SEATTLE — NASA’s Hubble Space Telescope achieved a whopping 23 years in orbit April 24, but astronomers are hopeful that the iconic instrument can keep studying the heavens for years to come.

The Hubble team is aiming to keep the telescope — which launched aboard the Space Shuttle Discovery April 24, 1990 — operating through 2020. That would ensure at least one year of overlap with its $8.8 billion successor, the Northrop Grumman-built James Webb Space Telescope (JWST), which is slated to launch in late 2018.

“At this point in time, that appears to be feasible,” said Hubble Mission Office head Ken Sembach of the Space Telescope Science Institute (STScI) in Baltimore, which manages Hubble’s science operations.

“It may not be operating quite as well as it’s operating today, because it will degrade with time, obviously,” Sembach said. “But that’s our hope, and that’s our plan, and we expect that that should actually be possible.”

A bumpy start

Though the Hubble Space Telescope is known today for its gorgeous cosmic images and contributions to astronomy — its observations revealed, for example, that the expansion of the universe is accelerating, leading astronomers to propose the existence of a mysterious force called dark energy — the telescope’s mission had a decidedly bumpy start.

Hubble launched with a primary mirror that was ground to the wrong prescription, and many of the images it captured in its first three years were thus frustratingly fuzzy.

“Hubble was the butt of a lot of jokes — satirizing cartoons, in newspapers and on late-night talk shows,” Sembach said. “The poor observatory was kind of a laughingstock there in the beginning.”

But the Lockheed Martin-built Hubble was designed to be serviced by spacewalking astronauts, and the problem was solved with the installation of corrective optics in December 1993. Astronauts repaired and upgraded Hubble four more times over the years, once each in 1997, 1999, 2002 and 2009.

This on-orbit attention played a major role in extending Hubble’s surprising scientific lifetime, Sembach said.

“I don’t think when Hubble was first envisioned that anybody expected it to last more than five or 10 years, let alone 20 years,” he said. “I think that the repairs and everything else that has been done to the observatory have been far more spectacular than had ever been envisioned originally.”

Teaming up with JWST

NASA has committed to funding Hubble through April 30, 2016. But support for the telescope — whose annual operating costs total about $98 million — should continue beyond that, Sembach said, provided Hubble keeps returning good data.

“As long as the observatory remains scientifically productive, I think that the country will still be willing to support the great science that it’s producing,” he said. “If it gets to the point that the science isn’t compelling anymore, then that will be the time to turn it off.”

There will be no more servicing missions now that NASA’s space shuttle fleet is retired, so the telescope is on its own. If Hubble does manage to hang on through 2020, it and JWST will make a powerful observing team, Sembach added, with Hubble’s sharp vision in optical and ultraviolet wavelengths complementing the infrared-optimized JWST well.

“There’s going to be all kinds of discoveries coming from JWST in its first year or two of observations,” Sembach said. “There are going to be many things that you’d like to have exquisite optical images of that JWST’s looking at in the infrared.”

Such observations could not always be made by the two telescopes sequentially. They would both have to be operating simultaneously, for example, to study one-off cosmic events like supernova explosions or the spectacular 1994 crash of comet Shoemaker-Levy 9 into Jupiter, STScI astronomer Mario Livio said.

“Things that are time-critical — there is no other way of doing it, other than the two telescopes overlapping,” Livio said.

Looking ahead, and looking back

Astronomers have used Hubble, which is a joint effort involving NASA and the European Space Agency, to investigate a variety of cosmic phenomena and objects over its first 23 years, and the telescope’s workload will be similarly diverse in the future. But Sembach mentioned a few areas that should receive particular attention in the coming years.

One is exoplanet research. Hubble was the first instrument to obtain the spectrum of an alien planet’s atmosphere, Sembach said, and scientists are eager to do more such work as the tally of known worlds beyond our solar system continues to grow.

Hubble will also devote considerable observing time during the next three years to a project called Hubble’s Frontier Fields, which should reveal the most distant objects known in the universe, Sembach said.

Frontier Fields follows in the footsteps of three other Hubble efforts that spotted extremely far-flung cosmic objects — the groundbreaking Deep Field photo in 1996, 2004’s Ultra Deep Field and the eXtreme Deep Field in 2012.

Such work will add to Hubble’s legacy, which Sembach said is already impressive on the scientific and popular culture fronts.

“For astronomers, Hubble is the go-to observatory. If you have something that you really need to understand — you really want to know about it in detail — the observatory of choice is almost always Hubble,” Sembach said, noting that the telescope has made more than 1 million science observations, which have led to the publication of more than 11,000 scientific papers.

“And from the American public’s standpoint, I think it’s really hard to underestimate the impact that Hubble’s had. There are Hubble pictures on classroom walls in just about every school in the country. You see Hubble imagery on television shows, you see it in books, you see it in art,” he added. “I think it’s become part of the culture.”

Livio echoed those sentiments.

“Ask any person on the street the name of one telescope, and they’ll say Hubble,” he said. “So that just shows you the level of impact.”