Archive for ESA

Top Ten Gaia Facts

Posted in Astrohype, The Universe and Stuff with tags , , , on December 20, 2013 by telescoper
Gaia looks nothing like the Herschel Space Observatory shown here.

Gaia looks nothing like the Herschel Space Observatory shown here.

Since yesterday’s successful launch of the European Space Agency’s Gaia mission I have been inundated with requests for more information about this impressive satellite and the science behind it. As a service to the community, and for the edification of the public at large, I therefore thought I’d share my list of top ten Gaia facts via the medium of this blog:

  1. The correct pronunciation of GAIA is as in “gayer”. Please bear this in mind when reading any press articles about the mission.
  2. The GAIA spacecraft will orbit the Sun at the Second Lagrange Point, the only place in the Solar System where the  effects of cuts in the UK science budget can not be felt.
  3. The data processing challenges posed by GAIA are immense; the billions of astrometric measurements resulting from the mission will be analysed using the world’s biggest Excel Spreadsheet.
  4. To provide secure backup storage of the complete GAIA data set, the European Space Agency has commandeered the world’s entire stock of 3½ inch floppy disks.
  5. As well as measuring billions of star positions and velocities, GAIA is expected to discover thousands of new asteroids and the hiding place of Lord Lucan.
  6. GAIA can measure star positions to an accuracy of a few microarcseconds. That’s the angle subtended by a single pubic hair at a distance of 1000km.
  7. The precursor to GAIA was a satellite called Hipparcos, which is not how you spell Hipparchus.
  8. The BBC will be shortly be broadcasting a new 26-part TV series about GAIA. Entitled WOW! Gaia! That’s Soo Amaazing… it will be presented by Britain’s leading expert on astrometry, Professor Brian Cox.
  9. Er…
  10. That’s it.

Planck (but only in name?)

Posted in Science Politics, The Universe and Stuff with tags , , , , , , on March 3, 2013 by telescoper

First, a serious announcement. It appears that the announcement of results from the Planck Mission will be streamed live from ESA HQ on 21st March from 10.00 to 12.00 CET (whatever that is). The UK will remain on GMT until 31st March so the  ESA web server will probably crash at 9am British time on 21st March.

There’s a short press release making this announcement here. It says:

On Thursday 21 March 2013, the main scientific findings from the European Space Agency’s Planck spacecraft will be announced at a press briefing to be held at ESA’s Headquarter in Paris. Simultaneously with this event, data products and scientific papers based on the “nominal” operations period will be made public through the Planck Legacy Archive.

I was interested in the appearance of the word “nominal” in quotes in there so I searched for its meaning in the One True Chambers Dictionary, where I found:

nominal, adj relating to or of the nature of a name or noun; of names; by name; only in name; so-called, but not in reality; inconsiderable, small, minor, in comparison with the real value, hardly more than a matter of form…

Interesting. It seems that the “nominal” could mean, on the one hand, that ESA are being unusually modest about the importance of the forthcoming Planck results or, on the other, that there will now be a host of conspiracy theorists suggesting that the Planck results aren’t real….

That reminds me that years and years ago I had an idea for a crime novel with a plot that revolves around the murder of a prominent cosmologist just as some important scientific discovery is about to be announced. Suspicion gathers that the whole thing is an enormous hoax and the discovery bogus. But the experiment is shrouded in secrecy, and so expensive that it can’t easily be repeated, so  who can tell, and how?

It’s very difficult to know for sure whether any scientific discoveries are genuine or not, even if the data and analysis procedures are made public. There’s always the possibility that everything might have been fabricated simulated, but in most cases the experiment can be repeated at a later date and the fraud eventually exposed, such as in the Schön Scandal.  In Big Science, this may not be practicable. However, Big Science requires big teams of people and the chances are someone would blow the whistle, or try to…

Anyway, I know that there are people out there who take everything I write on this blog absurdly literally so I’ll spell it out that I am in no way suggesting that the Planck mission is a fraud. Or predicting that there’ll be a murder just before the announcements on March 21st. Any similarity purely coincidental and all that. And I’ve never had time to write the book anyway – perhaps a publisher might read this and offer me an advance as an incentive?

Moreover, going back to the Chambers Dictionary, I note the final definition omitted above

…according to plan (space flight)

So that’s that. Nothing sinister. I’m not sure how “nominal” acquired that meaning, mind you, but that’s another story…

The case for JUICE

Posted in Science Politics, The Universe and Stuff with tags , , , on May 8, 2012 by telescoper

telescoper:

Here’s a nice blog peace giving the case for JUICE (The Jupiter Icy Moon Explorer recently selected by the European Space Agency for its next L-class mission).

Originally posted on Well-Bred Insolence:

There’s been a lot of chatter in astronomy circles about the negative consequences of ESA’s latest L-class (i.e. large) space mission selection.  JUICE (The JUpiter Icy moon Explorer) was selected over two rival missions – the New Gravitational wave Observatory (NGO), and the Advanced Telescope for High ENergy Astrophysics (ATHENA).  In the current age of global austerity, one group’s win is several groups’ losses, and understandably the X-Ray and gravitational wave communities are upset at the choice.  Indeed, reading the comments section on astro blogs might make planetary scientists go a little pale. Not least the fact that ATHENA supporters have already delivered a 1450 signature petition demanding a rethink.  The fact that the decision making process has been somewhat cloudy doesn’t help matters.

It does indeed suck that this is a zero-sum game (in fact, probably…

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It’s JUICE!

Posted in Science Politics, The Universe and Stuff with tags , , on May 3, 2012 by telescoper

Not unexpectedly, the European Space Agency announced yesterday that it’s next large mission will be the Jupiter Icy Moon Explorer (aka JUICE). There’s a piece in Physics World about the selection – and rejection of the other two contenders, NGO and ATHENA. Andy Lawrence has commented already on his own blog and is also quoted extensively in the Physics World article.

A lot of allegations are flying around about how the selection process was conducted, specifically relating to conflicts of interest. I don’t know any details, so I won’t comment on whether this is justified outrage or simply sour grapes.

Anyway, for what it’s worth, I think I agree with what Andy Lawrence says in the Physics World story in that the final decision was pretty inevitable after NASA’s decisions in the areas of gravitational waves and X-ray astronomy pulled the rug out from under the other contenders. I’ll also add that, although it’s far from my own specialism, I think JUICE looks like a very exciting mission. I wish it every success.

It just remains to be seen how long the recriminations will rumble on.

Controversy brewing at ESA?

Posted in Science Politics with tags , , , , on April 23, 2012 by telescoper

telescoper:

Interesting stuff over at the e-astronomer relating to ESA’s handling of the process of selecting its next L-class mission. The plot thickens.

Originally posted on The e-Astronomer:

So the Athena folk are somewhat miffed at being pipped by Juice. (This metaphor doesn’t seem quite right ? Ed.) But what about Horse Number Three ? Aren’t the NGO folk doing a Grand Petition ? Nope. It seems their tactic is a semi-formal complaint about inadeqacies in the process : an email letter direct to Gimenez. I am not sure how widely it has been circulated, but I understand it is stern stuff, bringing up issues of inappropriate revisions of costings and risk factors, and inadequately resolved conflicts of interest. Feel free to comment if you have clear knowledge, but please (a) do not leak things that are confidential, and (b) keep coments about process and not about individuals.

Its not really clear what competition means when a very small number of items is under consideration, and moreoever each item represents one community-segment, each of which ESA wishes to…

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On the Dearth of Dark Matter in the Solar Neighbourhood

Posted in Astrohype, The Universe and Stuff with tags , , , , , , , , on April 22, 2012 by telescoper

I’m a bit late getting onto the topic of dark matter in the Solar Neighbourhood, but it has been generating quite a lot of news, blogposts and other discussion recently so I thought I’d have a bash this morning. The result in question is a paper on the arXiv by Moni Bidin et al. which has the following abstract:

We measured the surface mass density of the Galactic disk at the solar position, up to 4 kpc from the plane, by means of the kinematics of ~400 thick disk stars. The results match the expectations for the visible mass only, and no dark matter is detected in the volume under analysis. The current models of dark matter halo are excluded with a significance higher than 5sigma, unless a highly prolate halo is assumed, very atypical in cold dark matter simulations. The resulting lack of dark matter at the solar position challenges the current models.

As far as I’m aware, Oort (1932, 1960) was the first to perform an analysis of the vertical equilibrium of the stellar distribution in the solar neighbourhood. He argued that there is more mass in the galactic disk than can be accounted for by star counts. A reanalysis of this problem by Bahcall (1984) argued for the presence of a dark “disk” of a scale height of about 700 pc. This was called into question by Bienaymé et al. (1987), and by Kuijken & Gilmore in 1989. In a later analysis based on a sample of stars with HIPPARCOS distances and Coravel radial velocities, within 125 pc of the Sun. Crézé et al. (1998) found that there is no evidence for dark matter in the disk of the Milky Way, claiming that all the matter is accounted for by adding up the contributions of gas, young stars and old stars.

The lack of evidence for dark matter in the Solar Neighbourhood is not therefore a particularly new finding; there’s never been any strong evidence that it is present in significant quantities out in the suburbs of the Milky Way where we reside. Indeed, I remember a big bust-up about this at a Royal Society meeting I attended in 1985 as a fledgling graduate student. Interesting that it’s still so controversial 27 years later.

Of course the result doesn’t mean that the dark matter isn’t there. It just means that its effect is too small compared to that of the luminous matter, i.e. stars, for it to be detected. We know that the luminous matter has to be concentrated more centrally than the dark matter, so it’s possible that the dark component is there, but does not have a significant effect on stellar motions near the Sun.

The latest, and probably most accurate, study has again found no evidence for dark matter in the vicinity of the Sun. If true, this may mean that attempts to detect dark matter particles using experiments on Earth are unlikely to be successful.

The team in question used the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory, along with other telescopes, to map the positions and motions of more than 400 stars with distances up to 13000 light-years from the Sun. From these new data they have estimated the mass of material in a volume four times larger than ever considered before but found that everything is well explained by the gravitational effects of stars, dust and gas with no need for a dark matter component.

The reason for postulating the existence of large quantities of dark matter in spiral galaxies like the Milky Way is the motion of material in the outer parts, far from the Solar Neighbourhood (which is a mere 30,000 light years from Galactic Centre). These measurements are clearly inconsistent with the distribution of visible matter if our understanding of gravity is correct. So either there’s some invisible matter that gravitates or we need to reconsider our theories of gravitation. The dark matter explanation also fits with circumstantial evidence from other contexts (e.g. galaxy clusters), so is favoured by most astronomers. In the standard theory the Milky Way is surrounded by am extended halo of dark matter which is much less concentrated than the luminous material by virtue of it not being able to dissipate energy because it consists of particles that only interact weakly and can’t radiate. Luminous matter therefore outweighs dark matter in the cores of galaxies, but the situation is reversed in the outskirts. In between there should be some contribution from dark matter, but since it could be relatively modest it is difficult to estimate.

The study by Moni Bidin et al. makes a number of questionable assumptions about the shape of the Milky Way halo – they take it to be smooth and spherical – and the distribution of velocities within it is taken to have a very simple form. These may well turn out to be untrue. In any case the measurements they needed are extremely difficult to make, so they’ll need to be checked by other teams. It’s quite possible that this controversy won’t be actually resolved until the European Space Agency’s forthcoming GAIA mission.

So my take on this is that it’s a very interesting challenge to the orthodox theory, but the dark matter interpretation is far from dead because it’s not obvious to me that these observations would have uncovered it even if it is there. Moreover, there are alternative analyses (e.g. this one) which find a significant amount of dark matter using an alternative modelling method which seems to be more robust. (I’m grateful to Andrew Pontzen for pointing that out to me.)

Anyway, this all just goes to show that absence of evidence is not necessarily evidence of absence…

Bad News for Astrophysics from ESA

Posted in Science Politics, The Universe and Stuff with tags , , , , , , , , on April 18, 2012 by telescoper

Just a quick post to pass on the news (which I got from Steinn Sigurdsson’s blog) that the ESA Executive (see correction in comments below) Space Science Advisory Committee (SSAC) of the European Space Agency (ESA) has made a recommendation as to the next large mission to be flown. The short list consisted of a mission to Jupiter’s moons (JUICE), an X-ray observatory (ATHENA), and a gravitational wave observatory (NGO). The last two of these are severely de-scoped versions of missions (IXO and LISA respectively) that had to be re-designed in the aftermath of decisions made in the US decadal review not to get involved in them.

Not unexpectedly, the winner is JUICE. Barring a rejection of this recommendation by the ESA Science Programme Committee (SPC) this will be the next big thing for ESA space science.

The School of Physics and Astronomy at Cardiff University has a considerable involvement in gravitational wave physics, so the decision is disappointing for us but not entirely surprising. It’s not such a big blow either, as we are mainly involved in ground-based searches such as LIGO.

The biggest local worry will be for the sizeable community of X-ray astronomers in the UK. With no big new facilities likely for well over a decade one wonders how the expertise in this area can be sustained into the future, even if LOFT is selected as one of the next medium-sized missions. Or, given that STFC funding is already spread extremely thin, perhaps this is time for the UK to organize a strategic withdrawal from X-ray astronomy?

Planck Publications

Posted in Science Politics, The Universe and Stuff with tags , , , , on December 2, 2011 by telescoper

I just noticed that a Special Issue of Astronomy and Astrophysics which contains the early science papers from Planck has now finally appeared, swelling a considerable number of personal bibliographies just in time for the next round of grant and/or job applications!

The thing is, though, that these papers were all placed on the arXiv in January 2011, so it has taken almost 11 months for them to get officially published. Such a delay seems ridiculous to me in this digital age.  I wonder why it took A&A  so long to publish these papers? Were they all held up by refereeing delays? Are the final published versions significantly different from the arXiv version? I’ve only looked at a few, and can’t see any major changes.

Or maybe this is all normal for A&A?

If you know, please tell…

Of course the main science results from Planck won’t be out until 2013. I wonder how long they’ll take to referee?

JWST: Over and Out?

Posted in Science Politics, The Universe and Stuff with tags , , , , on August 23, 2011 by telescoper

News filtered through recently that the cost of the James Webb Space Telescope, which is already  threatened with cancellation owing to cuts in NASA’s budget, is now estimated to be around $8.7 billion dollars, about $2.2 billion higher than previous figures. In fact about a decade ago, when I was a lad, and chair of the old PPARC Astronomy Advisory Panel, the price tag of  the NGST (Next Generation Space Telescope), as it was then called, was put at significantly less than one billion dollars.

The implications of cancelling JWST are profound on both sides of the Atlantic. As Mark McCaughrean explains in detail over on the e-astronomer, the European Space Agency has already made a substantial investment in JWST and planned future contributions include the launch and substantial operating costs. The instrument development is nearly finished, but whether there will actually be a telescope to put instruments on remains to be seen. It’s clear that this, together with previous unilateral decisions by NASA, is putting some strain on the relationship with ESA.

There were many who reacted to the initial suggestion that JWST should be cancelled by arguing that it was mere political posturing by Republicans in the House of Representatives and that it could and would be reversed if appropriate campaigning took place. To this end there has been, e.g.,  a letter to the White House Science Advisor (here for non-US astronomers and there for US ones). There’s also been a letter of support from the President of the Royal Astronomical Society. NASA’s administrators have also apparently come up with a plan to divert funds from other projects to support it. These efforts notwithstanding I get the distinct feeling that cancellation of JWST is a very real prospect and it goes without saying that the chances of avoiding it are not helped by  the increased estimated expense.

I’ve talked about this to a number of astronomers and cosmologists over the summer and found very mixed views not only about  (a) whether JWST will be cancelled or not but also about (b) whether it should be cancelled or not. Even astronomers have expressed exasperation with the spiralling cost of JWST and pointed out that if we had known a decade ago that it would take so long and involve such an outlay then it would never have gone ahead in the first place.

So let me try a straw poll:

Not Now, Voyager

Posted in The Universe and Stuff with tags , , , , , , on July 10, 2011 by telescoper

Last week I found myself a bit perplexed by the frenzy of twitter angst surrounding the last ever launch of the Space Shuttle. It’s not the first time something like this has happened. I’ve often felt like there must be something wrong with me for not getting agitated over such things. After Altantis returns to Earth in a couple of weeks’ time she will be taken out of service and, for the foreseeable future, America will no longer have the ability to put humans into orbit. This does mark the end of an era, of course, but is it really something to get all upset about?

I find myself agreeing with the Guardian editorial, which I’ve taken the liberty of copying here:

Fewer than 600 people have been admitted an exclusive club: space travel. Now, with the last flight of the space shuttle under way, the membership list is harder to join than ever. When Yuri Gagarin orbited the earth, half a century ago, and when astronauts landed on the moon eight years later, it would have been inconceivable to think of a time when manned space flight began to slip from the present to the past. But America, at least for the moment, no longer has the capacity to send people into space. In terms of national pride, this may be a failure. In terms of scientific advancement, it may not matter that much at all. Deep space exploration – using robot probes – is a very different and more useful thing than the expensive and unreliable effort to send human beings into low earth orbit, no further from Cape Canaveral than New York. The shuttle has been an icon of its age, but its human passengers – however brave and skilled – have made their flights as much to show the world what America could do as for any particular and necessary purpose. Even the International Space Station, extraordinary though it is, could operate without a human presence, its experiments automated. The only good argument for sending people into space is the simple daring of it – the need, as Star Trek used to claim, “to boldly go where no man has gone before”. Visit Mars, by all means – but there is little to be gained by sending astronauts to orbit this planet, not all that far above our heads.

For me, the most remarkable thing about the Space Shuttle is how matter-of-fact it has become. It’s rather like Concorde, which was an engineering marvel that people would drop everything and gawp at when it  first appeared, but which soon became a part of everyday life. Technology is inevitably like that – what seemed remarkable twenty years ago is now pretty commonplace.

I had similar feelings a couple of  years ago, when Planck and Herschel were launched. Of course I was extremely nervous then , because many of my colleagues had invested so much time and effort in these missions. However, watching the behaviour of the mission control staff at ESA during the launch it struck me how routine it all was for them. It’s a great achievement, I think, to take something so complex and turn it into an everyday operation.

Incidentally, it always strikes me as curious that people use the phrase “rocket science” to define something incredibly difficult. In fact rocket science is extremely simple: the energy source is one of the simplest chemical reactions possible, and the path of the rocket is a straightforward consequence of Newton’s laws of motion. It’s turning this simple science into working technology where the difficulties lie, and it’s a powerful testament to the brilliance of the engineers working in the space programme that workable solutions have been found and implemented in working systems.

So now the era of the Shuttle has passed, what next? Should America (and Europe, for that matter) be aiming to send people to Mars? Should manned spaceflight resume at all?

Different people will answer these questions in different ways. Speaking purely from a scientific point of view I would say that manned space exploration just isn’t cost effective. But going to Mars isn’t really about science; going to the Moon wasn’t either. It’s partly an issue of national pride – note how loss of the Shuttle programme has effectively ended America’s dominance in space, and how keenly that has been felt by many US commentators.

Others argue that manned space flight inspires people to become scientists, and should be done for that reason. I can’t speak for anyone but myself, and I’m sure there will be many who disagree with me, but it wasn’t the Apollo missions that inspired me to become a scientist. When I was a kid I found the footage of people jumping around on the Moon rather boring, to be honest. What inspired me was the excellent science education I received at School. And just think how many physics teachers you could train for the cost of, e.g. the ESA Aurora program

Another argument is “because it’s there” or, as Walt Whitman put it,

THE untold want, by life and land ne’er granted,
Now, Voyager, sail thou forth, to seek and find.

As a species we have an urge to set challenges for ourselves, whether by asking difficult questions, by designing and building difficult devices, or by attempting difficult journeys – sometimes all three! This is our nature and we shouldn’t shy away from it. But we should also recognize that “going there” is just one of the ways in which we can explore the cosmos. Modern telescopes can see almost to the visible edge of the Universe, the Large Hadron Collider can probe scales much smaller than the nucleus of an atom. I worry sometimes that the political lobbying for manned space flight often seems to be arguing that it should be funded by taking money from other, more fundamental, scientific investigations. Astronomers and particle physcisists are explorers too, and they also inspire. Don’t they?

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