WFIRST: Moving Closer to a Mission

by Paul Gilster on February 19, 2016

We learned on Wednesday that the Agency Program Management Council, which works under the aegis of NASA, has made the decision to proceed with the Wide Field Infrared Survey Telescope. WFIRST is the next step in major astrophysical observatories after the launch of the James Webb Space Telescope in 2018, an instrument that will work at near-infrared wavelengths to study dark matter and dark energy, with a significant exoplanet component.

All these issues are relevant to what we do here at Centauri Dreams, but the exoplanet aspect of the mission, which includes a coronagraph to allow the close inspection of distant solar systems, is particularly interesting. Blocking the otherwise overwhelming glare of a host star (even at these wavelengths), the WFIRST coronagraph should help to reveal the planets around it, a crucial separation that will allow us to make spectrographic measurements of the chemical makeup of planetary atmospheres.

Paul Hertz, director of NASA’s astrophysics division in Washington, notes that the instrument responds to the astronomical community’s top priorities for research:

“The Wide-Field Instrument will give the telescope the ability to capture a single image with the depth and quality of Hubble, but covering 100 times the area,” Hertz adds. “The coronagraph will provide revolutionary science, capturing the faint, but direct images of distant gaseous worlds and super-Earths.”

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Image: WFIRST, the Wide Field Infrared Survey Telescope, is shown here in an artist’s rendering. It will carry a Wide Field Instrument to provide astronomers with Hubble-quality images covering large swaths of the sky, and enabling several studies of cosmic evolution. Its Coronagraph Instrument will directly image exoplanets similar to those in our own solar system and make detailed measurements of the chemical makeup of their atmospheres. Credit: NASA/Goddard Space Flight Center/Conceptual Image Lab.

The mission will carry a 2.4-meter telescope and will operate at the Lagrangian point L2, about 1.6 million kilometers from the Earth in a direction directly opposite the Sun. Launch is scheduled for the mid-2020s. Monitoring millions of stars in the galactic center, WFIRST is likely to uncover thousands of new exoplanets, following on directly from the phenomenal work of the Kepler mission and the upcoming Transiting Exoplanet Survey Satellite (TESS). The latter takes the exoplanet hunt from the single star-field Kepler used to compile its statistical data and homes in on closer and brighter stars, deepening our catalog of nearby planets.

WFIRST’s roots are in dark energy studies, looking into the negative pressure that is evidently speeding up the expansion of the universe, an issue that can be studied by measuring the distances of thousands of supernovae. As a matter of fact, the mission was first examined in the Decadal Survey of 2010 as primarily a dark energy research telescope, with exoplanet studies via microlensing as no more than a secondary goal. But the donation of two 2.4-meter telescopes to NASA from the National Reconnaissance Office made alterations to the original configuration possible with a primary mirror the same size as the Hubble Space Telescope’s.

The full story of WFIRST’s changing configuration can be found in Ashley Baldwin’s article The Shape of Space Telescopes to Come, which appeared here in 2015 and looked at coronagraph technologies as well as starshades, the latter being large occulting disks that operate as independent spacecraft and are placed between the primary telescope and the star being studied. Exoplanet light comes through as the light of the central star is blocked. The coronagraph WFIRST has wound up with will be delivered from the Jet Propulsion Laboratory.

In his article, Baldwin refers to WFIRST as ‘the first true exoplanet telescope.’ The first, that is, that will be able to see a distant exoplanet as a point source, an instrument capable of direct imaging of exoplanets using its coronagraph while also discovering them through gravitational micro-lensing, where the light of a distant object is bent by the passage of an intervening star and associated planets, allowing one or more planets to be revealed. Planets should turn up in the thousands through transit discoveries as well as astrometry for relatively nearby stars.

WFIRST, in other words, is a mission that has evolved as the various scientific interests have had their say and developed mission concepts for exoplanets, dark energy and dark matter. Although it carries a coronagraph along with its Wide Field Instrument, the space telescope could presumably be rendered ‘starshade-ready’ in hopes of subsequent studies using that method. The success of both the James Webb Space Telescope and WFIRST should have a lot to say about the shape of the coming Decadal Survey that will chart the course after 2020.

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{ 26 comments… read them below or add one }

Larry Kennedy February 19, 2016 at 14:04

Despite all that we mess up, it does my heart good to see us support these types of missions.

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Ashley Baldwin February 19, 2016 at 14:09

For a mission that started off as a “dark energy explorer” ,WFIRST offers the true first true steps to the advanced exoplanet imagers of the future. Full credit to Professors Gehrels and Spergel for seeing the opportunity to upgrade the mission to include exoplanet imaging by taking advantage of the much larger mirror provided by the NRO donated 2.4m telescope . It was this that provides the aperture to allow the trial of stable direct imagining with high contrast and spectroscopic resolution in space for the first time. In just the space of a few years contrasts of 1e9 are achievable with perhaps better still to come , by the inclusion of a rapidly developed high performance coronagraph system . This mission has almost appeared from nowhere, though the intention was always to include a critical exoplanet census via microlensing . All credit to Nasa and Congress for achieving the necessary additional funding too though at about $2.5 billion for at least six years in terms of science return per dollar this mission is in effect a snip. All this with a telescope design that is anything but perfect for this kind of work speaks volumes of all those involved. Add in thousands of planets from the now traditional “transit photometry” as an accompanyment is going to see yet another revolution in exoplanet science to match the compemporaneous transit spectroscopy of JWST . And there may still be more to come. If WFIRST undergoes minor adaptations for later star shade use ( an external occulting device ) as is still hoped , then for less than a billion extra dollars additional even more sensitive imaging missions could be conducted on completion of the telescope’s primary work. A telescope that has been built to last and likely to be serviceable too. I raise a glass to a likely long and successful mission starting its journey to launch and into the astrophysics halls of fame along side Hubble.

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Dominic Benford February 22, 2016 at 12:48

Thank you for your support, as always, and for mentioning the microlensing campaign! I know that it doesn’t get the same attention as the coronagraphic capabilities, but the microlensing survey is still an essential tool for establishing our understanding and I’m very glad to see that you call attention to it. The vastly successful Kepler mission, had it viewed our own solar system from afar, would have seen no planets here. WFIRST would likely be able to measure the distance and masses of all the planets but Mercury. There is still so much we don’t know about what exoplanetary systems are like, and so much we should discover to inform how to use the precious time on direct imaging with the coronagraph. WFIRST is designed to make two, not just one, major leap forward in learning about exoplanets.

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Hop David February 19, 2016 at 15:51

Sounds similar to WISE. SEL2 is a great place of an infrared scope. From the scope’s POV, the sun, earth and moon all occupy the same region of the sky so a small shade serves to block all 3 heat sources.

I’m hoping infrared scopes will help us find and learn about the asteroids in our neighborhood.

Carbonaceous ivunas have high water content but low albedo. The low albedo makes them harder to see in the visible wavelengths. They’d be a lot easier to detect in infrared.

Also simultaneously measuring an asteroid’s visible reflected light and infrared gives us a pretty good idea of its size.

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Dominic Benford February 22, 2016 at 12:41

WISE and WFIRST, besides the similarity in name, are really very different. The wavelength coverage of WISE was roughly 3 microns to 25 microns, and covered the portion of the spectrum where near-room-temperature objects have their emission peak. Hence, WISE’s longer wavelengths did indeed provide the emitted light while the shorter wavelengths provided reflected light, and albedos have been determined. WFIRST is optimized for the near-infrared, at wavelengths out to about 2 microns, and hence is most sensitive to starlight (and therefore reflected starlight). Ironically, the colder WISE telescope is in a polar sun-synchronous low Earth orbit while the baseline for the warmer WFIRST telescope is to be at L2.

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Hop David February 24, 2016 at 18:33

Thanks.

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Marc Longoria February 19, 2016 at 16:43

I feel like we really need to work hard on finding a way to mass produce telescopes such as these. That way we can get a complete picture of the space around us, instead of homing in on one section of space, even if it is larger than Hubble’s scope. Waiting until the mid-2020s for a launch that may or may not be successful doesn’t seem to make too much sense. I know there are budget constraints but perhaps there is a private venture that can find profitability by making these for NASA, ESA or whomever? One can dream I guess.

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Phil February 19, 2016 at 18:36

What is going to happen to the other ‘donated’ 2.4m mirror? There were 2 right?

P

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Michael February 20, 2016 at 11:00

It is a pity that two spacecraft can’t be built and circulated in a wide orbit at L2 to give higher resolution images, the data could be time stamped and processed later for special observations.

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Steven Torry Rappolee February 20, 2016 at 17:04

Two mirrors in housing but not a spacecraft bus or avionics, There is a third mirror in storage

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Ashley Baldwin February 21, 2016 at 10:21

Good point. The only even vague suggestion I have heard is that it might be kitted out as a dual Mars mapper and “deep space ” observatory either in orbit around the red planet or presumably somewhere near, perhaps it’s L2 Lagrange point. Only a rumour though. The bottom line is I don’t think they know what to do with it as it will cost a fair bit of money to achieve anything with this telescope and in the absence of dedicated astrophysics funds ( akin to Discovery or New Frontiers ) .That just leaves flagship missions , of which there is generally one per decade and are already spoken for for some time. JWST for the current decade (2018) , WFIRST for the next (2023-2025?) .I would think (indeed hope) that Nasa’s 2030 mission ( a number of choices for this are currently being assessed by a number of science definition teams ahead of Decadel 2020 ) would aim for something somewhat larger than a 2.4m mirror which will be 30 years old at that point.

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Christopher Phoenix February 19, 2016 at 19:29

The first, that is, that will be able to see a distant exoplanet as a point source, an instrument capable of direct imaging of exoplanets using its coronagraph…

Very exciting news! Someday this time will be remembered as the golden age of exoplanet discoveries. It’s certainly an exciting time to be alive.

I don’t think it will be too long before we identify all the suitable destinations for interstellar missions within, say, 10-25 lys of the Sun. I think it will be a lot easier to generate enthusiasm for interstellar exploration when we have actual targets to point too, some of which may have the signatures of oxygen and water vapor in their atmospheres.

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Ashley Baldwin February 21, 2016 at 10:48

It’s impossible to get across just what a miraculous achievement imaging any exoplanet is. Especially with a coronagraph that requires the highest quality telescope and apparatus that provides pico meter levels of stability both mechanical and thermal. WFIRST has driven coronagraph technology forward by a huge amount , perhaps even by a decade. Developing star shade technology as a back up is wise though as this ,despite having technical difficulties of its own , bypasses many of the difficulties associated with coronagraphs. There are no current plans to use a star shade with WFIRST, ,far too early for that yet , but it’s crucial to get WFIRST adapted to function with star-shades so the option of such a mission remain open at a later date. Not a huge amount of difficulty or cost involved at this point and could provide a huge science return mission at very reasonable cost .

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Gregory Benford February 19, 2016 at 22:01

BTW, the Principal Science for WFIRST is Dominic Benford, coauthor also on our papers about Smart SETI, becons, etc.
He’s well aware of WFIRST’s ability to get the first direct images of planets, enough pixels to see atmosphere spectro lines, light reflecteed from oceans, etc.

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Hop David February 24, 2016 at 18:34

Are you and Dominic related?

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Paul Gilster February 24, 2016 at 22:15

Hop, Dominic is Greg’s nephew, and Jim Benford’s son.

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yoram February 20, 2016 at 18:21

I just hope they have better project/budget management than Webb, and won’t eat all other projects with overruns like Webb did.

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Ashley Baldwin February 21, 2016 at 10:29

WFIRST is an absolute snip compared to JWST. Possibly as little as $2.5 billion so the ideal mission for a decade after the ground breaking but pricy JWST. A good follow up though and with an expected long life hopefully with plenty of potential for additional science after the primary mission is over and indeed an ideal stop gap to the hopefully very large telescope of the 2030s. No one has said it officially but WFIRST for me is more likely to be a Hubble 2 , versatile long lived all rounder , than JWST .
That said , it’s only because of what both JWST especially , but also WFIRST with its high performance direct imaging technology , have achieved in terms of driving forward new technology , that we will eventually get 10m plus space ELTs. Between them they have made things that were utterly inconceivable even five years ago a near reality for the telescopes of the not too distant future.

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PW February 21, 2016 at 11:29

It’s when I read of projects like this one that I lose faith in the possibility of efficient inter-stellar travel. Really!
This is after all a great and vital mission. EXACTLY the kind of next steps we need to make to know where the planets are and especially the earth-like ones.
It’s so obvious, it’s what you would expect any other respectable intelligent civilization to do. “They” would have long since built the same scopes, with the same ideas in mind; detect other worlds and, ultimately, other life and other civilizations. Just what we are doing.
So “they” should see us! They should have known about earth for a long time and if they were explorers worth their salt (or some other mineral) they should have been here prospecting as we would certainly do.
But there is no sign of them; they must either not be there at all, or there is just no way to get from there to here.
Hence my old fashion Fermi frustrations.
I hope I live to see the results of this scope. A telescope is a wonderful thing, even if you are the only fella in the galaxy with one.

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Scott Gordon February 22, 2016 at 6:34

Hi PW

The fundamental flaw in your way of viewing this is that you assume that any extraterrestrial civilisation out there is actually interested in finding us or life on other planets. If they aren’t then there is no reason why we should have heard from them or seen any sign of them. They could be perfectly content the way they are.

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Wojciech J February 23, 2016 at 15:17

“But there is no sign of them; they must either not be there at all, or there is just no way to get from there to here.”
Or they do not want us to contact them, or they were here 100 mln years ago…. There are many other options.

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ole burde February 21, 2016 at 12:52

It’s great to see how talented people managed to strap some exoplanet-capabilities onto ‘the next step in major astrophysical observatories’ , but it would have been MUCH greater if the same money had been spent on a dedicated and ambitious exoplanet telescope -program .
Exoplanet dicoveries have in the last 5 years captured public atention and imagination in a way not seen since the apolo program , and this goodwill should have been converted into big funding as fast as possible .
This is called building on sucses , and has proven itself in million ways .
In a short time the public opinion will probably get bored with exoplanets like anything else , and a great opportunity to acellerate our reach for the stars will have been missed .

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Ashley Baldwin February 23, 2016 at 4:19

In a way it has. WFIRST was recently granted $90 million in the latest budget, vastly more than Nasa requested . This enabled it to go into “formulation ” phase a year early . That is a big vote of confidence and signal of intent . With TESS and JWST on the horizon it’s highly likely we will see some very exciting discoveries overvthevnextvfew years or so with JWST being able for the first time to offer detailed exoplanetary characterisation on a good number of the best targets. That will certainly get big coverage in the media which can only help. The public interest and support has been because of the exciting nature and potential of exoplanets , even at the simpler levels of discovery so far with much more complex things to follow. TESS/JWST represent a new and big step forward in capability with WFIRST following hot on their heels. JWST may be able to characterise just 250 planets , but that is vastly more than have been done so far and most importantly in far greater detail ,including terrestrial planets in potentially habitable zones . This hasn’t been remotely possible before. This is why the TESS team at MIT are so excited as they know that it is likely to deliver the first opportunity to scrutinise habitable zone “Earth-like” planets in previously unthought of detail .
The science of transit spectroscopy has taken massive steps forward in the last couple of years ( see the recent post on characterisation of a “Super Earth ” ) culminating in the recent calculation of an exo Jupiter’s rotation period . All of this was done by adapting Hubble which is twenty five years old and was never remotely envisaged of doing such things. JWST is developed to do transit spectroscopy perfectly , across a wide spectral range and with much larger mirror can collect far more light for analysis.
Stay tuned as anything can happen !
We mustn’t forget that exoplanet science is still a relatively new branch of astrophysics and is currently manoeuvring itself into an increasingly favourable position to hopefully get the big and dedicated missions it requires . The achievements of Kepler, TESS and JWST will all help with this even before we get to WFIRST.

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Larry Kennedy February 21, 2016 at 17:10

@ PW I’ve said before that I lean toward us being alone in this galaxy,but;
If kilometer wide instruments had been designed for stealth these could’ve been in our system for 10 million yrs. without us knowing.

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Michael February 22, 2016 at 16:53

yip, could be out there gathering dust and we would never know!

mmmm

http://img.thesun.co.uk/aidemitlum/archive/00991/Moon-and-Deathstar__991797a.jpg

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Jean Schneider February 22, 2016 at 6:31

Note that the European Space Agency ESA has opened a call to european astronomers to join WFIRST:
http://www.cosmos.esa.int/web/wfirst

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