NASA launched the Chandra X-ray Observatory 25 years ago this week, opening a new eye on the Universe and giving astronomers vision into unimaginably violent cosmic environments like exploding stars and black holes. But Chandra's mission may soon end as NASA's science division faces a nearly billion-dollar budget shortfall.
NASA says it can no longer afford to fund Chandra at the levels it has since the telescope launched in 1999. The agency has a diminished budget for science missions this year, and the reductions may continue next year due to government spending caps in a deal reached between Congress and the Biden administration last year to suspend the federal debt ceiling.
Congress and the White House have prioritized funding for NASA's human spaceflight programs, primarily the rockets, spacecraft, landers, spacesuits, and rovers needed for the Artemis program to return astronauts to the Moon. Meanwhile, the funding level for NASA's science mission directorate has dropped.
Mark Clampin, director of NASA's astrophysics division, said the agency doesn't want to shut down Chandra, but it must find savings somewhere.
“This is a zero-sum game discussion, so if we continue to operate and Chandra at the previous levels, we will be canceling something else," Clampin told NASA's Astrophysics Advisory Committee on Tuesday. Clampin said NASA is trying to balance the costs of continuing to operate aging missions, like Chandra, with spending on next-generation telescopes, such as a large observatory, to look for habitable worlds around other stars.
Scientists are trying to fight back against the proposed cuts, but time is running out. NASA's current budget runs out September 30, and if next year's planned budget goes into effect, dozens of scientists and engineers operating Chandra will lose their jobs. Grant Tremblay, an astronomer who works on Chandra, said managers will issue notices of impending layoffs on August 5. Their positions would be terminated at the end of September.
"Most have families, kids in school, roots planted, and so a huge number will be forced to leave astronomy," Tremblay said.
Chandra is the most powerful X-ray telescope ever built, with optics and detectors sensitive to the glow emanating from debris scattered by the cataclysmic explosions of old stars. Chandra's high-resolution imaging capability has made it a black hole hunter. Astronomers can't directly observe black holes, but X-rays emitted by the material swirling around them provide insights into their structure and behavior.
Named for the late Indian-American astrophysicist Subrahmanyan Chandrasekhar, the observatory orbits on an oval-shaped path around Earth that takes it a third of the way to the Moon. X-rays don't penetrate Earth's atmosphere, so observing them requires putting a telescope in orbit. Astronomers often combine Chandra X-ray data with similarly exquisite observations from the Hubble Space Telescope and James Webb Space Telescope in other wavelengths of light.
"For a quarter century, Chandra has made discovery after amazing discovery," said Pat Slane, director of the Chandra X-ray Center located at the Smithsonian Astrophysical Observatory, in a NASA press release. "Astronomers have used Chandra to investigate mysteries that we didn’t even know about when we were building the telescope—including exoplanets and dark energy."
What’s at stake
The White House's budget request released in March called for "an orderly drawdown to minimal operations" with Chandra. To put numbers on it, NASA set aside $68.3 million for Chandra operations in fiscal year 2023 but proposed a 40 percent reduction to $41.1 million in fiscal year 2025, followed by further cuts to $26.6 million over the following years and eventually down to $5.2 million in 2029.
That would be the death knell for Chandra, according to Robert Kennicutt, a professor of astronomy at the University of Arizona. Earlier this year, he served on a panel that NASA tasked with assessing the practical impacts of the proposed budget cuts to Chandra. The panel, called the Operations Paradigm Change Review (OPCR), concluded the cuts would effectively shut down the mission.
"Option 1 is close the observatory," Kennicutt said in a presentation to NASA's Astrophysics Advisory Committee. "This would be horrible."
Kennicutt was one of eight scientists NASA asked to examine options for operating the agency's two remaining "Great Observatories"—Chandra and the more famous Hubble—with a lower budget. The proposed cuts for Hubble are less drastic, and NASA has some flexibility in streamlining Hubble operations in ways that might reduce its scientific output, but it wouldn't kill the mission, according to Kennicutt. Hubble also has long-standing support in Congress, primarily from lawmakers representing Maryland.
This isn't the case for Chandra. The OPCR committee determined the funding NASA proposed for Chandra over the next few years would barely cover the costs of responsibly closing out the program. Slane, who manages the team running Chandra operations, agreed with this assessment, writing in a letter to the science community that "the minimal operations referred to in the budget document would actually be decommissioning activities."
"The committee agreed continuation of a scientifically viable Chandra mission is not possible within the funding guidance of the OPCR," Kennicutt said. "That is not a bluff. No way. There’s a serious threat to the observatory."
The findings of the review panel confirmed the worst fears of astronomers who regularly use data from the Chandra mission. David Pooley, chair of the Chandra Users' Committee, said the review made it "abundantly clear" that "NASA's proposed cuts will have an outsized impact on X-ray astrophysics and multi-messenger astrophysics, and should not be enacted."
"Chandra continues to produce top-tier science with an astounding return on investment," Pooley said. "Many members of Congress know this and support continued full funding for Chandra."
Last month, 10 members of Congress wrote to NASA Administrator Bill Nelson urging him to maintain Chandra's budget. They wrote that the cuts would "cause damage to US leadership" and "prematurely end the mission of a national treasure." Most of the lawmakers who signed the letter represent Massachusetts, home of Chandra's operations center.
"Chandra has been a mission that has given us so many gifts, but it's been there for 25 years, and it's time for new missions," Nelson told a House committee during a hearing in April.
NASA's budget dilemma has forced officials to make other hard choices. Last week, the agency announced it plans to cancel the VIPER rover, a craft that would have prospected for water ice on the Moon, after spending some $450 million to build it. The rover is already assembled, but it ran over budget and behind schedule, and NASA would need $84 million to finish prelaunch testing on the vehicle.
Kennicutt said it's possible for Chandra to operate with a "greatly reduced capability" at an intermediate funding level, between the mission's current budget and the levels NASA proposed for the next few years. Reducing Chandra's budget by one-third, he said, would effectively cut the mission's scientific productivity in half.
Congress hasn't yet decided on a final NASA budget for the next fiscal year, which begins October 1. There's a good chance lawmakers won't pass a final spending bill until after October 1. NASA officials say they must go through machinations of winding down work on Chandra, including layoff notices, with the assumption that Congress won't act to save Chandra.
Chandra's performance has steadily degraded over the quarter-century it has been in space, but engineers are confident it could continue operating into the 2030s. Ground controllers must take more care in managing temperatures on the observatory because it is susceptible to overheating. In the budget request published earlier this year, NASA wrote that "temperature issues are reducing the ability to provide uninterrupted extended observing time and have greatly increased complexity of mission planning."
Slane differed in his view of the complexity of Chandra's mission operations. In his letter to the Chandra science community earlier this year, Slane wrote that the observatory's operators have developed ways to manage the thermal situation "with amazing success."
Adjusted for inflation, NASA spent more than $3 billion to design, build, and launch Chandra, which was originally designed for a five-year lifetime. NASA has other X-ray telescopes in orbit, but they are designed for specific types of observations, and there's no replacement all-purpose X-ray observatory with the sharp-eyed vision of Chandra.
The European Space Agency is developing an X-ray telescope named Athena for launch in 2037. Athena will have a wider field of view than Chandra, but won't have Chandra's high-resolution imaging capability.
Anniversary week
This discussion of Chandra's future has clouded celebrations of its 25th anniversary in space. Built by TRW, now part of Northrop Grumman, the bus-size observatory launched from NASA's Kennedy Space Center in Florida on July 23, 1999, inside the payload bay of the space shuttle Columbia.
Chandra, combined with its booster rocket, filled Columbia's payload bay. It was the heaviest payload ever launched on a space shuttle, coming in at more than 50,000 pounds, or about 22.7 metric tons.
The launch of Columbia on the STS-93 mission was historic for another reason. NASA astronaut Eileen Collins became the first woman to command a US space mission. She and four crewmates deployed Chandra a few hours after launch, then the telescope used a booster rocket to propel into a higher orbit for the start of science observations.
Seconds after rising from the launch pad, alarms started blaring in the cockpit of Columbia. Mission controllers in Houston quickly started diagnosing what happened. A piece of frayed wiring short-circuited just after liftoff, knocking two main engine control computers offline. At almost the same time, vibrations from the launch knocked loose a small bullet-shaped gold-plated pin from an injector on one of Columbia's engines. The dislodged pin struck the engine's nozzle, slicing into coolant channels and causing a leak of flammable liquid hydrogen fuel.
Wayne Hale, a veteran flight director and former shuttle program manager, describes the drama of the STS-93 launch on his blog. The problems meant two of the shuttle's main engines lost redundancy in their controllers, which manage things like propellant flows and valve positions. And one of the engines was leaking hydrogen. It was probably the closest any shuttle got to having to abort its launch and attempt an emergency landing, either back in Florida or downrange in Africa.
"How much more exciting can you get," Hale wrote. "Give me a nominal, boring launch any day."
NASASpaceflight.com has a video of the launch that incorporates audio from mission control. You can hear John Shannon, NASA's flight director for this mission, conversing with his team overseeing the launch of Columbia. Once the shuttle was safely in space, Shannon exclaimed: "Yikes! We don't need any more of these."
This is a fascinating video to watch for any space enthusiast.
As it so happens, this was the first rocket launch I watched in person. I grew up a space buff and watched space shuttles streak across the sky growing up in Texas. In middle school, I convinced my parents to take me to Florida for a summer vacation, but not to a theme park. I wanted to see something real, and this was the springboard into my career as a space reporter.
I've witnessed and covered hundreds of launches since then. In a quarter-century of spaceflight, I've watched the space shuttle fly into retirement, new rockets come and go, and covered NASA's long-awaited pivot back to exploring the Moon.
Despite lacking the name recognition of Hubble or Webb, the Chandra X-ray Observatory has been an integral part of NASA's science fleet through it all, too. If astronomers have their way, Chandra will continue beaming down science data for a decade more. But there's now a risk Chandra will fall victim to the politics of government spending and perhaps NASA's desire to move on to something new. There's plenty on NASA's to-do list.
