Archive for ESA

To Edinburgh for Euclid

Posted in The Universe and Stuff with tags , , on December 17, 2015 by telescoper

This morning I flew from London Gatwick to Edinburgh to attend the UK Euclid meeting at the Royal Observatory, which lasts today and tomorrow. It turns out there were two other astronomers on the plane: Alan Heavens from Imperial and Jon Loveday from my own institution, the University of Sussex.

The meeting is very useful for me as it involves a number of updates on the European Space Agency’s Euclid mission. For those of you who don’t know about Euclid here’s what it says on the tin:

Euclid is an ESA mission to map the geometry of the dark Universe. The mission will investigate the distance-redshift relationship and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to redshifts ~2, or equivalently to a look-back time of 10 billion years. In this way, Euclid will cover the entire period over which dark energy played a significant role in accelerating the expansion

Here’s an artist’s impression of the satellite:


Do give you an idea of what an ambitious mission this is, it basically involves repeated imaging of a large fraction of the sky (~15,000 square degrees) over a period of about six years. Each image is so large that it would take 300 HD TV screens to display it at full resolution. The data challenge is considerable, and the signals Euclid is trying to measure are so small that observational systematics have to be controlled with exquisite precision. The requirements are extremely stringent, and there are many challenges to confront, but it’s going well so far. Oh, and there are about 1,200 people working on it!

Coincidentally, this very morning ESA issued a press release announcing that Euclid has passed its PDR (Preliminary Design Review) and is on track for launch in December 2020. I wouldn’t bet against that date slipping, however, as there is a great deal of work still to do and a number of things that could go wrong and cause delays. Nevertheless, so far so good!



The Cliffs of Comet Churyumov–Gerasimenko

Posted in The Universe and Stuff with tags , , on December 23, 2014 by telescoper

I don’t often post pictures from the excellent Astronomy Picture of the Day but today’s is so beautiful I couldn’t resist.


Image Credit & Licence (CC BY-SA 3.0 IGO): ESA, Rosetta spacecraft, NAVCAM; Additional Processing: Stuart Atkinson

The explanation published with the picture goes:

These high cliffs occur on the surface of a comet. They were discovered to be part of the dark nucleus of Comet Churyumov–Gerasimenko (CG) by Rosetta, a robotic spacecraft launched by ESA which began orbiting the comet in early August. The ragged cliffs, as featured here, were imaged by Rosetta about two weeks ago. Although towering about one kilometer high, the low surface gravity of Comet CG would likely make a jump from the cliffs, by a human, survivable. At the foot of the cliffs is relatively smooth terrain dotted with boulders as large as 20 meters across. Data from Rosetta indicates that the ice in Comet CG has a significantly different deuterium fraction — and hence likely a different origin — than the water in Earth’s oceans. The Rosetta spacecraft is scheduled to continue to accompany the comet as it makes its closest approach to the Sun in 2015 August.

For me, Rosetta has undoubtedly been the science highlight of the year. It has been an absolute triumph, and it’s not over yet as Rosetta will now follow the comet on its journey towards the Sun. With a bit of luck, the lander Philae will also awaken (hopefully in March) as the Sun begins to shine more brightly on its solar panels.

I think we should all wish a special Merry Christmas and Happy New Year to everyone involved with this wonderful adventure!

Rosetta and Philae: So Much More Than Science

Posted in The Universe and Stuff with tags , , , , on November 15, 2014 by telescoper

Time to break radio silence, so to speak, with a short post about the main event that’s happened in the astronomical world while I’ve been indisposed, namely the separation of the probe Philae from its parent spacecraft Rosetta and subsequent successful landing  on  Comet 67P/Churyumov-Gerasimenko. There’s been  a huge amount of media coverage and in-depth specialist analysis of this going on over the past few days, and it isn’t reallly in my own area of specialism, so there isn’t much point in trying to do my own version of events here. If you’re looking for a science briefing then you could do a lot worse than the official European Space Agency web pages here. I’ll confine myself to a few general reflections.

First, as has been widely reported, the final stages of Philae’s  approach were clearly a bit hairy (appropriately enough, since the word “comet” is derived from the Greek word for “hair”).  Although it homed in on its intended landing site pretty accurately, when it got close the thrusters intended to help it settle onto the surface didn’t fire and the “harpoons” supposed to fasten it to the surface also failed. As a consequence of all this, Philae bounced off the surface, floated in space for about two hrs, during which it travelled about 1km across the surface of the comet; that’s an average speed of about 0.14 m/s relative to the surface of the comet. It then encountered the surface again, bounced again for about 7 min, and then come to rest on 2 legs, with one pointing into space, against a cliff on the edge of a crater, with only one solar panel in operation because of the shade from the cliff.

It’s worth noting that the escape velocity from the surface of Comet 67P/Churyumov-Gerasimenko is only about 0.5 m/s and the probe met the surface of the comet at about twice that speed. Without significant intervention to stick it down, Philae could quite easily have bounced off and into space forever. The loss of the thruster and the failure of the harpoons made that a very likely outcome, but the mission’s luck held out. Fortune favours the brave.

Here’s just one of the remarkably vivid pictures taken of the surface of the Comet taken by Philae from its precarious resting place. I don’t know about you but to me it looks very eerie but at the same time it almost makes me feel like I am there in person, as if I could reach out and touch it…


It then became clear that the rate at which Philae was using power from its batteries was exceeding the rate at which it could recharge using its solar panel. For a time it was by no means obvious that it could perform all its science tasks in the short time (~60 hours) remaining before it would run out of juice, but in the end, according to the experts, it did accomplish about 80% of its science goals before going into hibernation.

I’ve heard some folk – including a few astronomers – claiming that Philae’s difficulties have cast a big shadow over the Rosetta mission. That’s clearly nonsense. In fact, the odds that Philae would ever  attach itself to its target were only about 50-50. And even if it did succed there was a chance some of its on board instruments may well have failed. After all, they had spent 10 years in the hostile environment of space waiting to be called into action. As it turned out, Philae’s achievements are at the upper end of the range of expectations. But even if the probe had failed entirely then there would still have been the huge amount of science being done by Rosetta itself. Overall, I think the mission so far has been a stunning success and there’s a lot more to come.

From a non-scientific point of view the perilous landing of Philae was even a bonus, as it made a public that is in danger of becoming blasé about spaceflight realise (a) that it is incredibly difficult and (b) there are people clever enough to make it work. The tension that mounted as events unfolded had people gripped largely because people could see in their mind’s eye this little thing, like a washing machine on legs, bouncing about in slow motion across an alien landscape. It was a drama largely acted out in our own imagination, and all the more absorbing for that.

Yesterday I was chatting with a friend who was trying to understand what Philae was doing as it bounced. It is quite difficult, if you think about it, to apply physical intuition to this situation. On the Earth we think of the “up” and “down” directions as being unambiguously defined, but “up” actually means two different things: (i) perpendicular to the Earth’s surface; and (ii) in the opposite direction to which gravity makes things fall (“down”) . On a spherical object such as a planet, gravity acts towards the centre, hence “what goes up  (i)  must come down  (ii)” .

Comet 67P/Churyumov-Gerasimenko, however, is far from spherical (even by the standards of a theoretical physicist):


This means that bouncing up off the surface does not necessarily result in coming straight back down again – gravity may well pull in a quite different direction. Add to that the spinning of the comet and its uneven surface, and you can understand how difficult it was to figure out where Philae ended up and precisely how it had got there!

Another comment I’ve heard concerns the cost. At €1.4 Billion it does sound expensive, but divide that among the population of the European Union (currently over 500 million) and it doesn’t sound so much, about the cost of a cup of coffee, and remember that the mission has lasted over years.  Philae has succeeded in generating a  huge amount of scientific data and I have no doubt that important conclusions will soon be drawn from the measurements it has made, but it’s not just the science that justifies the (modest) pricetag. Rosetta is an achievement that all humanity can celebrate. It is a demonstration of what we can achieve collectively if we have ambition, imagination and determination. Setting ourselves targets and reaching them. Asking ourselves questions and answering them. This is what makes us humans what we are. Venturing into space changes our perspective on our own world, something we need to do urgently if humanity is to survive on Earth.




Rendezvous Rosetta!

Posted in The Universe and Stuff with tags , , on August 6, 2014 by telescoper

Just a quick post to remind you (as if you needed it) that, in about 5 minutes’ time at 10am BST, the ESA spacecraft Rosetta will begin its encounter with a comet (actually Comet 67P/Churyumov-Gerasimenko).

As it approached its target, Rosetta took this picture that revealed the comet to be a rather peculiar beast, rather like a rubber duck:


Here’s a more recent, closer, view:


Rosetta’s journey began on 2 March 2004 when Rosetta was launched on an Ariane 5 from Europe’s Spaceport in Kourou, French Guyana. Since then, the spacecraft has orbited around the Sun five times, picking up speed through three gravitational “slingshots” at Earth and one at Mars, to enter an orbit similar to that of its target, said comet 67P/Churyumov–Gerasimenko, which is in an elliptical 6.5-year solar orbit that takes it from beyond the orbit of Jupiter at its furthest point, and between the orbits of Mars and Earth at its closest to the Sun.

To perform its rendezvous Rosetta has to match the pace of the comet – currently about 55 000 km/h – and travel alongside it to within just 1 m/s between them. This has required a complex and delicate series of manoeuvres:

The spacecraft will then travel alongside the comet as it approaches the Sun. In November 2014 the Philae probe will be deployed and will land on the comet surface. Rosetta will follow the comet to its closest distance to the Sun on 13 August 2015 and as it moves back towards the outer Solar System. The nominal mission end is December 2015.

I bet there’s quite a lot of stress in the ESA control centre in Darmstad, Germany, as the probe’s epic journey nears its end, not least because telemetry is lost while the burn happens. Those ten years in space will count for little if something goes wrong now. Good luck everyone involved!

You can watch a live feed of the encounter here.

UPDATE: after an agonizing wait – it takes 23 minutes for telemetry to reach Earth from Rosetta – the spacecraft has entered orbit correctly. Well done everyone!

UPDATE: click here for an amazing collection of images of the comet.

UPDATE: Relief at ESA HQ as The Clangers finally emerge to greet the Rosetta Spacecraft:


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

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).

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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