Hubble’s 35th Birthday

Happy Birthday Hubble!! It was 35 years ago, on April 24, 1990, that the game-changing Hubble Space Telescope was lofted into orbit in the cargo hold of the Space Shuttle Discovery. Its reign as the undisputed foremost space observatory may have been upended by the Webb Space Telescope, but Hubble is still wowing us on the regular.

Of course it hasn’t been all smooth sailing. Hubble has had one heck of a life so far. In honor of the birthday of one of the greatest tools in the history of human scientific endeavors (no, that is not an exaggeration), let’s look back at the road so far. 

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Origin Story

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All the way back in 1923, physicist and rocket scientist Hermann Oberth was imagining how to launch a telescope into space. The problem with a telescope on Earth is the atmosphere—it’s great for things like breathing but boy can it screw up your observations, what with all its movement and light scattering. It’s why we like to put ground-based telescopes atop the highest mountains we can find. That way they’re above at least some of the atmosphere.

In 1946 astronomer Lyman Spitzer began an active campaign for the idea of a space observatory (ambitious considering humanity was still eleven years out from its first satellite). As the world entered the Space Age, he kept at it, joined by increasing numbers of other scientists, even as NASA began to launch small, short-lived telescopes.

In 1968 NASA began pursuing the idea of a Large Space Telescope (LST). This project was quickly kneecapped due to budget cuts, prompting a surge of activism from astronomers across the country. In 1975 the European Space Agency joined in, pitching in 15% of the projected budget, and by 1977 Congress had approved enough funding to revive the project.

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It’s here I want to call out the work of Nancy Grace Roman. She was NASA’s Chief Astronomer in the 1960s and 1970s, and was a tireless advocate for the need for an orbiting space telescope. Once it was approved, she was key to shepherding the project to completion. She is commonly known in astronomy circles today by her nickname, the Mother of Hubble, and (if it can make it through the next round of NASA budgeting, which is uncertain at this point) she’ll be the namesake of the next great space observatory, the Roman Telescope, due to launch in 2027. 

In 1983 the Large Space Telescope was officially renamed the Hubble Space Telescope in honor of pioneering astronomer Edwin Hubble. By 1985 (two years behind schedule) the telescope was fully assembled. It just needed a ride on a Space Shuttle. This, of course, is right when the Shuttle fleet was grounded by the explosive loss of Challenger in January 1986. It would take four more years to get Hubble into space. 

Is It Supposed to Look Like That?

On April 25, 1990, one day after its launch, the Space Shuttle Discovery used its manipulator arm to carefully lift Hubble out of its cargo bay and release it into space. In May Hubble achieved that crucial moment, first light, when a telescope first turns its eye to the sky.

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It became immediately evident that there was a problem. Hubble’s images were blurry. Its oh-so-carefully-shaped primary mirror, it turns out, was ground just a shade too flat by less than the width of a human hair. But for something as sensitive as Hubble, it was enough. This, to put it extremely mildly, was a problem. 

Fortunately, Hubble is specifically designed to be serviced and upgraded by visiting astronauts. It wasn’t until December 1993 that a crew (including friend of the Museum Jeff Hoffman!) made it out to Hubble and essentially gave it glasses—a carefully calibrated set of lenses installed on its instruments to account for the flaw in the mirror.

I have heard Jeff talk about the incredible experience of actually putting his hands on Hubble, and I have heard him talk about how he felt when he received a phone call in early 1994, after the return of his crew to Earth, bearing the news: they’d done it! Hubble was fixed! And the images it was returning were incredible.

Changing the Game

For astronomers, there’s Before Hubble and After Hubble. Once its optics were working as advertised, it could see the cosmos like nothing ever had before. In terms of scientific achievements, I could fill a book listing them out (and plenty of people have!) and just picking a few is like picking favorite children, so I’ll just throw some quick numbers at you instead.

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Over the last 35 years, 25,000 astronomers worldwide have used Hubble data as the basis for 21,000 scientific publications, an average of 600 papers a year. So many proposals are submitted each year for the use of Hubble time that only 20% of them can actually be implemented. Hubble has taken over 1.6 million observations of over 100 million astronomical objects. Prior to the launch of Webb in 2021 Hubble was the record holder for the farthest galaxy ever observed and remains the record holder for discovering the farthest individual star ever seen.

That is a lot of science.

But Hubble changed the game in other, harder to measure ways as well. Suddenly images of space—incredible, beautiful images of space—were everywhere. Space was no longer this distant and esoteric realm that could be understood only by PhDs in the hallowed halls of academia or by mysterious masterminds at their remote mountaintop telescopes. It was on posters in classrooms, on US stamps, on the background desktops of home computers.

Heck, I’m old enough to remember when the image titled “The Pillars of Creation” came out. This Hubble picture of dusty star-forming pillars in the Eagle Nebula became one of the most famous pictures of all time (Webb’s recreation of the photo in infrared wasn’t because the Pillars are scientifically interesting, though of course they are. It’s because thanks to Hubble they are iconic, and Webb had to do its own picture of them).

The number of people whose first exposure to astronomy came via a Hubble image is impossible to quantify, but it likely makes up a significant portion of today’s global population.

A Telescope of a Certain Age

And now Hubble is 35! Which is, like, 193 in spacecraft years. Age isn’t kind to any form of machine with moving parts, and machines in space have it particularly rough. Fortunately, Hubble got the occasional facelift and was visited by five Shuttle missions (including that first one that compensated for the mirror flaw) to upgrade its components. But the last of those missions was in 2009, and the telescope has continued to age.

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The major issue these days is its gyroscopes. Hubble uses gyroscopes to point itself—critical for something that switches targets frequently. Traditionally It used three of these in tandem for normal operations, though it proved it could operate in two-gyro mode prior to the 2009 servicing mission. Hubble has six gyroscopes in total, and all of its current ones were installed on the 2009 servicing mission. But they don’t last forever.

The first gyroscope failed in 2014, followed by two more in 2018. When a fourth gyro failed in June 2024, leaving only two usable ones, it was time for a new strategy. With two working gyros left, Hubble had two options. One was to keep running with both of them, imposing wear on both and speeding up the date at which there would be no working gyros left and the telescope would be unusable, but giving Hubble the best possible pointing efficiency for that duration.

Tempting, but NASA eventually went with the other option: shutting one of the remaining functional gyroscopes down and running Hubble in one-gyro mode for the rest of its days. When the gyro currently in use inevitably fails, there will still be one working one left, extending the life of the telescope. Only having one gyro operating makes it slower to swing Hubble from target to target, reducing the number of observations it can make by about 12%, but it is estimated that Hubble can operate in this mode into the 2030s.

Legacy

I got the sense once the James Webb Telescope launched that a lot of folks coming through the Planetarium thought Hubble was no longer needed. Webb is after all a bigger, more sensitive telescope, able to see even farther targets than Hubble. But it’s a little like saying you don’t need your glass of water anymore because you now have a bigger smoothie. They’re both delightful, but they’re not the same, and you wouldn’t consider them interchangeable. 

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The two observatories see in completely different wavelengths of light, which means they see the universe in entirely different ways. Just look at those famous Pillars of Creation images from the two telescopes—the same target looks very different, because the observatories are designed to see different things. We need both of them to get a fuller understanding of the universe. Webb isn’t Hubble’s replacement or its descendent. They’re not competitors. They’re teammates.

And that’s why it’s so great that we’ve been able to extend Hubble’s life the way we have. The longer we can give it to overlap operations with Webb, the better our comprehension of the cosmos can become. And with any luck five years from now we’ll be wishing Hubble a happy 40th.

So 35th Happy Birthday, you grand old telescope! May your days be long and prosperous!