Archive for ESA

Our Solar Neighbourhood

Posted in The Universe and Stuff with tags , , , on December 3, 2020 by telescoper

Here’s a very nice movie showing the stars in the Solar neighbourhood (defined to be within 100 parsecs of the Sun) with positions and colours mapped by the European Space Agency’s Gaia mission.

P.S. The video is timed to coincide with Gaia’s third data release: for more information about DR3 see here.

The Comet – The Video!

Posted in The Universe and Stuff with tags , , , on August 14, 2019 by telescoper

I couldn’t resist sharing this remarkable video about the rendezvous and subsequent landing of the European Space Agency’s Rosetta spacecraft on the comet Churyumov-Gerasimenko 67P. You can find a few posts I did about this at the time (2014) here. Here’s one of the memorable from one of those posts:


Anyway, after the end of the mission, in 2017, the European Space Agency released over 400,000 images from Rosetta, based on which Christian Stangl and Wolfgang Stangl worked together to create this short film. The sequences are digitally-enhanced versions of real pictures taken by the Rosetta Probe and they’re stunning!

BepiColombo goes to Mercury

Posted in The Universe and Stuff with tags , , , on October 24, 2018 by telescoper

You may have missed the news that the joint Japanese-European (JAXA-ESA) Mission BepiColombo was successfully launched on October 19th 2018 and is now on its way to the planet Mercury, where it will arrive in December 2025.

As it happens I’ve just finished delivering a set of lectures on gravitational dynamics, part of which was devoted to orbital mechanics. One of the problems I worked out during these lectures was the Hohmann Transfer Orbit which is the simplest way to get a spacecraft from Earth to, e.g., Mars (which take 8 to 9 months to reach).

Since the radius of Mercury’s orbit is 0.39 AU (compared with Mars’s 1.52 AU) you might think it would take a similar time to reach Mercury, but designing a trajectory that results in a controlled encounter with Mercury in an efficient manner is much harder than for Mars (largely because Mercury is moving much faster). The solution to this problem involves a series of encounters with VEarth, Venus and Mercury each of which results in an adjustment to BepiColombo’s orbit until it finally encounters the target planet at a reasonable speed. This approach takes over seven years, but it saves an enormous amount on fuel – using the gravitational boost from planetary encounters instead of firing rockets.

Here’s a video showing this complex but fascinating example of orbital mechanics in action:

p.s. the dates in the video correspond to the originally planned launch date of 5th October, so are off by a couple of weeks.

Ariel to Fly

Posted in The Universe and Stuff with tags , , , , on March 23, 2018 by telescoper

All hail, great master! Grave sir, hail! I come
To answer thy best pleasure. Be ‘t to fly,
To swim, to dive into the fire, to ride
On the curled clouds, to thy strong bidding task
Ariel and all his quality.

The Tempest, Act I, Scene 2.

It’s nice to be able to pass on a bit of good news for the good folk of the Astronomy Instrumentation Group here in the School of Physics & Astronomy at Cardiff University.

The ARIEL mission has been given the green light by the European Space Agency and will launch sometime around 2028. It will produce the first ever large-scale survey of the atmospheric chemistry of planets outside our solar system. Ariel will extract the chemical fingerprints of the gases in the atmospheres of over 1000 exoplanets, as well as capturing information about the temperatures and pressures in their atmospheres and the presence of clouds.

Whenever I read of exciting news from the field of exoplanet research – which happens quite frequently nowadays – it reminds me that when I started my graduate studies (in 1985) the field didn’t really exist. Now it’s one of the biggest and most active areas of astronomy! Another thing that makes me feel a bit of a dinosaur is that when Ariel actually launches I’ll be 65…

As with all such missions, a large international collaboration will be involved in Ariel, and much of the detail of who will do what is yet to be worked out, but Cardiff scientists will be providing detailed computer simulations of the Ariel satellite and its instruments, ensuring that the scientific observations can be carefully planned and the resulting data can be analysed correctly. The team will also be involved in the ground segment after launch, interpreting the data from the observations to characterise the atmospheres of the exoplanets. The Principal Investigator of the whole mission is Professor Giovanna Tinetti of University College, London, who I see regularly at dinner with the RAS Club.

Head Irishman of the School, Matt Griffin, who will himself is quoted in the news item as saying

The decision to select the Ariel mission demonstrates the scientific vision and ambition of ESA, and it’s the start of a great adventure for everyone involved. This is a mission that will hugely advance our understanding of the nature of planets and of our place in the Universe, and at Cardiff we are very much looking forward to our participation in the project.

The launch date of 2028 is some way off but space missions are exceedingly complicated things and there’s a lot to do in the next decade or so until Ariel finally flies. Hopefully neither swimming, nor diving into fire nor riding on the curled clouds will be involved, but the scientific quality is something of which we can be very confident.

Congratulations to everyone involved in getting this mission selected and best wishes to all those involved in Cardiff and elsewhere!

LISA gets the go-ahead!

Posted in The Universe and Stuff with tags , , , , , on June 21, 2017 by telescoper

Just taking a short break from examining duties to pass on the news that the European Space Agency has selected the Laser Interferometric Space Experiment (LISA) – a gravitational wave experiment in space – for its large mission L3. This follows the detection of gravitational waves using the ground-based experiment Advanced LIGO and the success of a space-based technology demonstrator mission called Lisa Pathfinder.

LISA consists of a flotilla of three spacecraft in orbit around the Sun forming the arms of an interferometer with baselines of the order of 2.5 million kilometres, much longer than the ~1km arms of Advanced LIGO. These larger dimensions make LISA much more sensitive to long-period signals. Each of the LISA spacecraft contains two telescopes, two lasers and two test masses, arranged in two optical assemblies pointed at the other two spacecraft. This forms Michelson-like interferometers, each centred on one of the spacecraft, with the platinum-gold test masses defining the ends of the arms.

Here’s an artist’s impression of LISA:

This is excellent news for the gravitational waves community, especially since LISA was threatened with the chop when NASA pulled out a few years ago. Space experiments are huge projects – and LISA is more complicated than most – so it will take some time before it actually happens. At the moment, LISA is pencilled in for launch in 2034…

New: Top Ten Gaia Facts!

Posted in Astrohype, The Universe and Stuff with tags , , , on September 14, 2016 by telescoper

After today’s first release of data by the Gaia Mission, as a service to the community, for the edification of the public at large, and by popular demand, here is a list of Top Ten Gaia Facts.

Gaia looks nothing like the Herschel Space Observatory shown here.

Gaia looks nothing like the Herschel Space Observatory shown here.


  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.

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: