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Massive Radio Telescope Starts Observing the Skies

timothy posted more than 2 years ago | from the give-me-a-big-enough-radio dept.

Space 44

New submitter cyachallenge writes with this excerpt from New Scientist: "RadioAstron, effectively the largest radio telescope ever built, is up and running. The telescope's main component, a 10-metre radio dish aboard the spacecraft Spectr-R, launched in July to an oblong orbit that extends between 10,000 and more than 300,000 kilometres from Earth. By coordinating observations with radio telescopes on Earth in a technique called interferometry, the telescope can make observations as sharp as a single dish spanning the entire distance between the two farthest dishes. When Spectr-R is at its farthest from Earth, the system acts like one enormous telescope about 30 times as wide as our planet, boasting about 10,000 times the resolution of the Hubble Space Telescope."

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Too bad (0, Redundant)

Pikoro (844299) | more than 2 years ago | (#38323980)

Too bad this is a radio telescope and not optical. No comparison to Hubble.

Re:Too bad (2)

The Master Control P (655590) | more than 2 years ago | (#38324170)

It's all photons, so it's quite comparable.

And given the nature of redshifting, simply observing things near the surface of last scattering in the radio presents what would've originally been visible light images.

Re:Too bad (3, Insightful)

SuricouRaven (1897204) | more than 2 years ago | (#38324326)

That's one hell of a shift.

Re:Too bad (5, Informative)

buchner.johannes (1139593) | more than 2 years ago | (#38325084)

Actually, in radio astronomy you can't really say it's photons. The wavelengths are centimeters to meters (a pretty large photon), and you get wave-effects everywhere.
It's not true that this or other radio telescopes are no match for Hubble. This satellite links up with ground-based telescopes and does VLBI. The baseline of VLBI -- equivalent to the aperture diameter for optical telescope -- is the distance between the linked telescopes. If you want to have a telescope as powerful as Hubble, you need to compare diameter/wavelength (Hubble example: 2.4m/440nm = 5e6). So for radio (e.g. 21 cm), you need a baseline of 1050 km. Ground-based VLBI networks, like the Australian LBA (3300km Perth-Sydney, 5500km Perth-Auckland) or the European EVN, the VLBA (8000km) reach these lengths. This brings you down to milliarcsecond resolutions, incidentally similar to the optical VLT interferometer.
RadioAstron will be on an "orbit that extends between 10,000 and more than 300,000 kilometres from Earth".

So yes, it will be a match for Hubble by a factor of 100. However, this comparison is not really helpful, as optical and radio telescopes see different things and probe different physical processes. To understand the universe, information from all wavelengths is relevant.

Re:Too bad (1)

Nethead (1563) | more than 2 years ago | (#38328840)

You touch on something that I've been wondering about. From what I've read I understand that electromagnetic waves, such as light and radio, can also be understood as photons. And the frequency of the wave is in proportion to the energy of the photon. My question is at what frequency does one stop thinking of RF as photons. Is my little ham walkie-talkie pumping out 73cm photons when I transmit at 445MHz? Is an AM radio station pumping out a lot of football field sized photons or are photons actually just a point and these would be just very low energy photons?

Re:Too bad (1)

ProfessorPillage (1964602) | more than 2 years ago | (#38329848)

I think it has to do with both the photon density and the size of the thing you use to observe them. If there are few photons per cubic wavelength (even less than one), EM waves look more like photons in the sense that you need to describe them with quantum mechanics. If there are many, they look more like classical waves. Also, if the wavelength is small compared to the observer, then they are more likely to look like photons. So if you have 1 photon/cm3, and a wavelength of 1cm, it might look more like a photon in that you observe quantum behavior because there is 1 photon per cubic wavelength. But if the wavelength is 1m, then there are 1,000,000 photons per cubic wavelength and you will observe more wave effects with a detector small compared to 1m, or it will still look like particles if your detector is large compared to 1m. Both views can accurately describe them, but one might be more informative in a given situation.

The size of a photon is tricky. They can be spread out over an arbitrarily large area, with a probability distribution of "appearing" at any given spot in that area. The spot in which it would appear (for example to be absorbed by an antenna) would be wavelength-sized, in the sense that this is the amount of space over which it would interact with something. I believe this means cubic-wavelength (or square-wavelength times period if you want to look at it that way), but I'm not completely sure. But if you're thinking about it as a particle, then you can probably think of it as a point, because if its size was relevant, you'd be thinking about it as a wave.

Re:Too bad (1)

Nethead (1563) | more than 2 years ago | (#38329956)

Thanks for the explanation, I think I'm starting to get this now.

Re:Too bad (1)

LordVader717 (888547) | more than 2 years ago | (#38334452)

The wave/particle duality is true for any and all energies, and it is wrong for anybody to try to convince you otherwise. A single photon is incredibly difficult to observe, yet even a single photon shows wave-like behavior, smearing out results. So it depends on your observation technique. A quantum optics guy told me that their rule of thumb is that anything beyond five photons is a wave.
From a theoretical standpoint however photons are absolutely necessary to describing the situation. Without it you wouldn't be able to describe the emission lines which are incredibly important for radio astronomy. The Hydrogen line is at 1.4GHz, comfortably in the radio band of the spectrum.

Re:Too bad (2)

Have Brain Will Rent (1031664) | more than 2 years ago | (#38329312)

you can't really say it's photons. The wavelengths are centimeters to meters (a pretty large photon), and you get wave-effects everywhere

Well if it's not photons carrying that electromagnetic energy then what is is it? You get wave effects with solid matter too... in fact you get wave effects with everything... so?

As Feynman said in one of his Auckland lectures, to the best of my recollection (so throw in some salt) - "We may talk about [it] as waves because that's convenient for certain problems but never forget it's really a particle."

Re:Too bad (1)

ProfessorPillage (1964602) | more than 2 years ago | (#38329966)

You're talking about two different kinds of waves. Matter is also a waves in the quantum mechanical sense. EM in some cases is better described by waves in the classical sense, i.e. with Maxwell's equations. Though often EM is better described as photon particles, or as photon waves that describe things like the probability of being detected at a given location.

Re:Too bad (1)

Have Brain Will Rent (1031664) | more than 2 years ago | (#38330762)

You're talking about two different kinds of waves.

I was pointing out that saying you get wave effects everywhere - without describing the effects and how they are particular to photons at radio astronomy wavelengths - is kind of content free since everything exhibits wave effects.

And my main point was that in my understanding it is not true that "you can't really say it's photons. The wavelengths are centimeters to meters (a pretty large photon)", i.e., having a long wavelength doesn't make a photon not a photon - the observer see that that photon either hits the detector or doesn't, which essentially was what Feynman was pointing out.

But maybe I'm just misinterpreting and should instead have asked for clarification of the vague statement.

Re:Too bad (1)

RockDoctor (15477) | more than 2 years ago | (#38333920)

EM in some cases is better described by waves in the classical sense, [...] Though often EM is better described as photon particles,

Our concepts of "wave" and "particle" are not terribly good fits for what photons are. Photons are photons and need to see no psychoanalysts about their identity problems ; we have problems matching the reality of photons to our concepts of "wave" and "particle", but that's our problem, not the photon's problem.

My school physics labs included a series of experiments in how semiconductors and LEDs work (emitting the "particle" aspect of photons with well-defined energies), how EM waves propagate in series of inductors and capacitors (then, with the inductance and capacitance of the vacuum, the speed of light), and how waves interfere with each other. All perfectly good physics experiments, well presented. Then we did an experiment that slightly puzzled me at the time : setting up a dim (red) LED in a dark room and doing a double-slit experiment, then turning down the drive current on the LED to see what the dimmest setting was that we could detect the interference pattern. It turned out to be essentially a test of people's quality of vision (not a surprise, really).
Then we did the calculations : from the drive current and the characteristics of the LEDs, we could calculate how often the "particle" aspect of the photons were being generated ; the speed of light told us the spacing between the photons (on average) ; and the interference pattern showed us that the "wave" aspect of the photons were interfereing between the "particle" aspects. The trouble was ... our spacing between photons was on the order of 10-15m (depending on the vision quality of the experimenters) ... but our apparatus was barely 2 metre between LED and eye.
So, each photon was interfering with either the photon before it (which had already been absorbed by the eye), or the photon following it (which had not been emitted yet). Huh?

10 years later, I realised that this had been the climax of the 2-year long course. And I can now say, with certainty, "I have seen the wave-particle duality problem with these here [points] eyes."

Well-designed course. Nuffield Foundation. Recommended.

Re:Too bad (2, Interesting)

Anonymous Coward | more than 2 years ago | (#38324184)

Wrong! Some incredibly amazing images have come from radio telescopes such as the VLA. You can find some of those pics on the National Radio Astronomy Observatory (NRAO) Image Gallery website.

Re:Too bad (1)

Thing 1 (178996) | more than 2 years ago | (#38326720)

Plus, with the radio telescope tuned to the correct frequency, you can hear Mars Needs Women, in the original.

Re:Too bad (3, Interesting)

somegeekynick (1011759) | more than 2 years ago | (#38324394)

Astronomy isn't exactly about pretty pictures, you know! But even then, you can make pretty pictures out of data from other bands of the EM spectrum, like the AC mentioned earlier.

Re:Too bad (0)

Anonymous Coward | more than 2 years ago | (#38326526)

Yeah I was thinking that same thing. What would we see if we'd take a radio wavelengeth picture of a New York, for example?

Could we even see a civilization in the pic? If we couldn't, then, um... boring much?

Re:Too bad (2)

jd (1658) | more than 2 years ago | (#38329970)

Optical interferometry is done, so there's nothing to stop someone setting up an array of optical telescopes in which Hubble was one of the telescopes involved. Ideally, since large optical telescopes are very difficult to launch, future optical space telescopes should be designed to be used in interferometry arrays. The problem is one of synchronizing, since you can't use interference when the signals aren't in phase and relativistic time matters if they're not on a common orbit, but if you record the signal and timestamp points along it, it should be possible to do the interference offline rather than live.

The other thing to remember is that telescope diameter is only one variable. Another is collecting area. You could park two radio telescopes in geostationary orbit such that they were at opposite ends. This would give you a gigantic telescope diameter, but almost no collecting area. SKA, when it is finally built, will have a superb collecting area, vastly greater than what's described here, but a much smaller effective dish diameter than the telescope described in TFA. As such, it'll be far more sensitive but have lower resolution. Combining the two would be awesome.

(Dotting a SKA across the entire length of Earth's orbit would be even more awesome, but I don't see that happening for a while.)

Re:Too bad (1)

arkenian (1560563) | more than 2 years ago | (#38332328)

Optical interferometry is done, so there's nothing to stop someone setting up an array of optical telescopes in which Hubble was one of the telescopes involved. Ideally, since large optical telescopes are very difficult to launch, future optical space telescopes should be designed to be used in interferometry arrays. The problem is one of synchronizing, since you can't use interference when the signals aren't in phase and relativistic time matters if they're not on a common orbit, but if you record the signal and timestamp points along it, it should be possible to do the interference offline rather than live.

So you start to say there's nothing to stop them from doing it, and then, actually, very elegantly explain exactly what does prevent it. I would say that, at this point, our spacecraft technology would be severely taxed by multiple-vehicle interferometry. Multiple-vehicle cooperative satellite projects have been nixed for much less stringent stationkeeping requirements than an interferometer has, although there are ideas on the subject that have been discussed. Still I'd say we're a ways away from it, at this point.

Re:Too bad (1)

jd (1658) | more than 2 years ago | (#38337472)

Well, I said why live interferometry can't be done at this point. If you timestamp the data at regular intervals, a base station would be capable of stretching recorded data and doing the interferometry that way.

Re:Too bad (1)

arkenian (1560563) | more than 2 years ago | (#38337792)

Well, I said why live interferometry can't be done at this point. If you timestamp the data at regular intervals, a base station would be capable of stretching recorded data and doing the interferometry that way.

Still requires location information beyond what we currently have available on satellites, generally

Re:Too bad (2)

LordVader717 (888547) | more than 2 years ago | (#38334516)

One of the more fundamental problems is that we don't have phase-sensitive detectors for visible light.

Re:Too bad (1)

jd (1658) | more than 2 years ago | (#38337436)

Re:Too bad (1)

LordVader717 (888547) | more than 2 years ago | (#38391558)

You do realize that the paper basically confirms what I say? We cannot detect phase, which is why optical interferometry relies on overlaying the light directly. No signal, no timestamp. You have to keep your optics aligned to within micrometers.

Re:Too bad (0)

Anonymous Coward | more than 2 years ago | (#38330436)

It'll have better resolution than any telescope before it: better than Hubble by 100x or so. Being a radio telescope means that it'll see different things, too: it won't see the optically bright star-forming galaxies that you see in the Hubble Deep Field images, but it will see the radio-bright jets emanating from the supermassive black holes in the nuclei of gas-rich galaxies.

oblong?? (0)

Anonymous Coward | more than 2 years ago | (#38323990)

Is that a word (still) ? Not in reference to a (highly) flattened eliptical orbit surely.

Re:oblong?? (2)

stms (1132653) | more than 2 years ago | (#38324040)

Is that a word (still) ?
  Not in reference to a (highly) flattened eliptical orbit surely.

Why wouldn't it be? Oblong is a perfectly cromulent word.

Re:oblong?? (1)

Anonymous Coward | more than 2 years ago | (#38324056)

From Wiktionary:
Adjective
oblong (comparative more oblong, superlative most oblong)
        Describing something that is longer than it is wide.
        Roughly rectangular or ellipsoidal.
Noun
oblong (plural oblongs)
        Something with an oblong shape.
        A rectangle having length greater than width.

Looks like a valid description of a comet-style orbit.

Re:oblong?? (3, Insightful)

rossdee (243626) | more than 2 years ago | (#38324088)

I always thought Oblong was more rectangular than elliptical. Of course the rectangle with rounded corners was invented by apple.

Re:oblong?? (1)

Anonymous Coward | more than 2 years ago | (#38324218)

In before Parent is sued for billions.

Re:oblong?? (3, Interesting)

jbeaupre (752124) | more than 2 years ago | (#38326054)

Forget "oblong", how about "massive"? Massive has to do with, well, mass. Seems that Aricebo might have the best claim for that (using the Earth itself as part of the structure).

it _will_ find extraterrestrial life (5, Funny)

Gravis Zero (934156) | more than 2 years ago | (#38323998)

it's too big to fail.

Nice target (0)

DrD8m (307736) | more than 2 years ago | (#38324100)

Aliens, just come and kill us all!!

Re:Nice target (1)

JustOK (667959) | more than 2 years ago | (#38324186)

Except me. I will tell you the secret codes...for a price.

It has good resolution but... (5, Informative)

Anonymous Coward | more than 2 years ago | (#38324136)

.. it still "only" has 10m of aperture (+ the aperture from radio telescopes on Earth) so it will have a hard time detecting faint objects near its maximum resolution. It will be excellent at detecting small details of bright objects though.

Hats off to Russian scientists (5, Insightful)

blind biker (1066130) | more than 2 years ago | (#38324256)

Unlike the Chinese, that seem to do a lot of "me, too" stuff (which is very impressive, of course), the Russians do work that is nicely complementing the US, European (ESA) and Japanese efforts. The Spektr-R (and RadioAstron) is something novel and unique, and will provide insights in the astrophysics and astronomy beyond the Milky Way with high angular resolution.

Another example is ill-fated Phobos Grunt. It would have been another interesting and unique experiment.

Ponies [Score:5, Interesting] (-1)

Anonymous Coward | more than 2 years ago | (#38324428)

Watch My Little Pony: Friendship Is Magic.
Today on the Hub.

Why such a pitifully small dish? (1)

tp1024 (2409684) | more than 2 years ago | (#38324488)

Seriously, 10m is a lot smaller than the state of the art in regular comm-sats. TerreStar-1 [wikipedia.org] has an 18m dish. Yes, it's large but massive isn't exactly the right expression.

Re:Why such a pitifully small dish? (2, Insightful)

Anonymous Coward | more than 2 years ago | (#38325402)

But what is the curvature error of the TerreStar-1 dish? And of the RadioAstron? You have to compare _that_, not just dish diameter, to understand why they did not/could not make it bigger... Besides, a larger dish means more orbital interference from solar wind, etc.

Re:Why such a pitifully small dish? (1)

gzipped_tar (1151931) | more than 2 years ago | (#38326414)

The radio telescope and the communication satellite has wildly different design goals and specs. You can't get much by just comparing the size.

Did Africans build all this? (-1)

Anonymous Coward | more than 2 years ago | (#38324788)

Why not? Genes, perhaps?

(Cue insane liberals trying to find excuses for the ongoing destruction of every white country on Earth, by millions of unwanted third world INVADERS...)

Yes, but . . . (2)

erick99 (743982) | more than 2 years ago | (#38327706)

Despite the shortcomings (perceived and real) that many will discuss regarding this particular telescope, it is still a very good thing that the U.S. and other countries continue to spend the money to develop, build, and implement new 'scopes. Considering how tight money is (worldwide) it can't be easy to find the funding for these projects.

Re:Yes, but . . . (0)

Anonymous Coward | more than 2 years ago | (#38330800)

You do realize that the USA has absolutely nothing to do with this telescope, right? It's Russian. Or do you work for Apple and so default to claiming everything as your own?

Diffraction (1)

ChrisMaple (607946) | more than 2 years ago | (#38332102)

Two 10 m dishes 100 km apart do not have the same resolution as a 100 km dish. You get diffraction effects appropriate to 10 m dishes, which messes up the "image" something awful. You can do interferometry equivalent to the 100 km dish (ignoring undersampling errors) and other such things, but pretending they're the same is just sloppy.
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