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The 'dark science' and poker of space telescopes

Jonathan Amos | 17:06 UK time, Monday, 16 August 2010

Pick your dream space mission. That's what a panel of US scientists has done.

The Decadal Survey produced by the National Research Council has listed what it believes the big priorities should be in the coming 10 years for American astronomical and astrophysical research.

The document is based on wide consultation within the scientific community, and it puts a concept known as WFIRST at the top of the pile.

JDEM ConceptThe Wide-Field Infrared Survey Telescope is regarded as a must-have because it would help settle some fundamental questions about the nature of "dark energy", the mysterious phenomenon which appears to be driving the Universe apart at an accelerating rate.

The existence of dark energy was established in 1998 and is one of the great discoveries of recent years, but science understands precious little about it.

WFIRST is envisaged as a 1.5m telescope costing about $1.6bn.

It would be despatched to a gravitational "sweetspot" in space known as L2, a location more than a million kilometres from Earth on its night side where the observatory could have an unencumbered view of the sky.

One key objective would be to spy as many stellar explosions, or supernovas, as possible. Scientists will want to see how their light has been stretched by the expansion of space. This will give them greater insight into how dark energy has worked through time and perhaps give them some clues as to how it might operate in the future.

WFIRST would get complementary information by mapping the distribution of some two billion galaxies. The pattern in the great voids that exist between the galaxies can be used as a kind of "yardstick" also to probe the expansion through time.

And a third technique, known as weak lensing, would look at how the light from far-distant galaxies has been subtly shaped by intervening matter, again giving insights into the influence of dark energy through the epochs.

The cosmic webWFIRST wouldn't be just a dark energy mission, though. It would address broader issues, too, including undertaking a survey of exoplanets in the Milky Way to try to put some better statistics on how many Earth-like objects might be out there.

The idea for WFIRST hasn't come out of thin air. Like all mission concepts, it's had a long gestation [50KB PDF]. Previous ideas have been some of this way before, most notably a concept known as the Joint Dark Energy Mission (JDEM).

And from this blog's perspective, there's a European Space Agency mission (Esa) already in study that would do much of what WFIRST aspires to do. It's called Euclid.

Euclid is currently in a competitive selection process with a couple of other Esa space concepts for two launch opportunities, in 2017 and 2018.

Would the US and Europe independently fly their own, very similar missions, or would they seek to merge the two concepts? The latter would seem the logical option, but achieving a happy marriage is by no means a straightforward task.

Euclid conceptEurope expects to make a decision on whether to fly Euclid within the next 12 months; the US probably wouldn't make up its mind on whether to go with WFIRST for three or four years for what would be a launch in 2020. So the timelines are different.

Whilst the Decadal Survey indicates it would like to see international cooperation on WFIRST, it is adamant that the US should lead such an important dark energy mission.

European scientists, on the other hand, have stated already that a Euclid-type mission is a top priority for them too, and they (and European industry) would also want to lead any co-operative venture. So, primacy would be a sticking point.

Technically, Europe needs American involvement in Euclid. The European telescope's infrared detectors would have to be sourced from the US because they do not exist on this side of the Atlantic. But then Europe is in the advantageous position of having a far-more advanced design which is now undergoing detailed industrial assessment. It's in a good position to drive a hard bargain.

An important observation to make is that the Decadal Survey is a report from an influential panel; it's not an agency that implements the science. That's Nasa's job. And starting in September, at bilateral talks, Nasa will begin to talk to Esa inearnest about how their dark energy ambitions can both be met.

The poker, the horse-trading - whatever you call it - will start to get serious. How it will turn out is anyone's guess.

Professor Bob Nichol from Portsmouth University, UK, is working on Euclid. He believes the European concept is in a strong position right now:

"Euclid is one of three remaining missions in the M-class Cosmic Vision process with Esa. The decision will be made mid-2011 and two of the three will go forward for construction. So Euclid has a two in three chance of being selected and flying. Esa has an announcement of opportunity out at present to select the team that will complete the definition phase for Euclid by mid-2011, so it is an interesting time and Esa is making good progress in selecting its Cosmic Vision missions.
"It is worth stressing that Euclid already could include upto 20% involvement from Nasa and this is written into all the Euclid documents as an option. US scientists have been involved in parts of the discussions, and Esa certainly continues to talk with Nasa about Euclid involvement."

One aspect that bears down on both agencies, and which is likely to shape the stances they adopt, is the present fiscal environment.

The 2000 Decadal Survey top-rated the James Webb Space Telescope, which is due for launch in 2014/2015. This observatory's cost has spiralled in recent years to something like $5bn (Esa is the "junior partner", providing instrumentation and the launch rocket).

Neither the US nor Europe can afford to repeat the JWST experience.


  • Comment number 1.

    Jonathan Amos.

    "The existence of dark energy was established in 1998 and is one of the great discoveries of recent years.."

    no. postulated (in desparation :-)) NOT established.

  • Comment number 2.

    Your reference to dark energy indicates that it was postulated to explain an increase in the expansion rate of the universe. No reference to his observation was given.

    Four dimensional space is wrongly supposed to have three dimensions of space and one of time.
    Distance in the fourth dimension is given by the speed of light times the duration between two events.
    The fourth dimension is therefor space not time. Dimensionally (L/T) * T=L
    The universe is expanding at the speed of light in the fourth dimension.

    Initially the expansion rate may well have been smaller initially due to the large mass in the smaller universe.
    There is no need for "dark energy" to do any thing.
    I would like an opportunity to discuss this with you.

  • Comment number 3.

    Dark matter and dark energy have not been discovered. They have only been postulated because the theoretical math of the orthodox “Standard Cosmology” used to describe the universe did not and still does not describe the universe as observed. They amount to what was called in the Cosmology Statement, made by 500+ cosmologists and published in the New Scientist a few years back, as being “fudge factors”.

    There are alternative, credible models of the universe that do not require either dark matter or dark energy but because these are not considered to be in line with orthodox views they are dismissed. I refer you to “Starlight, Time and the New Physics” by Dr John Hartnett for an easily understandable account of one example.

    So BBC, please can we the get the facts right before you report them so as not to mislead.

  • Comment number 4.

    In response to FVP:

    I'm trying to get my head round what you've just said, so I'd appreciate it if you could explain further.

    But as I understand your comment - my interpretation of a 'dimension' would be something that has only one variable (e.g. for the standard 3 dimensions: to get movement in just one dimension, then if x & y are constant, then you can move along the z axis).

    If the Speed of Light is a constant (which as I understand it, most of physics relies upon that fact), then to say:
    4th dimension = Speed of Light * Time between two events
    You can effectively rule out the Speed of Light and are left with the Time between two events.

    Expect I've missed something, so please could you elaborate....

  • Comment number 5.

    Hey folks, forget theory for a moment - what we need are *data*! :-)

  • Comment number 6.

    "The existence of dark energy was established in 1998"

    Balderdash. Dark energy is a theory invented to explain another theory, the expansion of the universe, which in turn was invented to explain another theory, so-called cosmological redshifts. Although there is evidence that is consistent with all these theories, none have been proven. Personally, I prefer the "plasma universe" theory, which although it is not as well developed, is also consistent, without the need for dark energy, dark matter and invisible black holes.

  • Comment number 7.

    The Decadal Survey produced by the National Research Council has listed what it believes the big priorities that should be undertaken in the coming 10 years for American astronomical and astrophysical research. No where among these will you find wasteful expenditure on primitive imperialism and warfare.
    The Decadal Document is based on wide consultation; it puts a concept known as WFIRST (Wide-Field Infrared Survey Telescope) as a must-have because humankind must know more about dark energy as well as universe expansion and potential retraction.
    WFIRST is actually the second of two major projects; the 1.5-meter space observatory, is planned for injection iton the L2 Lagrangian point.
    The first project is called the "Cerro Chajnantor Atacama Telescope". Cerro Chajnantor is the location in Chile where the new telescope is to be constructed. The 25-meter (82-foot) instrument will be charged with witnessing cosmic evolution, and monitoring galactic formation processes.
    WFIRST would address broader issues, including undertaking a survey of exoplanets in the Milky Way.
    The European version (European Space Agency Mission - Esa) is already in competitive study mode. Esa plans for launch in 2017 and 2018. Europe expects to make a decision on whether to fly Euclid within the next 12 months; the US probably won't be in a make-up-your-mind mode for at least ten years because of current deficits.
    Whilst the Decadal Survey indicates it would like to see international cooperation on WFIRST, it is adamant that the US should lead such an important dark energy mission. What? I disagree? European scientists have already stated that a Euclid-type mission is a top priority for them, and the European industry is quite capable to lead the venture.
    Anyway, starting in September, bilateral talks will begin between Nasa and Esa.
    One thing for sure, the 2000 Decadal Survey placed the “James Webb Space Telescope” (which is due for launch in 2014/2015) as the number 1 issue. This Telescope has cost about $5B (Esa provided the instrumentation and the launch rocket). Neither the US nor Europe can afford to repeat the JWST experience.
    I can foresee Europe taking a giant leap forward in space exploration, leaving the United States wallowing in the bloody mayhem of Iraq, Afghanistan, Pakistan, and potentially Iran. There is only so much money to go around, and the American deficit is already so terribly high.

  • Comment number 8.

    Dark energy is unnecesary.

    Hubble Shift is proportional to distance squared, an artfact of observation, as is the CMB.
    At the maximum observable distance the sky is black, like the surface of a black hole.

  • Comment number 9.

    FVP #2.

    while I'm inclined to agree with you that there "is no need for "dark energy"", I disagree with your description/use of dimensions ("The universe is expanding at the speed of light in the fourth dimension.").

    the three/four dimensions referred to do not actually exist themselves, they are simply a notational convenience for locating places and events in an agreed manner.

  • Comment number 10.

    The community could really benefit from competing efforts - Hubble/NIRSPEC, HERSHEL and WISE are all flying at the same time. Great! they have overlapping but essentially complementary missions. having EUCLID and WFIRST both flying would be very great especially if Euclid was launched a few years ahead. With the surveys it is important to have lots of data spread over time. These mission have relatively short lifetimes- maybe five years on the outside. so.. fly both.. you Euro-types are encouraged to launch first to follow up as the WISE mission soon as possible. by the way, there are likely significant, relatively large objects to be found withing a couple of light years of earth. lets see some of these near neighbors ( closer than proxima or alpha centauri) show up on the longer wave infrared images!

  • Comment number 11.

    I rather like the idea that we have been exploring space for centuries and have only just discovered the we knew nothing about 90% or so of it.

  • Comment number 12.

    People forget that the only part of space we actually see is the historical light cone, a razor thin slice of space and time/ and in fact about 10^17:1 or 99.99999..% of the universe is outside it in our FTL shadow. Even our own sun is hidden in the FTL shadow about 8 light minutes away.
    As to whether space time is four dimensional that is a pretty complex argument. Minkowski space time is a four dimensional space with time as a dimension, but it is a phase space, that is a notional space. Time is its 'fourth' dimension but it is a notional dimension, Newtonian physics also uses time in the same way for instance graphing distance against time.
    The really difficult question is about the reality of time -do the future and past actually have a separate existence or are they simply part of the present? It is a stumbling block that causes problems for all physics not just general relativity but Newtonian mechanics, electronics, and most classical physics.

    When you relate scale and time.- In general relativity because time is tied to space by the speed of light- time itself scales with size. - So the universe as a whole (across billions of light years) is only a few seconds old. If time does not scale then neither does the speed of light and general relativity fails on large scales.
    Special relativity offers a very different solution because on large scales its inertial frames behave like a classical linear hyperspace and its physics would remain sensible in the FTL region.
    Either way it all boils down to another very subtle question - the actual speed of time - the propagation speed of causality itself through space. Generally time must either move at the speed of light or at simultaneous/instantaneous speeds but this is still a very open area (hyperspace type models generally need to allow both).

    Quantum mechanics allows something even worse in temporal indeterminacy, this is a place where time itself behaves like a dimension. Although on an extremely small scale if its coherency could be amplified it would allow computation with temporal superpositions/ or at higher energies still a true step into harry potter territory. Who said physics was the most solid of the sciences? :)

  • Comment number 13.

    Robert Lucien #12.

    if one were to have (for the sake of argument) a perfect vacuum, say 1 km3 in size, would time pass/exist in there? isn't time simply an attribute of matter?

  • Comment number 14.

    Not an easy question to answer jr5512. If there is some inertial field or 'hyperspace' then the answer is positive yes. The same is true of General Relativity because time and distance are tied together.
    Quantum mechanics maybe says different, if a space is totally empty and totally shielded from all EM radiation and other energy including heat then no quantum events should happen there and maybe time wouldn't exist or would come to a stop.

    Of course the big problem is as always gravity, gravity gets inside anything and is seemingly almost unstoppable, if relativity is correct even a completely curved space time cannot stop gravity. (A completely curved space time is theoretically a barrier to everything even time itself - but not gravity!)


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