On February 9, NASA’s Chandra X-ray Observatory unexpectedly went into safe mode, the result of a glitch with the power supply systems for its High Resolution Camera that sent engineers scrambling to diagnose the problem. The orbiting space telescope was out of action until February 20, and even as its other instruments come back online, the HRC remains down.

For those 11 days, astronomers around the world had to contemplate an existential problem. Orbiting high above Earth, Chandra is the most powerful instrument capable of seeing high-powered X-rays, which are blocked by Earth’s atmosphere. The most high-energy objects and events in the universe often reveal themselves only in X-ray, including black holes, supernovae, and the central regions of galaxies, powered by some of the most massive objects in the universe. Without the telescope, astronomers would lose access to high-quality images of the electromagnetic spectrum, and with it, crucial data about the universe.

“Chandra is unique,” Paul Hertz, the director of astrophysics at NASA, tells Inverse. “Chandra is the only X-ray observatory that can take pictures as sharp as it does.”

Chandra’s other main instrument, the Advanced CCD Imaging Spectrometer (ACIS), is still working fine. But the glitch highlights the risks of losing the orbiting observatory for good should something more serious happen. While NASA recently launched the Imaging X-ray Polarimetry Explorer mission to explore similar wavelengths, it doesn’t have the sharp clarity to rival Chandra. And it’s an issue facing other key pieces of NASA equipment as well, some of which are running long past their initial missions have ended.

“You kind of want to milk them for every drop of data you can.”

In 2019, a component of the battery charging system aboard the International Space Station failed unexpectedly, scrambling NASA’s plans to replace the batteries themselves. While astronauts aboard the station were able to swap out the broken equipment, more worrying are recent warnings from the Russian space agency Roscosmos that 80 percent of the in-flight systems in the Russian segment are past their expiration date, as the BBC reports.

As the agency’s fleet of observational hardware gets progressively older, the threat of catastrophic failures grows more pressing. And with timelines and budgets for next-generation telescopes continually expanding, replacements for many key telescopes could be years off. It’s tempting to wonder to what extent NASA’s run of amazingly durable spacecraft is due to luck — and what might happen should that luck run out.

Why are there so many old spacecrafts?

The most recent glitch at Chandra was not an unprecedented event. The telescope’s HRC instrument went offline for months in 2020 due to a different glitch, and a gyroscope issue in 2018 also briefly put Chandra out of commission. The recurring issues are worrying, but perhaps understandable. Chandra, launched in 1999, was only supposed to work for five years. More than two decades later, the orbital observatory is still kicking.

Surprising longevity is a common theme among NASA hardware. Most famous, of course, is the venerable Hubble Space Telescope, which was launched in 1990 and continues to operate over 30 years later. Similarly, the Spitzer Space Telescope, launched in 2003 and planned to run for less than three years, stretched its lifespan to nearly two decades, until it was shut down in 2020. And NASA recently extended the lifetimes of its Juno and InSight missions, which are studying Jupiter and Mars, respectively.

The spacecrafts’ durability is a testament to the exacting specifications of NASA engineers, and it’s often been a boon to the space agency, not to mention scientists hungry for more data on the universe. It’s also a logical choice for NASA and other space agencies, says Casey Dreier, senior space policy advisor at non-profit The Planetary Society.

“These are bespoke, beautifully-designed, one-off missions that are so rare that you kind of want to milk them for every drop of data you can get out of them,” Dreier tells Inverse.

“If we turned off all of our missions, we could only build one extra mission.”

NASA takes a roughly two-part mentality when it designs space missions. Orbital observatories like the JWST or Chandra are designed with a very high probability of carrying out their initial goals, what’s often called the “prime mission.” After that period, which typically lasts just a few years, most spacecraft are still functioning well, and the agency will usually elect to continue running them to gather whatever additional data it can.

Keeping missions going costs millions of dollars per year. That’s just a fraction of the cost of building a spacecraft, but it can add up when extended across multiple missions.

“It’s this tension between maximizing the hardware that you have without having to impoverish yourself as an organization to build new hardware,” Dreier says.

In other words, keeping older missions running could be hampering our ability to build new ones.

Against the backdrop of that eternal trade-off, it’s worth keeping in mind the longstanding truism in science: It’s easier to get funding for shiny new things than it is to get money to fix old ones, says Patrick McCray, a historian of science at the University of California, Santa Barbara.

To what extent that applies to NASA spacecraft is a bit unclear. Much of NASA’s budget in coming years is likely to go toward the Artemis program to put humans back on the Moon, a far sexier mission than repairing old space telescopes. A recent report by the agency’s Office of Inspector General estimated Artemis costs will total $93 billion by 2025. NASA’s budget for 2022 is $24.8 billion. How those priorities will affect other future missions remains to be seen.

Keeping the satellites on

Hertz points out that NASA has elected to keep the majority of its space missions running past their prime missions, spending money to staff and service even older telescopes, and for good reason.

“The cost of operating a mission is so much smaller than the cost of building a mission. If we turned off all of our missions, we could only build one extra mission,” Hertz says. “To trade the science from tens of missions for the science from one mission is not a tension, it’s a no-brainer.”

Hubble, for example, costs about $90 million a year to maintain, though its five servicing missions cost hundreds of millions each. But compared to the roughly $16 billion costs for the space telescope over time, that amount is tiny. Smaller missions, like the still-functioning Voyager spacecraft, might cost tens of millions of dollars per year or less to maintain while continuing to return valuable data.

Hertz says NASA realizes most missions will reach a point where they stop working and succumb to one mechanical or software problem or another.

“It’s like the lightbulbs in your house,” he says. “Someday they’re going to burn out, and you just don’t know when it is.”

“If something happened to Webb now, there is no way you could replace it.”

Still, it’s much easier to replace a lightbulb than a space telescope. Prolonging the lifetime of spacecraft only increases the chance they might break irreparably, something that becomes more worrying as new telescopes take longer and longer to build. That’s especially true for NASA’s flagship space telescopes, like Hubble and the recently-launched James Webb Space Telescope. Each telescope has different goals and capabilities, meaning they’re not direct replacements for one another. But had Hubble gone down before JWST launched, it would have left astronomers without some key capabilities.

In fact, the Webb Telescope was meant to launch years earlier but ran into delays and cost overruns that pushed it back by more than a decade, leaving Hubble to soldier on. Now, the next big infrared telescope after the JWST is years away.

“If something happened to Webb now, there is no way you could replace it with anything on the ground or anything in space because literally nothing else is designed to answer those questions,” Dreier says.

Other examples include the Mars Reconnaissance Orbiter, which launched in 2005, and which helps relay transmissions from rovers and landers on the planet’s surface back to Earth. Should it go down, we’d lose a key link in the system connecting us to the Red Planet, with no backup on the way. There’s no backup for the ISS right now, either, and commercial space stations are likely to be years away. Without a working space station, NASA would have to halt ongoing orbital experiments into how the human body responds to space, 3D printing in microgravity, and more.

The impact of losing a telescope like Chandra wouldn’t be quite so devastating. In many cases, it’s simply a fact of life that telescopes eventually die. And newer spacecraft like the JWST should keep running for years to come. But we’re keeping our fingers crossed anyway.