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Giant Telescopes Of The Future
mindpixel writes: "Mindjack just published my article about the the future of very large telescopes, such as the VLT and the OWL which I talked about in my /. interview. In addition, I talk about a future space-based telescope that would use the Sun's gravity to 'image large surface features,' of extrasolar planets, which telescpes like the VLT can just detect, 'such as oceans, continents or ice caps, or even the impact of civilization on such features.'"
I remember seeing on either "The Planets" or "Stephen Hawking's Universe" documentaries, mention of plans (prolly drawingboard stuff) to place an array of hubble like telescopes past the asteriod belt to create a VLT in space...
I'm curious to know - because of the limited size (surface area) on earth (which cosmologically is a pinprick in space) what kind of performance increase would one get by placing those telescopes in space and would it be a better move in the long run?
-- Dan =)
LL
You can get books telling how to make telescopes from Willman-Bell and ask for help on the Amateur Telescope Maker's mailing list. Dan Cassaro can sell you a reasonably priced mirror grinding kit.
You can find many products for amateur astronomers at the Astronomy Mall.
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Would it be possible to use ordinary parabolic satellite TV antennas for radio telescopy? Could they be combined to create a huge radio telescope?
If that's possible, maybe when people are not using their satellite antennas for TV they could be combined to create a world-wide radio telescope.
I'm thinking of something along the ideas of SETI@home. There, the unused computer time of many people is combined for the SETI program. Maybe unused satellite TV antenna time could be combined in a similar way.
To create a large and powerful telescope you combine several smaller telescopes. There is an enormous amount of unused TV antenna time. If ordinary satellite dishes are suitable for this purpose, you'd get an extremely powerful telescope.
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Look at the second and third generation space telescopes from the "Origins" program.
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Has already become a factor in how big telescopes can be on earth. But, it's already been "fixed", too. The new giant scopes use adaptive optics that actually compensate for atmospheric distortion in realtime.
To me, that is simply amazing. Adjusting 1600 mirrors realtime to correct tiny air currents!
Could a space-based array be designed so that once it reaches its target location, it spreads itself out, gradually increasing the distance between its elements in a coherent manner, thereby increasing the effective size of the array over time? I would assume that a space-borne array would already be designed with plenty of fuel/rocketry for compensating for massive objects passing nearby and tugging on its corners... The same principle might be handy for adjusting/balacing the spacing between elements if an asteroid hits the jackpot, or a failure is detected.
:).
Yes, but you'd be trading off angular resolution against aliasing artifacts (the less of your aperture is filled, the worse aliasing artifacts will be, even when you assume constant sources and integrate over time). IMO, you'd be better off just adding more satellites
By coincidence, I recently did the calculations for the size of a metre-band radio telescope array needed to resolve features 100 km in size at a distance of 10 light-years (enough to resolve the aurorae of earth-sized planets, show thunderstorms on gas giants, and so forth). You'd need thousands of radio telescopes in solar orbits out to a radius of about 4 AU, but you could do it. Put them in eccentric polar orbits (i.e. away from most of the junk in the ecliptic), add excellent GPS-style beacons in precisely known orbits (constantly observed from Earth) to let the satellites track themselves, and you could get a very nice radio telescope for a surprisingly modest price (cheap satellites, well-known technologies and electronics, and the benefits of mass production, since you'll be making a thousand or more of them).
Such a telescope would be able to see aurorae and civilization-induced radio junk from Earth-sized planets out to around 10 light-years, map the magnetospheres of Earth-like planets and see detailed magnetic features in gas giants out to about 100 light-years, and get very detailed pictures of the outer envelopes of stars out to about 1000 light-years. It would be a very useful project.
Would it be possible to use ordinary parabolic satellite TV antennas for radio telescopy? Could they be combined to create a huge radio telescope?
If that's possible, maybe when people are not using their satellite antennas for TV they could be combined to create a world-wide radio telescope.
You could in principle do this, but in practice there are problems.
The main problem is that the electronics in the detector used with the dish are completely unsuited to radio astronomy. To use a radio telescope as a part of the array, you need a high-fidelity sample of the radio signal being received, timestamped to atomic-clock accuracy. A satellite TV pickup doesn't have a sub-nanosecond-accurate clock, and won't give you a digitization of the raw signal. Instead, it looks for strong signals in specific, narrow bands and blindly decodes them through combined analog and digital means (i.e. it treats everything it hears as a TV signal).
A secondary problem is that your satellite dish is pointed directly at a strong source of radio noise in the frequencies it's tuned to detect (the satellite).
The idea is a great one, but because you'd need to completely replace the electronics rig with something far more expensive, a better approach might be to sell radio telescope array "kits" built from stock parts and forget about using peoples' TV dishes.
This would probably be quite practical from an engineering standpoint, as most of the parts (including timestamping radio sampling boxes) can be bought off-the-shelf. I have no idea if enough amateur astronomers would buy these for them to be marketable (they wouldn't be cheap - tens of thousands of dollars per kit).
I am writing about this topic, and have corresponded with a number of NASA and Space Telescope Institute scientists about the idea of using the sun's gravity to magnify distant objects. The consensus is that while this is an interesting idea to play with, it won't be happening for generations, if ever.
To start, our most distant Pioneer probe won't be at 550 AU for 180 years. Pluto, remember, is just at 39 AU. Radically increase speed and you'll have a probe there in what, 80 years?
Once there, where will you point it? You'd have to spend hundreds or thousands or years arcing the telescope into different positions to see a broad sweep of space. And we don't have that kind of fuel technology, including nuclear.
I was in love with the 550 AU idea (I've read that 763 AU might be ideal), but the reality check dampened that more than a bit.
I hope this helps.
Erik Baard