The recent announcement of the 2025 fiscal year budget by the US government reveals significant cuts in funding for space telescopes. Consequently, NASA will be forced to shut down the Chandra X-ray Observatory (commonly known as Chandra), which has been in operation for nearly 25 years.
Chandra is the most sensitive X-ray telescope in low Earth orbit in the past 25 years. Image source: NASA.
This move has sparked strong opposition from astronomers. They argue that the telescope's efficiency remains high as ever and it continues to be a cornerstone of American high-energy astrophysics. Shutting down Chandra would be a "disaster" for X-ray astronomy in the United States.
Launched in 1999, Chandra has been under study by Elisa Costantini of the Netherlands Institute for Space Research since its launch. She states that shutting down Chandra would leave a "gap" in the knowledge of high-energy astrophysics.
According to Science magazine, the X-ray mission received $68.3 million in the fiscal year 2023. However, according to the budget proposed by the Biden administration, this figure will decrease to $41.1 million by fiscal year 2025 and further to $26.6 million the following year. By 2029, the mission will receive only $5 million. The reduction in funding could result in half of Chandra's 180 employees being laid off.
X-rays reveal the hottest and most violent places in the universe, such as swirling gas around supermassive black holes, debris from supernova explosions, and overheated gas within massive galaxy clusters. Since 1999, Chandra and the European XMM-Newton space telescope have been pillars of X-ray astronomy. Chandra boasts the highest resolution among X-ray telescopes launched to date, capable of producing images and spectra comparable to optical telescopes.
Chandra first observed X-rays emitted by the supermassive black hole Sagittarius A* at the center of the Milky Way and also discovered the shockwave from the nearby supernova 1987A. It, along with another telescope, discovered gamma-ray bursts originating from stellar nurseries in distant galaxies.
Chandra's filters and thermal protection were initially designed for a 5-year mission, and as expected, these components have degraded in recent years. Nevertheless, supporters argue that Chandra remains highly productive, generating about 400 papers annually, with five times as many astronomers applying to use the telescope as it can accommodate.
"Chandra has achieved remarkable success - observing efficiency has hardly decreased, far exceeding the initial requirements of the mission," said Patrick Slane, director of the Chandra X-ray Center in the United States, rebutting the Biden administration's claim that managing this aging spacecraft is becoming unaffordable.
Moreover, Chandra has enough propellant for another 10 years of operation. If it were to be shut down, astronomers worry that there are currently no X-ray detection missions with similar capabilities to replace it. Although NASA has proposed the flagship mission "Lynx" as a potential successor to Chandra, this X-ray detection satellite has not yet been approved for construction.
"If NASA prematurely shuts down Chandra without any replacement plans, it will harm the X-ray community," said Esra Bulbul of the Max Planck Institute for Extraterrestrial Physics in Germany.
