The Hubble Space Telescope is slowly falling out of the sky, and it could burn up in Earth’s atmosphere as soon as 2032. Researchers are urging NASA to rescue it, arguing that the ageing instrument is still vital for science and will leave a stark capability gap if lost.
Hubble was launched in 1990 and, following an infamous design flaw in one of its mirrors that was only fixed in 1993, has provided a wealth of new science ever since. NASA claims that more than 23,000 peer-reviewed scientific papers have emerged from its images.
But the space-based telescope requires periodic servicing and raising of its orbit, as atmospheric drag causes it to slowly lose altitude. Hubble has gyroscopes that allow it to shift position to image different parts of the sky, but no propulsion of its own.
The last time that Hubble was lifted to a higher orbit was in 2002, when the space shuttle Columbia visited – one of five shuttle missions to the telescope. Since then, NASA has retired the shuttle fleet and no longer has any spacecraft with the capability to carry out the task. NASA estimates that Hubble has a 10 per cent probability of re-entry by September 2032, and a 50 per cent probability by December 2033.
The space agency has put out a call for ideas from the commercial sector, giving companies until 30 November to submit plans for either raising the orbit of Hubble to at least 600 kilometres or safely de-orbiting it and letting it crash into the ocean. The telescope has parts of sufficient density that they would probably survive atmospheric re-entry.
Such a move wouldn’t be unprecedented. Earlier this year, a NASA-funded mission carried out by commercial outfit Katalyst Space was launched to boost the orbit of the Neil Gehrels Swift Observatory, whose orbit was decaying in a similar fashion to Hubble’s. The mission failed due to a steering problem, but was widely regarded to be possible. Katalyst Space didn’t respond to request for comment.
Alise Fisher at NASA says the agency is open to ideas from inside or outside the organisation, and isn’t taking anything off the table. “It wouldn’t be appropriate for the agency to speculate about specific potential responses, so we don’t inadvertently limit them, but NASA is looking to explore a range of technologies and approaches, including those the agency may not have considered previously.”
NASA’s call-out explains that a private company would need to supply everything for the mission: the launch vehicle, the spacecraft and, if applicable, the crew. The space agency issued a similar call for ideas in 2022, but did not proceed with any despite reportedly receiving eight submissions. It did investigate a proposal by SpaceX, but the company didn’t respond to questions on whether it would be submitting a new proposal this time.
Thomas Haworth at Queen Mary University of London is part of a panel of scientists advising NASA on what direction to take with Hubble, which he describes as “the greatest telescope of all time”. He went into discussions with colleagues expecting the focus to be on how NASA could be advised to extract the most science from Hubble before the end of its life, but found that re-boosting its orbit was actually higher on the agenda, he says.
“It’s within the realms of possibility,” says Haworth. “The overall document that we’re coming up with, which still isn’t submitted yet, is going to try and strongly make that recommendation. There is quite a lot of effort to argue for a boost.”
NASA is likely to make a decision quickly once that recommendation is in, because planning a boost mission will take years, says Haworth. “You need to decide now.”
Stephen Wilkins at the University of Sussex, UK, says Hubble has unique abilities unmatched by any other instrument – including the James Webb Space Telescope, the Nancy Grace Roman Space Telescope and the European Space Agency’s Euclid telescope.
Hubble can do high-resolution ultraviolet imaging better than anything currently available. NASA aims to launch the Ultraviolet Explorer in 2030, which will cover the same part of the spectrum but with a tenth of the resolution, and the Habitable Worlds Observatory (HWO) may launch in the 2040s and match Hubble’s ability. But if Hubble is allowed to burn up in 2032, this could leave a decade or more of lost science, and if the HWO is cancelled, then that could be a virtually permanent setback.
Launching a mission to physically grapple with the telescope, which is 13 metres long and weighs over 12,000 kilograms, will be no easy task. But it could also bring intangible benefits besides lengthening Hubble’s lifespan, says Wilkins.
“While repair is more complex now that we don’t have the space shuttle, attempting to repair Hubble helps maintain key skills that will be essential for future space exploration or exploitation,” he says. “Whether or not repair makes sense ultimately depends on the cost, but maintaining skills should also be considered.”
Mark Norris at the University of Lancashire, UK, was previously funded by the Hubble budget to scour archived images for ultra-compact dwarf galaxies. “I’d worked out that, in the archive of these galaxies that Hubble had been surveying for other projects, the things I was interested in were must have been in the images by chance,” he says. “It basically built the foundation of my career. I wouldn’t have a permanent job now if it hadn’t been for that insight.”
Hubble was always designed to be serviced, says Norris, so it is fitted with grapple points for robotic arms to grab hold of. But raising its orbit wouldn’t be a permanent solution and it has begun to show its age.
“The instruments are gradually degrading through exposure to the space environment,” he says. “It’s a bit of a miracle it’s still going, but they over-engineer these things and they did service it so many times – they made sure that when the last service was done, everything was left working. It’s still doing really great science.”
NASA administrators will need to make difficult decisions about costs, as ongoing servicing and ground support will be needed on top of any mission to boost Hubble’s orbit.
“If they can save it, it makes sense, but it depends how much [it costs] and what gets axed in order to save it,” says Hayworth. “Say, for example, if they cut LISA [a plan to build a space-based gravitational wave detector]. This is probably personal and biased, but I think the science from that is so exciting that it would be a shame to lose that for the sake of an old instrument.”