With the James Webb Space Telescope now declared ‘a fully assembled observatory’ by NASA, environmental tests loom for the instrument, which is now slated for launch in March of 2021. Within that context, we need to place WFIRST (Wide-Field Infrared Space Telescope), whose development was delayed for several years because of cost overruns on JWST. Recall that WFIRST was the top priority for a flagship mission in the last astrophysics Decadal Survey.
The good news is that NASA has just announced that WFIRST has passed what it is calling ‘a critical programmatic and technical milestone,’ which opens the path to hardware development and testing. With a viewing area 100 times larger than the Hubble instrument, WFIRST will be able to investigate dark energy and dark matter while at the same time examining exoplanets by using microlensing techniques applied to the inner Milky Way. Its exoplanet capabilities could be significantly extended if additional budgeting for a coronagraph — which would allow direct imaging of exoplanets — winds up being approved.
And that is a big ‘if.’ No one doubts the power of a coronagraph onboard WFIRST to block the light of a central star in order to examine any planets found around it, but this telescope has already suffered considerable budget anxiety, leading NASA to separate the coronagraph, now described as a ‘technology demonstration,’ from the $3.2 billion budget estimate. Adding the coronagraph and subsequent operations would take the total WFIRST tally to $3.9 billion.
Image: This graphic shows a simulation of a WFIRST observation of M31, also known as the Andromeda galaxy. Hubble used more than 650 hours to image areas outlined in blue. Using WFIRST, covering the entire galaxy would take only three hours. Credits: DSS, R. Gendle, NASA, GSFC, ASU, STScI, B. F. Williams.
Will Congress approve funding for the coronagraph, or will WFIRST fly without it? Will WFIRST fly at all, given that Congress has already had to save the telescope twice from cancellation? The current FY2021 budget request proposes terminating the telescope, but it continues to receive congressional support and remains on schedule for a 2025 launch. It should be noted that a coronagraph was not part of the Decadal Survey’s recommendations, which factors into the discussion and may put pressure on those hoping to raise the needed additional funding.
Note this from NASA’s March 2 statement:
The FY2020 Consolidated Appropriations Act funds the WFIRST program through September 2020. The FY2021 budget request proposes to terminate funding for the WFIRST mission and focus on the completion of the James Webb Space Telescope, now planned for launch in March 2021. The Administration is not ready to proceed with another multi-billion-dollar telescope until Webb has been successfully launched and deployed.
The expectation is that Congress will keep WFIRST in the budget but the corongraph remains an open question. So the first priority is keeping the mission alive, while it’s clear that the cost overruns that have so exasperated astronomers and politicians alike with the James Webb instrument have played a role in keeping the brakes on WFIRST spending. As we saw recently in these pages, the Decadal Surveys (from the National Academies of Sciences, Engineering, and Medicine) set science priorities for NASA and other science agencies. The lack of a coronagraph within the last astrophysics Decadal Survey doesn’t help its chances now.
It’s just sinking in that – should the human race last long enough – we will have a proper, separate star catalogue specific to the stellar population of the Andromeda Galaxy. By at least mid-21st Century.
Who knows ?
However, regardless of outcome , what WFIRST development has done for coronagraph and through it exoplanet science , will not go to waste. The high performance versions of these precision devices were no more than theoretical concepts or crude laboratory test bed models until WFIRST development – and its substantial accompanying funds. Over just five years.
Now coronagraphs with performance of better than 1e9 contrast reduction are at a high level of technological readiness. That’s enough to image an exo (cold) Jupiter in a solar system like our own. Now. With an inner working angle, IWA of less than 200 mas and in multiple relatively broad wavelength bands. As opposed to monochromatic light with no options for spectroscopy. That’s less than one order of magnitude away from being able to directly image an Earth mass planet around a sun-like star in terms of contrast. Just twice the necessary IWA to see it in its star’s habitable zone. Accompanied by with the sensitive wavefront /adaptive optics required to keep that tiny dim image steady over the course of days to weeks long observations . With detailed spectroscopy. All it needs now is a telescope.
WFIRST or not there is too much scientific inertia to delay the advent of operational hardware – and exoplanets , specifically associated with the search for extent life /biosignatures – will figure prominently in the upcoming Decadal survey.
The Cosmic Origins Programne Advisory Group, COPAG, at NASA are responsible for driving astrophysical research and are lobbying strongly for a funded “Probe” class Programne – akin to and in parallel with planetary sciences Discovery and New Frontiers . Perhaps with a $2.5 billion budget for two to three missions per decade – in addition to the one flagship mission.
The “Great observatories ” are beginning to drop off line and NASA have realised that one flagship telescope per decade won’t be able to replace them. Nor can Nasa do proper science without them. All . But a budget of $0.8-1.5 billion dollars can still produce potent instruments . Spitzer for instance would only have costed just over one billion in 2020 adjusted dollars. To this end COPAG invited Probe concept submissions in 2016 – with a wide range of very capable telescopes produced. Operating from Far infrared through UV and visible down to X and gamma rays. With apertures up to Hubble’s 2.4m. Amongst these was the exoplanet imager, EXO-C , a capable circa 1.4m UVOIR exoplanet telescope with a WFIRST style coronagraph and optimised unobscured aperture. Or the 1.1,m Exo-S scope with its 30m plus Star-shade.
So still reason for hope, without waiting till the next flagship telescope is built in the lates 2030s ( can only be the versatile LUVOIR-B, surely ?) .
Meantime lets not forget that WFIRST’s exoplanet science isn’t just limited to direct imaging. Scott Guardi’s critical microlensing survey – discovering several thousand exoplanets of all sizes , temperatures and orbital distances – and the only method of exoplanet science that covers their whole discovery space .
To impunity and beyond.
Yes lets hope this might happen, I had gotten the idea that JWST overruns might rule out even larger, costly and more complicated scopes. All happy to hear there at least is some ideas still discussed.
It is only when combined with the coronagraph technology in whatever adaptation we will have a chance for the grand price.
What I don’t understand is how an extreme widefield like WFIRST with instrumentation for cosmological work would benefit or even be able to do such studies or benefit much from a coronagraph.
Now that Luvoir / HDST is an even larger bird, one that might end up with a truly astronomical price tag – would there be any idea to downscale a bit and propose building a near copy of JWST with a different focal length and instrumentation now they worked out all the problems in that project – and use that with a coronagraph?
You’ve hit the nail on the head though not quite in the way you think .
The main driver for the whole deployable JWST design was the limiting factor of the circa 5.5m fairing width of EELVs at the time of its conception as far back as the late 90s. To squeeze as large an aperture out as possible for the Ariane 5 ESA funded launcher specifically. Not just the 6.5m telescope array either . It’s huge sunshield too. This required a whole spectrum of new technology to be invented – with the development costs woefully underestimated . Repeatedly .
The telescope has over a hundred moving parts. Not a good combination with vacuum operation . Indeed the most recent delays ( with resultant cost escalation ) have been due to sunshield damage on deployment testing. It actually fractured ! I don’t mind telling you that I will be one very nervous person when this telescope is launched AND during the ensuing months in transit and final deployment . Far from the only one too. As a UK citizen , it’s not even my taxes on the line either . The consequences of JWST overspend as Paul says are wide reaching . The price of failure is unthinkable .
So to cut the long, sad story short the whole JWST journey has been about making a very large ( complex and fragile ) square peg fit into a small ( 5.4m) circular hole.
Ironically with the imminent arrival of 7m plus fairings available through some or all of SLS, Starship and New Glenn , I believe that given their time over again, NASA and their Northrop Grumman contractors would have plumped for a much simpler, rigid and proven monolithic mirror telescope . Yes NASA haven’t tested bigger than Hubble’s 2.4m mirror in practice ( though even Hubble was down scoped from its proposed 3m) but its only a question of scale and building and testing a large monolithic mirror would prove substantially less unpredictable, risky and ( much) cheaper than JWST .
Even if JWST performs flawlessly for five years and beyond I don’t believe that it’s technology will realistically be economically scalable to larger apertures. Bearing in mind the success of the monolithic lightweight 3.5m Herschel telescope and the durability of Hubble, I think NASA’s next space telescope after ( monolithic ) WFIRST will be monolithic too with an aperture around 8m. ( unless falling launch costs and automation make modular in orbit assembly viable ) Like Luvoir B – which to all intents and purposes is an all purpose bigged up Hubble 2. The Probe class concepts I describe will be used to create very capable telescopes for wavelengths north and south of UV, Optical and NIR. The next gen Great Observatories .
I forgot to mention that another Probe concept is for a stars-shade rendezvous mission with WFIRST. The telescope would only need a few tens of millions of dollars to adapt it prelaunch and this might yet be offered as a sop/compromise should the coronagraph be dropped .
So I got something right, thank you. :)
But yes I am indeed aware that JWST is poking Murphy’s law in several ways. I had a discussion with a person who know even less than me and described a scenario where one of the mirror elements had failed to snap exactly in the right place and a purpose built repair mission had to be sent with a piece of opaque material to be placed over the offending mirror segment.
I am anything but an engineer, but as far as I understand the star shade could work WFIRST, it is still less of an optimal instrument for such work. But if it’s considered a test/precursor experiment – why not?
Assuming the JWST works, and it will make a lot of new discoveries which will inspire funding for a chronograph for WFIRST.
A question; What is the status of the second mirror and could there be enough spare parts for that mirror to be used? They same goes for the JWST, is there many spare parts left?
The simplest answer is yes. The second mirror is currently in storage . Not alone but as part of a wider OTA, ‘optical telescope array’- essentially the skeleton of a telescope without any supporting technology such as the sensor array et al. Everything else was removed before the NRO donated it.
CCDs may be reasonably cheap but modern IR sensors are not.Especially as part of the tens of millions of dollars large arrays required by a 2.4m telescope. I have seen one concept from Alfred McEwen to convert it to an ultra high res Mars orbiter telescope ( the NRO donated on the understanding that the mirror could look anywhere – apart from down on Earth. But not other planets ) – but that was a few years back and things have gone quiet since then. I think that’s due to the $3.2 billion WFIRST price tag.
Ironically it might actually be much cheaper to build a similarly sized scope from scratch than convert non bespoke technology . ‘Free’ ain’t always what it seems.
The bottom line being that the OTA represents only a small part and cost of a finished telescope.
A point about the true statement that “a coronagraph was not part of the Decadal Survey’s recommendations”. While correct, the Decadal Survey did recommend that “candidate starlight suppression techniques should be developed to a level such that mission definition for a space-based planet imaging and spectroscopy mission could start late in the decade in preparation for a mission start early in the 2020 decade.” NASA decided to develop the WFIRST coronagraph as a means of making a great leap in advancing one starlight suppression technique. NASA then asked the National Academies to evaluate this approach, and in 2014 their report stated that the WFIRST coronagraph “satisfies some aspects of the broader exoplanet technology program recommended by NWNH by developing and demonstrating advanced coronagraph starlight suppression techniques in space.” Hence the WFIRST coronagraph does stem from and is consistent with the recommendation, but because it is a very advanced technology and less mature than the rest of the mission, its development carries more risk.
Excellent commentary from someone deeply involved in the development of the WFIRST mission. Thank you, Dominic! Your insights are always deeply appreciated here.
I would like to add my thanks , appreciation and congratulations .
I’ve followed this process from the sidelines from the beginning . The coronagraph development and maturation to its current level is an incredible achievement. I hope it flies on WFIRST.
I appreciate the attached risks , including mitigation through redefinition as a ‘technological demonstration’ . However, as an ignorant lay person Im having difficulty seeing how this equates to $700 million and why now?
The $734M difference is between the full (with reserves) development cost of the mission without the coronagraph and the total including the coronagraph development ($334M) and five years of operations ($400M). The separation of its cost effectively means the coronagraph team has greater authority within their budget to deliver what they can, on schedule, without worrying that the rest of the mission would be prioritized over them (and vice versa). It protects both ways.
Curious if anyone can tell me whether the image of M31 at the top of the article is flipped? The N/E arrow is reversed so that I imagine if flipped (and the E arrow pointed right) it would read as if the eye was seeing Andromeda? Tx in advance for this spurious question!
It’s common for astronomical images to have the N/E axes pointing that way. In astronomical coordinates, East is to your left. Imagine yourself lying on the ground looking at the night sky, with your head pointing North. Then, East (on Earth) is to your left. OTOH, Earth maps are drawn as if you were flying and looking down. In that case, if your head is pointing North, then East is to your right.
Such a wonderful series of informative comments on this article. Thanks to all of you for so much interesting information.