eVLBI makes history

VLBI, or very long baseline interferometry, is a method for synthesizing a gigantic telescope. Basically, you record signals at several radio telescopes in different locations and play them back together on a computer. This process synthesizes a telescope as big as the biggest distance between the telescopes you have. Obviously you don't have a telescope that big but you do get the same resolution as one.

Up to now, these signals have been recorded on tape and then shipped to a correlator where they are all played back. In recent years, with the improved bandwidth of modern network connections, people have been trying to carry this process out in real-time. Back on 10th September the first real-time fringes (fringes occur when everything works), between the Arecibo radio telescope and three telescopes in Europe, were detected. The longest baseline in the observation - possibly the longest ever - was between Arecibo and Torun in Poland. They managed to create the first real-time transatlantic image of the source 0528 134. Note the low declination of 13 degrees as the source had to be visible to the Arecibo dish which has a limited field of view.

You can see the busy group in the Torun control room; the 32m is outside to the right in the image and you can see Genek sat in one of the controllers chairs. I bet Andrzei Kus is about to give an interview to the TV crew. The last time I saw the Mark 5 terminal at Torun, it had just been delivered and was still in its box, but I think the idea was to mount in one of the racks to the right.

Posted in astro blog by Stuart on Monday 27th Sep 2004 (14:12 UTC) | Permalink

More Interference

A few points to add about radio interference. The House of Commons Select committee report made mentions of radio interference in astronomy and said that they may look at the problem in a future inquiry. There are a few International Astronomical Union (IAU/UAI) commissions doing a good job fighting the corner of radio astronomers, despite the efforts of other groups. For instance Brian Robinson (1999) summarized the situation faced by the Inter-Union Commission for the Allocation of Frequencies for Radio Astronomy and Space Science (IUCAF):

"IUCAF members had to evolve from being starry-eyed astronomers as they encountered a world of politics, lobbying, entertainment, threats, espionage and bribery. On one occasion, an offer (in Geneva) of two million dollars in cash 'to shut up' proved no match for dedication to the joys and excitement of twentieth-century astrophysics."

Posted in astro blog by Stuart on Saturday 25th Sep 2004 (23:31 UTC) | Permalink

The End of Radio Astronomy?

In the last year or so I have noticed more and more articles talking about new types of wireless technology. As well as the traditional devices with fixed bands such as WiFi and Bluetooth, there is now more talk of an open radio spectrum, perhaps using something like Ultra-Wide Band (UWB). The idea of spread spectrum technologies like UWB, is to make full use of big swathes of the radio spectrum by transmitting over many frequencies at the same time. This approach is championed by people like Lawrence Lessig - the man behind the excellent Creative Commons license - as they say the spectrum should not be 'owned' by corporations like TV and radio companies but used more like a commons.

The idea with UWB is that there wouldn't be problems for existing users of the spectrum as it uses "a new band of spectrum in the noise floor". Indeed Lawrence Lessig also talks about picking signals out of the noise to point out how broadcasts could be distinguished from one another. This all sounds great; allowing more people to use the radio spectrum to transmit data and let each other know they are on the train. However, as you might have guessed, I am not too keen on the idea.

Radio astronomers spend their time trying to look at radio waves emitted by various objects in space such as clouds of hydrogen and ethanol, stars such as pulsars and energetic galaxies called quasars to name but a few. Of all the radiation emitted by these objects, only a small amount reaches us on the Earth and the job of a radio astronomer is to collect this tiny amount, measure it and try to work out as much as they can about the Universe. As I said these signals are extremely faint with the brightest radio sources coming in at about 10-23 Watts per Hertz per square metre (i.e. about 0.00000000000000000000001 Watt/Hz/m2) - in more straightforward terms, a mobile phone on the Moon would be considered 'bright'.

We already suffer from radio frequency interference (RFI), and it is easy to see the effects of 'spillover' transmission into radio astronomy bands by satellites already. It isn't just confined to satellites either; internet access, mobile phones, CCTV, balloon platforms and even garage door openers add to the problem. It isn't even as if radio astronomers can change their frequency bands. This isn't because they have build expensive receivers that they don't want to change but because the Universe only emits at specific freqencies so we have to use what we are given.

Radio astronomy bands shouldn't be thought of as equivalent to a commercial communications band and therefore open to anyone that wants to transmit in it. They already are open to all that want to 'listen' just not those that want to 'talk'. Radio astronomy bands should be treated in the same way as National Parks are, as a place to be protected from development so that anyone who wants to can listen to the Universe.

Posted in astro blog by Stuart on Saturday 25th Sep 2004 (22:36 UTC) | Permalink

Dome C Seeing

An article in Nature last week discussed the possibility of putting an optical telescope in Antartica. The article was written by astronomers from the University of New South Wales and the Cerro-Tololo Inter American Observatory in Chile.

They measured the seeing at a site called Dome C, about 75 degrees south, high on the Antarctic plateau. As they say, the results were remarkable with a median seeing in winter of 0.27 arcsec, and below 0.15 arcsec 25 per cent of the time. That would make it one of the best places in the world for doing optical astronomy. The claim is that a fairly modest telescope would be able to do much better than big telescopes in other sites.

If an optical telescope was to be built there, it wouldn't be the first time astronomers or particle physicists had taken observations with telescopes near or under the south pole.

Posted in astro blog by Stuart on Friday 24th Sep 2004 (00:05 UTC) | Permalink

Reflections on SEST

Nico Housen, a software engineer based at the European Southern Observatory (ESO) took a fantastic picture of the milky way reflected in the Swedish-ESO Submillimetre Telescope (SEST). In the reflection you can also make out the light pollution from the city of La Serena which is about 100km away; nothing compared to Manchester! The picture was taken with a Nikon D100 digital camera with a 40 second exposure.

Posted in astro blog by Stuart on Wednesday 15th Sep 2004 (17:32 UTC) | Permalink

An image of an exo-planet?

In the news over the past couple of days, has been the story of the first image of an extra-solar planet around a star other than the Sun. First I should point out that the European Southern Observatory (ESO) currently class it as a "Giant Planet Candidate Companion (GPCC)" which somehow doesn't sound as exciting.

It was observerd near to a brown dwarf (failed star) called 2MASSWJ1207334-393254 - a classic name that nobody could forget! When I say near it was very close in angular terms; it was only 0.8 arcseconds which is less than the normal 'seeing' disk on the surface of the Earth. Seeing, or twinkling of stars, is due to atmospheric turbulence and basically means that you can't see any detail finer than about 0.5 arcseconds from a good site. However, the images were taken on the Very Large Telescope (VLT) using adaptive optics which counteracts the effect of 'twinkling' by constantly deforming the telescope's mirror.

They have been able to confirm that it is a substellar object by observing the spectrum of light it emits and comparing it to other substellar objects. At the moment though, they can't rule out the possibility that it is an older and more massive, foreground or background, cool brown dwarf.

Posted in astro blog by Stuart on Wednesday 15th Sep 2004 (17:22 UTC) | Permalink

Step into Cheshire

During the weekend of 18th and 19th September, the Step into Cheshire event will be celebrating all the things the county has to offer. As part of this, Jodrell Bank will be holding "Meet an Astronomer" sessions where members of the public can talk to astronomers and have a guided tour of the observatory. What was the Big Bang? How big is the Universe? How does a radio telescope work? What do astronomers do all day? This event will be a great chance to come and ask some real life astronomers the answers to life, the Universe and everything. I will be helping out on the tours, so I hope the weather is good to us.

Posted in astro blog by Stuart on Thursday 09th Sep 2004 (11:43 UTC) | Permalink

Genesis Crash

I am currently watching NASA TV who are showing live footage of this afternoon's Genesis recovery. The Genesis Sample Return Capsule was supposed to be caught in mid-air by a helicopter although it would appear that the parachute failed to deploy, meaning that the 'hook' from the helicopter was unable to catch it. Currently it seems to be half embedded in the Utah desert floor and there are various NASA employees walking around it taking photographs.

Posted in astro blog by Stuart on Wednesday 08th Sep 2004 (16:31 UTC) | Permalink

Space on Five Live

The Simon Mayo programme on Radio Five Live just had a fairly long segment on space mainly because of the SETI signal, the return of Genesis (in less than four minutes time) and the discovery of some more extra-solar planets. You can listen to the programme on the BBC website until tomorrow afternoon. The panellists included Ian Morison (Sir Professor according to one of our local papers) from Jodrell, Professor Colin Pillinger (of Beagle II fame) and Professor Chris French (of The Sceptic Magazine). They had a discussion of life, the Universe and everything but mainly concentrating on the possibility of life elsewhere. Ian managed to correct one caller who thought that the nearest star was 65,000 light years away. However, Colin Pillinger claimed that the Sun was 15 light minutes away rather than eight - is that why Beagle II went missing? ;-)

Posted in astro blog by Stuart on Wednesday 08th Sep 2004 (16:15 UTC) | Permalink

Stellarium

For the last few months I have been using Stellarium which is a very nice photo-realistic sky simulator that is free. At version 0.6 it is still in development but is very good nevertheless. I have shown it to a couple of people at Jodrell and I have just noticed that Ian Morison has started to use the images from it on his night sky this month page. Some time ago I remember he was worried about using screengrabs from other software due to copyright considerations.

Posted in astro blog by Stuart on Friday 03rd Sep 2004 (00:09 UTC) | Permalink

ET?

Today was a very strange day at Jodrell. After an article appeared in New Scientist yesterday announcing that a particular signal observed using the Arecibo telescope as part of the SETI@home project has now been detected three times, the press seem to have taken this to mean that extra-terrestrial life has been detected.

It seems that the initial quotes from the researchers were quite enthusiastic about the signal being worth following up, but not one of them ever said (as far as I can see) that this was proof of aliens. In fact, Dan Werthimer, a radio astronomer at the University of California and a SETI@home scientist said "We're not jumping up and down, but we are continuing to observe it."

All the excitement has meant that reporters from all over the place have been calling Jodrell all day trying to get an interview with an astronomer. Tim O'Brien was interviewed by both Classic FM and the BBC this evening, and an American lady even called the MSc room asking to speak to the telescope controller!

It does look interesting, but I'm not convinced. It seems much more likely that the signal is noise generated either by the receiver or something locally. There is a famous (and therefore possibly completely made-up) story about some researchers who saw a signal appear in their data at the same time every day for a week. At first they were astounded and convinced that they had found evidence of intelligent life. Eventually someone realised that the signal was actually coming from a nearby building where one of the staff was heating up his dinner in a microwave oven. Whether it's true or not, it just goes to show that you can't always believe what you see in your data.

Posted in astro blog by Megan on Thursday 02nd Sep 2004 (23:07 UTC) | Permalink
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