In more than 50 years of operation, the Arecibo Observatory has enabled some momentous discoveries. Researchers at the observatory in Puerto Rico found in 1965 that the length of a day on Mercury is more like two Earth months than three. The first binary pulsar, detected at Arecibo in 1974, earned its discoverers the 1993 Nobel Prize in Physics. The observatory’s telescope made the first confirmed discovery of extrasolar planets in the early 1990s. And two years ago, astronomers reported using Arecibo to find Leo P, a dwarf galaxy that had gone undetected just 2 megaparsecs from the Milky Way.

Unfortunately, that five-decade streak of discoveries could be near its end. Arecibo is long in the tooth and certainly shows its age, but the problem is not that the observatory has exhausted its scientific potential. Its telescope remains the largest single-dish radio instrument in the world, and is in demand from those who study topics such as pulsars, asteroids and Earth’s upper atmosphere.

The problem is money, as it so often is. Operating Arecibo costs about US$12 million per year, a price that its owner — the US National Science Foundation (NSF) — feels increasingly unable to pay. Arecibo’s bell began to toll almost a decade ago, when a panel charged with balancing the NSF’s astronomy budget put the observatory on its list of potential cuts. The agency’s astronomy division has long been under intense pressure to support the development of new instruments such as the Large Synoptic Survey Telescope, currently under construction in Chile, without any increase in budget. But few in the astronomy community or the NSF seem to relish the idea of closing a facility as scientifically productive as Arecibo. So the agency has endeavoured to find parties willing to contribute to the observatory’s operation or, better yet, to take over the enterprise entirely. Although they may differ on how exactly to proceed, all sides share an interest in the advancement of science. Although they may differ on how exactly to proceed, all sides share an interest in the advancement of science. In July, a glimmer of hope appeared in the form of the Breakthrough Listen project, a$100-million effort sponsored by Internet billionaire Yuri Milner to scan the nearest 1 million stars for signals suggesting the presence of intelligent life. The project has already arranged to purchase about 20% of the observing time at another NSF radio facility, the Green Bank Telescope in West Virginia.

But no similar agreement has been reached at Arecibo. One stumbling block may have been conflicts with the observatory’s director, Robert Kerr, who has said that the NSF told him that it would cut its contribution to Arecibo by an amount equal to any contribution from Breakthrough Listen. Such an arrangement, he feared, would give the agency an opportunity to absolve itself entirely of the need to fund the telescope (see page 142).

NSF officials vigorously deny any such intent, and insist that they never even suggested a one-for-one reduction of funding as a condition of a Breakthrough Listen deal. Nevertheless, Kerr’s objections led to his resignation as operations director. On 26 October, the science agency distributed an open letter soliciting “strategies and goals for continued operations that involve a substantially reduced funding commitment from NSF”.

It might seem difficult to understand why the NSF has so much trouble accepting help from a private source. But the agency deserves some sympathy. It has a mandate to support a research agenda dictated by the scientific community through peer review, not by the interests of deep-pocketed philanthropists.

That is not to say that Breakthrough Listen’s goals lack legitimacy — the argument that intelligent life must exist somewhere else in the universe is strong, the confirmation of a signal from an alien civilization would arguably be the greatest scientific discovery ever made and the Arecibo telescope is one of the world’s best instruments for making such a discovery. But accepting Breakthrough Listen’s offer without minimizing its impact on the general community’s access to the tele­scope would be irresponsible. The NSF is right to proceed slowly.

Such episodes are likely to be repeated as long as public science funding remains tight and the technology sector continues minting billionaires with the curiosity and intellect to put their money to work expanding the frontiers of human knowledge. In the case of Arecibo, and in future disagreements over how to best combine private and public resources, it is important to remember that although they may differ on how exactly to proceed, all sides share an interest in the advancement of science. Elected officials are unlikely to increase funding for research any time soon, so it would be wise for managers at funding agencies and at publicly funded institutions to embrace the spirit of compromise.