Studying Space - The Launch of Planck and Herschel

Thursday 14th May, all being well, we are going to see the launch of the European Space Agency’s Herschel and Planck missions which are studying the formation of stars and...
10 May 2009

Interview with 

Dr Anthony Challinor, Institute of Astronomy, Cambridge University


Kat - Thursday 14th May, all being well, we are going to see the launch of the European Space Agency's Herschel and Planck missions which are studying the formation of stars and galaxies and background radiation, all sorts of exciting things.

On the show today we are joined by Dr. Anthony Challinor who is here to tell us about the mission and how he is going to be looking at some of the data from it.  So thanks coming on the show Anthony.

Anthony -   That's quite alright.

Kat -   So tell me what is the mission that you are involved in and what is it doing?

Planck satelliteAnthony -   So we are involved in the Planck mission and what Planck is trying to do is study what's called the cosmic microwave background radiation.  So this is really the oldest light in the universe.  It was essentially created in the big bang itself and what we are going to try and do is study very sensitively the tiny variations in temperature in this radiation when you look in different directions and from that we have to learn a lot about both the early universe and also something about what the universe is composed of, what its geometry is and perhaps even the ultimate fate of the universe.

Kat -   Crikey. What's the actual satellite going to be like?  Where is it shooting off to?

Anthony -   Planck, its ultimate home is going to be what's called the second Langrange point which is a very special point about one and half million kilometres from the Earth and it is peculiar in that it rotates at exactly the same angular speed about the Sun as the Earth does.  So thermally it's a very stable environment which is exactly what you need when you are looking for these tiny temperature variations - just about a millionth of a degree fluctuations we are looking for.  

Kat -   And so you are looking for these tiny fluctuations in temperature, how far back in time are you hoping to be able to look, you know you are hoping that this data will shed light on?

Anthony -   So the cosmic microwave background radiation was produced very, very early in the history of the universe and the early universe is very, very opaque but eventually it became essentially transparent about 400,000 years after when we think the big bang occurred and at that time the microwave background effectively decoupled from all the matter in the universe.

A contour plot of the effective potential of a two-body system. (the Sun and Earth here), showing the 5 Lagrange points. An object in free-fall would trace out a contour (such as the Moon, shown).So when we look at it today, we are effectively seeing a snapshot of conditions in the universe 400,000 years after the big bang or about 13 billion years, 14 billion years back in time from now.

Kat -   And how is the Planck mission special or different from the sort of previous microwave measuring experiments that have been there before?

Anthony -   Well so Planck is Europe's first satellite mission to try and measure the microwave background.  There have been two other NASA missions before, the first called KOBE, the second called WMAP which is actually still observing.  

Planck is an improvement in that it is much more sensitive. It will observe very, very much wider range of wavelengths and it has better angular resolution as well.

Kat -   And if it is so far away from the Earth how is it sending the signals all the way back for you to analyse back in the lab?  How long does it take that data to get to you?

Anthony -   Well the data is transmitted, it is not transmitted continuously but it's sort of buffered on board and then there's an hour or two-hours' slot everyday when it is all transmitted back.

Kat -   And how long does it take to get back to you?

Anthony -   What from the...

Kat -   Yeah, from the satellite.

Anthony -   It takes, it is 1.5 million kilometres so however long light takes to travel that distance.

Kat -   I don't know, any of our listeners would like to do that calculation and tell us, that will be great.  Tell us a little bit about Herschel, the other satellite as well, what's that up to?

The Cosmic Microwave Background temperature fluctuations from the 5-year Wilkinson Microwave Anisotropy Probe data seen over the full sky.Anthony -   Okay, so we are not directly involved in Herschel although there are groups in the U.K. that are and what Herschel is basically trying to do is it is looking at dust within the universe.  

So it is an infrared satellite and it is basically looking at galaxies that otherwise we can not see in optical light because that the star light is sort of shrouded and absorbed by dust.  But that dust is then heated by the star light and re-radiates in the infrared.  So Herschel will be able to see those sorts of environments directly.    

Kat -   I love the idea of a satellite going out looking for dust out to the universe and doing the dusting, "How Clean is Your Galaxy?"

Anthony -   Some people are very interested in dust, yeah.

Kat -   Some people are.  So where is the mission launching from this Thursday?

Anthony -   So it's going to launch from Kourou in French Guiana.

Kat -   And you didn't manage to get a ticket out there?

Anthony -   Unfortunately no.

Kat -   And when are the first, the first bits of information going to be coming back?  How long is it going to take to get into position?

Anthony -   So it takes about three months for Planck to reach L-2 where it will start observing from and the plan then, it takes a couple of months further to sort of settle down and properly be commissioned but after that Planck will do basically two complete surveys of the sky, which will take about 15 months.

Kat -   And then you get all the data back and come back on the show and tell us all about it.

Anthony -   That's right, I mean we get the data back essentially as soon as Planck starts observing but it will be probably about three years before there is any real public data release of the cosmological data.

Kat -   Brilliant, well we will really look forward to hearing that.  Thank you very much.  That's Dr. Anthony Challinor from the Institute of Astronomy here in Cambridge.  So if you are a space-excited person then watch out for the launch of the satellite this Thursday.  


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