Slashdot Mirror
Prototype Telescopes Complete Key Test
Matthew Sparkes writes "Two prototype antennas for the world's largest array of millimeter-wave telescopes have passed a key test, working to track and image Saturn for more than an hour. Ultimately, ALMA (Atacama Large Millimeter/submillimeter Array) is expected to resolve details 10 times finer than the Hubble Space Telescope when it is completed in 2012."
Two prototype antennas for the world's largest array of millimetre-wave telescopes have passed a key test, working together to track and image Saturn for more than an hour on 2 March. Ultimately, ALMA (Atacama Large Millimeter/submillimeter Array) is expected to resolve details 10 times finer than the Hubble Space Telescope when it is completed in 2012.
ALMA will use up to 64 antennas and will be located in the Atacama desert, 5 kilometres above sea level in the Chilean Andes. Designed to look through dust clouds to reveal star formation, image embryonic planets and probe the early universe, it will be the world's most sensitive telescope at wavelengths of 0.3 to 9.6 millimetres - a regime obscured at lower altitudes by atmospheric moisture.
But making all of the 12-metre dishes function like a single giant telescope will be a challenge. Fibre-optic cables will link each dish to every other dish in the array, and to a giant special-purpose electronic computer called a correlator.
"It collects the amplitude and phase information from each of the antennas, and knowing their distances from each other, it lines everything up to produce a coherent picture of the source," says Jeff Mangum, an ALMA project scientist at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia, US.
'Fringes of the universe'
The 2 March test actually linked two prototype antennas at another observatory, the Very Large Array site in New Mexico, US, with each other and with a small-scale prototype of the correlator. But the test, called 'first fringes', bodes well for ALMA's future, Mangum told New Scientist: "It verifies that ALMA can make measurements not just as single telescopes, but as a collection of antennas, which is the primary mode of operation."
Millimetre waves are at the upper end of the radio spectrum, just below infrared radiation. They can reveal important organic molecules, but are obscured by atmospheric moisture.
Small arrays at lower elevations have probed the sky since the 1980s, but atmospheric moisture made observations difficult at wavelengths shorter than 3 millimetres. A 1990 report urged building a large array at high elevation, and the NRAO, the European Southern Observatory, and the National Astronomical Observatory of Japan later picked the Atacama site. The altitude puts the array above most of our atmosphere's water, allowing observations down to 0.3 millimetres.
Although plans call for up to 64 antennas, present funding can pay for only 50 or so dishes. The dishes will be movable, allowing baselines from 150 metres to 18 kilometres, with the longest baseline and the shortest wavelength giving resolution as fine as 0.005 arcsecond, a factor of 10 better than Hubble.
Because millimeter waves can penetrate dust that blocks visible light, ALMA's large collecting area "will make it much easier to detect very faint objects at the fringes of the universe", says Mangum.
Censor the raw data coming from out of this too, like they have with the Hubble?
I'm a ham operator, and the signals coming from the Hubble are a jumbled mass of unintelligible garble. Further research shows they are using military hardware for secure connections.
I do understand that control codes are administered via ground, however, public key signing would allow transparency while providing a secure platform.
Why do they hide the whole data stream? What do they not want us to see?
I have no problems believing that the control data is encrypted for the hubble. For one thing, you don't want others taking it over.
As for the data, I'd imagine that it'd be compressed, encoded, and multiplexed to the point that you'd need special equipment that no normal HAM operator* would have, much less the settings needed to sort it all out and make sense of it.
For public key stuff - that's more computationally intense than private key military encryption methods. Remember, we're talking about systems where a 386 would be considered 'high end'.
*I'm not saying that you're a 'normal' Ham operator, Crawler, but we're talking the space industry here.
I don't read AC A human right
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
I'm actually beginning to wonder if space-telescopes still have their use (in regard to costs/benefits). I mean, thanks to interferometry one can get the resolution (equal or better) with earth based telescopes for a fraction of the price of space-telescopes like hubble and consorts. And thanks to adaptive optics there is hardly any atmospheric blurring which smears out the pictures anymore, neither. And, since the mirrors can be bigger then those send into space, the light-gathering power is way superior for earth-based telescopes.
The only advantages left are for specific wavelengths (like near-infrared), because the atmosphere absorbs most of that, but even that is more and more debatable, now that new instruments and detectors are becomming so sensitive that they can detect and use it on Earth too. I'm wondering, with the multi-billion costs of space-telescopes, if it's really worth the money? With the same amount of money, one could make a huge interferometer-telescope with a diameter of the Earth (though it would need to consist out of many 10-meter telescopes for light-gathering purposes). I'm all for space-exploration, but what still justifies the expense of a space-telescope, if earth-bound ones can do as well for a fraction of the price?
--- "To pee or not to pee, that is the question." ---
Call me back when they complete the Turing test.
It would call you by itself
Table-ized A.I.
---I have no problems believing that the control data is encrypted for the hubble. For one thing, you don't want others taking it over.
:-) .
No, of course you dont want some random joe to take Hubble over. However, they could implement in which "packets" are signed. The data would be separate from the authenticated signature. Along with that, they would want to implement a proper timecode to prevent replay attacks.
But controlling is aside the issue.
And I do hate to mince words but "normal HAM operator"... There isnt such a thing as a normal ham operator these days. Many hams specialize in one or two distinct fields of RF study. I like examining digital commms and remote communications (EME and meteor scatter).Along with my interests, I have bought that A/D board recommended by GnuRadio (normal HAM operator). All I needed was a RF front end and just to downsample to the range of the AD board (0-20 MHz).
I asked for help from some people at NASA and they said the connection was encrypted, and it does seem to be the case.
It doesnt really matter what Im required to build for receiving gear. It's all multi-purpose for us hams. And I do like the idea of splitting the transmitters from the receivers (well, you do have 2 antenna then per kit).
---I'm not saying that you're a 'normal' Ham operator, Crawler, but we're talking the space industry here.
Too true. No offense taken. Still, I can decode the majority of transmissions (the old freq shift Symbol cards are really neat under a scope) and can transmit on quite a few bands. I dont know if you've ever been in a Ham's shack, but the amount of gear they can have (and I too) is pretty immense. I just focus on the digital side a bit more
Hubble releases public images, but much of the research is just that - research - done by labs who are trying to maintain the integrity and proprietary nature of their work. Hubble data is supposed to go to the researcher first and the public second. IIRC it's a default six month delay unless overridden by the lab collecting the data. It's not censorship so much as embargo, and it's really no different from what any researcher does in order to not be scooped on the research they're doing.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
Hmm... My extent of satellite experience was working with 8" floppies and multiplexors at Schriever AFB years ago, and more recently training in how to configure slightly more modern multiplexors for field applications. Fun time: spending three hours troubleshooting while in chem gear only to have the instructors realize that their satellite simulator(couldn't get real sat time for the exercise) had been jarred out of position.
No, of course you dont want some random joe to take Hubble over. However, they could implement in which "packets" are signed. The data would be separate from the authenticated signature. Along with that, they would want to implement a proper timecode to prevent replay attacks.
I've learned that satellites tend to keep their control and data bands seperate, and the usage of multiplexing* is common, especially when you're talking about multiple instruments. And our demuxers run in the hundreds of thousands of dollars for our stuff, much less NASA science stuff. Remember what I said about military private-key encryption being cheaper computationally? Timing is already part of the security, and the hubble was designed back in the '80s and would have to use a system cleared for space and capable of remaining secure through decades of operation. Public key infrastructure is too new, computationally expensive, and expaning of a field. After that, it's easier to encrypt the whole channel than to worry about packets.
Are you even sure that you were trying to listen in on a data channel? From my reading it looks like the hubble stores it's data and then transmits it down in batches.
*For the uninitiated, a multiplexor takes multiple data streams and merges it into one stream, which a demultiplexor then splits back into multiple streams. For example, something like 60 voice lines, two ip networks, a crash-net(think red phone), etc... I'm sure Creepy Crawler knows this, but other readers might not
I don't read AC A human right