What’s Coming After Hubble and James Webb? The High-Definition Space Telescope

Decades after its momentous launch, the ever popular Hubble Space Telescope merrily continues its trajectory in low-earth orbit, and it still enables cutting-edge science. Astronomers utilized Hubble and its instruments over the years to obtain iconic images of the Crab Nebula, the Sombrero Galaxy, the Ultra Deep Field, and many others that captured the public imagination. Eventually its mission will end, and people need to plan for the next telescope and the next next telescope. But what kinds of space exploration do scientists want to engage in 20 years from now? What technologies will they need to make it happen?

A consortium of physicists and astronomers attempt to answer these questions as they put forward and promote their bold proposal for a giant high-resolution telescope for the next generation, which would observe numerous planets, stars, galaxies and the distant universe in stunning detail. In addition to encouraging support for scientific discoveries that could be made, the telescope’s advocates also must investigate the potential technical challenges involved in constructing and launching it. An event organized at a SPIE optics and photonics conference in San Diego, California on Tuesday served as another step in this long-term process.

The Association of Universities for Research in Astronomy (AURA), an influential organization of astronomers and physicists from 39 mostly US-based institutions, which operates telescopes and observatories for NASA and the National Science Foundation, laid out its proposal of a multi-wavelength High-Definition Space Telescope (HDST) in a new report last month. Julianne Dalcanton of the University of Washington and Sara Seager of the Massachusetts Institute of Technology—veteran astronomers with impressive knowledge and experience with galactic and planetary science—led the committee who researched and wrote the 172-page document.

“It’s the science community staking out a vision for what’s the next thing to do,” said Phil Stahl, former SPIE president and senior physicist at NASA’s Marshall Space Flight Center. Speaking at the optics and photonics conference about the telescope provided “an opportunity to speak to the people who will be building it,” as many of the audience work on instrumentation.

As the HDST’s name suggests, its 12-meter wide segmented mirror would give it much higher resolution than any current or upcoming telescopes, allowing astronomers to focus on many Earth-like “exoplanets” orbiting stars outside our solar system up to 100 light-years away, resolve stars even in the Andromeda Galaxy, and image faraway galaxies dating back 10 billion years of cosmic time into our universe’s past. The 24x increased sharpness compared to Hubble and the upcoming James Webb Space Telescope is similar to the dramatic improvement of an UltraHD TV over a standard television, according to Marc Postman, an astronomer at the Space Telescope Science Institute.

A simulated spiral galaxy as viewed by Hubble and the proposed High Definition Space Telescope at a lookback time of approximately 10 billion years. Image credit: D. Ceverino, C. Moody, G. Snyder, and Z. Levay (STScI)
A simulated spiral galaxy as viewed by Hubble and the proposed High Definition Space Telescope at a lookback time of approximately 10 billion years. Image credit: D. Ceverino, C. Moody, G. Snyder, and Z. Levay (STScI)

In particular, “exoplanets are the main science driver for the HDST,” said Seager. “Are there other planets like Earth, and are there signs of life on them?” Her and her colleagues’ excitement came through as she explained that, if the telescope comes to fruition, they predict it would find dozens, if not hundreds, of Earth-like planets in the habitable zone. They would look for evidence of oxygen and water vapor as well, transforming astronomers’ knowledge of such planets, currently limited to only 1 or 2 candidates detected by the Kepler telescope.

The Hubble telescope required 20 years of planning, technological development, and budget allocations before it was launched in 1990. Planning for NASA’s James Webb Space Telescope (JWST), which was also first proposed by AURA, began not long afterward. Rome wasn’t built in a day, but many years of preparations and research will come to fruition as it is set to launch in 2018. Its scientists and engineers hope that, like Hubble, it will produce spectacular images with its infrared cameras, become a household name, and expand our understanding of the universe.

Nevertheless, James Webb has been plagued by a ballooning budget and numerous delays, and Congress nearly terminated it in 2011. The telescope proved controversial even among some astronomers and space exploration advocates. As scientists develop the next generation of telescopes, JWST remains the multi-ton multi-billion-dollar elephant in the room. David Redding of Jet Propulsion Laboratory was quick to point out that, “for Hubble, almost every technology had to be invented!” For the proposed HDST, the task appears less daunting.

Nonetheless, scientists have technological challenges and difficult questions to look forward to. For example, they must choose among multiple competing designs and consider different methods for getting the telescope into space, possibly utilizing the Space Launch System (SLS). They also expect to leverage research on JWST’s sunshield, which will be necessary to keep the proposed telescope at an extremely stable temperature, and on its detectors, when developing optimized gigapixel-class cameras. Vibrational stability on the order of one trillionth of a meter will present an additional challenge for them.

If the astronomical community comes on board and prioritizes this project for the next decade, then it likely would be designed and constructed in the 2020s and then launched in the 2030s. In the meantime, they will need major investments of funding, research and development. According to Seager, it will certainly be worth it “to observe the whole universe at 100 parsec-scale resolution” and “discover dozens of Earths.” Adding emphasis, “that’s the killer app,” Postman concluded.

20 Replies to “What’s Coming After Hubble and James Webb? The High-Definition Space Telescope”

  1. Exciting yes, but I was hoping for something FAR more ambitious. Just 12-meter diameter?? Should be more like 120 m. Commercial launch providers like Space X should have extremely inexpensive services in the next decades. Think tens of thousands of mirror segments and structural parts being sent into orbit autonomously, along with advanced robotics to essentially self-assemble this thing – with a few spacewalks thrown in for good measure, only if necessary. This would all be doable today but should be entirely feasible in 20 years.

    Just get an Elon Musk involved – he has a tendency to get things (e.g. Hyperloop) done where others sit around and say it’s not possible. The goal should be whatever it takes to see exoplanet surface detail, even if it means say a 1-km mirror. The calculation for resolving power is simple I know, but I haven’t done it. This may take more than a 120-m telescope, but then there are other options like an annular mirror.

    1. I like how you think. In space, there is no limit as to how big a telescope could be built. It’s just a matter of time and missions. And where the eventual orbit will be placed. And who said the telescope had to orbit the Earth? It could orbit the sun or be stationed in a lagrange point.

      1. The Webb Telescope is to be built at L2.

        Adaptive optics is allowing earth-based telescopes to compensate to a large degree for atmospheric issues. It’s not as good as space-based, but the tradeoff is it’s much cheaper to build a much bigger aperture on earth. And it would be maintainable, instruments can be upgraded, etc. The Webb might be the last space telescope, except for observing in frequencies that are blocked by atmosphere.

    2. JWST costs 9 billion dollar. Launch cost is not important in comparison. I suppose astronomers need uniquely capable instruments in order to make new discoveries. I would like to see a telescope sent to the gravitational focus of the Sun at least 550 AU away. It would essentially use the entire Sun as a lens! 20 times further away than Pluto but still only .2% of the distance to Proxima Centauri. It could be done this century. Unfortunately a new such telescope is needed per target, its pointing cannot be changed. But if we find a really interesting exoplanet, we could resolve it fantastically well at least at radio frequencies AFAIK.

      1. Interferometry does magic too. The largest space telescope is the Russian Spektr-R or Radioastron with a 10 meter radio antenna. It is hooked up with the very long baseline array which spans Earth’s surface and extends all the way out to a lunar distance! A 400,000 km diameter telescope in resolution, not in sensitivity unfortunately. But a long term launch campaign maybe could contribute to bigger and bigger space interferometers where every new telescope adds to the already existing ones. Harder to do for optics, though. Optical interferometers on the ground today use heavy equipment and only work across tens of meters or so.

    3. Agreed on the larger size. It would be nice to read the license plates of the cars on an exoplanet. If we have to wait for the next, next generation, I’m afraid I won’t be here to see it.

    4. I did the math once. It takes a 100 000 km diameter telescope to resolve continent sized pixels on an earth sized exoplanet around our nearest neighboring star. Assuming perfect diffraction limited optics in the visible range. Even if the mirror could be paper thin and didn’t need any support structure at all it would still weigh more then all thats ever been lifted from the surface of the earth to LEO or higher. Its simply not doable.

      But we can still learn a lot about space by building something in the range of 100 – 1000 m diameter. Thats slightly realistic with a fresnel phase plate design thin foil, and another thin foil that shades the sun and solar wind. With slightly realistic i mean at least 30 years from now, if all goes perfect. Financing, technological development etc.

      1. Well I did do the quick calculation for Tau Ceti C which is a good candidate according to Wikipedia, and I come up with about a 3,000 meter diameter objective to resolve the planetary disc itself. I really think the key is to have this monster robotically built. We know how to do this – robotics on the ISS, docking ability, etc. Just need a clever design that will allow this sort of assembly.

        So either this, or space interferometry. There was such a mission planned (SIM) but was cancelled in 2010. Ridiculous.

      2. Great! The Sun’s diameter is about 14 times 100,000 km. I suppose that means that a Solar gravitational lensing telescope could resolve continents 14 times further away (if the squares of the diameter of the lens and the distance to the object cancel each other out). There are thousands of stars within that range.

  2. It seems that we have missed something very important with regards to propulsion;

    The Electromagnetic Force is 10^42 greater than Gravity !!

    The shear quantity of observational records of Alien UFO’s that have been visiting Earth for many thousands of years. Is overwhelming !!!
    They Show several common characteristics .
    Their close proximity disrupts radio communication.
    They don’t disrupt the air around themselves as they travel at very high velocities and accelerations.
    They can remain stationary in flight and are without any visible means of propulsion
    They effect ‘Time’ !!!
    This suggests very intense Electromagnetic Fields that are being directed and precisely controlled by intelligent beings !!!

    There are many different models and a large variety of sizes
    The UFO’s travel vast distances faster than ‘C’. Probably by distorting Space/Time.

    I get the strong feeling that we have missed something very important !!

    Anyone else out there have the same ideas ??? Or better???

      1. Still about 1,000,000 / year +- 5% UNEXPLAINED = +- 50,000 / YEAR Those odds are not to be discounted !!! 500,000 / 10 years unexplained !!!

      2. Where are the UFO photos?
        I’m just trying to help you here. People WANT to believe that what they see is an alien spaceship. That would be fantastic, they’d personally become the most famous discoverers of all history. But it hasn’t and won’t happen. This wish to discover UFO’s is used by fraudsters. Are you aware of that or not? Do you think that there are deliberate UFO fraudsters who actually lie to try to earn money from their lies? Maybe they have fooled you too, think about it.

  3. What comes after the High Definition Space Telescope? Of course the Full High Definition Space Telescope and then the Ultra High Definition Space Telescope.

    1. I think the generation after will use a form of highspeed cameras.

      Luminosity
      1) you either observe long to catch low luminosity / far away objects. causing pixel oversaturation from parent stars
      2) you reset the pixels as fast as needed to avoid any over saturation

      Information
      1) You can have 1 image collected over 10 seconds
      2) You can have 1000’s of images collected over 10 seconds, which you merge afterwards into a single image, over those 10 seconds.
      NOTE) this is already done with two or more long exposures.
      NOTE) 1000’s of images over 10 seconds means 1000’s of blank intervals, so its less than 10 seconds of photon collecting.

      Quantum Computing
      1) Photon collecting could be enhanced IF single photon information could be achieved.

      1. How would quantum computing enhance it? Isn’t interferometry already kind of about using photons as qubits?

      2. interferometry is more accumulative information deviation
        not quite at qubit level, more on lightbulb level.

      3. I understand iota of this, and that is a small letter. But quantum computing actually seems to be happening. If it somehow improves telescopes, that’d be great.
        A gang of not-yet-decohered(?) photons captured from the deepest of space caught in a quantum computer. Future telescopes will not only be larger, they will be… different.

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