Science News

Mapping the milky way

Tue, 11th Feb 2014

Chris Smith

Listen Now    Download as mp3 from the show Green Food

Chris -   First this week, the Gaia space mission which was launched on the 19th of December is now orbiting around a virtual point in space Artistwhich is called L2.  Itís about 1.5 million km from Earth.  Gaiaís goal is to create the most accurate map yet of the Milky Way.  This week, its 1 billion pixel camera was tested successfully which is presumably a very big relief for Cambridge professor Gerry Gilmore whoís leading the project.  Hello, Gerry.

Gerry -   Hi, Chris.  Good to see you again.

Chris -   Are you a relieved man?

Gerry -   Doubly actually.  I was at the launch and one felt really quite relaxed after it was over, seeing Gaia flying off so successfully.

Chris -   How much money was invested in that?

Gerry -   The lifetime cost of the project is getting on for a billion Euros, 600 or 700 million pounds.  

Chris -   Or a third of an LHC to put it another way, I suppose.  

Gerry -   Well, itís the peopleís lives that is their real cost.  There's hundreds of really smart engineers that have devoted decades to this so that's the bit you can't get back.  

Chris -   The announcement this week that the camera works, so when you put one of these things into space, how do they power them up?  Do they do it system by system to do a series of checks to make sure that everything works sequentially then?  

Gerry -   Yes.  The whole turn on process is still underway, but you turn on the really smart brains of the system which themselves then turn on other bits of the system and so on.  There are some bits like the atomic clocks that take weeks to settle down, so they're turned on early and they're still settling down.  So, Gaia wonít actually be in full science operation for another three or four months yet.  But as the systems are turned on and tested, we  then know whether they're working or not.  The really critical systems which is the computing, the brain, the clocks, and the camera and telescopes, they're all working fine.  That's a really magnificent tribute to the people who built it and a spectacular relief for those in it.  

Chris -   How do you know that the camera is working correctly because all you get back is what it tells you itís seeing?  

Gerry -   So essentially, all Gaia is is two telescopes feeding a very, very large camera.  These things are billion pixels, biggest camera ever put into space.  Itís about a metre long.  Compared to the one in your phone, which is about the size of your little finger nail, this thing is the size of your tabletop.  What itís going to do is essentially feed down a high definition movie for the next 5 or 6 years.  And so, the first frame of that movie is down and it looks good.  So, by comparing it with previous studies of the same cluster which by pure coincidence happen to be a study I did using the newly repaired Hubble Space telescope in the late 1990s.  So, itís pure chance that that happens to be the same cluster.  But by comparing it with those Hubble measures, we know how sensitive the camera is, we know how accurately the things in focus.  So, we know how clean the optics are and all the news is good.  I mean, there are few technical things that will come out in the next week or two, but fundamentally we know the mission is going to work.  Itís terrific!  

Chris -   Congratulations!  Have there been any problems or has it all been a bed of roses so far?  

Gerry -   No, there's always a few problems.  Everybody knows the famous spectacular Hubble problem and Gaiaís predecessor actually went in the wrong orbit.  The rocket didnít fire because some twit left a bit of cloth in it.  But Gaia has nothing like that.  there's a few little technical issues that weíll be able to work through.  But fundamentally, itís looking good.  

Chris -   How long before the data begins to land on your desk here in Cambridge so that you can begin to see these amazing maps in extraordinary detail, emerging of our galaxy?  

Gerry -   Well, weíre processing the test data right now.  Thatís where that image came from.  So, we know what's going on.  Weíre contributing to the team that's actually testing out the hardware and checking that everything is working, and putting the telescope in focus.  That's actually a non-trivial thing to do.  Itíll take another month yet before itís perfectly in focus.  But then the real science data will start coming in in April.  So then weíll do the science verification.  So, that's the real hard Ė how good is the science going to be.  So, we know that technically, the thing is looking promising.  About April, weíll come back and weíll show you the first science results and then weíll expect to be in full routine, doing nothing but exciting science from May onwards to another five or six years.  

Chris -   You must come back and tell us how youíre getting on. Gerry thank you very much and congratulations. Great to have you on the programme. Gerry Gilmore from Cambridge Universityís Cavendish laboratory.



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