James Webb telescope's 'first light' instrument ready to ship

 

BBC correspondent Jonathan Amos gets to see the Mid-Infrared Instrument (Miri) close up before its shipment to the US

One of Europe's main contributions to the James Webb Space Telescope (JWST) is built and ready to ship to the US.

The Mid-Infrared Instrument (Miri) will gather key data as the $9bn (£5.5bn) observatory seeks to identify the first starlight in the Universe.

The results of testing conducted at the Rutherford Appleton Laboratory in the UK have just been signed off, clearing Miri to travel to America.

James Webb - regarded as the successor to Hubble - is due to launch in 2018.

It will carry a 6.5m primary mirror (more than double the width of Hubble's main mirror), and a shield the size of a tennis court to guard its sensitive vision from the heat and strong light of our Sun.

The observatory has been tasked with tracking down the very first luminous objects in the cosmos - groupings of the first generation of stars to burst into life.

To do so, Webb will use its infrared detectors to look deeper into space than Hubble, and further back in time - to a period more than 13 billion years ago.

"The other instruments on James Webb will do massive surveys of the sky, looking for these very rare objects; they will find the candidates," explained Miri's UK principal investigator, Prof Gillian Wright.

"But Miri has a very special role because it will be the instrument that looks at these candidates to determine which of them is a true first light object. Only Miri can give us that confirmation," she told BBC News.

JWST design
  • James Webb's main mirror has around seven times more collecting area than Hubble's 2.4m primary mirror
  • The sunshield is about 22m by 12m. There will be a 300-degree difference in temperature between the two sides
  • James Webb's instruments must be very cold to ensure their own infrared glow does not swamp the observations
  • The mission will launch in 2018 on an Ariane rocket. The observing position will be 1.5 million km from Earth

JWST is a co-operative project between the US (Nasa), European (Esa) and Canadian (CSA) space agencies.

Europe is providing two of the telescope's four instruments and the Ariane rocket to put it in orbit.

Miri is arguably the most versatile of the four instruments, with a much wider range of detectable wavelengths than its peers (5-28 microns).

Fundamentally, it is a camera system that will produce pictures of the cosmos.

JWST mirror segments All of JWST's mirror segments are now complete

But it also carries a coronagraph to block the light from bright objects so it can see more easily nearby, dimmer targets - such as planets circling their stars. In addition, there is a spectrograph that will slice light into its component colours so scientists can discern something of the chemistry of far-flung phenomena.

Miri is a complex design, and will operate at minus 266C. This frigid state is required for the instrument's detectors to sample the faintest of infrared sources. Everything must be done to ensure the telescope's own heat energy does not swamp the very signal it is pursuing.

The hardware for Miri has been developed by institutes and companies from across Europe and America.

The job of pulling every item together and assembling the finished system has had its scientific and engineering lead in the UK.

Miri has just gone through a rigorous mechanical and thermal test campaign at the Rutherford Appleton Laboratory (RAL) in Oxfordshire.

This included shaking the instrument to simulate the pounding it will receive during the ascent to orbit on the Ariane.

It was also put in a vacuum chamber and subjected to the kind of temperatures it will experience in space.

"It's been a real privilege to work on Miri and great to see it finally ship out," said Paul Eccleston, the engineer at RAL who has overseen the test campaign.

"It will be so exciting when we put it on top of the rocket and light the blue touch paper, so to speak, and watch it go up into space."

The paperwork signing off the test results has now been accepted by Nasa.

The next step is for Miri to be put in a special environment-controlled shipping box, so it can travel to the US space agency's Goddard centre. The Maryland facility is where the final integration of James Webb will take place.

Miri will be fixed inside a cage-like structure called the Integrated Science Instrument Module and positioned just behind the big mirror.

The years to 2018 promise yet more testing.

Mirror comparisons (BBC)
  • James Webb's instruments will be tuned to light beyond the detection of our eyes - at near- and mid-infrared wavelengths
  • It is in the infrared that very distant objects will show up, and also those objects that in the visible range are obscured by dust
  • Hubble is a visible light telescope with some near-infrared capability, but its sensitivity will be dwarfed by JWST's technologies
  • Europe's far-infrared Herschel space telescope has a bigger mirror than Hubble, but JWST's mirror will be larger still

Recommended 16 years ago as the logical evolution beyond Hubble, the JWST has managed to garner a fair amount of controversy.

Technical difficulties and project mismanagement mean the observatory is now running years behind schedule and is billions of dollars over-budget.

Elements of the US Congress wanted to cancel the telescope last summer. That did not happen, but Capitol Hill now has James Webb on a very short leash, with Nasa required to provide monthly updates on milestones met or missed.

Dr Eric Smith, Nasa's deputy programme director for James Webb, explains what the telescope can do

Much of the talk around James Webb tends to centre on cost. The current estimate for the US side is $8.8bn, which covers the full life cycle of the project from its inception to the end of initial operations. Extra to that bill is some $650m for the European contributions like Miri and Ariane.

Dr Eric Smith is Nasa's deputy programme director for James Webb. He believes taxpayers do appreciate the venture.

"When you're able to show people that James Webb will do things that not even Hubble can do - then they understand it," he told BBC News.

"People recognise how iconic Hubble has been, and how much it has affected their lives.

"The images and scientific results that Hubble has returned have permeated popular culture. Webb pictures will be just as sharp but because the telescope will be looking at a different part of the spectrum, it will show us things that are totally new."

 
Jonathan Amos, Science correspondent Article written by Jonathan Amos Jonathan Amos Science correspondent

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  • rate this
    +4

    Comment number 11.

    I'm just an average 'man in the street' and of an age where I shall not be around when we get the information that this new development will obtain for us to study. However I'd like to say how incredibly fortunate we are to be alive at a time when so many wonderful insights are available. 'Hershel's' Lockman Hole photos are staggering; new answers seem to ask ever more Questions.

  • rate this
    +7

    Comment number 10.

    If you shudder at the cost of this instrument, consider the relative disparity in the USA between funding for science, and funding for the military, then consider which brings Humanity more benefit.
    I can't wait to see the images.

  • rate this
    +5

    Comment number 9.

    This is very promising. This is evidence of how much can be accomplished in the scientific community with such measly funding.

    The US need to get their priorities straight. The budget for NASA is half a penny on a tax dollar.

    Sadly, blurred and unrecognisable is the the day when a politician sacrifices now for a much greater payoff later.

  • rate this
    +12

    Comment number 8.

    The USA spends 0.6% of one penny of the tax dollar on science in TOTAL. The $8.8bn is chicken feed in relative terms.

    The benefits from any discoveries or applied technologies may well happen decades in the future. We must be patient and not focused on a short term view.

    Scientists who discovered the electro magnetic effect thought initially it was a "toy". Now look where that has led!

  • rate this
    +13

    Comment number 7.

    I can hardly wait for first light from the Webb! $8.8bn seems a bargain, especially compared to the trillions wasted on wars and spent bailing out poorly-managed financial companies. And unlike wars and bailouts, new knowledge adds to the human experience.

  • rate this
    +6

    Comment number 6.

    The most important fact about the mirror is not that it is "more than double the width of Hubble's main mirror" but that it has 7.3 times the area and therefore captures 7.3 times more light.

  • rate this
    +3

    Comment number 5.

    This will also help generate accurate counts of blackholes, and accurate locations. And who knows what else it will reveal about blackholes.

  • rate this
    +6

    Comment number 4.

    The direct cost may seem high to many, particularly in the current economic climate.

    However, the innovations in technology derived from this and the expansion of knowledge that will be gained, so vastly outweighs the cost.

    This is a landmark in human scientific history, and therefore in human progress. This is something to celebrate, not deride.

  • rate this
    +2

    Comment number 3.

    looks great value to me, you couldn't bail out a bank branch with that little money!

  • rate this
    +7

    Comment number 2.

    I'm so glad this project is ready to go. It was a serious low point, last year, when Congress considered not funding it. These projects have an immensely positive impact on public morale and inspire new generations of kids to get excited about maths and sciences.

    The images will be something everyone -- everywhere -- can really look forward to. We share this planet, this reality, together.

  • rate this
    +13

    Comment number 1.

    We should feel a modest pride that an important part of a major space project is made in Britain.
    It is also good news that the JWST is going ahead, after recent financial uncertainties.

 

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