Potential Paths Forward for Hubble and Chandra in the Face of Budget Cuts

In the face of tight budgets, NASA announced late last year that they would be conducting a review of the Hubble Space Telescope and the Chandra X-Ray Observatory to determine cost-saving options. Both missions are NASA flagship missions that are now well into extended operations, and both continue to provide excellent science results that cannot be achieved with any other existing observatory. However, both have also faced technical challenges as they continue in operations well beyond their intended lifespan. Hubble and Chandra make up nearly 10% of the NASA Astrophysics Division budget combined, so when NASA leadership looked to budget saving measures, it seemed like reducing the operating budgets for Hubble and Chandra would be the best way to prevent cancellations of smaller missions.  

In March, the agency released their FY25 budget request to Congress, which laid out NASA’s planned budget cuts to the programs. Hubble was set to receive a reduction from $98.3 million in FY24 to $88.9 million, while Chandra would drop nearly 40% from $68.3 million to $41.1 million. Chandra was also set to receive further cuts in future years, eventually receiving just $5.2 million in FY29. To many astronomers, this signaled the closeout of Chandra. NASA leadership, meanwhile, maintained that they were looking for ways to operate the missions more efficiently rather than close them out entirely.  

NASA formalized the review of the missions with the Operations Paradigm Change Review (OPCR) panel to examine what the possible options were for operating Hubble and Chandra under a reduced budget. The independent panel of 8 experts submitted their findings to NASA on 20 May and presented their findings publicly during the NASA Astrophysics Advisory Committee (APAC) meeting on 23 July.  

For Hubble, the panel found three main pathways to reduce funding to fit within NASA’s planned budget while maintaining overall operations. First is to focus reductions on General Observer (GO) funding, which would preserve most of the instrument functionality for Hubble at the cost of community funding. Another option is to reduce the number of instrument modes. At the harshest level, this would eliminate 5 out of the 9 instrument modes — including the telescope's entire infrared capability, as this could partially be covered by JWST. The remaining instrument modes reflect Hubble’s unique ultraviolet capabilities and still account for nearly 75% of the telescope’s current utilization. Once shut down, the lost instrument modes are not likely to be restored, as the mission would no longer have the personnel with relevant experience to do so. The third pathway to reduce funding would be to focus the reductions on mission operations, which would protect most of the instrument functionality and GO funding but could lead to increased risk in operations, as there would be fewer experienced staff to respond to potential problems. Bringing Hubble operations within the planned budget would require some combinations of cuts within these three pathways, but the panel did not make any recommendations as to which option was preferred.  

When the panel examined Chandra, they determined that the only way the mission would remain under the planned budget would be if the mission were to immediately move into closeout operations. Reducing the mission to focus only on time domain/multi-messenger programs, joint observing programs with other observatories, and the Legacy program could save $20 million. This option would also require 50% less observing time due to operational reductions. And while this plan would accommodate a significant reduction in funding relative to FY24, it would still be significantly above the planned budget for FY26 and beyond. 

There is, of course, the option to implement smaller reductions for one or both missions to save their science capabilities. However, such an act would require new funding agreements by Congress. And without a similar increase in funding for the overall Astrophysics Division, any increase would need to be offset with reductions for other missions. The House recently unveiled their budget proposal for NASA and a NASA Reauthorization bill, which both include language in support of Chandra but do not attach exact funding levels to either Chandra or Hubble. The Senate is set to unveil its budget proposal on the 25 July, and it will likely contain a different set of funding priorities. With limited time left in the Legislative calendar and the impending election, it is unlikely that the House and the Senate will be able to reconcile their differences before the end of the fiscal year on 30 September. Congress would then have to pass a continuing resolution to avoid a government shutdown. Funding for Hubble would remain at FY24 levels as Congress directed specific funding to the mission, but Chandra could face immediate cuts. NASA leadership will now use the findings of the OPCR panel, along with feedback from the community and from Congress, as they determine which, if any, cuts will be made to the missions.