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

More on This Story

Related Stories

The BBC is not responsible for the content of external Internet sites

Comments

This entry is now closed for comments

Jump to comments pagination
 
  • rate this
    0

    Comment number 111.

    @ Digi JWST is optimised mostly for IR and some long wavelength visible. That doesn't meant we won't be able to "see" anything in the data. The pictures will be colour enhanced so we will still get stunning pictures of unimaginable beauty. What is really cool though is some visible light is absorbed by gas and dust. Less so IR. So galactic objects will look different.

  • rate this
    0

    Comment number 110.

    I can't wait for the first pictures from JWST. Though I have to admit that the Hubble (mostly) visible light images were the most beautiful images of space ever made and I hope JWST won't focus on IR that much. After all the beauty of the universe as seen by Hubble brought major attention to the beautiful subjects of astronomy and physics.

  • rate this
    0

    Comment number 109.

    @ #107 and 105. Light in a vacuum does travel at the same speed - c. The Doppler shift affects the wavelength but the speed remains unchanged.

  • rate this
    0

    Comment number 108.

    Also, can light be curved by centrifugal force?

  • rate this
    0

    Comment number 107.

    Yes, astrophysics is not my forté. I thought light travels at the same speed whether the source is receding or approaching. So light from a receding star 1 L Y away would not take more than 1 year to arrive even if the source was travelling away at near the speed of light (unless the light was slowed by gravity).

 

Comments 5 of 111

 

Features & Analysis

BBC Future

(Thinkstock)

How polio eased Cold War tensions

In conflict, Hungary faced another enemy Read more...

Programmes

  • JellyClick Watch

    Can Twitter’s co-founder Biz Stone break the mould with his social Q&A Jelly app?

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.