The Blurry Mirror That Explains Why We Build Telescopes in Space
A telescope in orbit escapes the atmosphere that blocks and blurs light from the ground — a trade that has taken astronomers eight decades, several funding crises and one very embarrassing mirror to get right.
In short
What happened. Space telescopes exist because Earth’s atmosphere blocks and blurs the light astronomers most want to study. The newest generation — the James Webb Space Telescope, launched in 2021, and the Nancy Grace Roman Space Telescope, due in 2026 — descends from an idea first proposed in 1946.
What it means. Moving a telescope into orbit does not remove the difficulty; it trades atmospheric interference for extreme cost, long delays and, apart from Hubble, no chance of repair once something breaks after launch.
Risks and impact. The people most affected are astronomers and the agencies that fund them. NASA’s own planning documents warn of possible gaps between one space-telescope generation and the next if funding is not sustained.
What can be done. Readers can follow NASA, ESA and CSA mission pages directly rather than relying on “next Hubble” headlines, which tend to flatten how differently each instrument actually works.
What to watch. Whether the Nancy Grace Roman Space Telescope launches on schedule in 2026, continuing a pattern of new space telescopes arriving roughly once a decade.
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What happened
In April 1990, the Space Shuttle Discovery released the Hubble Space Telescope into orbit, and NASA engineers waited for the first clear pictures of the universe. What came back instead was stubbornly blurry. Hubble’s main mirror had been ground into the wrong shape, a flaw called spherical aberration, and it took a dedicated 1993 servicing mission, with astronauts working outside the spacecraft, to fix what the ground-based construction process had gotten wrong before launch.
That failure and repair sit inside a bigger question: why build a telescope in space at all, when one on a mountaintop is cheaper and easier to fix. The answer is the atmosphere itself. It scatters and absorbs much of the light astronomers most want to study, and it blurs the rest through the same turbulence that makes stars appear to twinkle. A telescope in orbit skips all of that.
Space telescopes fall into two broad jobs: survey instruments that map the whole sky, and instruments aimed at specific objects. The first ones flew in the late 1960s and early 1970s — the American Orbiting Astronomical Observatory OAO-2 in 1968, and the Soviet Orion 1 ultraviolet telescope aboard the Salyut 1 space station in 1971. Hubble, launched in 1990, was not first. It became the most famous because of what came after the fix, and because it later helped pin down how fast the universe is expanding.
What the evidence supports
What’s solidly established is basic physics, not open to dispute. Earth’s atmosphere blocks X-rays almost entirely and heavily absorbs infrared and ultraviolet light, which is why observatories built for those wavelengths — the Chandra X-ray Observatory, the James Webb Space Telescope, the XMM-Newton observatory and the now-deactivated International Ultraviolet Explorer — had to sit above the atmosphere to work at all. It’s also why Webb needed a mirror two and a half times wider than Hubble’s just to reach comparable sharpness: it observes longer, infrared wavelengths, and matching Hubble’s resolution at those wavelengths takes more collecting area, not more magnification.
What’s well documented but less discussed is the reliability side. Hubble’s mirror flaw was real, and the repair was only possible because Hubble was designed, uniquely among space telescopes, to be serviced by astronauts. Five Space Shuttle missions repaired, upgraded and eventually replaced every one of its five main instruments. Webb has no such option. It operates roughly 1.5 million kilometres from Earth, far beyond any current crewed repair capability, so its 2021 launch and 2022 deployment had to work correctly the first time.
What remains genuinely uncertain is which of NASA’s next proposed missions — including the Habitable Worlds Observatory and a program described as the “New Great Observatories,” announced in January 2023 — will actually fly, and when. The sources describing these plans are explicit that future availability depends on continued, sufficient funding, and that scientists are concerned about coverage gaps between one generation of space telescopes and the next.
How the story is being framed
Three honest, documented positions run through this story, and none of them is a straw man.
The scientific case is the simplest: some kinds of light never reach the ground at all, so a telescope on a mountaintop cannot see certain X-ray sources, most of the infrared sky, or the faint, ancient galaxies near the edge of the observable universe, no matter its size or cost. Webb was built specifically because Hubble, however good, could not see far enough into the infrared to study the earliest galaxies.
The budget-realist case is just as well documented, because it shows up in the funding history itself. Congress deleted all funding for the Hubble project in 1974 over cost concerns, and it took a deliberate, high-stakes move by NASA management — proposing zero dollars instead of a token amount, specifically to provoke astronomers into lobbying harder — to get the project restarted. Webb’s own budget grew from an estimated one billion dollars in 1999 to roughly ten billion dollars by its 2021 launch, fourteen years later than first hoped. Expensive instruments that cannot be repaired if something goes wrong are a reasonable thing to be nervous about funding.
A third, quieter position comes from ground-based astronomy itself. Adaptive optics, which corrects for atmospheric turbulence in real time, has closed part of the gap for large terrestrial telescopes. It does not solve the absorption problem — the atmosphere still blocks X-rays and much of the infrared and ultraviolet spectrum outright — but it is a genuine, far cheaper partial answer to the blurring problem specifically, and it shapes how funding agencies choose between building on a mountain and building in orbit.
The background
The idea is older than the technology needed to do it. In 1923, rocketry pioneer Hermann Oberth wrote about a telescope carried into orbit by a rocket. It took until 1946 for the case to be made properly, when astrophysicist Lyman Spitzer published a paper arguing that an observatory above the atmosphere would have two decisive advantages: sharper images, limited only by the telescope’s own optics rather than atmospheric turbulence, and access to infrared and ultraviolet light the atmosphere absorbs before it reaches the ground.
Small missions built the case first. The United States launched the Orbiting Solar Observatory in 1962; the United Kingdom launched an orbiting solar telescope of its own the same year; NASA’s Orbiting Astronomical Observatory program followed in 1966, and OAO-2 ran productive ultraviolet observations from 1968 to 1972, far beyond its planned one-year lifetime. By 1968, NASA had firm plans for a three-metre Large Space Telescope, explicitly designed for crewed maintenance because the Space Shuttle was being developed at the same time.
Funding was never guaranteed. Congress questioned the budget repeatedly through the 1970s and zeroed it out entirely in 1974. Nancy Grace Roman, NASA’s first Chief of Astronomy, spent that decade giving public lectures and writing testimony to keep the project alive; the mission’s historians later called her its “Mother.” What eventually launched as Hubble in 1990, sixteen years after Congress had cut its funding to nothing, still needed a 1993 repair mission before it worked as intended.
The pattern repeated with Webb: initial design work began in 1996, a hoped-for 2007 launch slipped to December 2021, and the cost grew roughly tenfold from its original billion-dollar estimate. The gap between Hubble’s 1990 launch and Webb’s 2021 launch was thirty-one years. NASA’s next major instrument, the Nancy Grace Roman Space Telescope, is due to follow in 2026, carrying a mirror the same size as Hubble’s but built for a field of view roughly a hundred times wider — named for the person who spent a career arguing this was worth doing, decades before its final design existed.
Who it touches
Two people, working decades apart, hold this story together. Lyman Spitzer proposed the idea in 1946 and then spent much of his career lobbying scientists, NASA officials and members of Congress to fund something that, for most of that time, existed only on paper. Nancy Grace Roman joined NASA as its first Chief of Astronomy and became, in effect, the project’s translator: turning what astronomers wanted into a case that engineers, budget officers and politicians could act on. She wrote congressional testimony throughout the 1970s, chaired the committee that turned astronomers’ wish lists into an achievable design, and helped set the standard for how NASA still manages large scientific missions today.
Neither of them operated a telescope. Their work was slower and less visible than that: persuading people who controlled money that a machine which would not exist for decades was worth building anyway.
The deeper story
Set the hardware aside for a moment and look only at the timeline. Spitzer proposed the idea in 1946. Hubble did not reach orbit until 1990 — forty-four years later, and Spitzer lived to see it. Webb, first sketched out in the 1990s, did not launch until 2021. The Roman Space Telescope, named for a woman whose advocacy predates its final design by decades, is expected to follow in 2026.
That is an unusual kind of patience to ask of any institution, let alone a government funding process that answers to election cycles and annual budgets. It’s worth asking what allows a forty-year bet on a machine whose payoff is images of galaxies that formed before Earth existed — nothing a taxpayer can use, sell, or vote on in any ordinary sense.
Part of the answer is that curiosity, at this scale, behaves less like a project and more like a habit that has to be defended again and again by people who will not personally see it finished. Roman’s real contribution was not a mirror or an instrument; it was keeping a question alive across budget cycles long enough for someone else to finally answer it. Spitzer’s case for space telescopes was never really about avoiding a twinkling night sky. It was an argument that some questions are worth funding before anyone can prove the answer matters — and that the only way to find out is to keep making the argument until the technology catches up to it.
Something to sit with
What is something you believe is worth doing, even if you may not live to see it finished?
Where in your own work do you find yourself playing Roman’s role — keeping an idea alive for someone else to eventually build?
Sources
- Wikipedia — Space telescope — https://en.wikipedia.org/wiki/Space_telescope
- Wikipedia — Hubble Space Telescope — https://en.wikipedia.org/wiki/Hubble_Space_Telescope
- Wikipedia — James Webb Space Telescope — https://en.wikipedia.org/wiki/James_Webb_Space_Telescope
- Wikipedia — Nancy Grace Roman Space Telescope — https://en.wikipedia.org/wiki/Nancy_Grace_Roman_Space_Telescope
We report facts from the sources above in our own words and link to the originals. Interpretation is ours, not theirs.
Why did the James Webb Space Telescope need a mirror two and a half times wider than Hubble's just to reach similar image sharpness?
Resolution depends on both wavelength and mirror size. Because Webb observes in the infrared instead of visible light, it needs a much larger mirror to see as sharply as Hubble does in visible light.
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