude bigger than what you get from atmospheric blurring, so it's much easier (translation - possible) to design a mount that's good to this level.

 

[twofish-quant]

Also the killer for microwave astronomy is water vapor. Microwave frequencies are just at the right wavelength to cause water molecules to vibrate which means that water is an excellent absorber of microwaves. Putting things on a balloon gets you above most of the water vapor.

The fact that water is a great absorber of microwaves has some practical applications (i.e. you take a source of microwaves, put it into a box, and you can dump massive amounts of energy into your favorite frozen dinner or cup of coffee.)